GB2340125A - Low density materials - Google Patents

Description

2340125 LOW DENSITY MATERJALS The present invention relates to materials

which have a matrix and a particle suspended in the matrix. The matrix can either be an organic or an inorganic binder.

Specific materials of this general class of materials have been previously disclosed in September 1996 at theSth International Conference on Inorganic Bonded Wood and Fibre Composite Materials, Volume 5, pp 49- 63, and the PIRA Conference in October 1996 and published in their conference proceedings, Volume 1, Uses for Non-Wood Fibres, Cement - Cellulose Composites.

The above papers describe materials with a cement matrix. Ground organic particles with a particle diameter of up to 5 mm are suspended in the cement matrix, Other products can be created by mixing exfollated clays or ash with cement, gypsum and suspended particles.

This technology derived from work on damp-proofing, materials, where it was shown that large quantities of air in cement mixers did not cause any s12nficant loss of crushing streng I I -D _-th. It was hard to control the size of the air vacuoles in the mix.

Expanded polystyrene was added to the mix to perform the same function as the air vacuole. This work was done using expanded polystyrene beads of Imm and less in diameter- The materials developed during this work are known as STYROCRETE or STYROCEM (suspended polystyrene particles), CORKCRETE or COPKCE%,l (cork), STRA'XCRETE or STRAWCEM (straw), WOODCRETE or WOODCEM (sawdust), P.A- PFRCRFTE or PA-PERCEM (paper), CELLUCKETE or CELLUCEM (general 2 cellulose). The "CRETEs" have a particle diameter of less than 5mm and the"CEMs" have a particle diameter of less than Imm.

These materials produce considerable advantages. They are lighter than conventional cement, they can have good fire retardant properties, low thermal and electrical conductivity and a high heat tolerance. Their fire retardant properties and heat tolerance stem from the fact that the matrix is heat tolerant and has a very low thermal conductivity. The low thermal conductivity is enhanced by the suspended particles in the matrix.

Slabs of cement with expanded polystyrene particles have now been made with 50% by volume recycled expanded polystyrene. Thus, the weight of the slabs is reduced by nearly 501,10. These slabs are useful for the home DIY market. Also, garden ornaments, coping stones for the building industr-y and low density garden wall decorative screens have been manufactured usinc, this material. CladdinQ sections also benefit from the reduction in weight.

Further improvements have been made to these types of materials.

The rigidity of inorganic matrixes can be reduced by adding about 2% by weight of styrene type material to inorganic clays. More or less styrene can be added depending on the required end properties.

In addition, water repellent preparations can be added to prevent ingress of moisture into the finished products or materials made with the inorganic matrixes.

It has been mentioned above that not only styrene pa,-ticles can be suspended in the matrix. Cellulose materials can be used instead. It has been disclosed in the above referenced papers that cellulose materials can retard the setting of cements, The curing of cement based materials is dependent on the chernistr-y of the cements and their additiVes.

3 As an example only, the curing of calcium aluminate cement (a specialist cement used in high temperature applications), or Portland cement (a conventional cement used in construction), in the presence of cellulose retarders is dependent on the number of molecules of water of crystal lisation, attached to the cement molecule. In the presence of sugars, tannins, lignins, cellulose molecules and other polyhydroxy molecules, the setting properties are retarded so that the crystal structure of the cement cannot form.

This retardation effect is attributed to the establishment of hydrogen bonding between h,,-droxvl group of the retarding molecule and the water molecules attached to the cement molecule. The water of crystallisation plays a vital part in the stabilivy of the cement crystal and the number of water molecules, (being part of the cement molecule) affects the properties of the cement crystal to a considerable extent. The cement crystal cannot form properly if the number of water molecules attached to the cement molecule 'Is too large. Controllinc, the number of molecules of water of crystallisation is therefore a factor which controls the rate of crystal formation and therefore the rate of settin2 of a iziven cement.

Heat can be used to reduce the quantity of water in the slurry in an effort to achieve the optimum water of crystal I isation. Heating the slum, to 80'C from about 8 hours achieves the required state for Portland cement type binders- When CAC is used, heating to 80'C for about 2 hours allows the cement to ach'eve most of ultimate strength.

I In the presence of retarding additives such as cellulose fibres, there is retardation of this setting process For Portland cement, heating at SO'C for 24 hours, drives off enouQh water to allow cement crystals to form. Higher temperatures can be used (eg. I SOC) to speed up the remo,,,-al of water from the slurrv. The time for the drlvinL, oT,f vat,!r i c, reduced at higher temperatures.

4 When CAC is used as a binder in the presence of cellulosic fibres, adding the Lithium Carbonate accelerator, facilitates the formation of the crystal phase within 2 hours of kiln dr-ying. Most of the final strength of this cement is achieved within this time span.

The problem of retardation with cellulose based materials has been recognised in the above described publication- In a first aspect, the present invention provides a method of makin2 a low density material, the method comprising the steps of a) mixing cement powder with water to form a mixture" b) addin2 orcanic or inorganic particles to the mixture and C) heating the product of (b) to drive off the excess water This serves to drive off the surplus water molecules and allows the cement to set bv achievinc, a thermo-dynamically stable state. It may be preferred to continue heating the cement mixture for a prolonged period eg. 12-24hrs. In this case, as a number of,A,-ater molecules is gradually reduced, the cement is able to align itself i I in proper relationship for it to crystallise into a thermo-dynamically stable state.

The setting of the cement is therefore a process whereby the cement molecules are hvdrated and achieve a lower ener2v state in the crvstallised form they possess in the slurry state. The number of water molecules attached to the cement molecule in the slum, state, exercise a vital roll in the change of phase leading to the cr-ystallised thermodynamically stable state.

It is more preferable if in the method according to the first aspect of the present invention, the product of (b) is heated to above 60'C.

If the cement is calcium aluminate cement, it is preferable if the product of (b) is heated to a temperature in the range of 700C to 900C If the cement is Portland cement, it is preferable if the product of step (b) is heated to a temperature in the range of 1700C to 1900C.

1.

Recently it has been surprisingly found that a small amount of accelerator needs to be used in the settinc, of such cements. Therefore, it is preferable if the method comprises the step of adding, an accelerator. The accelerator used with calcium aluminate cement is Lithium Carbonate. In the construction iridustrv, all measurements are in welaht so that composite materials are weight batched.

Accelerated calcium aluminate cement preferably requires about 0.059/'o' ie. typically 0.04% to 0.06% of Lithium Carbonate by weight of added cement, to provide accelerated settinc, of Calcium aluminate cement.

C The cement and water content is determined by the manufacturer's instructions for preparing the cement in the conventional manner, le. no particles added. When using cellulose particles, the cellulose is usually saturated before adding to the cement.

It has been mentioned above that these types of materials can have suspended organi I I I g c part cles with diameters of less than 5 mm, and in some cases preferablN less than I mm. It is expensive to reduce organic materials to the required size. Most of the cost is incurred where, (for example, the reduction of straw to a suitable size particle) requires the use of heavy duty milling machinery. The wear and tear and the grinding components is very heavy because there is a high silicone content in the fibres.

