WO2023281014A1

WO2023281014A1 - Aerosol-forming substrate with expanded graphite

Info

Publication number: WO2023281014A1
Application number: PCT/EP2022/068988
Authority: WO
Inventors: Francesco FEDELI; Houxue HUANG
Original assignee: Philip Morris Products S.A.
Priority date: 2021-07-07
Filing date: 2022-07-07
Publication date: 2023-01-12
Also published as: KR20240032911A; AU2022308895A1; EP4366561A1; BR112023027395A2; CA3224266A1; KR20240032921A; EP4366562A1; WO2023281012A1; BR112023026946A2; AU2022305828A1; CA3225440A1; IL309598A; IL309589A; KR20240053037A; EP4366563A1; WO2023281017A1

Abstract

An aerosol-forming substrate for use in a heated aerosol-generating article comprises expanded graphite particles. Expanded graphite particles have high thermal conductivity and low density and may improve efficiency of aerosol delivery from the substrate.

Description

AEROSOL-FORMING SUBSTRATE WITH EXPANDED GRAPHITE

The present disclosure relates to an aerosol-forming substrate. The present disclosure also relates to a method of making an aerosol-forming substrate, an aerosol-generating article, and an aerosol-generating system.

A typical aerosol-generating system comprises an aerosol-generating device and an aerosol-generating article comprising an aerosol-forming substrate. In use, the aerosol generating device interacts with the aerosol-generating article to heat the aerosol-forming substrate and cause the aerosol-forming substrate to release volatile compounds. These compounds then cool to form an aerosol which is inhaled by a user.

Known aerosol-forming substrates typically have relatively low thermal conductivities. This may be undesirable, particularly in aerosol-generating systems in which a blade is inserted into the aerosol-forming substrate and heated in order to heat the aerosol-forming substrate. This is because the low thermal conductivity of the aerosol-forming substrate may lead to a relatively large temperature gradient in the aerosol-forming substrate during use. This may mean that portions of the aerosol-forming substrate which are located furthest from the blade do not reach a high temperature and so do not release as many volatile compounds as they would if the aerosol-forming substrate had a higher thermal conductivity. In other words, the low thermal conductivity of the aerosol-forming substrate may undesirably result in a low usage efficiency of the aerosol-forming substrate.

Further, known aerosol-forming substrates are typically not heatable to operating temperatures by induction. This means that, for inductive heating, a separate susceptor element is typically required. This can increase costs. In addition, this can lead to the same issues as discussed above. For example, where an inductively heated susceptor element is placed in a central position in the substrate, portions of the aerosol-forming substrate which are located furthest from the susceptor element may not reach a high temperature and therefore may not release many volatile compounds.

Attempts have been made to increase the thermal conductivity of aerosol-forming substrates. However, to date, these attempts have been inadequate in one or more respects.

It is an aim of the present invention to provide an improved aerosol-forming substrate, for example an aerosol-forming substrate having an increased thermal conductivity.

According to the present disclosure, there is provided an aerosol-forming substrate comprising expanded graphite particles. The aerosol-forming substrate may comprise the expanded graphite particles and an aerosol-forming material, such as an aerosol-former. The aerosol forming substrate may comprise greater than 0.1 weight percent (wt. %) of the expanded graphite particles. The volume mean particle size of the expanded graphite particles may be greater than 5 microns, for example greater than 10 microns. The aerosol-forming substrate may have a thermal conductivity that is greater than thermal conductivity of a homogenised tobacco substrate. For example, the aerosol-forming substrate may have a thermal conductivity of greater than 0.12 W/mK in at least one direction, for example when measured at a temperature of 25 degrees Celsius. In some specific embodiments the aerosol-forming substrate may have a thermal conductivity of greater than 0.22 W/mK in at least one direction, for example when measured at a temperature of 25 degrees Celsius.

An exemplary aerosol-forming substrate may comprise, on a dry weight basis: between 1 and 90 wt. % expanded graphite particles, each expanded graphite particle of the expanded graphite particles having a thermal conductivity of at least 1 W/(mK) in at least one direction at 25 degrees Celsius; between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12 W/(mK) in at least one direction at 25 degrees Celsius. For example, an exemplary aerosol-forming substrate may comprise, on a dry weight basis: between 1 and 10 wt. % expanded graphite particles, each expanded graphite particle of the expanded graphite particles having a thermal conductivity of at least 1 W/(mK) in at least one direction at 25 degrees Celsius; between 7 and 20 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12 W/(mK) in at least one direction at 25 degrees Celsius. The aerosol forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco.

Advantageously, the expanded graphite particles may increase the thermal conductivity of the aerosol-forming substrate. The increased thermal conductivity of the substrate may provide a more even temperature distribution throughout the substrate during use. This may result in a greater proportion of the aerosol-forming substrate reaching a sufficiently high temperature to release volatile compounds, and thus a higher usage efficiency of the aerosol-forming substrate. Further, the increased thermal conductivity of the substrate may allow a heater, for example a heating blade configured to heat the substrate, to operate at a lower temperature and thus require less power. Further still, the increased thermal conductivity of the substrate may allow a heater to heat the substrate to a temperature in which volatile compounds are released in less time. Thus, the increased thermal conductivity may reduce the time required to form an inhalable aerosol for a user.

Expanded graphite is a modified graphite material. Expanded graphite has a layered structure, just as graphite, but with increased or expanded interlayer spacing. Particularly advantageously, expanded graphite has a lower density than graphite. Thus, an aerosol-forming substrate comprising expanded graphite particles may be formed with a lower density compared with a similar substrate produced using equivalent particle sizes of normal, unexpanded, graphite or other conductive particles. A lower density substrate may allow aerosol-generating articles to be produced with lower overall weight while providing comparable aerosol deliveries. This may advantageously lower shipping costs. A lower density aerosol-forming substrate but possessing equivalent or higher thermal conductivity, may possess a lower thermal inertia, thereby allowing a shorter preheating time, potentially reducing time to first puff.

Advantageously, one or both of the fibres and the binder may increase a tensile strength of the aerosol-forming substrate. The increased tensile strength may allow the production of a sheet of the aerosol-forming substrate which does not easily tear. The increased tensile strength may allow the production of a sheet of the aerosol-forming substrate using existing production machinery.

As set out above, the aerosol-forming substrate may have a thermal conductivity of at least 0.12 W/(mK), for example at least 0.22 W/mK, in at least one direction at 25 degrees Celsius. This thermal conductivity may be measured when a moisture content of the substrate is between 0 and 20, or 5 and 15, for example around 10%. This thermal conductivity may be measured when the substrate comprises between 0 and 20, or 5 and 15, for example around 10 wt. % water. The moisture or water content of the substrate may be measured using a titration method. The moisture or water content of the substrate may be measured using the Karl Fisher method.

Expanded graphite particles may possess anisotropic thermal conductivity values. Some or each of the expanded graphite particles may have a thermal conductivity greater than 2, 5, 10, 20, 50, 100, 200, 500 or 1000 W/mK, in at least one direction, for example when measured at 25 degrees Celsius.

Expanded graphite may be expanded up to between 100 times and 300 times compared to unexpanded graphite. Expanded graphite may have a density less than 2, 1.8, 1.5, 1.2, 1, 0.8, or 0.5, 0.2, 0.1 , 0.05, 0.02 grams per centimetre cubed (g / cm³). Expanded graphite may have a density greater than 0.01, 0.02, 0.05, 0.1 , 0.2, 0.5, 0.8, 1, 1.2, 1.5 or 1.8 grams per centimetre cubed (g / cm³). Expanded graphite may have a density between 0.01 and 3, 0.01 and 2, 0.01 and 1.8, 0.01 and 1.5, 0.01 and 1.2, 0.01 and 1, 0.01 and 0.8, 0.01 and 0.5, 0.02 and 3, 0.02 and 2, 0.02 and 1.8, 0.02 and 1.5, 0.02 and 1.2, 0.02 and 1, 0.02 and 0.8, 0.02 and 0.5, 0.01 and 3, 0.05 and 2, 0.05 and 1.8, 0.05 and 1.5, 0.05 and 1.2, 0.05 and 1, 0.05 and 0.8, 0.05 and 0.5 g/cm³, 0.1 and 3, 0.1 and 2, 0.1 and 1.8, 0.1 and 1.5, 0.1 and 1.2, 0.1 and 1, 0.1 and 0.8, 0.1 and 0.5, 0.2 and 3, 0.2 and 2, 0.2 and 1.8, 0.2 and 1.5, 0.2 and 1.2, 0.2 and 1 , 0.2 and 0.8, 0.2 and 0.5, 0.5 and 3, 0.5 and 2, 0.5 and 1.8, 0.5 and 1.5, 0.5 and 1.2, 0.5 and 1 , 0.5 and 0.8, 0.8 and 3, 0.8 and 2, 0.8 and 1.8, 0.8 and 1.5, 0.8 and 1.2, 0.8 and 1 grams per centimetre cubed (g / cm³).

The expanded graphite particles may each have a “particle size”. The meaning of the term “particle size” and a method of measuring particle size is set out later.

The expanded graphite particles may be characterised by a particle size distribution. The particle size distribution may have number D10, D50 and D90 particle sizes. The number D10 particle size is defined such that 10% of the particles have a particles size less than or equal to the number D10 particle size. Similarly, the number D50 particle size is defined such that 50% of the particles have a particles size less than or equal to the number D50 particle size. Thus, the number D50 particle size may be referred to as a median particle size. The number D90 particle size is defined such that 90% of the particles have a particles size less than or equal to the number D90 particle size. Thus, if there were 1 ,000 particles in the distribution and the particles were order by ascending particle size, one would expect the number D10 particle size to be roughly equal to the particle size of the 100^th particle, the number D50 particle size to be roughly equal to the particle size of the 500^th particle, and the number D90 particle size to be roughly equal to the particle size of the 900^th particle.

The particle size distribution may have volume D10, D50 and D90 particle sizes. The volume D10 particle size is defined such that 10% of the sum of the volumes of all of the particles is accounted for by the sum of the volumes of the particles having a particles size less than or equal to the volume D10 particle size. Similarly, the volume D50 particle size is defined such that 50% of the sum of the volumes of all of the particles is accounted for by the sum of the volumes of the particles having a particles size less than or equal to the volume D50 particle size. And the volume D90 particle size is defined such that 90% of the sum of the volumes of all of the particles is accounted for by the sum of the volumes of the particles having a particles size less than or equal to the volume D90 particle size.

Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size, wherein the number D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size, wherein the number D10 particle size is no more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

A compromise has to be made when deciding the sizes of the particle. Larger expanded graphite particles may advantageously increase the thermal conductivity of the aerosol-forming substrate more than smaller expanded graphite particles. However, larger expanded graphite particles may reduce the space available for aerosol-forming material in the substrate.

Optionally, the expanded graphite particles have a particle size distribution having a number D50 particle size, wherein the number D50 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the expanded graphite particles have a particle size distribution having a number D50 particle size, wherein the number D50 particle size is no more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns. Optionally, the expanded graphite particles have a particle size distribution having a number D90 particle size, wherein the number D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the expanded graphite particles have a particle size distribution having a number D90 particle size, wherein the number D90 particle size is no more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size and a number D90 particle size, wherein the number D90 particle size is no more than 50, 40, 30, 20, 10, or 5 times the number D10 particle size.

Optionally, the expanded graphite particles have a particle size distribution having a number D10 particle size and a number D90 particle size, wherein the number D90 particle size is at least 1.5, 2, 3, 5, 10, or 20 times the number D10 particle size.

A compromise must be made in relation to the particle size distribution. A tighter particle size distribution, for example characterised by a smaller ratio between the D90 and D10 particle sizes, may advantageously provide a more uniform thermal conductivity throughout the aerosol forming substrate. This is because there will be less variation in particle size in different locations in the substrate. This may advantageously allow for more efficient usage of the aerosol-forming material throughout the aerosol-forming substrate. However, a tighter particle size distribution may disadvantageously be more difficult and expensive to achieve. The inventors have found that the particle size distributions described above may provide an optimal compromise between these two factors.

Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is at least 0.1, 0.2, 0.5, 1 , 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is no more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns

Optionally, the expanded graphite particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is at least 0.1, 0.2, 0.5, 1 , 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the expanded graphite particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

Optionally, the expanded graphite particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Optionally, the expanded graphite particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

It may be particularly preferable for the expanded graphite particles have a particle size distribution having a volume D10 particle size between 1 and 20 microns. Alternatively, or in addition, it may be particularly preferably for the expanded graphite particles have a particle size distribution having a volume D90 particle size between 50 and 300 microns, or between 50 and 200 microns.

Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, wherein the volume D90 particle size is no more than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size.

Optionally, the expanded graphite particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, wherein the volume D90 particle size is at least 1.5, 2, 3, 5, 10, or 20 times the volume D10 particle size.

The expanded graphite may have a volume mean particle size of greater than or equal to 1 , 2, 3, 5, 10, 20, 30, 35, 50, 75, 100, 150, 200, 250, 500, or 900 microns.

It may be particularly preferable that the volume mean particle size of the expanded graphite particles is greater than 10 microns.

The expanded graphite particles may have a volume mean particle size of less than or equal to 1000, 900, 500, 200, 100, 150, 100, 75, 50, 35, 30, 20, 10, 5, 3 or 2 microns. The expanded graphite particles may have a volume mean particle size of between 1 and 1000, 35 and 1000, or 100 and 900 microns. These particle size ranges may be particularly preferable where the aerosol-forming material comprises, or is in the form of, one or more of: cut-filler, powder particles, granules, pellets, shreds, spaghettis, strips or sheets.

The expanded graphite particles may have a volume mean particle size of between 1 and 1000, 10 and 200, 30 and 150, or 50 and 75 microns. These volume mean particle size ranges may be particularly preferable where the aerosol-forming material comprises, or is in the form of, a sheet, such as a gathered sheet.

The expanded graphite particles may have a volume mean particle size at least 2, 3, 5, 8, 10, 15, or 20 times the number mean particle size.

As explained above, a compromise must be made in relation to the particle size distribution, and the inventors have found that the particle size distributions above may provide an optimal compromise.

Optionally, each of the expanded graphite particles has a particle size of at least 0.01 , 0.1 , 0.2, 0.5, 1 , 2, 5, 10, 20, 50, 100, 200, or 500 microns. Optionally, each of the expanded graphite particles has a particle size of no more than 1,000, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns. It may be particularly preferable for each of the expanded graphite particles to have a particle size of at least 1 micron. Alternatively, or in addition, it may be particularly preferable for each of the expanded graphite particles to have a particle size of no more than 300 microns. Particles smaller than 1 micron may be difficult to handle during manufacturing. Particles greater than 300 microns may take up a rather large amount of space in the substrate which could be used for aerosol-forming material. Thus, it may be particularly advantageous for each of the expanded graphite particles to have a particle size of at least 1 micron, or a particle size of no more than 300 microns, or both.

Optionally, each of the expanded graphite particles has three mutually perpendicular dimensions, a largest dimension of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a smallest dimension of the three dimensions. Optionally, each of the expanded graphite particles has three mutually perpendicular dimension, a largest dimension of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a second largest dimension of the three dimensions. Optionally, each of the expanded graphite particles is substantially spherical.

Optionally, the aerosol-forming substrate comprises at least 10, 20, 50, 100, 200, 500, or 1000 particles of expanded graphite. Advantageously, a greater number of particles of expanded graphite in the aerosol-forming substrate may allow the thermal conductivity of the substrate to be more uniform.

In some embodiments, the aerosol-forming substrate may have a relatively low proportion of expanded graphite particles. For example, the substrate may comprise an aerosol forming material such as homogenised tobacco which contains between 0.1 and 25 wt. % expanded graphite particles. The expanded graphite particles may make up less than or equal to 80, 50, 20, 10, or 5 weight percent of the aerosol-forming substrate. The expanded graphite particles may make up more than or equal to 0.1 , 0.2, 0.5, 1, 2, 3, 5, 10, 20 or 50 weight percent of the aerosol-forming substrate. The expanded graphite particles may make up between 0.1 and 20, 0.2 and 20, 0.5 and 20, 1 and 20, 2 and 20, 3 and 20, 5 and 20, 0.1 and 15, 0.2 and 15, 0.5 and 15, 1 and 15, 2 and 15, 3 and 15, 5 and 15, 0.1 and 10, 0.2 and 10, 0.5 and 10, 1 and 10,

2 and 10, 3 and 10, or 5 and 10 weight percent of the aerosol-forming substrate. The expanded graphite particles may make up between 0.1 and 20, 0.2 and 20, 0.5 and 20, 1 and 20,2 and 20,

3 and 20, 5 and 20, 0.1 and 15, 0.2 and 15, 0.5 and 15, 1 and 15, 2 and 15, 3 and 15, 5 and 15, 0.1 and 10, 0.2 and 10, 0.5 and 10, 1 and 10, 2 and 10, 3 and 10, or 5 and 10 weight percent of the aerosol-forming substrate.

It may be particularly preferable that the expanded graphite particles make up greater than 1 weight percent of the aerosol-forming substrate. It may also be preferable that the expanded graphite particles make up less than 20 weight percent of the aerosol-forming substrate. Advantageously, the inventors have found that such weight percentages provide an optimal compromise between increasing the thermal conductivity of the aerosol-forming substrate and maintaining enough aerosol-forming material, for example homogenised tobacco, to form an adequate quantity of aerosol. It may be particularly preferable that the expanded graphite particles make up between 1 and 20, 2 and 15, or 3 and 10, weight percent of the aerosol-forming substrate. This is because the inventors have found that, for particular aerosol forming substrates, these weight percent ranges may provide more consistent glycerol and nicotine deliveries over around 12 puffs. Without wishing to be bound by theory, this is thought to be because having less than 1 , 2 or 3 weight percent of expanded graphite particles does not have a sufficiently large effect on the thermal conductivity of the substrate, but having greater than 10, 15 or 20 weight percent expanded graphite particles raises local substrate temperatures too high too soon, resulting in relatively high glycerol and nicotine deliveries in early puffs but relatively low glycerol and nicotine deliveries in later puffs. In addition, the inventors have surprisingly found that, for particular aerosol-forming substrates, the total yields of glycerol and nicotine over around 12 puffs appear to reach maximums for substrates having between 1 and 20, 2 and 15, or 3 and 10 weight percent expanded graphite particles. This may be advantageous as less substrate may be required to deliver an equal amount of glycerol and nicotine to a user.

In some embodiments the aerosol-forming substrate may comprise a relatively high proportion of expanded graphite particles, for example expanded graphite particles, a binder, a fibre component, and an aerosol-former. Optionally, the substrate comprises, on a dry weight basis, at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85 wt. % of the expanded graphite particles. Optionally, the substrate comprises, on a dry weight basis, no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt. % of the expanded graphite particles. Optionally, the substrate comprises, on a dry weight basis, between 10 and 90, 20 and 90, 30 and 90, 40 and 90, 50 and 90, 60 and 90, 70 and 90, 80 and 90, 10 and 80, 20 and 80, 30 and 80, 40 and 80, 50 and 80, 60 and 80, 70 and 80, 10 and 70, 20 and 70, 30 and 70, 40 and 70, 50 and 70, 60 and 70, 10 and 60, 20 and 60, 30 and 60, 40 and 60, 50 and 60, 10 and 50, 20 and 50, 30 and 50, 40 and 50, 10 and 40, 20 and 40, 30 and 40, 10 and 30, 20 and 30, or 10 and 20 wt. % of the expanded graphite particles. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 50 and 90, or more preferably between 60 and 90, or even more preferably between 65 and 85, wt. % of the expanded graphite particles.

A comprise must be made in relation to the weight percent of expanded graphite particles in the substrate. Increasing the weight percent of particles in the aerosol-forming substrate may advantageously increase the thermal conductivity of the substrate. However, increasing the weight percent of particles in the aerosol-forming substrate may also reduce the available space for one or more of the aerosol former, binder, and fibres, so could result in a substrate which forms less aerosol, or which has lower tensile strength.

Optionally, the substrate comprises, on a dry weight basis, at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt. % of an aerosol former. Optionally, the substrate comprises, on a dry weight basis, no more than 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt. % of the aerosol former. Optionally, the substrate comprises, on a dry weight basis, between 7 and 60, 10 and 60, 20 and 60, 30 and 60, 40 and 60, 50 and 60, 7 and 50, 10 and 50, 20 and 50, 30 and 50, 40 and 50, 7 and 40, 10 and 40, 20 and 40, 30 and 40, 7 and 30, 10 and 30, 20 and 30, 7 and 20, 10 and 20, or 7 and 10 wt. % of the aerosol former. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 15 and 25 wt. % of the aerosol former.

Optionally, the aerosol-former comprises or consists of one or more of: polyhydric alcohols, such as propylene glycol, polyethylene glycol, triethylene glycol, 1 , 3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or tri-acetate; and aliphatic esters of mono-, di- or poly-carboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Optionally, the aerosol-forming substrate comprises one or both of glycerine and glycerol.

Optionally, the substrate comprises, on a dry weight basis, at least 2, 4, 6, 8, 10, 12, 14, 16 or 18 wt. % of fibres. Optionally, the substrate comprises, on a dry weight basis, no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt. % of the fibres. Optionally, the substrate comprises, on a dry weight basis, between 4 and 20, 6 and 20, 8 and 20, 10 and 20, 12 and 20, 14 and 20, 16 and 20, 18 and 20, 2 and 18, 4 and 18, 6 and 18, 8 and 18, 10 and 18, 12 and 18, 14 and 18, 16 and 18, 2 and 16, 4 and 16, 6 and 16, 8 and 16, 10 and 16, 12 and 16, 14 and 16, 2 and 14, 4 and 14, 6 and 14, 8 and 14, 10 and 14, 12 and 14, 2 and 12, 4 and 12, 6 and 12, 8 and 12, 10 and 12, 2 and 10, 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, or 2 and 4 wt. % of the fibres. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 2.1 and 9.8 wt. % of the fibres.

Optionally, the fibres are cellulose fibres. Advantageously, cellulose fibres are not overly costly and can increase the tensile strength of the substrate.

Optionally, each of the fibres has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a smallest dimension of the three dimensions. Optionally, each of the fibres has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a second largest dimension of the three dimensions.

Optionally, the substrate comprises, on a dry weight basis, at least 4, 6, or 8 wt. % of the binder. Optionally, the substrate comprises, on a dry weight basis, no more than 8, 6, or 4 wt. % of the binder. Optionally, the substrate comprises, on a dry weight basis, between 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, 2 and 4 wt. % of the binder. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 2.1 and 10 wt. % of the binder.

Suitable binders are well-known in the art and include, but are not limited to, natural pectins, such as fruit, citrus or tobacco pectins; guar gums, such as hydroxyethyl guar and hydroxypropyl guar; locust bean gums, such as hydroxyethyl and hydroxypropyl locust bean gum; alginate; starches, such as modified or derivatized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl cellulose; tamarind gum; dextran; pullalon; konjac flour; xanthan gum and the like. It may be particularly preferable for the binder to be or comprise guar. It may be particularly preferable for the binder to comprise or consist of one or more of carboxymethyl cellulose or hydroxypropyl cellulose or a gum such as guar gum.

Optionally, the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the aerosol former is substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the fibres are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Advantageously, a homogenous distribution of components of the substrate may result in the substrate have more spatially uniform properties. For example, substantially homogeneously distributed expanded graphite particles may result in the substrate having a substantially uniform thermal conductivity. As another example, substantially homogeneously distributed binder or fibres may result in the substrate having a substantially uniform tensile strength.

Optionally, the substrate comprises nicotine. Optionally, the substrate comprises, on a dry weight basis, at least 0.01, 1 , 2, 3, or 4 wt. % nicotine. Optionally, the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2, or 1 wt. % nicotine. Optionally, the substrate comprises, on a dry weight basis, between 0.01 and 5, 1 and 5, 2 and 5, 3 and 5, 4 and 5, 0.01 and 4, 1 and 4, 2 and 4, 3 and 4, 0.01 and 3, 1 and 3, 2 and 3, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % nicotine. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.5 and 3 wt. % nicotine.

Optionally, the nicotine is substantially homogeneously distributed throughout the aerosol forming substrate.

