CA2161279A1 - Pyrotechnic sheet material - Google Patents
Pyrotechnic sheet materialInfo
- Publication number
- CA2161279A1 CA2161279A1 CA002161279A CA2161279A CA2161279A1 CA 2161279 A1 CA2161279 A1 CA 2161279A1 CA 002161279 A CA002161279 A CA 002161279A CA 2161279 A CA2161279 A CA 2161279A CA 2161279 A1 CA2161279 A1 CA 2161279A1
- Authority
- CA
- Canada
- Prior art keywords
- layer
- substrate
- oxidizable
- gas
- generating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06C—DETONATING OR PRIMING DEVICES; FUSES; CHEMICAL LIGHTERS; PYROPHORIC COMPOSITIONS
- C06C9/00—Chemical contact igniters; Chemical lighters
-
- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component
- C06B45/20—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an organic explosive or an organic thermic component
- C06B45/22—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an organic explosive or an organic thermic component the coating containing an organic compound
- C06B45/24—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an organic explosive or an organic thermic component the coating containing an organic compound the compound being an organic explosive or an organic thermic component
-
- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/12—Compositions or products which are defined by structure or arrangement of component of product having contiguous layers or zones
- C06B45/14—Compositions or products which are defined by structure or arrangement of component of product having contiguous layers or zones a layer or zone containing an inorganic explosive or an inorganic explosive or an inorganic thermic component
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Laminated Bodies (AREA)
- Automotive Seat Belt Assembly (AREA)
Abstract
The invention provides pyrotechnic sheet material comprising a substrate of oxidizing polymeric film, for example a film of halogenopolymer, having a coating layer of oxidizable material, for example magnesium, on at least part of its surface, the substrate and the oxidizable material being conjointly capable of reacting together on ignition. Overlying at least a portion of the surface area of the substrate and/or the oxidizable material is a layer of gas-generating deflagrating material, for example a nitrocellulose propellant, which may for example be an adherent layer or a separate layer such as a co-rolled layer.
The deflagrating material enhances the flame transmission properties and igniting ability of igniferous booster charges comprising the pyrotechnic sheet material. It also protects the oxidizable material from atmospheric oxidization.
The deflagrating material enhances the flame transmission properties and igniting ability of igniferous booster charges comprising the pyrotechnic sheet material. It also protects the oxidizable material from atmospheric oxidization.
Description
~EC 40320/50059 - 21~1279 PYROTEC~NIC ~ H 1~.~; l MATERIAL
Field of Invention This invention relates to gas-generating pyrotechnic sheet material which is especially useful in igniferous booster charges (hereafter termed ignition elements or igniters) for propellant compositions. In vehicle occupant restraint safety systems the material may be 5 used advantageously in ignition elements for gas-generating compositions for gas-bag ("air bag") infiation and heating elements for heating stored gas in hybrid inflators. The invention also relates to the method of m~nllf~cturing said pyrotechnic sheet material.
Back~round of Invention Pyrotechnic sheet material consisting of one or more substrate layers of oxidizing polymeric film having a layer of oxidizable material, preferably metal, on at least a portion of at least one surface of the, or each, substrate layer, the polymeric film and the oxidizable material being conjointly capable of reacting together exothermically on ignition, has been described in PCT International Publications Nos WO 90/10611 and WO 90/10724.
15 Improved pyrotechnic sheet material having enhanced burning rate has been described in United Kingdom patent specification No. C~B 2,282,136A.
The use of the aforesaid pyrotechnic sheet material to ignite a gas-generating propellant charge for air bag inflation has been described in European patent publication no.
505024.
The pl~relled oxidizing polymeric film is halogenated film such as polytetrafiuoroethylene containing little if any hydrogen and the pl erell ed oxidizable material of the aforedescribed pyrotechnic sheet material comprises a metal selected from the group consisting of lithium, sodium, m~gn~ m, beryllium, calcium, strontium, barium, aluminium, titanium, zirconium, and alloys of any one or more thereof, the most preferred metal being magnesium. Advantageously the metal is vapour-deposited on the film by known methods, the amount of metal being preferably subst~nti~lly stoichiometric at the location of the film underlying the metal. On ignition this pyrotechnic sheet material produces substantially only solid products, any gases such as metal fluoride produced in the combustion zone 21~ 1279 inct~nt~neously ct nden.~ing to solid form. Such gasless material is advantageous in certain applications where blast effects must be avoided, but in applications where the material is primarily required to propagate ~ame to a further charge of combustible material the absence of gaseous products can be a disadvantage.