It is preferable if the organic materials are reduced using a crvo-en such as liquid nitrogen. In this method, organic particles (straw, for example) are immersed in liquid nitrogen to solidify into a very brittle state. The very low temperatures required to liquefy nitrogen, freezes the straw cells into a rigid form that cannot flex. In this state, the straw is passed between crushing, rollers to shatter the structure into tiny particles. The arrangement and design of the crushers controls the size of the particles resulting from the process. Particles of any size can be produced by this method.

6 The larger sized particles that are to be coated in the various matrixes for use as a loose fire retardant insulating material can be mechanically sieved or separated by cyclotron separators.

The various fractions resultinc, from the fracturin2 process can be separated into various 2rades suitable for the various proposed material deslqn. If the lareer size particles are to be further reduced, these fractions can be recirculated into the liquid nitrogen and passed through the rollers again.

The fractured material is delivered to the evaporating containers designed within machinery, where the temperature is allowed to rise The liquid nitroRen vaporises to be recirculated and condensed into liquid and used repeatedly. The dry fractured straw is then moved and subjected to cyclotronic air flow or vortex separators to separate the fractured particles into various receptacles for predetermined sizes. This process has the advanta-e that no arindinQ and the wear and tear on the crushers is minimal.

Liquid nitrogen does not wet the cellulose material being fractured. As the temperatu're is allowed to increase from the cr-yogenic temperature, the liquid nitrogen chanaes state from its liquid phase into the vapour phase (-77K). The gas evaporates from the straw particles, and the cryogenised straw remains in a powdered or particle state.

The reduction of cellulose matter in this wav becomes cost effective for many industrial processes, be it for the paper industry or the manufacture of a cement bonded material This --zchnique can also be used to make small particles of polystyrene from second han, -,:panded polystyrene packagin'a etc Also, tyres can be used to produce small hvdrocai-,:n pa-cles 7 The usefulness of the above technology developed to produce low densitv cements continues to be extended. The addition of expanded polystyrene and the other group of materials consisting of hydrocarbon and cellulose additives as a means of controlling the size of the vacuoles is proving exceptionally useful for further applications.

A new class of materials has now been developed based on the above principles. These materials have an or2anic matrix. They possess some fire retardant proper-ties but appear exceptionally useful for padding or protective purposes. a group of materials that have ven7 low density. They are generally hydrophobic.

In a second aspect, the present invention provides a material comprising a substantially homocenous mixture of particles with diameters of less than 5 mm and an oreanic material which serves as an orcanic matrix and binder for the particles.

C Preferablv, the orRanic matrix is chosen from one or more of the following: bitumen, polyesters, phenolics, ureas, melamines, epoxides, etc and known viscous hydrocarbon matrixes such as polymers, polypropylenes, polyurethanes, rubbers, latex, plastics, acr-ylics, resins, silicone rubbers and tar. Tar is a waste product from oil distillation. Therefore, tar is a particularly preferable matrix.

The above list is not exhaustive, the organic matrix can be anv synthetic or natural material that can be mixed with a particle to produce pliable., resilient, or hard materials that have a very low density and lend themselves to considerable number of different applications.

The suspended particle can either be organic, inorganic or a combination of both A particular example of this type of material has an elastomeric matrix with expanded polystyrene or recycled plastics, rubbers, synthomers and expedited inorganic 4W.8 materials as additives. This material is pliable and also possesses the low density and heat resident properties of the so-called "crete" group of materials.

Preferably, the diameter of the particles is between I tm and 5mm. Mixtures of different particle sizes can be used.

More preferably, the particles make up between 99.5% by volume and 25% by volume of the total volume of the compound. The quantities used determine the properties of the finished product. Cellucrete has 30% by volume of cellulose additive. Because the quantity of the binder material is compared to the volume of the particles, these materials typically have a very small "heat sink capacity".

Preferably, the elastomeric matrix is an acrylic, a rubber or a plastic.

If the suspended particle is polystyrene, beads or sanded or re-processed expanded polystyrene can be used. Also, recycled plastics, rubbers (e.g. tyres etc). or other recycled materials can be used.

These materials can be applied to designs for protective padding, cushioning, sound absorption systems and the like.

In all cases, the addition of expanded polystyrene provides a physical entity which can be coated by the matrix to control the size of the vacuole. The size of the added bead controls the size of the vacuoles in the material. Inorganic materials such as ceramic clays, (or glass) silicone based aerated spheres such as "floaters" can also be used to provide a measured vacuole.

The relationship between the size of the beads and the streno I is _-th of the material proportional. Strength decreases as the size of the beads increase. The smaller the size of the bead, the areater the surface area of the beads and the zreater the volume of the matrix material, that have to be used to cover all the particles. Therefore, it Is 9 preferable if the diameter of the particle is in the range of 2.5mm to 3. 5mm. The particles can be separated by the method discussed in the published papers or discussed earlier in this document.

Materials accordincy to a second aspect of the present invention have a continuity of matrix that makes them useful for puncture proof tyres on vehicles. Such materials can be used on their own or in combination with other reinforcing materials to provide a variety of designed materials for specific uses. They can encase other materials to provide an outer resilient component.

Experiments with the above concept materials continues and in situations where soft organic matrixes such as rubber, polyurethanes, plastics and other available organic matrixes need to be used because of their flexible characteristics, very novel features have emerged.

A mixture of the above matrixes e.g. rubber, pre vulcanised rubber solution, or -vulcanised rubber, when mixed, for example, with powdered perlite, provides a novel material that has "smart" characteristics. The density of the rubber matrix increases during heat stress, the greater the amount of heat the greater the density increase. This in fact is a passive phenomenon due to the expansion of air trapped in the exfollated material used as an example only, perlite, vermiculite, expanded polystyrene or any of the aforementioned additives whose space expands to compress the rubber matrix.

Compression of the matrix increases the density of the matrix. This is also seen in other organic matrix materials. However, it should be noted that as the total volume of the heat stressed material increases, the surface layers are obviously stretched and become less dense.

The other useful characteristic of these materials is the crust formation of the heat damaged area of material. In this case, the organic material is burnt at the surface and as the organic material melts the inorganic perlite or vermiculite powder or nar,P71- -Fabout I mm to I tm emerge out of the matrix to "coagulate" at the surface AV 10 of the dama2ed area of the material. As more of the or(zanic matrix is oxidised in the fire, more additive is freed from the matrix to add to the thickness of the inorganic "crust". The inoroanic "crust" soon forms an impermeable "membrane" which retards the ingress of oxygen into the heat stressed material and retards the rate of burning. These materials therefore achieve fire retardant properties because much of the impinging heat is reflected by the "Crust" area of inorganic additive protecting the rubber matrix of the product. Another advantage is realised in that, the temperature 2radient within the material is decreased, and hence the rate of damage is also decreased.

A verv useful ramae of soft fire retardant materials is obtained. These materials can be used as fire retardant mastics. Bv manufacturing components made from the above mixes of organic matrixes and inorganic additives a new group of "smart" materials is produced. These materials increase their density as they are heat stressed and form "coa--ulates" of inorganic crusts only in areas of damage which are severe enou2h to bum the organic material- When silicone rubber matrixes are used, temperatures of less than 1000'C can effectively be contained without being damaged.