Optionally, the substrate comprises an acid. Optionally, the substrate comprises, on a dry weight basis, at least 0.01 , 1 , 2, 3, or 4 wt. % of the acid. Optionally, the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2 or 1 wt. % of the acid. Optionally, the substrate comprises, on a dry weight basis, between 0.01 and 5, 1 and 5, 2 and 5, 3 and 5, 4 and 5, 0.01 and 4, 1 and 4, 2 and 4, 3 and 4, 0.01 and 3, 1 and 3, 2 and 3, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % of the acid. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.5 and 3wt % of acid.

Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

Optionally, the acid is substantially homogeneously distributed throughout the aerosol forming substrate.

Optionally, the substrate comprises at least one botanical. Optionally, the substrate comprises, on a dry weight basis, at least 0.01, 1, 2, 5, 10, or 15 wt. % of the at least one botanical. Optionally, the substrate comprises, on a dry weight basis, no more than 20, 15, 10, 5, 2 or 1 wt. % of the at least one botanical. Optionally, the substrate comprises, on a dry weight basis, between 0.01 and 20, 1 and 20, 2 and 20, 5 and 20, 10 and 20, 15 and 20, 0.01 and 15, 1 and 15, 2 and 15, 5 and 15, 10 and 15, 0.01 and 10, 1 and 10, 2 and 10, 5 and 10, 0.01 and 5, 1 and 5, 2 and 5, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % of the at least one botanical. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 5 and 15 wt. % of the at least one botanical.

Optionally, the at least one botanical comprises or consists of one or both of clove and rosmarinus.

Optionally, the at least one botanical is substantially homogeneously distributed throughout the aerosol-forming substrate.

Optionally, the substrate comprises at least one flavourant. Optionally, the substrate comprises, on a dry weight basis, at least 0.1 , 1, 2, or 5 wt. % of the at least one flavourant. Optionally, the substrate comprises, on a dry weight basis, no more than 10, 5, 2 or 1 wt. % of the at least one flavourant. Optionally, the substrate comprises, on a dry weight basis, between 0.1 and 10, 1 and 10, 2 and 10, 5 and 10, 0.1 and 5, 1 and 5, 2 and 5, 0.1 and 2, 1 and 2, 0.1 and 1 wt. % of the at least one flavourant. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.5 and 4.0 wt. % of the at least one flavourant.

Optionally, the at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate. Alternatively, or in addition, the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate.

Optionally, the aerosol-forming substrate comprises at least one organic material such as tobacco. Optionally, the at least one organic material comprises one or more of herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco and expanded tobacco. Optionally, the at least one organic material is substantially homogeneously distributed throughout the aerosol-forming substrate. The substrate may comprise, on a dry weight basis, less than 10, 5, 3, 2, or 1 wt. % tobacco. Optionally, the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

The aerosol-forming substrate may be in the form of a rod. As such, there may be provided a rod of aerosol-forming substrate.

A susceptor element may be located within the rod of aerosol-forming substrate. The susceptor element may be an elongate susceptor element. The susceptor element may extend longitudinally within the rod of aerosol-forming substrate. The rod may be substantially cylindrical, for example right cylindrical, in shape. The susceptor element may be positioned in a radially central position within the rod of aerosol-forming substrate. The susceptor element may extend along a central, longitudinal axis of the rod of aerosol-forming substrate. The susceptor element may extend all the way to a downstream end of the rod of aerosol-forming substrate. The susceptor element may extend all the way to an upstream end of the rod of aerosol-forming substrate. The susceptor element may have substantially the same length as the rod of aerosol forming substrate. The susceptor element may extend from the upstream end to the downstream end of the rod of aerosol-forming substrate. The susceptor element may be in the form of a pin, rod, strip or blade. The susceptor element may have a length of between 5 and 15, 6 and 12, or 8 and 10 millimetres. The susceptor element may have a width of between 1 and 5 millimetres. The susceptor element may have a thickness of between 0.01 and 2, 0.5 and 2, or 0.5 and 1 millimetres.

Alternatively, there may be no susceptor materials present in the aerosol-forming substrate or in the rod of aerosol-forming substrate.

Optionally, some or each of the expanded graphite particles may be inductively heatable, for example to a temperature of at least 100, 150, or 200 degrees Celsius. The expanded graphite particles may comprise or be the only susceptor material(s) present in the aerosol-forming substrate or in the rod of aerosol-forming substrate. That is, there may be no susceptor elements present in the aerosol-forming substrate or in the rod of aerosol-forming substrate except for the expanded graphite particles.

Optionally, the aerosol-forming substrate has a thermal conductivity of greater than 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.25, 1.5, 2, 5, 10, 20, 50, 100, 200, or 500 W/(mK) in at least one direction at 25 degrees Celsius.

Optionally, the aerosol-forming substrate has a density of no more than 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, 650, or 600 kg/m³. Optionally, the aerosol-forming substrate has a density of between 600 and 1400, 800 and 1200, or 900 and 1100 kg/m³. Advantageously, reducing a density of the substrate may reduce transportation costs of the substrate. Optionally, the aerosol-forming substrate has a moisture content of between 1 and 20, or 3 and 15 wt. %. This moisture content may be measured after 48 hours equilibration at 50 % relative humidity at 20 degrees Celsius. Optionally, the aerosol-forming substrate comprises between 1 and 20, or 3 and 15 wt. % water. The moisture or water content of the substrate may be measured using a titration method. The moisture or water content of the substrate may be measured using the Karl Fisher method.

Optionally, the aerosol-forming substrate comprises, or is in the form of, one or more of: cut-filler, powder particles, granules, pellets, shreds, spaghettis, strips, threads, ribbons, or sheets. Optionally, the aerosol-forming substrate comprises, or is in the form of, one or more sheets or strips.

Optionally, the aerosol-forming substrate comprises, or is in the form of, one or more sheets, for example gathered sheets or rolled sheets. Optionally, the aerosol-forming substrate comprises, or is in the form of, a plurality of strips. Optionally the aerosol-forming substrate is in the form of a tube.

Optionally, the or each sheet or strip has a thickness of at least 5, 10, 20, 50, 100, 150, or 200 microns. Optionally, the or each sheet or strip has a thickness of no more than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the or each sheet or strip has a thickness of between 100 and 350, or 150 and 300 microns.

Optionally, the or each sheet or strip has a width of at least 100, 200, 500, or 1000 microns. Optionally, the or each sheet or strip has a width of no more than 2000, 1000, 500, 400, 300, 250, or 200 microns. Optionally, the or each sheet or strip has a width of between 100 and 2000, or 500 and 1000, or 600 and 1000 microns.

Optionally, the or each sheet or strip has a length of at least 100, 200, 500, 1000, 2000, or 3000 microns. Optionally, the or each sheet or strip has a length of no more than 6000, 5000, 3000, 2000, 1000, 500, or 200 microns. Optionally, the or each sheet or strip has a length of between 100 and 6000, or 500 and 5000, or 1000 and 4000 microns.

Optionally, the or each sheet or strip has a grammage of at least 20, 50, or 100 g/m². Optionally, the or each sheet or strip has a grammage of no more than 300 g/m². Optionally, the or each sheet or strip has a grammage of between 20 and 300, 50 and 250, or 100 and 250 g/m².

Optionally, the or each sheet or strip has a density of at least 0.1 , 0.2, 0.3, or 0.5 g/m³. Optionally, the or each sheet or strip has a density of no more than 2, 1.5, 1.2, or 1 g/m³. Optionally, the or each sheet or strip has a density of between 0.1 and 2, 0.2 and 2, 0.3 and 2, 0.3 and 1.5, or 0.3 and 1.2 g/m³.

Where the substrate comprises one or more gathered sheets, the or each gathered sheet may have a width of at least about 1, 2, 5, 10, 25, 50, or 100 mm. Optionally, the aerosol-forming substrate comprises an aerosol-former and expanded graphite particles constituting between 3 wt. % and 90 wt. % of the second material on a dry weight basis, the second material being configured to generate an aerosol when heated to a temperature of between 120 degrees Celsius and 395 degrees Celsius. Optionally, the aerosol forming substrate comprises tobacco and an aerosol-former and expanded graphite particles constituting between 3 wt. % and 90 wt. % of the second material on a dry weight basis, the second material being configured to generate an aerosol when heated to a temperature of between 120 degrees Celsius and 395 degrees Celsius. Optionally, the aerosol-forming substrate is a thermally conductive homogenised tobacco material, comprising the expanded graphite particles, and further comprises fibres and a binder.

Optionally, the aerosol-forming substrate does not comprise tobacco, for example in which the substrate is a thermally conductive tobacco-free material, comprising the expanded graphite particles, and further comprises fibres and a binder.

According to a second aspect of the present disclosure, there is also provided an aerosol generating article.

The article may comprise an aerosol-forming substrate as described above, for example the aerosol-forming substrate according to the first aspect.

Optionally, the article is in the form of a rod and comprises a plurality of components, including the aerosol-forming substrate or the combined aerosol-forming substrate, assembled within a wrapper or casing.

Optionally, the aerosol-generating article comprises a front plug. Optionally, the aerosol generating article comprises a first hollow tube, for example a first hollow acetate tube. Optionally, the aerosol-generating article comprises a second hollow tube, for example a second hollow acetate tube. Optionally, the second hollow tube comprises one or more ventilation holes. Optionally, the aerosol-generating article comprises a mouth plug filter. Optionally, the aerosol generating article comprises wrapper, for example a paper wrapper.

Optionally, the front plug is arranged a most upstream end of the article. Optionally, the aerosol-forming substrate is arranged downstream of the front plug. Optionally, the first hollow tube is arranged downstream of the aerosol-forming substrate. Optionally, the second hollow tube is arranged downstream of the first hollow tube. Optionally, the mouth plug filter is arranged downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth plug filter is arranged at a most downstream end of the article. Optionally, the most downstream end of the article, which may be referred to as a mouth end of the article, may be configured for insertion into a mouth of a user. A user may be able to inhale on, for example directly on, the mouth end of the article. Optionally, the front plug, the aerosol-forming substrate, one or both of the first hollow tube and the second hollow tube, and the mouth plug filter are circumscribed by a wrapper, for example a paper wrapper.

Optionally, the front plug has a length of between 2 and 10, 3 and 8, or 4 and 6 mm, for example around 5 mm. Optionally, the aerosol-forming substrate has a length of between 5 and 20, 8 and 15, or 10 and 15 mm, for example around 12 mm. Optionally, the first hollow tube has a length of between 2 and 20, 5 and 15, or 5 and 10 mm, for example around 8 mm. Optionally, the second hollow tube has a length of between 2 and 20, 5 and 15, or 5 and 10 mm, for example around 8 mm. Optionally, the mouth plug filter has a length of between 5 and 20, 8 and 15, or 10 and 15 mm, for example around 12 mm. The lengths of one or more of the front plug, the aerosol forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter may extend in a longitudinal direction.

One or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter may be substantially cylindrical, for example right cylindrical, in shape.

According to a third aspect of the present disclosure, there is provided an aerosol generating system.

The system may comprise an aerosol-generating article and an electrical aerosol generating device. The article may be an article as described above, for example an article according to the second aspect.

Optionally, the electrical aerosol-generating device is configured to resistively heat the aerosol generating article in use.

Optionally, the electrical aerosol-generating device is configured to inductively heat the aerosol generating article, for example the aerosol forming substrate of the aerosol-generating article, in use.

According to the present disclosure, there is provided a method of forming an aerosol forming substrate, for example a substrate as described above such as the substrate according to the first aspect. The method may comprise forming a slurry comprising one or more or all of the expanded graphite particles, the aerosol former, the fibres, and the binder. The method may comprise casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming into the aerosol-forming substrate.

Thus, according to a fourth aspect of the present disclosure, there is provided a method of forming an aerosol-forming substrate, for example a substrate as described above such as the substrate according to the first aspect. The method comprises forming a slurry comprising the expanded graphite particles, the aerosol former, the fibres, and the binder; and casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming into the aerosol-forming substrate.

Optionally, the slurry comprises water. Optionally, the slurry comprises between 20 and 90, 30 and 90, 40 and 90, 40 and 85, 50 and 80, 60 and 80, or 60 and 75 wt. % water.

Optionally, the slurry comprises an acid. Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

Optionally, the slurry comprises nicotine.

Optionally, forming the slurry comprises forming a first mixture. The first mixture may comprise the aerosol former. The first mixture may comprise the fibres. The first mixture may comprise water. The first mixture may comprise the acid. The first mixture may comprise the nicotine. Forming the slurring may comprise forming a second mixture. The second mixture may comprise the expanded graphite particles. The second mixture may comprise the binder. Forming the slurry may comprise adding the second mixture to the first mixture to form a combined mixture.