s Summary of Invention We have now found that the ease of igr~ition and flame tr~n.~mi~sion properties of the aforedescribed pyrotechnic sheet material can be enhanced by providing the sheet with a cont~ctin~: layer of gas-generating de~agrating material. The res-~ltin~ pyrotechnic sheet has the fast burning rate of the original material and also produces gas which rapidly travels to, 0 and penetrates, any ignitable gas-generating main charge in contact with the sheet material, thereby accelerating the ignition of the main charge. In addition to Pnh~ncin~ the flame tr~n~mi~ci~n capability, the layer of deflagrating material can also act as a protective barrier material to prevent or retard oxidation of a layer of oxitli7~ble material such as m~gnPsillm which oxidizes at a significant rate under normal atmospheric conditions. When Pnh~nced 5 ease of ignition only is required this effect can be achieved by the application of the deflagration material over a small portion of the pyrotechnic sheet material adjacent to an ignition point and the amount of deflagrating material need not be sufficient to produce a significant amount of gaseous products on combustion.
Thus, in accordance with this invention pyrotechnic sheet material comprises a substrate of 20 oxidizing m~tPri~l; a coating layer of oxidizable material on at least a portion of at least one surface of said substrate, the said substrate and the said layer of oxi(li7.~ble material being conjointly capable of reacting together exothermically on ignition; and a layer of gas-generating deflagrating material overlying at least a portion of the surface area of the substrate and/or the layer of oxidizable material, said deflagrating material being in ignition 25 ~l~n.~",;c~ion relationship with said substrate and oxidizable material. Deflagrating material in this context refers to material capable of sustained rapid burning without reaction with further oxidizing or red~lcing material.
The gas-generating deflagrating material may be applied as an adhering layer to the substrate and/or the layer of oxidizable material or it may be provided as a separate layer over 30 a free surface ofthe substrate and/or the oxi(li7~hle m~P.n~l, for example as a co-rolled sheet.
21fi 127~ -~_ 3 The substrate may advantageously be coated on both sides with oxidizable material and at least a portion of at least one of the layers of oxidizable material may advantageously be covered with a layer of gas-generating deflagrating material.
The gas-generating deflagrating material may, for example, comprise any gas-5 generating propellant material. A nitrocellulose based propellant is advantageous andconvenient and may, for example, be applied to the film or oxidizable material as a separate sheet in laminar pyrotechnic sheet material of the invention, or as a solution in a solvent, for example ~cetonP, which is subsequently removed to leave an adherent layer of nitrocellulose propellant material on the film or oxidizable material. Other gas-generating propellant 0 materials which may be used include deflagrating materials such as black powder, sodium a_ide/oxidizer compositions, potassium perchlorate/~ minil~m compositions or other solid pyrotechnic gas-genel~Ling composition. These may be applied over the coated substrate as a solution or dispersion in a carrier liquid which can be removed, or in a curable liquid polymer or in a polymer solution, such as polymelhylLlin~loroethylene in acetone or 1S polyvinyl~cet~te in water, from which the solvent can subsequently be removed.
The layer of gas-genel~Ling de~agrating material is conveniently from 3-100 microns thick and preferably from 10-40 microns thick.
The plerelled oxi~i7.ing substrate comprises polymeric film preferably co~ g atoms chemically bound therein selected from the group con~i~ting of halogens (especially 20 fluorine), oxygen, sulphur, nitrogen and phosphorous. One prerel,ed film substrate comprises fluoropolymer such as polytetrafluoroethylene (PTFE) which produces a high energy pyrotechnic sheet, but other suitable polymeric films include those comprising polychlorotrifluoroethylene, polyhexafluoropropylene, copolymers of trifluoroethylene and hexafluoropropylene, copolymers of trifluoroethylene and tetrafluoroethylene, copolymers 25 of hexafluoropropylene and tetrafluoroethylene, copolymers of hexafluoropropylene and vinylidene fluoride, copolymers of tetrafluoroethylene and partially fluorinated propylene, copolymers of chlorotrifluoroethylene and vinylidene fluoride, homopolymers of partially fluorinated propylene, copolymers of partially fluorinated propylene and vinylidene fluoride, - ~`J.61279 trichloroethylene homopolymers, copolymers of trichloroethylene and vinylidene fluoride, mixtures oftwo or more of such polymers or mixtures of any one or more of such polymers with PTFE.