The above group of materials can be pumped into conduits and openings, interfacial spaces, cavities and the like to form fire retardant protection for electrical., lat'on ducts etc. The containment of fi-,es in a aiven compartment being the object venti I of the exercise.

The low densitv of the orcanic matrix and the inorqanic particle material provides a material which can be used to seal junctions between construction elements bratina structures. The advantaoe of this non hard fire retardant material is that the in vI material adheres to all structural components it Is in contact with and forms a fire retardant movable seal. The fact that the components of the structure are vibrating or moving about prevents fire ingress from one compartment into another because the oraanic matrix allows movement to occur without fracturing the matr'x. Such materia s q,re id2ally suitqhle to moving structures anG may even be desirable to airborne utilities The "crust" formation can be achieved with other materials such as - ground sand and pulverised ash and other materials that can be properly prepared in the less than I mm. The exfoliated clays such as vermiculite and perlite are well established and easily available materials that can be used but many other additives are available and it is only a matter of practicality as to which of the many materials are used for the above purpose.

Above materials can be used as a first line of defence in fire retardant applications in ducts and through openings. By making rubber composite plugs in this material, the plug can retard the egress of fires from one space into another.

These organic matrix materials allow the design of a multitude of components designed to provide fire retardant structures for the ducting and shaft opening required for electric cables, plumbing fittings and other such conduits having to pass through the separating structure from one space into another.

The use of specially prepared cables would be of benefit in situations where fire retardation was desirable. The earlier described mixtures of organic and inorganic additives 4an act as heat reflectors when applied to services or electrical cables as coatings or factory applied coverings. A suitable formulation of the plastic coatings applied to electrical wires, can be modified with the addition of, for example, the perlite dust. The mixture is used to coat the electrical cables to provide fire retardant coatings to electrical wires and the like. This system can also be used to provide coatings to structural members such as girders, trunking for electrical cables and other services etc Materials according to a second aspect of the present invention can be preferabl-y used in end pieces for cable ducting. Thus, in a third aspect, the present invention ides an end piece for cable ducting comprising a block of material according to a provi I C - I - second aspect of the present invention with at least one hole through the block- of "iterial for insertion of a cable therethrou2h.

AW More preferably, the block of material of the end piece comprises two separable sections which abut along a line of attachment and said at least one hole lies on said line of attachment. Even more preferably, the end piece comprises more than two separable sections and said holes fie on the lines of attachment of the separable sections.

In a preferred example of the end piece, the block of material comprises two sections which a hin.-eably mounted to one another such that the two sections meet at a line of attachment and said at least one hole lies on the line of attachment. Even more preferably, the end piece comprises more than two separable sections and said holes lie on the lines of attachment of the separable sections.

The usefulness of the above system for soft matrix materials extends to the mastics specifically designed to expand as they are subjected to heat stress. These so called intumescent svstems work on the principal that vaporised water trapped 'in the material which is released to increase the volume of the bulk of the material to manifest the inturnescent. Other inturnescent systems'vvork by heated gas expanding the mass of the material.

Water filled expanded polystyrene or spheres, saturated perlite and vermiculite dust coated in this elastomeric matrix can provide a great deal of water in fire situations. Similarly, the spheres can be manufactured in inert aas atmospheres and become filled with inert 2as. Hence, the spheres can be used as inert Lyas carriers- Therefore, in materials accordincy to a second aspect of the present invention, it is preferable if the particle is a carrier containing an expandable substance. To clarify the above, and for the avoidance of doubt, an expandable substance in this context is taken to mean a material which has a laraer thermal coefficient of expansion than the material of the particle. Therefore, on heating, the expandable substance expands at a quicker rate than that of the particle or carrier and eventually bursts out of the particle Tvnicallv. the expandable substance either be water or an inert gas.

As an example only, water escapes from a carrier eg. an expanded polystyrene bead when the carrier melts or bursts due to heat stress.

Inturnescent mastics and other such materials are usually made from a mixture of compounds that are poor thermal conductors and can be vermiculite, carbon phosphates or other preparations and contain an expanding component. These components are carried within the organic component that can be acrylics or a number of other components suitable for the purpose. In a fire, the trapped water expands to force the mass of the material to expand giving the inturnescent effect. The oraanic matrix burns very slowly.

In order to maximise the effectiveness of the orizanic materials used in such materials, the addition of poor conductors to the mixture considerably reduces the heat transfer across the material. If additives of I mm to I pm are added to inturnescent mastics heat ingress during a fire is reduced. If for example expanded vermiculite or perlite is added in any proportion to the inturnescent mastic, the amount of heat transferred across the material is proportional to the amount of exfoliated material added.

Experiments have shown that even at a 50% mixture of expanded vermiculite to 50% inturnescent mastic provides an intumescent mastic material that degrades at a slower rate than existinc, inturnescent materials under the same conditions. The addition of poor conductors to inturnescent mastic materials be they vermiculite, carbon, perlite, floaters, carbon phosphate, or other composites is measurably better in reflectincr the impinging heat when compared to the existing inturnescent mastic formulations. Such additions have a very beneficial effect to the longevity of inturnescent and other mastic and orLyanic based matrix materials.

The rate of heat transfer across the material is lower in these materials than similar materials not containing the poor conductor additives.

14 These low density materials also open up the possibility of providing technology to build unsinkable flotation vessels.

For this use, bitumens provide a particularly useful matrix although any organic matrix could be used as a binder. Bitumens are long established materials in the maritime industry. Flotation vessels can be made which use materials with bitumen matrixes and alass spheres, ceramic spheres, expanded polystyrene, vermiculite, perlite and other exfoliated clavs or svrithetic exfollated materials as the particle, Bitumens are hydrophobic and do not dearade in sea or fresh water. Other matrixes can also be used and even two sta2e matrixes can be used i.e. a hardening compound, eg. as used in epoxy resins, to provide hard, inflexible low density materials.

In a fourth aspect, the present invention provides a flotation vessel comprising a material in accordance with a second aspect of the present invention.

If the matrix is tar and the particles are inorcranic particles, the method preferably comprises the step of heating the tar to over 1000'C prior to mixing. If the matrix is a silicon based rubber composite and the particles are an inorganic exfoliated material, the silicon based rubber composite preferably forms between 4011i'o to 60% by volume of the total mixture.

According to a fifth aspect, the present invention provides a method of making a low density material comprising the step oE Mixing particles of inorganic or organic material with a diameter of less than 5mm with an or(2anic component which serves as a matrix and a binder.

Preferabl', the matrix is water based bitumen. More preferably the water based bitumen forms between 5 and 15/o of the total volume.

Alternatively, the matrix can be a bitumen compound with a melting point of between 70'C and 90'C, the method further comprises the step of heating the compound to above the melting point prior to the step of mixing the compound with the particles. More preferably, the bitumen compound forms between 30% to 401/'0 of the total volume of the mixture.

Materials accordincr to a second aspect of the present invention can be used to produce synthetic materials for the clothing industry. Polymers provide a substantial number of composites which are useful in the material industry. Cloths made from these polymers such as polyamides ( nylons), polyesters, viscose, polypropylenes. rayon, the various resins etc., can all be usefully applied to the above technology.