Thus, forming the slurry may comprise: forming a first mixture comprising the aerosol former, the fibres, water, optionally, the acid, and optionally, the nicotine; forming a second mixture comprising the expanded graphite particles and the binder; and adding the second mixture to the first mixture to form a combined mixture.

The combined mixture may subsequently be formed into the slurry, for example by mixing.

Optionally, forming the first mixture comprises providing the aerosol former or a solution comprising the aerosol former and the nicotine.

Optionally, forming the first mixture comprises adding the acid to the aerosol former or the solution comprising the aerosol former and the nicotine to form a first pre-mixture.

Optionally, forming the first mixture comprises adding the water to the aerosol former or the solution comprising the aerosol former and the nicotine, or to the first pre-mixture, to form a second pre-mixture.

Optionally, forming the first mixture comprises adding the fibres to the second pre-mixture.

Optionally, forming the second mixture comprises mixing the expanded graphite particles and the binder.

Optionally, the method, for example the step of forming the slurry, comprises a first mixing of the combined mixture. Optionally, the first mixing occurs under a first pressure of no more than 500, 400, 300, 250, or 200 mbar. Optionally, the first mixing occurs for between 1 and 10, 2 and 8, or 3 and 6 minutes, for example for around 4 minutes.

Optionally, the method, for example the step of forming the slurry, comprises, after the first mixing, a second mixing. Optionally, the second mixing occurs under a second pressure which is less than the first pressure. Optionally, the second pressure is no more than 500, 400, 300, 200, 150, or 100 mbar. Optionally, the second mixing occurs for between 5 and 120, 5 and 80, 5 and 40, or 10 and 30 seconds, for example around 20 seconds.

Optionally, casting the slurry comprises casting the slurry onto a flat support, for example a steel flat support.

Optionally, after casting the slurry and before drying the slurry, the method comprises setting a thickness of the slurry, for example setting a thickness of the slurry to between 100 and 1200, 200 and 1000, 300 and 900, 500 and 700 microns, for example around 600 microns.

Optionally, drying the slurry comprises providing a flow of a gas such as air over or past the slurry. Optionally, the flow of gas is heated. Optionally, the flow of gas is heated to a temperature of between 100 and 160, or 120 and 140 degrees Celsius. Optionally, the flow of gas is provided for between 1 and 10 or 2 and 5 minutes. Optionally, drying the slurry comprises drying the slurry until the slurry has a moisture content of between 1 and 20, 2 and 15, 2 and 10, or 3 and 7 wt. %.

Optionally, drying the slurry forms the precursor for forming into the aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method comprises cutting the sheet of aerosol-forming material.

As would be understood by the skilled person having read this disclosure, the features described herein in relation to one aspect may be applicable to any other aspect. For example, features described in relation to the combined aerosol-forming substrate of the second aspect, or in relation to the first second material of the combined aerosol-forming substrate of the second aspect, may be applicable to the aerosol-forming substrate of the first aspect, and vice versa.

As used herein, the term “aerosol-forming substrate” may refer to a substrate capable of releasing an aerosol or volatile compounds that can form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may comprise an aerosol-forming material. An aerosol-forming substrate may be adsorbed, coated, impregnated or otherwise loaded onto a carrier or support. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or smoking article.

As used herein, the term “thermally conductive particles” may refer to particles having a thermal conductivity greater than 1 W/(MK) in at least one direction at 25 degrees Celsius, for example in all directions at 25 degrees Celsius. The particles may exhibit anisotropic or isotropic thermal conductivity.

As used herein, the term “expanded graphite” may refer to a graphite-based material, or a material having a graphite-like structure. Expanded graphite may have carbon layers (similar to graphite, for example) with spacing between the carbon layers greater than the spacing found between carbon layers in regular graphite. Expanded graphite may have carbon layers with elements or compounds intercalated into spaces between the carbon layers. As used herein, the term “particle size” may refer to a single dimension and may be used to characterise the size of a given particle. The dimension may be the diameter of a spherical particle occupying the same volume as the given particle. All particle sizes and particle size distributions herein can be obtained using a standard laser diffraction technique. Particle sizes and particle size distributions as stated herein may be obtained using a commercially available sensor, for example a Sympatec HELOS laser diffraction sensor.

As used herein, where not otherwise specified, the term “density” may be used to refer to true density. Thus, where not otherwise specified, the density of a powder or plurality of particles may refer to the true density of the powder or plurality of particles (rather than the bulk density of the powder or plurality of particles, which can vary greatly depending on how the powder or plurality of particles are handled). The measurement of true density can be done using a number of standard methods, these methods often being based on Archimedes’ principle. The most widely used method, when used to measure the true density of a powder, entails the powder being placed inside a container (a pycnometer) of known volume, and weighed. The pycnometer is then filled with a fluid of known density, in which the powder is not soluble. The volume of the powder is determined by the difference between the volume as shown by the pycnometer, and the volume of liquid added (i.e. the volume of air displaced).

As used herein, the term “aerosol-generating article” may refer to an article able to generate, or release, an aerosol, for example when heated.

As used herein, the term “longitudinal” may refer to a direction extending between a downstream or proximal end and an upstream or distal end of a component such as an aerosol forming substrate or aerosol-generating article.

As used herein, the term “transverse” may refer to a direction perpendicular to the longitudinal direction.

As used herein, the term “aerosol-generating device” may refer to a device for use with an aerosol-generating article to enable the generation, or release, of an aerosol.

As used herein, the term “gathered sheet” may refer to a sheet of an aerosol-forming substrate or aerosol-generating article that is convoluted, folded, or otherwise compressed or constricted substantially transversely to a longitudinal axis of the aerosol-forming substrate, or aerosol-generating article.

As used herein, the term “sheet” may refer to a generally planar, laminar element having a width and a length which are substantially greater than, for example at least 2, 3, 5, 10, 20 or 50 times, its thickness.

As used herein, the term “strip” may refer to a generally planar, laminar element having a width and a length which are substantially greater than its thickness. The width of a strip may be greater than its thickness, for example at least 2, 3, 5 or 10 times its thickness. The length of a strip may be greater than its width, for example at least 2, 3, 5 or 10 times its width.

As used herein, the term “aerosol former” may refer to any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol. The aerosol may be a dense and stable aerosol. The aerosol may be substantially resistant to thermal degradation at the operating temperature of the aerosol-forming substrate or aerosol-generating article.

As used herein, the term “aerosol-cooling element” may refer to a component of an aerosol-generating article located downstream of the aerosol-forming substrate such that, in use, an aerosol formed by the substrate or by volatile compounds released from the aerosol-forming substrate passes through and is cooled by the aerosol-cooling element before being inhaled by a user.

As used herein, the term “rod” may refer to a generally cylindrical, for example right cylindrical, element of substantially circular, oval or elliptical cross-section.

As used herein, the term “crimped” may refer to a sheet having one or more ridges or corrugations. The ridges or corrugations may be substantially parallel. When present in a component of an aerosol-generating article, the ridges or corrugations may extend in a longitudinal direction with respect to the aerosol-generating article.

As used herein, the term “ventilation level” may refer to a volume ratio between the airflow admitted into an aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer.

The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Example Ex 1. An aerosol-forming substrate for use in a heated aerosol-generating article, the aerosol-forming substrate comprising expanded graphite particles.

Example Ex 2. An aerosol-forming substrate according to Ex 1 further comprising an aerosol forming material, for example an aerosol-former.

Example Ex 3. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles make up less than or equal to 80, 50, 20, 10, or 5 weight percent of the aerosol-forming substrate.

Example Ex 4. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles make up more than or equal to 0.1 , 0.2, 0.5, 1, 2, 3, 5, 10, 20 or 50 weight percent of the aerosol-forming substrate. Example Ex 5. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles make up between 1 and 20, 2 and 20, 3 and 20, 5 and 20, 3 and 15, 5 and 15, or 3 and 10 weight percent of the aerosol-forming substrate.

Example Ex 6. An aerosol-forming substrate according to any preceding example comprising, on a dry weight basis: between 1 and 90 wt. % expanded graphite particles; between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder.

Example Ex 7. An aerosol-forming substrate according to any preceding example comprising, on a dry weight basis: between 10 and 90 wt. % expanded graphite particles; between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder.

Example Ex 8. An aerosol-forming substrate according to any preceding example, wherein each expanded graphite particle has a thermal conductivity of at least 0.3, 0.5, 1, 2, 5, or 10 W/(mK) in at least one direction at 25 degrees Celsius.

Example Ex 9. An aerosol-forming substrate according to any preceding example comprising, on a dry weight basis: between 1 and 90 wt. % expanded graphite particles, between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.22 W/(mK) in at least one direction at a temperature of 25 degrees Celsius.

Example Ex 10. An aerosol-forming substrate according to any preceding example comprising, on a dry weight basis: between 10 and 90 wt. % expanded graphite particles, between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.22 W/(mK) in at least one direction at a temperature of 25 degrees Celsius. Example Ex 11. An aerosol-forming substrate according to any preceding example, comprising between 1 and 15 wt. % expanded graphite particles.

Example Ex 12. An aerosol-forming substrate according to any preceding example, comprising between 3 and 6 wt. % expanded graphite particles.

Example Ex 13. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D10 particle size, wherein the number D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 14. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D10 particle size, wherein the number D10 particle size is no more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

Example Ex 15. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D50 particle size, wherein the number D50 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 16. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D50 particle size, wherein the number D50 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Example Ex 17. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D90 particle size, wherein the number D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 18. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D90 particle size, wherein the number D90 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Example Ex 19. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 20. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns Example Ex 21. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is at least 0.1 , 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 22. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Example Ex 23. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 24. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is no more than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Example Ex 25. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution having a number D10 particle size, a number D90 particle size, a volume D10 particle size, and a volume D90 particle size, wherein: the number D90 particle size is no more than 50, 40, 30, 20, 10, or 5 times the number D10 particle size, or the volume D10 particle size is no more than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size, or both the number D90 particle size is no more than 50, 40, 30, 20, 10, or 5 times the number D10 particle size and the volume D10 particle size is no more than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size.

Example Ex 26. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution and one or both of a number D10 particle size and a volume D10 particle size is between 1 and 20 microns.

Example Ex 27. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles have a particle size distribution, wherein one or both of a number D90 particle size and a volume D90 particle size is between 50 and 300 microns or between 50 and 200 microns. Example Ex 28. An aerosol-forming substrate according to any preceding example, wherein each of the expanded graphite particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Example Ex 29. An aerosol-forming substrate according to any preceding example, wherein each of the expanded graphite particles has a particle size of no more than 1,000, 500, 200,

100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Example Ex 30. An aerosol-forming substrate according to any preceding example, wherein each of the expanded graphite particles has three mutually perpendicular dimensions, a largest dimension of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than one or both of a smallest dimension of the three dimensions and a second largest dimension of the three dimensions.

Example Ex 31. An aerosol-forming substrate according to any preceding example, wherein each of the expanded graphite particles is substantially spherical.

Example Ex 32. An aerosol-forming substrate according to any preceding example, comprising at least 10, 20, 50, 100, 200, 500, or 1000 expanded graphite particles.

Example Ex 33. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85 wt. % of the expanded graphite particles.

Example Ex 34. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt. % of the expanded graphite particles.

Example Ex 35. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, between 1 and 95, 4 and 94, 10 and 90, 20 and 90, 30 and 90, 40 and 90, 50 and 90, 60 and 90, 70 and 90, 80 and 90, 10 and 80, 20 and 80, 30 and 80, 40 and 80, 50 and 80, 60 and 80, 70 and 80, 10 and 70, 20 and 70, 30 and 70, 40 and

70, 50 and 70, 60 and 70, 10 and 60, 20 and 60, 30 and 60, 40 and 60, 50 and 60, 10 and 50,

20 and 50, 30 and 50, 40 and 50, 10 and 40, 20 and 40, 30 and 40, 10 and 30, 20 and 30, or 10 and 20 wt. % of the expanded graphite particles.

Example Ex 36. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt. % of the aerosol former.

Example Ex 37. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, no more than 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt. % of the aerosol former.