The polymeric film may optionally be a porous film, the pores advantageously occupying 6-95% of the film volume (i.e. porosity of 6-95%). Preferably the pores are interconnecting vapour-permeable pores having at least part of the oxitli7.~ble material vapour-deposited therein. Pyrotechnic sheet material comprising such porous film generally has faster burning rates than that cont~ining only solid polymeric film.
A preferred pyrotechnic sheet of the invention has discontinuous portions in the0 oxidizing substrate and/or the layer of oxidizable material, preferably in the oxidizable material, these portions having flame-permeable apertures through which the interface between the o~ in~ substrate and the oxidizable material is exposed as described in United Kingdom patent specific~tion no.GB 2,282,136A which is incorporated herein by reference.
Such exposure of portions of the interface enhances the ease of ignition and rate of combustion of the pyrotechnic sheet. In an especially ple~lled pyrotechnic sheet the substrate and the oxidizable material are permanently deformable and have di~lenl strains for rupture value thereby enabling one ofthe materials to be ruptured by stretching to expose flame-permeable apertures at the interface. The stretching may advantageously be effected by st~mping protrusions (embossing) on the contacting substrate and layer of oxidizable material, the protrusions subsequently serving as spacer elements to ~nh~nce the rate of combustion of the pyrotechnic sheet material.
The oxidizable material may advantageously comprise metal selected from the group consisting of lithium, sodium, magnesium, beryllium, calcium, strontium, barium, ~ minillm, titanium, zirconium and alloys thereof, which metal may be advantageously be vapour-2s deposited on the substrate. A metal layer is especially advantageous as it significantly enhances the dimensional stability of the pyrotechnic sheet and is easily ruptured. A most preferred metal for high heat generation is magnesium or an alloy thereof preferably coated on to a substrate film comprising fluoropolymer. Preferably the ratio of metal to the substrate of ~itli7in~ polymeric film is substantially stoichiometric or there is a small excess s of metal at the location of the film underlying the metal. The reaction between PT~E and magnesium can be represented empirically as (C2F4)n - 2nMg --> 2nMgFz + 2nC
This reaction releases 5.98 megajoules/kilogram of reactant pyrotechnic material.
s The rate of energy release on ignition varies inversely with the thickness and directly with the porosity of the pyrotechnic sheet material and, accordingly, the thickness and porosity will be chosen to attain the desired energy release. Thus the pr~rel,~;d polymeric film will generally have an areal mass of 10 to l50g/m2, typically 25-75g/m2 and the total amount ofthe oxidizable m~t~.ri~l will be equivalent to a laminar thickness of 2 to 30 microns, 0 typically 4 to l S microns.
A typical pyrotechnic sheet comprises a film of halogenopolymer 3 to S0 microns,(preferably 10 - 30 microns) thick having on each side a vapour-deposited layer of magnesium 2 to 40 microns (preferably 4 - 15 microns) thick each m~gnesi~lm layer being overlaid with a cont~cting layer of gas-ge~ li"g defiagrating material 10 - 40 microns thick.
The invention also includes a method of m~nl-f~cturing a pyrotechnic sheet material which comprises depositing a layer of oxidizable material on at least a portion of at least one surface of a substrate of oxidizing material, the substrate and the oxidizable material being conjointly capable of reacting together exothermically on ignition, and applying to at least a portion of the surface of the oxidizable material and/or the substrate an overlying layer of gas-generating deflagrating material in ignition tr~n~mi~sion relationship with said substrate and oxidizable material.
Ple~l~bly the o~i~li7~ble material is vapour-deposited at low pressure on the polymer substrate by direct evaporation or magnetron sputtering.
Brief description of the drawing The invention is further described by way of example only with reference to the accompanying drawing which is a diagrammatic perspective, part-sectional view ofpyrotechnic sheet material of the invention.