The present invention can also be used to provide an absorbent material which can be used for nappies, kitchen towels, swabs, blotting paper, feminine towels, industrial absorbent socks etc, Therefore, in a preferred embodiment, the matrix comprises two sheets which face one another, the surfaces of the sheets which face one another beina rough, and the particles being dispersed on the roughened faces of the sheets.

More preferably, the matrix of the present invention is paper and the particles are provided by suspended straw particles.

The development of this absorbent material arose out of experiments working with wet mixtures and slurries with cellulose components. It was found, that an excessive amount of water was needed to achieve '"'ertingand in many cases, the mixed water required well over 50% of the volume of straw used, This was found to be due to the cellular nature of cellulose based materials. In strav,, a verv large proportion of the total volume is caverriulated. In a living plant, the cells are full of cytoplasm which shrink and recede when the plant is dried, The in-,I.le 16 of the cells becomes a cavity with a given capacity. The number of cells in a given unit will therefore have a given volumetric capacity, the sum of which constitutes the largest volume of any given straw substrate.

The absorbent material uses the fact that the porosity of the cell walls allows the cavities to fill up with fluid before and in preference to free water being available on the surface of the material. This is an extremely useful property. Not only can such a property be used for filtering purposes, but the sheer volume of liquid absorbed and held, makes straw in many ways an ideal absorption material.

Maximum absorption is achieved by preparing straw by the cryogenic method previously described. Straw reduced to a flour, i.e. particles with a diameter of less than I mm, has the best absorption characteristic. The cells absorb fluid by capillary action into the cell cavities. Wettina the surface of the very small particles takes up more fluid and the particle interspace absorbs yet more of the available fluid. The volume of liquid held by the above mechanism can be about equal in these materials to the volume of the straw flour.

A large number of applications lend themselves a ver-,,, high absorption properties- Industrial spillage can be contained, absorbed and swept up, contaminations of manv accidental of other spillages can be contained by the above preparation.

In biological applications, the absorbent properties of straw can be applied to manufacture swabs for surgical applications, dressings, incontinence pads, babies napples, feminine towels, applicators, liners etc- In other applications e.g. industrial and domestic situations, absorbent tov.,els, wipes, toilet paper, absorbent pads of many sorts, blotting applications etc lend themselves to mind. Absorbent paper mixtures of man sorts can be manufactured usin- this technique.

17 It is interesting to note that fibres from different parts of this plant have different properties. As an example only, fibres obtained from the root systems tend to be stronaer than fibres that are obtained from the trunk or branches.

With this in mind it is possible to use cellulose fibres that are obtained from root systems to manufacture "tough" paper that may make it suitable for applications where a lot of wear and tear is expected. Tough paper can have many uses in paper items which require a lot of mechanical strength.

The stren--th of this paper is derived from the additional cross-links that are achieved via the carbon 6 side chain of the glucose base unit in cellulose. The number of these cross links is greater in root cellulose than in trunk or branch cellulose.

The manufacturing process can be tailored to the material composition and its intended use. In the paper industry, it may be desirable to sandwich a straw flour filling in between layers of suitable paper for the intended use. In biological applications, the straw flour can be sandwiched between linen layers suitable for the rigors of sterilisation technology. In industrial applications, the material mav be loose or sandwiched in suitable compositions or incorporated into the fabric of the material.

In all cases, the movement of the fluid should be free via the linings, to allow the capillary forces to move liquid from one space into another. Once the liquid is inside the cells, fluid movement is restricted by surface tension forces.

Many cellulose fibres are available which lend themselves to the above uses. The intended use for the absorbent properties of the straw flour will dictate the composition, texture, adhesive methodology, shape etc of the finished product.

Straw, which is made from sugar molecules, is a very nutritious material, Many m I cro-organ isms thrive on the cellulose material once it becomes 'V-et. For this reason., straw base biological or medical products must be sterilised prinr to use and k-ent Hrv 18 during storage- In a dry state, the products have an indefinite storacre lifetime. Once wet, the products should not be used for extended periods but discarded and replaced with a fresh product. For industrial use, the straw can be wetted and dried completely. The straw component does not suffer serious degradation by repeated wetting and drying. Such products can only be stored in very dry conditions, The processing of straw can be achieved in many ways, but the end requirement wIII dictate the process. All straw can be bleached to provide vhire flour material that has no odour and does not release any coloration on being wetted. Textures of the straw can be controlled by mixing straws. Others can be controlled by chemical additives or by usInLy different varieties of stra'w or mixinc, with scented biolo2ical materials such as herbs or woods ea. pine wood particles. Such material are totally areen' environmentally and wholly decompose to useful organic nutrientsThe way the straw is processed will depend on the degree to which the liquids are absorbed onto the particle. In all cases, the smaller the particle, the greater the surface area of the particle. In grinding technolo y. the straws are ripped apart to Crive varving sized particles. The ripping effect produces a rough surface which produces a large surface area. The way that the straw (Including linseed straw, hemp straws) and other highly cellular cellulose base marelrials are broken up will depend on the purpose to which the end product is intended to be used.

A large number of treatments are available for the preparation of these process straws. If, as an example only, the straw is to be utilised as an absorbent material for sophisticated uses, where the natural smell of the straw is not acceptable, such as feminine towels, baby napples etc, the straw can be treated chemicalb, riot only to remove the smell but also to break up the cellular str-ucture of the straws to increase the total surface area of the particles.

The product can be treated chemically to sterillse the material so as to exclude ail livina orzanisms The straws can be chemically treated to remoe the natural colour 19 of the straw. A useful chemical to achieve these results is sodium peroxide which is a stron!a oxidising agent. Many other oxidising agents exist for the above sterilisincy and bleaching effect.

Straws have a waxy type material on the surface and this has the effect of forcing water (or some other liquid) to form spherical droplets of water that hold the shape because of the high surface tension. To reduce this effect, a suitable wetting aaent can be used to coat the surface of the processed particles so that the rate of wetting of the particles is increased. In this way, the absorbency of the material becomes faster in effect. If the 'wettinor' aoent is an orcranic solvent, the resultant material will be hydrophobic. Thus, it can selectively absorb organic spillages such as oil, petrol, paraffins etc.

The use of straw is very advantageous, not only because it is a naturally occurrin,2 material always available in surplus quantities but, because, provided it is not subject to microbial activity, it has an extended stable structure that lasts for thousands of vears. Straw does not decay readily in aseptic conditions.

Straw in its various forms can have many applications. For example, it can be used for decorative purposes. The technology which sandwiches straw particles between sheets of paper can also be extended to provide decorative materials that have a variety of straw particles embedded within the materials.

The above absorbent material should not only be limited to straw particles. For example, other absorbent materials such as vermiculite, pertite or other exfoliated inomanic materials, organically based hollow cellulose or plastic base materials can also be used.

Also, other organic materials can be used instead of paper. For example, cotton, st -, hemp, wool can all be used. Also, inorganic materials such as n",lon could be used in place of paper.