Example Ex 38. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, between 7 and 60, 10 and 60, 20 and 60, 30 and 60, 40 and 60, 50 and 60, 7 and 50, 10 and 50, 20 and 50, 30 and 50, 40 and 50, 7 and 40, 10 and 40, 20 and 40, 30 and 40, 7 and 30, 10 and 30, 20 and 30, 7 and 20, 10 and 20, or 7 and 10 wt. % of the aerosol former, particularly preferably between 15 and 25 wt.% of the aerosol former.

Example Ex 39. An aerosol-forming substrate according to any preceding example, wherein the aerosol-former comprises or consists of one or more of: polyhydric alcohols, such as propylene glycol, polyethylene glycol, triethylene glycol, 1, 3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or tri-acetate; and aliphatic esters of mono-, di- or poly- carboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Example Ex 40. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises one or both of glycerine and glycerol.

Example Ex 41. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, at least 2, 4, 6, 8, 10, 12, 14, 16 or 18 wt. % of the fibres.

Example Ex 42. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt. % of the fibres.

Example Ex 43. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, between 4 and 20, 6 and 20, 8 and 20, 10 and 20, 12 and 20, 14 and 20, 16 and 20, 18 and 20, 2 and 18, 4 and 18, 6 and 18, 8 and 18, 10 and 18, 12 and 18, 14 and 18, 16 and 18, 2 and 16, 4 and 16, 6 and 16, 8 and 16, 10 and 16, 12 and 16, 14 and 16, 2 and 14, 4 and 14, 6 and 14, 8 and 14, 10 and 14, 12 and 14, 2 and 12, 4 and 12, 6 and 12, 8 and 12, 10 and 12, 2 and 10, 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, or 2 and 4 wt. % of the fibres, particularly preferably between 2 and 10 wt.% of the fibres.

Example Ex 44. An aerosol-forming substrate according to any preceding example, wherein the fibres are cellulose fibres.

Example Ex 45. An aerosol-forming substrate according to any preceding example, wherein each of the fibres has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a smallest dimension of the three dimensions.

Example Ex 46. An aerosol-forming substrate according to any preceding example, wherein each of the fibres has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a second largest dimension of the three dimensions. Example Ex 47. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, at least 4, 6, or 8 wt. % of the binder.

Example Ex 48. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, no more than 8, 6, or 4 wt. % of the binder.

Example Ex 49. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, between 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, 2 and 4 wt. % of the binder, particularly preferably between 2 and 10 wt.% of the binder.

Example Ex 50. An aerosol-forming substrate according to any preceding example, wherein the binder comprises or consists of one or both of carboxymethyl cellulose or hydroxypropyl cellulose.

Example Ex 51. An aerosol-forming substrate according to any preceding example, wherein the binder comprises or consists of one or more gums such as guar gum.

Example Ex 52. An aerosol-forming substrate according to any preceding example, wherein the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 53. An aerosol-forming substrate according to any preceding example, wherein the aerosol former is substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 54. An aerosol-forming substrate according to any preceding example, wherein the fibres are substantially homogeneously distributed throughout the aerosol-forming substrate. Example Ex 55. An aerosol-forming substrate according to any preceding example, wherein the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Example Ex 56. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises nicotine.

Example Ex 57. An aerosol-forming substrate according to example Ex 56, wherein the substrate comprises, on a dry weight basis, at least 0.01 , 1 , 2, 3, or 4 wt. % nicotine.

Example Ex 58. An aerosol-forming substrate according to any of examples Ex 56 to Ex 57, wherein the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2, or 1 wt. % nicotine.

Example Ex 59. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises, on a dry weight basis, between 0.01 and 5, 1 and 5, 2 and 5, 3 and 5, 4 and 5, 0.01 and 4, 1 and 4, 2 and 4, 3 and 4, 0.01 and 3, 1 and 3, 2 and 3, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % nicotine, particularly preferably between 0.5 and 4 wt.% nicotine. Example Ex 60. An aerosol-forming substrate according to any of examples Ex 56 to Ex 58, wherein the nicotine is substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 61. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises an acid.

Example Ex 62. An aerosol-forming substrate according to example Ex 61, wherein the substrate comprises, on a dry weight basis, at least 0.01 , 1 , or 2 wt. % of the acid.

Example Ex 63. An aerosol-forming substrate according to any of examples Ex 61 to Ex 62, wherein the substrate comprises, on a dry weight basis, no more than 3, 2 or 1 wt. % of the acid.

Example Ex 64. An aerosol-forming substrate according to any of examples Ex 61 to Ex 63, wherein the substrate comprises, on a dry weight basis, between 0.01 and 3, 1 and 3, 2 and 3, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % of the acid, particularly preferably between 0.5 and 5 wt.% of the acid.

Example Ex 65. An aerosol-forming substrate according to any of examples Ex 61 to Ex 64, wherein the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

Example Ex 66. An aerosol-forming substrate according to any of examples Ex 61 to Ex 65, wherein the acid is substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 67. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises at least one botanical.

Example Ex 68. An aerosol-forming substrate according to example Ex 67, wherein the substrate comprises, on a dry weight basis, at least 0.01, 1, 2, 5, 10, or 15 wt. % of the at least one botanical.

Example Ex 69. An aerosol-forming substrate according to any of examples Ex 67 to Ex 68, wherein the substrate comprises, on a dry weight basis, no more than 20, 15, 10, 5, 2 or 1 wt. % of the at least one botanical.

Example Ex 70. An aerosol-forming substrate according to any of examples Ex 67 to Ex 69, wherein the substrate comprises, on a dry weight basis, between 0.01 and 20, 1 and 20, 2 and 20, 5 and 20, 10 and 20, 15 and 20, 0.01 and 15, 1 and 15, 2 and 15, 5 and 15, 10 and 15, 0.01 and 10, 1 and 10, 2 and 10, 5 and 10, 0.01 and 5, 1 and 5, 2 and 5, 0.01 and 2, 1 and 2, 0.01 and 1 wt. % of the at least one botanical, particularly preferably between 1 and 15 wt.% of the at least one botanical.

Example Ex 71. An aerosol-forming substrate according to any of examples Ex 67 to Ex 70, wherein the at least one botanical comprises or consists of one or both of clove and rosmarinus. Example Ex 72. An aerosol-forming substrate according to any of examples Ex 67 to Ex 71 , wherein the at least one botanical is substantially homogeneously distributed throughout the aerosol forming substrate.

Example Ex 73. An aerosol-forming substrate according to any preceding example, wherein the substrate comprises at least one flavourant.

Example Ex 74. An aerosol-forming substrate according to example Ex 73, wherein the substrate comprises, on a dry weight basis, at least 0.1 , 1 , 2, or 5 wt. % of the at least one flavourant.

Example Ex 75. An aerosol-forming substrate according to any of examples Ex 73 to Ex 74, wherein the substrate comprises, on a dry weight basis, no more than 10, 5, 2 or 1 wt. % of the at least one flavourant.

Example Ex 76. An aerosol-forming substrate according to any of examples Ex 73 to Ex 75, wherein the substrate comprises, on a dry weight basis, between 0.1 and 10, 1 and 10, 2 and 10, 5 and 10, 0.1 and 5, 1 and 5, 2 and 5, 0.1 and 2, 1 and 2, 0.1 and 1 wt. % of the at least one flavourant, particularly preferably between 0.1 and 5 wt.% of the at least one flavourant.

Example Ex 77. An aerosol-forming substrate according to any of examples Ex 73 to Ex 76, wherein the at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate.

Example Ex 78. An aerosol-forming substrate according to any of examples Ex 73 to Ex 77, wherein the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 79. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises one or more organic materials such as tobacco.

Example Ex 80. An aerosol-forming substrate according to any preceding example, wherein the organic material comprises one or more of herb leaf, tobacco leaf, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco and expanded tobacco.

Example Ex 81. An aerosol-forming substrate according to any preceding example, wherein the organic materials are substantially homogeneously distributed throughout the aerosol-forming substrate.

Example Ex 82. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

Example Ex 83. An aerosol-forming substrate according to any preceding example, wherein some or each of the expanded graphite particles acts as a susceptor material.

Example Ex 84. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.15, 0.2, 0.22, 0.3, 0.4, 0.5, 0.75, 1, 1.25, or 1.5 W/(mK) in at least one direction, or in all directions, at 25 degrees Celsius. Example Ex 85. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate has a density of less than 1500, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, or 650 kg/m³.

Example Ex 86. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate has a density of between 500 and 900 or 600 and 800 kg/m³. Example Ex 87. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate has a moisture content of between 1 and 20, or 3 and 15 wt. %. Example Ex 88. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises between 1 and 20, or 3 and 15 wt. % water.

Example Ex 89. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises, or is in the form of, one or more of: cut-filler, powder particles, granules, pellets, shreds, spaghettis, strips, sheets, rolled sheets, gathered sheets, or tubes.

Example Ex 90. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises, or is in the form of, one or more sheets or strips.

Example Ex 91. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises, or is in the form of, one or more gathered sheets.

Example Ex 92. An aerosol-forming substrate according to example Ex 91, wherein the or each gathered sheet has a width of at least about 5, 10, 25, 50, or 100 mm.

Example Ex 93. An aerosol-forming substrate according to any preceding example, wherein the aerosol-forming substrate comprises, or is in the form of, a plurality of strips.

Example Ex 94. An aerosol-forming substrate according to any of examples Ex 93, wherein each of the plurality of strips has a length of at least about 3, 5 or 10 mm.

Example Ex 95. An aerosol-forming substrate according to any of examples Ex 93 to Ex 94, wherein each of the plurality of strips has a width of less than about 3, 2 or 1 mm.

Example Ex 96. An aerosol-forming substrate according to any of examples Ex 90 to Ex 95, wherein the or each sheet or strip has a thickness of at least 100, 150, or 200 microns.

Example Ex 97. An aerosol-forming substrate according to any of examples Ex 90 to Ex 96, wherein the or each sheet or strip has a thickness of no more than 300, or 250 microns. Example Ex 98. An aerosol-forming substrate according to any of examples Ex 90 to Ex 97, wherein the or each sheet or strip has a thickness of between 100 and 300, or 150 and 250, or 200 and 250 microns.

Example Ex 99. An aerosol-forming substrate according to any of examples Ex 90 to Ex 98, wherein the or each sheet or strip has a grammage of at least 20, 50, or 100 g/m².

Example Ex 100. An aerosol-forming substrate according to any of examples Ex 90 to Ex 99, wherein the or each sheet or strip has a grammage of no more than 300 g/m². Example Ex 101. An aerosol-forming substrate according to any of examples Ex 90 to Ex 100, wherein the or each sheet or strip has a grammage of between 20 and 300, 50 and 250, or 100 and 250 g/m².

Example Ex 102. An aerosol-forming substrate according to any of examples Ex 90 to Ex 101, wherein the or each sheet or strip has a density of at least 0.1 , 0.2, 0.3, or 0.5 g/m³.

Example Ex 103. An aerosol-forming substrate according to any of examples Ex 90 to Ex 102, wherein the or each sheet or strip has a density of no more than 2, 1.5, 1.2, or 1 g/m³.

Example Ex 104. An aerosol-forming substrate according to any of examples Ex 90 to Ex 103, wherein the or each sheet or strip has a density of between 0.1 and 2, 0.2 and 2, 0.3 and 2, 0.3 and 1.5, or 0.3 and 1.2 g/m³.

Example Ex 105. An aerosol-generating article comprising an aerosol-forming substrate as defined in any of examples Ex 1 to Ex 104.

Example Ex 106. An aerosol-generating article according to example Ex 105 in which the article is in the form of a rod and comprises a plurality of components, including the aerosol-forming substrate, assembled within a wrapper or casing.

Example Ex 107. An aerosol-generating article comprising a gathered or rolled sheet of aerosol forming substrate according to any preceding example.

Example Ex 108. An aerosol-generating article according to any of examples Ex 105 to Ex 107, wherein the aerosol-generating article comprises a front plug.

Example Ex 109. An aerosol-generating article according to any of examples Ex 105 to Ex 108, wherein the aerosol-generating article comprises a first hollow tube, for example a first hollow acetate tube.

Example Ex 110. An aerosol-generating article according to Ex 109, wherein the aerosol generating article comprises a second hollow tube, for example a second hollow acetate tube. Example Ex 111. An aerosol-generating article according to example Ex 110, wherein the second hollow tube comprises one or more ventilation holes.

Example Ex 112. An aerosol-generating article according to any of examples Ex 105 to Ex 111, wherein the aerosol-generating article comprises a mouth plug filter.

Example Ex 113. An aerosol-generating article according to any of examples Ex 105 to Ex 112, wherein the aerosol-generating article comprises a wrapper, for example a paper wrapper. Example Ex 114. An aerosol-generating article according to any of examples Ex 105 to Ex 113, wherein the aerosol-generating article comprises a front plug, the aerosol-forming substrate arranged downstream of the front plug, a first hollow tube arranged downstream of the aerosol forming substrate, a second hollow tube arranged downstream of the first hollow tube, and a mouth plug filter arranged downstream of the second hollow tube. Example Ex 115. An aerosol-generating article according to example Ex 114, wherein the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter are circumscribed by a wrapper, for example a paper wrapper.

Example Ex 116. An aerosol-generating article according to any of examples Ex 108 to Ex 115, wherein the front plug has a length of between 2 and 10, 3 and 8, or 4 and 6 mm, for example around 5 mm.

Example Ex 117. An aerosol-generating article according to any of examples Ex 105 to Ex 116, wherein the aerosol-forming substrate has a length of between 5 and 20, 8 and 15, or 10 and 15 mm, for example around 12 mm.

Example Ex 118. An aerosol-generating article according to any of examples Ex 109 or Ex 110 to Ex 117 when dependent on example Ex 109, wherein the first hollow tube has a length of between 2 and 20, 5 and 15, or 5 and 10 mm, for example around 8 mm.

Example Ex 119. An aerosol-generating article according to any of examples Ex 110 or Ex 111 to Ex 118 when dependent on example Ex 110, wherein the second hollow tube has a length of between 2 and 20, 5 and 15, or 5 and 10 mm, for example around 8 mm.

Example Ex 120. An aerosol-generating article according to any of examples Ex 112 or Ex 113 to Ex 119 when dependent on example Ex 112, wherein the mouth plug filter has a length of between 5 and 20, 8 and 15, or 10 and 15 mm, for example around 12 mm.

Example Ex 121. An aerosol-generating system comprising an aerosol-generating article according to any of examples Ex 105 to Ex 120 and an electrical aerosol-generating device. Example Ex 122. An aerosol-generating system according to example Ex 121, wherein the electrical aerosol-generating device is configured to resistively heat the aerosol-generating article in use.

Example Ex 123. An aerosol-generating system according to any of examples Ex 121 to Ex 122, wherein the electrical aerosol-generating device is configured to inductively heat the aerosol-generating article, for example the aerosol forming substrate of the aerosol-generating article, in use.

Example Ex 124. A method of forming an aerosol-forming substrate according to any preceding aerosol-forming substrate example, for example any of examples Ex 1 to Ex 104, the method comprising: forming a slurry comprising the expanded graphite particles, the aerosol former, the fibres, and the binder; and casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming into the aerosol-forming substrate.

Example Ex 125. A method according to example Ex 124, wherein the slurry comprises water. Example Ex 126. A method according to any of examples Ex 124 to Ex 125, wherein the slurry comprises between 40 and 90, 40 and 85, 50 and 80, 60 and 80, 60 and 75 wt. % water. Example Ex 127. A method according to any of examples Ex 124 to Ex 126, wherein the slurry comprises an acid such as fumaric acid.

Example Ex 128. A method according to any of examples Ex 124 to Ex 127, wherein the slurry comprises nicotine.

Example Ex 129. A method according to any of examples Ex 124 to Ex 128, wherein forming the slurry comprises: forming a first mixture comprising: the aerosol former; the fibres; water; optionally, the acid; and optionally, the nicotine, forming a second mixture comprising: the expanded graphite particles; and the binder, and adding the second mixture to the first mixture to form a combined mixture.

Example Ex 130. A method according to example Ex 129, wherein forming the first mixture comprises providing the aerosol former or a solution comprising the aerosol former and the nicotine.

Example Ex 131. A method according to example Ex 130, wherein forming the first mixture comprises adding the acid to the aerosol former or the solution comprising the aerosol former and the nicotine to form a first pre-mixture.

Example Ex 132. A method according to any of examples Ex 129 to Ex 131, wherein forming the first mixture comprises adding the water to the aerosol former or the solution comprising the aerosol former and the nicotine, or to the first pre-mixture, to form a second pre-mixture. Example Ex 133. A method according to any of examples Ex 129 to Ex 132, wherein forming the first mixture comprises adding the fibres to the second pre-mixture.

Example Ex 134. A method according to any of examples Ex 129 to Ex 133, wherein forming the second mixture comprises mixing the expanded graphite particles and the binder.

Example Ex 135. A method according to any of examples Ex 129 to Ex 134, wherein the method comprises a first mixing of the combined mixture.

Example Ex 136. A method according to example Ex 135, wherein the first mixing occurs under a first pressure of no more than 500, 400, 300, 250, or 200 mbar. Example Ex 137. A method according to example Ex 135 or Ex 136, wherein the first mixing occurs for between 1 and 10, 2 and 8, or 3 and 6 minutes, for example for around 4 minutes. Example Ex 138. A method according to any of examples Ex 135 to Ex 137, wherein the method comprises, after mixing the first mixing, a second mixing.

Example Ex 139. A method according to example Ex 138, wherein the second mixing occurs under a second pressure which is less than the first pressure.

Example Ex 140. A method according to example Ex 139, wherein the second pressure is no more than 500, 400, 300, 200, 150, or 100 mbar.

Example Ex 141. A method according to example Ex 138 or Ex 139 or Ex 140, wherein the second mixing occurs for between 5 and 120, 5 and 80, 5 and 40, or 10 and 30 seconds, for example around 20 seconds.

Example Ex 142. A method according to any of examples Ex 124 to Ex 141, wherein casting the slurry comprises casting the slurry onto a flat support, for example a steel flat support.

Example Ex 143. A method according to any of examples Ex 124 to Ex 142, wherein after casting the slurry and before drying the slurry, the method comprises setting a thickness of the slurry, for example setting a thickness of the slurry to between 100 and 1,000, 200 and 900, 300 and 800, 500 and 700 microns, for example around 600 microns.

Example Ex 144. A method according to any of examples Ex 124 to Ex 143, wherein drying the slurry comprises providing a flow of a gas such as air over or past the slurry.

Example Ex 145. A method according to example Ex 144, wherein the flow of gas is heated. Example Ex 146. A method according to example Ex 145, wherein the flow of gas is heated to a temperature of between 100 and 160, or 120 and 140 degrees Celsius.

Example Ex 147. A method according to any of examples Ex 144 to Ex 146, wherein the flow of gas is provided for between 1 and 10 or 2 and 5 minutes.

Example Ex 148. A method according to any of examples Ex 124 to Ex 147, wherein drying the slurry comprises drying the slurry until the slurry has a moisture content of between 1 and 20, 2 and 15, 2 and 10, or 3 and 7 wt. %.

Example Ex 149. A method according to any of examples Ex 124 to Ex 148, wherein drying the slurry forms the precursor for forming into the aerosol-forming substrate, the precursor being a sheet of aerosol-forming material.

Example Ex 150. A method according to example Ex 149, wherein the method comprises cutting the sheet of aerosol-forming material.

Examples will now be further described with reference to the figures in which:

Figure 1 shows a schematic cross-sectional view of a first embodiment of an aerosol generating article; Figure 2 shows a schematic cross-sectional view of a first embodiment of an aerosol generating system comprising a first aerosol-generating device;

Figure 3 shows a schematic cross-sectional view of a second embodiment of an aerosol generating system comprising a second aerosol-generating device;

Figure 4 shows a schematic cross-sectional view of a second embodiment of an aerosol generating article;

Figure 5 is a bar chart showing the yield of nicotine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 2 compared to two alternative aerosol-generating articles;

Figure 6 is a bar chart showing the yield of glycerine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 2 compared to two alternative aerosol-generating articles;

Figure 7 is a bar chart showing the delivery efficiency of nicotine and glycerine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 2 compared to two alternative aerosol-generating articles;

Figure 8 is a bar chart showing the yield of nicotine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 3 compared to two alternative aerosol-generating articles;

Figure 9 is a bar chart showing the yield of glycerine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 3 compared to two alternative aerosol-generating articles;

Figure 10 is a bar chart showing the delivery efficiency of nicotine and glycerine from the aerosol-generating article of the first embodiment when used in the aerosol-generating device of Figure 3 compared to two alternative aerosol-generating articles.

Figure 1 shows a schematic cross-sectional view of a first embodiment of an aerosol generating article 10. The aerosol-generating article 10 comprises a rod 12 of aerosol-forming substrate and a downstream section 14 at a location downstream of the rod 12 of aerosol-forming substrate. Further, the aerosol-generating article 10 comprises an upstream section 16 at a location upstream of the rod 12 of aerosol-forming substrate. Thus, the aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or proximal or mouth end 20.

The aerosol-generating article has an overall length of about 45 millimetres.

The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of aerosol- forming substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1 , the upstream end of the support element 22 abuts the downstream end of the rod 12 of aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol-cooling element 24 located immediately downstream of the support element 22, the aerosol-cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of Figure 1 , the upstream end of the aerosol-cooling element 24 abuts the downstream end of the support element 22.

As will become apparent from the following description, the support element 22 and the aerosol-cooling element 24 together define an intermediate hollow section 50 of the aerosol generating article 10. As a whole, the intermediate hollow section 50 does not substantially contribute to the overall RTD of the aerosol-generating article. An RTD of the intermediate hollow section 26 as a whole is substantially 0 millimetres H2O.

The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an internal cavity 28 that extends all the way from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 20. The internal cavity 28 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 28. The first hollow tubular segment 26 - and, as a consequence, the support element 22 - does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the first hollow tubular segment 26 (which is essentially the RTD of the support element 22) is substantially 0 millimetres H2O.

The first hollow tubular segment 26 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (DFTS) of about 1.9 millimetres. Thus, a thickness of a peripheral wall of the first hollow tubular segment 26 is about 2.67 millimetres.

The aerosol-cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an internal cavity 36 that extends all the way from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The internal cavity 36 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 36. The second hollow tubular segment 28 - and, as a consequence, the aerosol-cooling element 24 - does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the second hollow tubular segment 34 (which is essentially the RTD of the aerosol-cooling element 24) is substantially 0 millimetres H2O.

The second hollow tubular segment 34 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (DSTS) of about 3.25 millimetres. Thus, a thickness of a peripheral wall of the second hollow tubular segment 34 is about 2 millimetres. Thus, a ratio between the internal diameter (DFTS) of the first hollow tubular segment 26 and the internal diameter (DSTS) of the second hollow tubular segment 34 is about 0.75. The aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. In more detail, the ventilation zone is provided at about 2 millimetres from the upstream end of the second hollow tubular segment 34. In this embodiment, the ventilation zone 60 comprises a circumferential row of perforations through a paper wrapper 70 and a ventilation level of the aerosol-generating article 10 is about 25 percent.

In the embodiment of Figure 1 , the downstream section 14 further comprises a mouthpiece element 42 at a location downstream of the intermediate hollow section 50. In more detail, the mouthpiece element 42 is positioned immediately downstream of the aerosol-cooling element 24. As shown in the drawing of Figure 1 , an upstream end of the mouthpiece element 42 abuts the downstream end 40 of the aerosol-cooling element 24.

The mouthpiece element 42 is provided in the form of a cylindrical plug of low-density cellulose acetate.

The mouthpiece element 42 has a length of about 12 millimetres and an external diameter of about 7.25 millimetres. The RTD of the mouthpiece element 42 is about 12 millimetres H2O. The ratio of the length of the mouthpiece element 42 to the length of the intermediate hollow section 50 is approximately 0.6.

The rod 12 of aerosol-forming substrate has an external diameter of about 7.25 millimetres and a length of about 12 millimetres.

The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of aerosol-forming substrate, the upstream element 46 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of aerosol-forming substrate. The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate. The upstream element 46 has a length of about 5 millimetres. The RTD of the upstream element 46 is about 30 millimetres H2O.

The upstream element 46, rod 12 of aerosol-forming substrate, support element 22, aerosol-cooling element 24, and mouthpiece element 42 are circumscribed by the paper wrapper 70.