The relationship between particle size and the surface are of the particles is well established (see, the earlier referenced papers). For best results, i.e. for the maximum absorption of liquids, the particles need to be small. All small particles will absorb liquid not only because of the werting effect, but the cellular fragments provide hollows which fill out, i.e. provide the receptacle for the liquid in question. Therefore, it was not surprising that in recent experiments, when expanded polystyrene reclaimed material w-as sanded down to a fine powder. , it absorbed large quantities of liquid. A wettina azent increases the rate of wetting.

All material with the cellular form manifest the same absorbent property. It is an interesting observation that the material with a high surface tension such as expanded polystyrene and the waxy coats on the surface of some cellulose materials act as hvdrophobic gates These gates repel water bome or water based liquids but absorb in preference hydrophobic liquids such as oils and fatty based liquids.

The use of surfactants is proven advantageous because it improves the rate at which particles are wetted. A cheap anionic or cationic or amphoteric sur-factant is very effective at.vettlnQ the waxv and hydrophobic materials to reduce surface tension. FrothinQ occurs when surfactant or soaps are added to water solution and an antifrothin- a-ent is effective in reducinc, foamino, of surfactant treated mixtures. Air vacuoles aenerally weaken the strenc-qh of the finished materials.

Preferably, the straw particles are dispersed in a suitable adhesive material or sandwiched between sheets of paper or other suitable containment material.

A Further class of materials has been found where a liaht %veight ceramic material is made by suspending an organic particle.%-Ithin the ceramic matrix. Therefore. in a sixth aspect, the present invention provides a thermall-", insulating material which cornpFises a substantially homogeneous mixture of hvdrocarbori particles suspended in a ceramic matrix 21 It is more preferable for high temperature work i.e. above 12000C, if the ceramic matrix is made from cordierite clay, zirkonia clay or a suitable fine clay.

The material of the sixth aspect of the invention achieves its fire retardant properties by virtue of the fact that it has an inorganically based matrix. It does not crack during excessive heat stress because the bridges between one particle and another I - are extremely thin and expand at an even rate.

Because the bridges between the particles are so thin, they act as a physical barrier to conducted heat. Only small quantities of heat or electrical energy can cross the thin laminar of the matrix between the vacuoles. The process of conduction of heat energy across the laminar is slow. The effect is increased by using materials, matri I ixes and fillers which are poor conductors of heat enerory.

The resistance to thermal shock is obtained bv reducing the quantity of the matrix material in the product. Failing of conventional fired clay materials once subjected to thermal shock occurs because of extreme stress imposed on the molecular bonds holdincr the material toaether. In conventional clay products, the sum of the forces in the material in the thermal shock conditions is sufficient to exceed the strencqh of the chemical bonds holdin2 the material together. The chemical bonds breaks to signal the structural failure of the material. By reducing the quantity of the material in the product the magnitude of the forces is considerably reduced. By reducing the quantity of clay material in any criven volume to a predetermined value, the sum of the expansive forces becomes insufficient to break the chemical bond binding the material matrix toQether and no shattering occurs. The highly aerated material is said to be able to tolerate thermal shocks.

The present invention according to a sixth aspect is particularly of use in the linin2 of kilns. Aerated fire clay bricks can be made i;,hich require considerably less 22 heat energy to bring the furnace to the working temperature than conventional linina, -I 'D materials.

In addition to the supporting structure, fire clay supports and tripods and platforms can also be made of the aerated fired clay composites.

All these materials can have their mass reduced by anN,-thing up to 80% of the conventional items performing similar functions in kilns. The reduction in the quantity of heat energy required to raise kiln temperature to working levels are ver-y considerable. In higher temperature clay products of about 1200'C, exfoliated vermiculite can be used. The aerated material resultant from the burninia of coal products in power stations such as the Floaters or Atmospheres, silicon oxide, glass, ceramic, perlite, can be used. Clay such as cordierite used for the manufacture of catalytic converters substrates or zirkonia silicon carbide or nitrate materials form good matrixes for hi-h temperature applications.

The use of a ceramic or porcelain matrix can be applied to manufacture teapots, mugs, veg I I I etable dishes, tureens or other containers designed to retain heat in the food industry or any similar use. The use can be extended to sheet materials for lining coatincy, moulding to any shape for example hot water carrying pipes, furnace fumiture and structure such as furnace supports and fire clay bricks.

This technology can also be extended to metals. Therefore, in a seventh aspect., the present invention provides a material which comprises a substantially homogeneous mixture of particles suspended in a metal matrix. The particles can be inorganic or organlc. In the case of organic particles, the material can be fabricated using metal vapour technology. Alternatively, the metal coating is applied using metal suspensions and the like.

23) The present invention will now be explained in more detail by reference to the following non-limiting preferred embodiments and with reference to the accompanying drawinas, inwhich 17 Fiaure I shows a material in accordance with a second aspect of the present invention-, Flo--ure 2 shows another example of a material in accordance with a present invention" Fuzure 3 shows two exfoliated particles which can be used to produce the present invention; Flaure 4 shows a material in accordance with the second aspect of the present invention with crust formation; Fl--ure 5 shows reclaimed particles which can be used as a par-ticle in the present invention" Figure 6 shows a duct for electric cables or other services using a material in accordance with the present invention; Figure 7 shows end pieces for the duct shown in Figure 6, made of a material according to a second aspect of the invention-, Flaure 8 and Figure 9 show respective grommet sections of the duct shown in FIRure 6.

AV 2 4 Figure 10 shows a grommet suitable for use with the duct of Figure J-f Figure I I shows a grommet, for assembly with the duct of Figure 12 Flaure 12 shows the arrangement of plua grommet 29, 3 1, 32, 34, 40, 43 and 45 positioned at the forward end of a service duct-, Fieure 13 shows how two different size wires can be accommodated 'in a arommet,' Flaure 14 shows the openings allowing the body section to be pulled apart; Flaure 15 illustrates the rear plu- grommets corresponding to the arrangement of FiQure 12, Flaures 16 and 17 shows mirror images corresponding to the views of Figures I I and 14, Fisaure 18 shows a further example of a grommet design, Fl-ures 19, 20 and 21 show details of components of the grommet construction Z - of Figure 18 in perspective, Figure 22 shows an example of a duct casing suitable for use with the duct of F12ure 6 that has dimensions standardised to a standard buildina material e.a. brick size or its multiples, FN,ure 23 shows how the duct casinE of FiQure 22 can be incorporated into a wall, Ficure 24 shows how a plurality of ducts using a material according to the present invention may be incorporated into a wall.

Flaure 25 shows two roughened pieces of paper with straw particles in accordance with a aspect of the present invention; Fit,ure 26 shows the two pieces of paper of figure 25 partially formed; and FiLyure 27 shows the two pieces of paper of figures 25 and 26 joined.

Figure 28 shows a plurality of electrical cables housed in a material accordinz to a second aspect of the present invention; Ficrure 29 shows a steel airder which is coated with a material in accordance with the present invention, Flaure 30 shows a cooker hob which uses a material in accordance with the present invention as an insulator; and Fiszure ')I shows a flotation vessel in accordance with the present invention.

Flaures I and 2 show particles 201 which are coated with a matrix 203).