The rod 12 of aerosol-forming substrate comprises an aerosol-forming material and thermally conductive particles 44. The aerosol-forming material comprises a reconstituted and gathered sheet comprising tobacco material and glycerine. The thermally conductive particles 44 are carbon particles, specifically expanded graphite particles, having a particle size distribution with a D10 particle size of 6.6 microns, a D50 particle size of 20 microns, and a D90 particle size of 56 microns. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume mean particle size of around 35 microns. Each of the expanded graphite particles is substantially spherical in shape. The expanded graphite particles have a density of less than 1000 kilograms per metre cubed. The aerosol-forming substrate, including the aerosol-forming material and the thermally conductive particles 44, have a combined density of around 760 kilograms per metre cubed. The expanded graphite particles make up approximately 4.6% of the aerosol-forming substrate by weight. Glycerine makes up approximately 1.7% of the aerosol-forming substrate by weight.

The rod 12 of aerosol-forming substrate is formed by a process including the following steps:

• pre-mixing a binder, guar gum, with an aerosol-former, glycerine, to form a first pre-mixture;

• pre-mixing finely shredded tobacco material and a powder consisting of the expanded graphite particles 44 and having a bulk density of around 0.065 grams per centimetre cubed, to form a second pre-mixture;

• mixing the first and second pre-mixtures with water to form a slurry;

• homogenising the slurry using a high-shear mixer;

• casting the slurry onto a conveyor belt;

• controlling a thickness of the slurry and drying the slurry to form a large sheet of aerosol forming substrate; and

• gathering and cutting the large sheet of aerosol-forming substrate to form the rod 12 of aerosol-forming substrate.

After forming the rod 12 of aerosol-forming substrate, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and wrapping the components in the wrapper 70.

Figure 2 shows a schematic cross-sectional view of a first embodiment of an aerosol generating system 100. The system 100 comprises an aerosol-generating device 102 and the aerosol-generating article 10 of Figure 1.

The aerosol-generating device 102 comprises a battery 104, a controller 106, a heating blade 108 coupled to the battery, and a puff-detection mechanism (not shown). The controller 106 is coupled to the battery 104, the heating blade 108 and the puff-detection mechanism.

The aerosol-generating device 102 further comprises a housing 110 defining a substantially cylindrical cavity for receiving a portion of the article 10. The heating blade 108 is positioned centrally within the cavity and extends longitudinally from a base of the cavity.

In this embodiment, the heating blade 108 comprises a substrate and an electrically resistive track located on the substrate. The battery 104 is coupled to the heating blade 108 so as to be able to pass a current through the electrically resistive track and heat the electrically resistive track and heating blade 108 to an operational temperature.

In use, a user inserts the article 10 into the cavity, causing the heating blade 108 to penetrate the upstream element 46 and rod 12 of aerosol-forming substrate of the article 10. Figure 3 shows the article 10 inserted into the cavity of the device 102. Then, the user puffs on the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 102, then through the article 10, from the upstream end 18 to the downstream end 20, and into the mouth of the user.

The user puffing on the article 10 causes air to flow through the air inlet of the device. The puff-detection mechanism detects that the air flow rate through the air inlet has increased to greater than a non-zero threshold flow rate. The puff-detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 so as to pass a current through the electrically resistive track and heat up the heating blade 108. This heats up the rod 12 of aerosol-forming substrate, which is in contact with the heating blade 108.

The expanded graphite particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. As such, these particles may act as local hot-spots and provide a more even temperature throughout the aerosol-forming substrate, particularly in a radial direction from the heating blade 108 where, with prior art substrates, there would be a significant temperature gradient. This may result in a greater proportion of the aerosol-forming substrate reaching a sufficiently high temperature to release volatile compounds, and thus a higher usage efficiency of the aerosol-forming substrate.

Heating of the aerosol-forming substrate cause the aerosol-forming substrate to release volatile compounds. These compounds are entrained by the air flowing from the upstream end 18 of the article 10 towards the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol-cooling element. The aerosol then passes through the mouthpiece element 42, which may filter out unwanted particles entrained in the air flow, and into the mouth of the user.

When the user stops inhaling on the article 10, the air flow rate through the air inlet of the device decreases to less than the non-zero threshold flow rate. This is detected by the puff- detection mechanism. The puff-detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 so as to reduce the current being passed through the electrically resistive track to zero.

After a number of puffs on the article 10, the user may choose to replace the article 10 with a fresh article.

Figure 3 shows a schematic cross-sectional view of a second embodiment of an aerosol generating system 200. The system 200 comprises an aerosol-generating device 202 and the aerosol-generating article 11 of Figure 1.

The aerosol-generating device 202 comprises a battery 204, a controller 206, an inductor coil 208, and a puff-detection mechanism (not shown). The controller 206 is coupled to the battery 204, the inductor coil 208 and the puff-detection mechanism. The aerosol-generating device 202 further comprises a housing 210 defining a substantially cylindrical cavity for receiving a portion of the article 10. The inductor coil 208 spirals around the cavity.

The battery 204 is coupled to the inductor coil 208 so as to be able to pass an alternating current through the inductor coil 208.

In use, a user inserts the article 11 into the cavity. Figure 3 shows the article 10 inserted into the cavity of the device 202.

Then, the user puffs on the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 202, then through the article 10, from the upstream end 18 to the downstream end 20, and into the mouth of the user.

The user puffing on the article 10 causes air to flow through the air inlet of the device. The puff-detection mechanism detects that the air flow rate through the air inlet has increased to greater than a non-zero threshold flow rate. The puff-detection mechanism sends a signal to the controller 206 accordingly. The controller 206 then controls the battery 204 so as to pass an alternating current through the inductor coil 208. This causes the inductor coil 208 to generate a fluctuating electromagnetic field. The rod 13 of aerosol-forming substrate is located within this fluctuating electromagnetic field and expanded graphite, the material of the particles 44, is a susceptor material. Thus, the fluctuating electromagnetic field causes eddy currents in the particles 44. This causes the particles 44 to heat up, thereby also heating nearby aerosol-forming material.

Heating of the aerosol-forming material cause the aerosol-forming material to release volatile compounds. These compounds are entrained by the air flowing from the upstream end 18 of the article 10 towards the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol-cooling element. The aerosol then passes through the mouthpiece element 42, which may filter out unwanted particles entrained in the air flow, and into the mouth of the user.

When the user stops inhaling on the article 10, the air flow rate through the air inlet of the device decreases to less than the non-zero threshold flow rate. This is detected by the puff- detection mechanism. The puff-detection mechanism sends a signal to the controller 206 accordingly. The controller 206 then controls the battery 204 so as to reduce the current being passed through the electrically resistive track to zero.

After a number of puffs on the article 11 , the user may choose to replace the article 11 with a fresh article.

Figure 4 shows a schematic cross-sectional view of a second embodiment of an aerosol generating article 510. This second embodiment is identical to the first embodiment of Figure 1 except that the rod 12 of aerosol-forming substrate has been replaced by an alternative rod 512 of aerosol-forming substrate. Identical reference numerals have been used for identical components in the embodiments of Figures 1 and 3.

The rod 512 of aerosol-forming substrate of the second embodiment of Figure 4 is identical to the rod 12 of aerosol-forming substrate of the first embodiment of Figure 1 except that the rod 512 of aerosol-forming substrate of the third embodiment of Figure 4 additionally includes an elongate susceptor element 580.

The susceptor element 580 is arranged substantially longitudinally within the rod 512 of aerosol-forming substrate so as to be approximately parallel with a longitudinal axis of the rod 512 of aerosol-forming substrate. As shown in the drawing of Figure 4, the susceptor element 580 is positioned in a radially central position within the rod and extends along the longitudinal axis of the rod 12.

The susceptor element 580 extends all the way from an upstream end to a downstream end of the rod 512 of aerosol-forming substrate. As such, the susceptor element 580 has substantially the same length as the rod 512 of aerosol-forming substrate.

In the embodiment of Figure 4, the susceptor element 580 is provided in the form of a strip of a ferromagnetic steel and has a length of about 12 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

The aerosol-generating article 510 of Figure 4 may be used with the aerosol-generating device 202 of Figure 3 in the same way as the aerosol-generating article 10 of Figure 1. Notably, the inclusion of the susceptor element 580 means that the article 510 may be inductively heated. In the example shown in Figure 4, both the expanded graphite particles and the susceptor element 580 are inductively heatable. So, both the susceptor element 580 and the expanded graphite particles 44 contribute to heating during use.

The rods of aerosol-forming substrate 12,512 of aerosol-generating articles 10,510 can be described as being thermally enhanced due to the inclusion of 4.6% expanded graphite particles by weight. It has been found by the inventors that such aerosol-generating articles according to the disclosure have an increased yield and delivery efficiency of nicotine and glycerine when compared to aerosol-generating articles comprising rods of aerosol-forming substrate that do not comprise expanded graphite particles.

The inventors measured the yield of nicotine and glycerine from an aerosol-generating article 602 that does not comprise any thermally conductive particles, an aerosol-generating article 604 in which 4.6% of the tobacco of the aerosol-generating article 602 has been replaced with graphite particles, and an aerosol-generating article 606 in which 4.6% of the tobacco of the aerosol-generating article 602 has been replaced with expanded graphite particles. In other words, the aerosol-generating article 606 is an aerosol-generating article according to the present disclosure and may be the aerosol-generating article shown in Figure 1.

Figures 5 to 7 show results when aerosol-generating articles 602 to 606 are used with a resistive aerosol-generating device (such as the device shown in Figure 2).

Figure 5 is a bar chart 600 showing the yield of nicotine per aerosol-generating article on the Y axis. The yield is measured in microgram per article and is the total yield achieved during a usage session. On the X axis are bars for each of aerosol-generating article 602 to 606. The yield of nicotine from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 1150 microgram per article. The yield of nicotine from the aerosol generating article 604 that comprises 4.6% graphite particles by weight is 1190 microgram per article. The yield of nicotine from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 1125 microgram per article.

Figure 6 is a bar chart 700 showing the yield of glycerine per aerosol-generating article on the Y axis. The yield is measured in microgram per article and is the total yield achieved during a usage session. On the X axis are bars for each of aerosol-generating article 602 to 606. The yield of glycerine from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 3640 microgram per article. The yield of glycerine from the aerosol generating article 604 that comprises 4.6% graphite particles by weight is 4150 microgram per article. The yield of glycerine from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 4540 microgram per article.

Figure 7 is a bar chart 800 showing the delivery efficiency of nicotine and glycerine for each of the aerosol-generating articles 602 to 608 during a usage session. The efficiency is shown on the Y axis and is a percentage. In particular, the efficiency is the percentage of that total initial nicotine or glycerine contained in the aerosol-generating article that is delivered to the user or a smoking machine throughout a usage session of that article. The bars 802 representing nicotine delivery efficiency have a diagonal hatching. The bars 804 representing glycerine delivery efficiency have a vertical dashed hatching.

The efficiency of nicotine delivery from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 29%. The efficiency of nicotine delivery from the aerosol-generating article 604 that comprises 4.6% graphite particles by weight is 31.5%. The efficiency of nicotine delivery from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 35.4%.

The efficiency of glycerine delivery from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 9.3%. The efficiency of glycerine delivery from the aerosol-generating article 604 that comprises 4.6% graphite particles by weight is 10.6%. The efficiency of nicotine delivery from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 12.1%.

Figures 8 to 10 show the results when aerosol-generating articles 602 to 606 are used with an inductive aerosol-generating device (such as the device shown in Figure 3).

Figure 8 is a bar chart 900 showing the yield of nicotine per aerosol-generating article on the Y axis. The yield is measured in microgram per article and is the total yield achieved during a usage session. On the X axis are bars for each of aerosol-generating article 602 to 606. The yield of nicotine from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 790 microgram per article. The yield of nicotine from the aerosol-generating article 604 that comprises 4.6% graphite particles by weight is 886 microgram per article. The yield of nicotine from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 1197 microgram per article.

Figure 9 is a bar chart 1000 showing the yield of glycerine per aerosol-generating article on the Y axis. The yield is measured in microgram per article and is the total yield achieved during a usage session. On the X axis are bars for each of aerosol-generating article 602 to 606. The yield of glycerine from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 3100 microgram per article. The yield of glycerine from the aerosol generating article 604 that comprises 4.6% graphite particles by weight is 3840 microgram per article. The yield of glycerine from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 4800 microgram per article.