In Figure 1, the particles 201 were mixed with a bitumen based matrix 203. The particles were mixed usina a conventional mixer such as a paddle mixer or a worm screw type mixer. Both of these types of mixers aim coat all of the particles 201 - The particles were mixed until it was observed that they were all coated. For this example, 100 11tres water based bitumen was mixed with 980 i1tres of expanded polystyrene beads. The volume of the finished product is almost a 100% expanded polystyrene 20 1, 26 The matrix 20') Just coats the surface. Very little matrix 20') is located in the interparticulate spaces 205.

The examples shown in Figure 2 also use a bitumen matrix. However, here a larger volume of bitumen was used (compared to that discussed above) and a low melting point bitumen compound was used. The melting point of the bitumen compound is 800C. Therefore, the matrix can be liquefied by heating it to above 800C. 500 litres of viscous bitumen was mixed with 750 litres of expanded polystyrene. A solid end product was produced which had a homogeneous distribution of matrix and particles. The end product is ridged with little flexibility- However, in the slurry state, the mixture can be moulded to exactly the shape of the cavity or mould used. In contrast to Figure 1, the matrix 20' 3 is seen to occupy the inter-parilculate spaces 205. About 250 litres of the matrix 203 is situated in the inter-particulate spaces 205. For this example, the size of the beads was between Imm and 5mm.

The above two examples have been discussed in relation to bitumen. However, it would be appreciated by a person skilled in the art that it could be repeated using similar quantities of any suitable matrix discussed in this specification.

The quantity of the matrix used is controlled as a means of providing the properties of the finished product. If the matrix is the largest component, the coating will be heavy and the properties of the matrix material will predominate.

Flaure 3 shows two fibres 211 and 213. Many fabrics for clothing, household furnishings etc are produced by weaving fibres which are made by extrusion processes In F12ure 3a, fibre 211 has a controlled viscosity matrix which is mixed with the particles with a diameter of about 1im (( 0.54m). The m_ztrix and particle mixtures then extruded to form fibres. The particles here are exfot. _red particles. However, it is apparent to a person skilled in the art that any of the previous particles discussed in this speci I ication could be used. Fabrics made from the t pe of fibre 211 can be used as AO 1 27 thermal materials or flotation safety garments. The outer surface of fibre 211 has been teased to provide additional softness.

The fibre shown in Figure 3b is similar to that shown in Figure 3 a. However, fibre 213 has a smooth surface 215 as opposed to a teased surface 212.

Figure 4 shows a "smart-type" material 221 which forms a crust 223 when it is subjected to extreme heat. The smart type material 221 has an organic elastomeric matrix 225 suspended in this matrix are exfollated inorganic particles 227 such as perlite or vermiculite. When the material 221 is subjected to extreme heat eg. in a fire, the elastomeric matrix 225 oxidises and the particles 227 are released from the matrix 225. The released particles 227 form clumps of exfoliated material which stick toSZether to form a low density heat retardant barrier or crust 223). The formation of such a crust 223 retards the in-ress of heat into the deeper layers of the material 221. This has the effect of reducing the rate of damacye to the body of the material. Adjacent areas of the material remain unaffected. The crust 223) is only formed in areas of the material where the heat intensity is high enough to oxidise the elastomeric matrix 22 -5.

C The structures shown in Figures I to 4 show perfectly round particles. Figure 5 shows a material where the particles are reclaimed particles 23 1. Reclaimed particles do not have a round shape, The diameter of such particles is taken to be the width of a particle. The matrix 23') coats the outside of these particles. In this particular example, no matrix is seen in the inter-particle spaces 23) 5. See Ficr 1.

Figure 6 represents a schematic cross section of a duct for electric cables or other services. Item I is the casing of the duct in any shape or form, 2 and 3 are organically based matrix prepared end pieces through which, pass the electric cables to traverse the space in the duct. Items 4, 5 and 6 are electric cables or any other service traversing the space. The space 7 is filled with, a cement organic material with suspended polystyrene beads hereinafter referred to as "the crete material". Items 8 and 9 are vent holes for the egress of pressurled crete 1,-Inpr numped under 28 pressure via opening 10. Space 7 is full when the crete material emerges via 8 & 9. The crete material is allowed to set and the cavity is protected against fires migrating from one space via the cavity into the adjacent space or room.

Figure 7 represents a schematic arranoement of one of the two or2ancally prepared end pieces 2, 3 of Figure 1. The end pieces 1, 2, 3 are made from an assembly of individual pieces which are so designed that holes 13, 14 and 15 through the substance of the end pieces 2,3 separate any suitable distance across the traversing section but ideally across the diameter of the section. The holes 13, 14 and 15 can be any size shape or form and any number depending on the proposed use. One of the sections has an open access hole at the bottom of the assembly for pumping the crete material type slurry into cavity 7, Figure 6. As the slurry fills up the space 7, being under pressure, it emerges out of the only openings in the section at the vent holes 8 and 9, see FicTure 6. Flaure 7 demonstrates the component via which the "slurries" are pumped into the ducts at hole 17. Hole 16 is the vent hole allowing the displaced air to escape from the cavity space 7, Figure 1. Section I I is the body of the plug and items 13, 14 & 15 are holes for services. Item 12 of F12ure 7 is the grommet periphery abuttin!a the cavity in the structure.

F12ures 8 and 9 illustrate the four sections 18, 19, 23 and 24 in this unit which comprise the plug and allows explanations to the method of application. Figure 9 comprises the other of the two plug sections 23, 24 which does not have the injection hole in the bottom section of section 24. Installation of this desian is initiated by placing section 24 into duct I of Figure 6- The electric cables are then situated in the holes 25. The section 23 is placed above the cables. The cables are thus sandwiched between section 23 and 24. Fur-ther cables are sandwiched between section 23 and 19 as section 19 Is places above section 23) and pressed into position. Services are firmly 1'clam7td" bv the elastomeric properties of the matrix, in the holes 13, 1 It, 15 provided between sections 18, 19, 23 and 24. The final sta2e of installation is achieved bv positioning the services into holes 20 and compressing the last piece 18 of this arran2ement into the duct, see I of Figure 6. All the cable-, qre thus sandwiched in 29 between the pieces of the plug and because the plug material is made from the organic material the compressed plug form a tight plug holding the services in place and C. C.) separated from each other.

Provision is made for the non use of holes which might be surplice to need. If plugs are made with more holes than is required, a small plug designed to block off the hole is inserted into the hole instead of the cable.

Once both ends of the plug are positioned, the cavity is pumped full of organic matrix material and the assembly is left to set.

A most effective fire egress system is established by the above arrangement. Similar use can be applied, for gas or water or liquid tight plugs.

Modifications to the arrangement of end pieces and their components are possible. As an example, the forward plug end pieces (as shown in Figure 7), in addition to four or more members can be designed to have structural pieces complemented by any number of interchangeable "Grommets" that are designed with one or more holes through its substance to serve one or more of the services passing through it. The grommet is designed with a split section through the middle of its mass or however otherwise is the more convenient access for the service.

The grommet is basically a hinged gate type of structure that is designed to open along it's central axis to allow insertion of the services to be encased in the fire retardant material- As an example only Figure 14 illustrates a grommet 45 designed to accommodate oniy two services. The grommet 45 is split along it's axis 46 so that the two halves can open up like the pages of a book. The services are then inserted into the holes and the two halves of the grommet closed to enclosed the service member, The grommet 45 is then positioned in the plug assembly and the various members of the plug assembled to provide the arrancement in Figure 7. The plug forms a tight 'uncti j ion with services passing through the grommet suhstance to be tightly held place An%- number of grommets can be provided and different grommets can be designed to have different sized holes of any shape or form. The grommets can be of the same circumventional dimension or they can be of different sizes. Grommets can be desimed to be mirror images to provide symmetry in the alignment of services. A service passing through the front grommet emerges in the same line through the back plug grommet. The grommets can for ease of alignment and assembly have additional features. The provision of a tongue and groove arrangement so that as the individual members of the pluc, are assembled, they slot into the tongue and groove sections to sit In line within the opening and exit holes of the service duct, The assembly of the forward and back plugs is similar. In Figure 12 the pluo, section 29 is positioned at the bottom of the containing service duct. Sections 3 1 and 34 are then placed in the perpendicular position and the grommets assembled with the services passing through the holes. Finally section 32 is forced into position to complete the assembly and form a tight junction to close off the opening of the duct.

j I - The procedure is repeated for the back plug (Figure 15).

The arommets are designed to accommodate services and in the case of electrical wiring the grommet in Figure 13 allows two different sized wires to be accommodated. Holes 41 allow a tlQht fit for a aiven size and holes 39 and 40 allow for a lar2er wire or service to pass through the substance. The body of the grommet 3 8 is a one piece arommet that has slits alon- the central axes of the accommodatino- hole so that the sections of the arommet can be lifted open to allow positioning of services. Figure I I demonstrates a three section grommetvvith the sectioned component 42 separating the sections 43) and the third section.

FiLyure 14 illustrates the openings 46 and 47 that allows the body section45 to be pulled apart to allow the positioning of services Figure 15 illustrates the back plug of the unit. Sections 49 to 52 comprise the mirror ima2e of the front plug design- Grommets 57 in Figure 10. 58 Figure 16 and 59 1 -- - in Flaure 17 illustrate mirror image sections that complement the grommets in the front plug. Item 30 in Figure 12 is a hole via which is Injected the fire retardant the crete j material or an-,,, of the other suitable fire retardant materials which are preferred such as the mixtures of the organic and inorganic materials specified earlier In both the front and the back plug there are bleeder holes, Figure 12, Item 33 and Figure 15 item 56, that allow the displaced air to vent out of the duct. The cavity in between the plugs is pumped full of the fire retardant material.

The 5zrommet desi2n will be dictated by the dimensions and configurations of the duct desians. It is intended to provide a complete system for the prevention of ifire egress form one compartment into another. The pro-,, isiori of specially designed ducts in co-operation with the service installation industry and in consideration of their requirements, might be optimised into one or multiples oil ducts assembled into partitioning Xk7 alls. The provision of the fire retardant "smart" organic matrix grommets and the Styrocrete will provide a permanent fire check at these points. A further example of grommet design is illustrated in Figure IS.

Styrocrete pumping access is achieved via 61 and terminated when the pumped material of choice emerges under pressure from 68. Service containina arommet 62, 63, 64, 651'66, 67 are arranged in any combination required by the ser-"Ice industries.

Three dimensional grommet presentation is demonstrated in Figures 19, 20, and 2 1 Items 69, 70 and 71 respectively, The duct castric, can be of any thickness, shape or form. and can be made from anv suitable material, metal, synthetic, or composite substances available to the inclustry In Figure 22, and as an example only, a rectangular box shape 100 is illustrated that is desione I I d to fit standard building material construction technology FlQure 23 illustrates the rectanaular metal box incorporated Into a %vall built of standard buildina blocks. The h1nrk-9 arp hiolt accordin2 to standard re2ulanoris and a 32 box is installed at the desired level in the wall. Mortar 74, is used to build in the box as illustrated and the block 72, construction continued along and above service duct box. The metal duct 73, accommodates the services passing from one compartment into another. The services are circumvented by the grommets 75 and 78, each as an example only, providing four opening 76, 79. The grommets open via slits e.g. 77 and are assembled within the duct according to site requirements.

In Flaure 2':) the smaller arommet is established at the top of the duct and being separated at 80 from the lower grommet. Once the services are installed Styrocrete concept material of choice is pumped into the duct via hole 81 and once the material emerges under pressure at 82 the compartment is full. The fire retardant material is allowed to set and the service will provide a permanent fire check- The designed ducts can be made to any specification required and where desirable a composition of ducts can be assembled.

Fic,ure 24 illustrates as an example only, a multiple arrangement of 6 ducts 8'), 84, 85, 86, 87and 88, built into a wall. The use is similar to the above description as in Figure 18 but allows for many more services to pass through the wall.

Ficures 25, 26 and 27 show an example of another embodiment of the present invention. Sheets of paper I and 2 are roughened on one side to release fibres of cellulose 3. Straw particles are sprinkled onto the surface and are trapped within the feltwork fibre 3. The straw particles 4. are trapped within the feltwork fibres 3 and interspersed with trapped air volumes 5.

Fizure 26 demonstrates the compounding of materials into double sided sheets. Sheets I and 2 are brouaht to2ether to form a sinQle sheet of material between which are trapped particles of the absorbent material Figure 26 demonstrates the compiling of sheets I and 21, in trapping within the cellulose fibre 3, the straw particles 4. The 33 feltwork also creates a large number of air volumes 5 which are Interspersed amongst the fibres.

Figure 27 demonstrates the completed article which in its various forms can act as an emergency mopping up product for spillages.

CD Figure 28 shows a plurality of electrical cables 301, The plurality of cables are incased in a smart material 303 (such as that described with reference to Figure 4). The particles used here contain an expandable substance such as an inert aas or water. If the cable is exposed to extreme heat, the particles move to the surface (as explained with relation to fi2ure 4). However, the particles also release either the inert gas or water. This provides a further barrier to the progress of the fire.

Fi-ure 29 shows a steel girder 31. 1 which is coated 313) by brush, trowel or spray technology with a smart material (as explained with reference to figure 4).

Figure 30 shows a cooker hob 341. The hob is separated from the surface of the C cooker 343 via a steel finishino, member 345 and an insulator member 347. The 0 insulatinc, member 347 is made from exfollated inorganic particles in a ceramic clay. fire clay or calcium alumina cement matrix.

Flaure ') I shows a flotation vessel 35 1. The flotation vessel has a carrying space 353 and two flotation members 355 and 357. Flotation chamber 355 and 357 are filled with an orcanic matrix material such a bitumen which is mixed with expanded polystyrene particles. An additional flotation chamber 359 which is at the base of the vessel can also be filled with the low intensity material if extra buoyancy is required.

Flotation vessel 351 can be used to carry passengers safely, manufacture of unsinkable z rescue vessels, recreation boats, commercial applications whereby booms. buoys and other maritime equipment., displacement members for flotation strucrures etc.

1 -4 Low Density Materials The refinement of industrially scaled quantities continues and the results of the finished product analyses show that the mix is commercially valid.