Figure 10 is a bar chart 1100 showing the delivery efficiency of nicotine and glycerine for each of the aerosol-generating articles 602 to 608 during a usage session. The efficiency is shown on the Y axis and is a percentage. In particular, the efficiency is the percentage of that total initial nicotine or glycerine contained in the aerosol-generating article that is delivered to the user or a smoking machine throughout a usage session of that article. The bars 1102 representing nicotine delivery efficiency have a diagonal hatching. The bars 1104 representing glycerine delivery efficiency have a vertical dashed hatching.

The efficiency of nicotine delivery from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 19.1%. The efficiency of nicotine delivery from the aerosol-generating article 604 that comprises 4.6% graphite particles by weight is 23.8%. The efficiency of nicotine delivery from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 31.4%.

The efficiency of glycerine delivery from the aerosol-generating article 602 that does not comprise any thermally conductive particles is 7.6%. The efficiency of glycerine delivery from the aerosol-generating article 604 that comprises 4.6% graphite particles by weight is 9.9%. The efficiency of nicotine delivery from the aerosol-generating article 606 that comprises 4.6% expanded graphite particles by weight is 12.1%.

So, the bar charts of Figures 5, 6, 8 and 9 demonstrate that both nicotine and glycerine yield is increased when an aerosol-forming substrate is thermally enhanced by replacing a small portion of tobacco with expanded graphite and that the yield increase is greater when particles of expanded graphite are used to thermally enhance the substrate, rather than particles of graphite. An increase is achieved regardless of whether an aerosol is generated as a result of resistive or inductive heating of the substrate.

Similarly, the bar chart of Figure 7 demonstrates that both nicotine and glycerine delivery efficiency is increased when an aerosol-forming substrate is thermally enhanced by replacing a small portion of tobacco with expanded graphite, and that the efficiency increase is greater when particles of expanded graphite are used to thermally enhance the substrate, rather than particles of graphite. An increase is achieved regardless of whether an aerosol is generated as a result of resistive or inductive heating of the substrate.

One specific embodiment aerosol-forming substrate comprising expanded graphite particles has been described above. Of course, the aerosol-forming substrate may differ in other embodiments. For example, the aerosol-forming substrate comprise a different quantity, proportion, size or density of expanded graphite particles to the specific embodiment described above. In any case, the presence of the expanded graphite particles may thermally enhance the substrate. Furthermore, other features of the substrate such as other features of the substrate’s chemical composition may differ.

Figure 11 shows an alternative embodiment of an aerosol-generating article 1110 comprising a thermally-enhanced aerosol-forming substrate 1112 that includes discrete elements of a first material 1113 and discrete elements of the second material 1114. Each discrete element of the second material 1114 may contact many discrete elements of the first material 1113 and can therefore act as a thermal pathway through the substrate. The proportions of first material and second material may be varied depending on the specific properties of the first material and the second material and on the desired properties of the aerosol-forming substrate 1112. Other than the differences in the substrate itself, the aerosol-generating article 1110 is identical to the aerosol-generating article 10 of Figure 1 and like features have been numbered accordingly.

Some specific thermally-enhanced aerosol forming substrates will now be identified as examples. The examples use combinations of three specific materials identified below; Material A, Material B, and Material C.

Material A Material A is a standard homogenised tobacco material. Material A comprises tobacco powder, about 4 wt. % cellulose fibres, about 3 wt. % of guar as a binder, and about 15 wt. % glycerine as an aerosol-former.

Material A is formed by a process including the following steps:

• pre-mixing the binder, guar gum, with the aerosol-former, glycerine, to form a first p re- mixture;

• pre-mixing the tobacco powder and water to form a second pre-mixture;

• mixing the first and second pre-mixtures to form a slurry;

• homogenising the slurry using a high-shear mixer;

• casting the slurry onto a conveyor belt;

• controlling a thickness of the slurry and drying the slurry to form a large sheet of reconstituted, substantially homogeneous, tobacco-containing, aerosol-forming material; and

• crimping and shredding the large sheet of reconstituted and substantially homogeneous aerosol-forming material to form cut-filler.

Material A has a thermal conductivity of 0.12 W/mK.

Material B

Material B is a homogenised tobacco material with augmented thermal conductivity. Material B comprises tobacco powder, about 5 wt. % expanded graphite particles, about 4 wt. % cellulose fibres, about 3 wt. % of guar as a binder, and about 15 wt. % glycerine as an aerosol- former.

The expanded graphite particles have a particle size distribution with a D10 particle size of 6.6 microns, a D50 particle size of 20 microns, and a D90 particle size of 56 microns. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume mean particle size of around 35 microns. Each of the expanded graphite particles is substantially spherical in shape. The expanded graphite particles have a density of less than 1000 kilograms per metre cubed.

Material B is formed by a process including the following steps:

• pre-mixing the tobacco powder, expanded graphite particles, and water to form a second pre-mixture;

• mixing the first and second pre-mixtures to form a slurry;

• homogenising the slurry using a high-shear mixer;

• casting the slurry onto a conveyor belt; • controlling a thickness of the slurry and drying the slurry to form a large sheet of reconstituted, substantially homogeneous, tobacco-containing, aerosol-forming material; and

Material B has a thermal conductivity of at least 10% higher than the thermal conductivity of material A, for example between 0.14 W/mK and 0.25 W/mK. The replacement of 5 wt. % of the tobacco powder with expanded graphite particles reduces the overall tobacco content, and therefore nicotine content, slightly. The thermal conductivity of the material is increased, however. In experiments, adding between 4.5 wt. % and 10 wt. % of expanded graphite particles to a homogenized tobacco material increased thermal conductivity by between 20% and 50%.

Material C

Material C is a non-tobacco aerosol-forming material with high thermal conductivity. Material C comprises, on a dry weight basis, around 76.1 wt. % expanded graphite particles.

Material C further comprises around 17.7 wt. % of an aerosol former. In this embodiment, the aerosol former is glycerol, specifically ICOF Europe food grade (>99.5% purity) glycerol.

Material C further comprises, on a dry weight basis, around 3.9 wt. % of fibres. In this embodiment, the fibres are cellulose fibres, specifically Birch cellulose fibers from Stora Enso OYJ.

Material C further comprises, on a dry weight basis, around 2.3 wt. % of a binder. In this embodiment, the binder is a guar gum, specifically guar gum from Gumix International Inc.

Material C may further comprise one or more of nicotine, an acid such as fumaric acid, a botanical such as clove or rosmarinus, water, and a flavourant.

Material C is formed by the process set out below.

A slurry is formed using a lab disperser capable of mixing viscous liquids, dispersing powders through liquids, and removing gas from a mixture (for example by applying a vacuum or other suitably low pressure). In this embodiment, a commercially available lab disperser from PC Laborsystem was used.

To form the slurry, a first mixture is formed by adding to the lab disperser around 7.11 grams of the aerosol former, then around 157.5 grams of water, then around 1.57 grams of the fibres. Then, these first ingredients are mixed at 25 degrees Celsius for 5 minutes at 600-700 rpm to ensure a homogeneous mixture and to hydrate the fibers. Then, a second mixture is formed by manually mixing around 32.95 grams of the thermally conductive particles and around 0.92 grams of the binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. Then, the second mixture is added to the first mixture to form a combined mixture. Then, the combined mixture is mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of around 200 mbar. The reduced pressure may help to ensure that the thermally conductive particles are homogeneously dispersed in the mixture and that there is little trapped air and few lumps in the combined mixture. Then, the combined mixture is mixed at 5000 rpm for 20 second minutes at 25 degrees Celsius and a second reduced pressure of around 100 mbar. This second reduced pressure may help to remove any remaining air bubbles. This forms a slurry for casting.

The slurry is then cast and dried using a suitable apparatus. In this embodiment, a commercially available Labcoater Mathis apparatus is used. This apparatus includes a stainless steel, flat support, and a coma blade for adjusting a thickness of slurry cast onto the flat support.

The slurry is cast onto the flat support and a gap between the coma blade and the flat support is set at 0.6 millimetres. This ensures that a thickness of the slurry is no more than 0.6 millimetres at any given point.

The slurry is then dried with hot air between 120 and 140 degrees Celsius for between 2 and 5 minutes. After this drying, a sheet of the aerosol-forming substrate is formed. This sheet has a thickness of around 159 microns, a grammage of around 125.7 grams per metre squared, and a density of around 0.79 kilograms per meter cubed.

The sheet is then crimped and cut to form Material C. The thermal conductivity of Material C is at least 0.28 W(mK).

It can be seen that a wide range of different aerosol-forming substrates may be produced simply by combining Material A, B, and C in different proportions.

Thus, a first exemplary aerosol-forming substrate 12 may comprise a mixture of 60 wt. % of discrete elements of Material A and 40 wt. % of discrete elements of Material B. Both Material A and Material B are homogenized tobacco material, but Material B has augmented thermal conductivity by virtue of the presence of expanded graphite particles. The presence of Material B in the first exemplary aerosol-forming substrate provides discrete elements that have increased thermal conductivity and, as a result, aerosol delivery and nicotine delivery are improved.

A second exemplary aerosol-forming substrate 12 may comprise a mixture of 70 wt. % of discrete elements of Material A and 30 wt. % of discrete elements of Material C. The presence of Material C in the second exemplary aerosol-forming substrate reduced the overall amount of tobacco in the substrate, but significantly improved the thermal conductivity. Material C also contribute to the generation of aerosol.

A third exemplary aerosol-forming substrate 12 may comprise a mixture of 80 wt. % of discrete elements of Material B and 20 wt. % of discrete elements of Material C. In this example, the first material is Material B, a homogenized tobacco material with augmented thermal conductivity and the second material is Material C. Any of these three exemplary aerosol-forming substrates may be used as the substrate in the aerosol-generating article 10 of Figure 1 or the substrate in the aerosol-generating article 1110 of Figure 11.

For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A ± 10 % of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

1. An aerosol-forming substrate for use in a heated aerosol-generating article, the aerosol forming substrate comprising expanded graphite particles.

2. An aerosol-forming substrate according to claim 1 in which the aerosol-forming substrate has a thermal conductivity of at least 0.12 W/(mK).

3. An aerosol-generating article according to any preceding claim in which the expanded graphite particles make up at least 1 wt. % of the aerosol-forming substrate.

4. An aerosol-forming substrate according to any preceding claim comprising, on a dry weight basis: between 1 and 90 wt. % expanded graphite particles; between 7 and 60 wt. % of an aerosol former; between 2 and 20 wt. % of fibres; and between 2 and 10 wt. % of a binder.

5. An aerosol-forming substrate according to any preceding claim, comprising between 1 and 15 wt. % expanded graphite particles.

6. An aerosol-forming substrate according to any preceding claim, wherein the expanded graphite particles have a particle size distribution having a volume D10 particle size between 1 and 20 microns.

7. An aerosol-forming substrate according to any preceding claim, wherein the expanded graphite particles have a particle size distribution having a volume D90 particle size between 50 and 300 microns.

8. An aerosol-forming substrate according to any preceding claim, wherein the expanded graphite particles are substantially homogeneously distributed throughout the aerosol-forming substrate.

9. An aerosol-forming substrate according to any preceding claim, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

10. An aerosol-forming substrate according to any of claims 1 to 8 comprising tobacco particles.

11. A method of forming an aerosol-forming substrate according to any preceding claim, the method comprising: forming a slurry comprising expanded graphite particles, an aerosol former, fibres, and a binder; casting and drying the slurry to form the aerosol-forming substrate or a precursor to the aerosol forming substrate.

12. A method according to claim 11, wherein forming the slurry comprises: forming a first mixture comprising: the aerosol former; the fibres; water; optionally, an acid; and optionally, nicotine, forming a second mixture comprising: the expanded graphite particles; and the binder, and adding the second mixture to the first mixture to form a combined mixture.

13. An aerosol-generating article comprising an aerosol-forming substrate according to any of claims 1 to 10 or formed by a method according to any of claims 11 to 12.

14. An aerosol-generating article according to claim 13 comprising a plurality of elements, including the aerosol-forming substrate, assembled within a wrapper.

15. An aerosol-generating system comprising an aerosol-generating article according to claim 13 or 14 and an electrical aerosol-generating device for heating the aerosol-forming substrate.