In the commercial quantities regime one part high alumina cement is mixed with 3.2 parts of exfoliated clay (Fibo) and 2.8 parts of brick or crushed volcanic ash (Basalt) or similar or other usable commercially available refractory grade materials were mixed in a paddle mixer for 90 seconds and just enough water added to produce a mix that was transferred into a block manufacturing machine. The machine produced building blocks of 440 215 100mm. nominal dimensioned blocks that were allowed to set. Samples of these blocks were crushed at intervals, see enclosed graph, and the crushing strength recorded. The blocks were then transferred int a kiln heated to one thousand degrees centigrade and the blocks heated for 24 hours.

The above mix was made with refractory grade materials and was seen to withstand high temperatures for a prolonged period. The ratio:

1 6 HAC Fondu Mixed aggregate (low density) was seen to be suitable for the manufacture of the high temperature tolerating cements.

It was also confirmed by the above procedure that a similar mixture but using sand or limestone as the fines material component in the nix, was not suitable for high temperature tolerating building material. The chemistry of the limestone broke down and the building material failed in use. similarly it was seen that the sand used was also unstable at high temperature. The chemistry of the sand molecules was unstable at high temperature and the material failed in use.

Building materials used for high temperatures therefore must use components all of which are capable of tolerating high heat stress, if the total material composition is to withstand high heat stress.

3 The tested technology therefore is well suited to tolerating high heat-, stress in whatever form it is composited. As an example only, the walls that are intended to be built using high heat tolerating building blocks using exfoliated backed clays mixed with crushed brick or volcanic fine materials in the above ration, can be extended to producing similarly batched materials but made entirely from the fine grade of material, ie. a mixture of materials whose particle size is 3mm to dust in diameter. Depending on the crushing strength of the finished product, the ratio of materials can be varied within certain parameters. In all cases it is aimed in the specified technology to produce a mortar that is made from the same ration of components as that used for the building block. The intention is to produce materials that have similar coefficients of expansion so that as the structure is subjected to high heat stress all the components of the structure will expand and contract at a similar rate. This compatibility of materials will reduce the rate of cracking in any fire as the materials are subjected to heat stress.

As a further extension to the concept the renders and plasterers used in conjunction with these blocks and mortars can also be made from a similar fines material so that the render also has high heat tolerating properties.

-3'7 The number of products designed to tolerate high heat stress can be extended to provide a great number of building materials and as a further example only, plasterboard can also be made from the above fines mix. In this case the boards so produced will be used for permanent fire retardant check for partitions, lining of other materials or forming ceilings etc.

Test data is available to confirm thst materials produced in this way tolerate high temperatures for prolonged periods. As an example only, a buiding block was heated for 24 hours, continuously, at 10000c, and tested for structuarl integrety. The block did not suffer in any way because of exposure to the heat stres.

The crushing strength of these blocks is summarised in Graph 1.

Claims (1)

1. CLAIMS:

   Y I A material comprising a substantialk homogeneous mixture of particles and an orc,anic material which serves as a matrix and binder for the particles, wherein the particles have a diameter of less than _5 mm.

   1) A material accordina to claim 1, wherelin the particles are inorganic.

   3. A material accordinsz to claim 2, %vherein the particles are vermiculite or perlite 4 A thermally insulating material comprising a substantially homogenous mixture of hydrocarbon particles suspended in a ceramic matrix.

   A material accordino to anr precedin!4 claim, wherein the diameter of the particles is bet-,,,-een 0.5 mm and 1.5 mm 6. A material according to any precedinQ claim, wherein the particles make up between 215 1/0' and 99.5 1/"0 of the total volume of the compound.

   / 7 A material accordincr to ariv precedina claim, wherein the particle is a carrier containing an expandable substance.

   8, A material accordInQ to claim 7, wherein the expandable substance is water or an inerl 2as.

   9 A material according to any prececina claim, wherein the matrix is bitumen I ID A flotation vessel, comprisina a material in accordance with any of claims I to 11. An end piece for cable ducting comprising a block of material according, to anV of claims I to 9, with at least one hole through the block of material for insertion of a cable therethrough.

   12. An end piece according to claim 11, wherein the block of material comprises two separable sections which abut along a line of attachment and said at least one hole lies on said line of attachment.

   1 1). An end piece according to claim 12, wherein the block of material comprises more than two separable sections and said holes lie on the lines of attachment of the separable sections.

   14. An end piece according to claim 11, wherein the block of material comprises two sections which a hingeably mounted to one another such that the two sections meet at a line of attachment and said at least one hole lies on the line of attachment.

   15. An end piece according to claim 14, wherein the block of material comprises more than two separable sections and said holes lie on the lines of attachment of the separable sections.

   16 A material according, to any of claims I to 9, wherein the matrix comprises two sheets which face one another, the surfaces of the sheets which face one another being rough, and the particles being dispersed on the roughened faces of the sheets.

   17. A material according to claim 16, wherein the matrix is paper and the particles are stra%v.

   18. A material comprising a substantially homogeneous mixture of particles suspended in a metal matrix.

   19. A material according to claim 18 wherein the particles are inorganic exfollated particles.

   20. A method of making a low density material comprising the step ff mixing particles of inorganic or organic material with a diameter of less than 5mm with an organic component which serves as a matrix and binder.

   21. A method accordin2 to claim 20, wherein the onzanic component which serves as a matrix is water based bitumen.

   A method accordina to claim 2 1, wherein the water based bitumen forms between 5 and 15% of the total volume of the bitumen and particles.

   23. A method accordina to claim 20, wherein the or2anic component Nvhich serves as a matrix is a bitumen compound with a melting point of between 70'C - 90'C, the method further comprising, the step of heating the bitumen compound to above melting point prior to the step of mixing C!, 24, A method accordin2 to claim 23, wherein the bitumen compound forms between 30% to 40% of the total volume of the mixture.

   2 5 - A method accordin2 to claim 20, wherein the organic matrix is provided by a silicon based rubber composite and the particles are an inorganic exfoliated material, the inoroanic exfollated mixture forming between 40% and 60% by volume of the total mixture- 26. A method according to claim 20, wherein the particles are inorganic particles and the or-anic component is tar, the method further comprising the step of heating the tar to over IOOOT in an inert atmosphere prior to the step of mixing.

   q<( 27. A method of making a low density material, the method comprising the steps of a) mixing cement powder with water to form a mixture; b) adding organic or an inorganic particles to the mixture; and heating, the product of (b) to drive off the excess water.

   28. A method accordinc, to claim 27, wherein the product of (b) is heated to above 600C.

   29. A method accordina to claim 26, wherein the cement is calcium aluminate 1:1 cement and the product of (b) is heated to a temperature in the range of 70'C to 900C.

   10.

   A method according to claim 28, wherein the cement is Portland cement and the product of step (b) is heated to a temperature in the range of 170--C to 190'C, 31. A method according to any of claims 27 to 30 wherein the method further comprises the step of adding an accelerator to the process.

   3) 2. A method accordina to claim 3 1, when dependent on claim 29 wherein the "n, accelerator is Lithium Carbonate.

   33. A method according to claim 32 wherein bemeen 0.04% and 0.06% of lithium carbonate accelerator is added.

   34. A material as substantially hereiribefore described with reference to the accompariving drawings.

   Z Z