~Z1612~ -Detailed description of the drawin~
Referring to the drawing, pyrotechnic sheet material design~ted generally by thenumber 10 consists of a substrate 11 of oxidizing polymeric film, for example ofpolytetrafiuoroethylene, coated on each side with a vapour-deposited layer of oxidizable 5 metal for example magnesium 12. Each layer of oxidizable metal is coated with a layer of gas-generating deflagrating material 13 .
Specific Examples The m~nl-f~ctllre of the pyrotechnic sheet material of the invention is further described in the following specific Examples wherein parts and percentages are given by 0 weight.
Example 1 A 25 micron thick solid sheet of P lF~ was coated on each side with an 8.5 micron thick vapour-deposited layer of m~gn~.~illm (appluxil"ately stoichiometric proportions). The coated sheet was embossed with regular rows of dimples by passing the sheet between a 15 patterned metal roll and a plain rubber roll. The dimples were spaced at 3rnm centres in each direction and each dimple was approximately 0.75mm square at the base, O.5mm square at the top, and 0.25mm high. The upper layer of magnesium was thereby ruptured around the periphery of the top of the dimples to expose the oxidizing polymeric film at the m~gnesillm/PTFE upper interface, the width ofthe exposed areas being up to 10 microns.
A sample portion of the embossed sheet having an area of 164 cm2 was coated witha solution in acetone of nitrocellulose, having a nitrogen content of 12.2%, and the acetone was evaporated offto leave a continuous contacting film of nitrocellulose over the layers of m~gnesium.
2s The sample was rolled into a helically wound charge assembly by winding around a central tubular phenolic resin former having an internal diameter of 6mm and 6mm wall thickness. Three longi~l~in~l slits e~P.n~ing to within lOmm from each end of the charge were cut through the spiral section of the pyrotechnic sheet. The assembled charge was ignited by a squib in a combustion test vessel (ballistic bomb) having a volume of 3 Scc.
21612~9 The pressure in the vessel after ignition was recorded. A sample coated with 0. lg nitrocellulose gave a maximum pressure of 22.1MPa in 2.02 milliseconds and a sample coated with 0.21g nitrocellulose gave a maximum pressure of 27.9MPa after 1.84 milliseconds. In a compa,~live test a sample without a nitrocellulose coating gave a s maximum pressure of 20MPa after 2.03 milliseconds.
These results clearly demonstrate the improved pressure (gas production) obtained with the nitrocellulose coated material.
Example 2 0 A pyrotechnic sheet comprising 25 micron thick PT~E film coated on each side with an 8.5 micron thick vapour-deposited layer of m~gn~.sjllm was prepa~ed and embossed as described in Example 1. A 10.61g sample of the embossed sheet was cut to the shape of a trapesium with opposite parallel sides having respective lengths of 150mm and 118mm and a length of 0.8 metres between opposite equal sides. The sample was coated on each side with a slurry co~ i";,lg 4 parts sodium azide, 0.065 parts carbon black, 1.81 parts vinylidene fluoridefhPx~fl-lolopl~ylene copolymer (binder and oxidizer for the sodium azide) available under the registered trade mark ~ITON and 8.37 parts ethyl acetate. The ethyl acetate was removed by evaporation leaving 3.09g of residual coating material. The sample was wound around a 12mm .I;~ ler tubular phenolic resin former with the shorter parallel edge on the side and inserted into a 28mm tli~met~.r x 11.7mm long thin steel tube leaving about 15mm at each end of the sample protruding beyond the steel tube. Each protruding end was 'petalled' by making 6 equally spaced longit~l~in~l cuts around the circumference, each cut extending to lcm from the end for a length of 15mm.
Two such wound samples were placed in proxi"Ji~y in a ballistic bomb having a volume of 7100 cc and ignited .~imlllt~neously at the end of one sample. A m~im~lm pressure of 1.6MPa was reached in 81.7 milliseconds.
In a comparative test two 16.51g samples of the uncoated pyrotechnic sheet generated a pressure of 1.4MPa in 103 milliseconds.
Field of Invention This invention relates to gas-generating pyrotechnic sheet material which is especially useful in igniferous booster charges (hereafter termed ignition elements or igniters) for propellant compositions. In vehicle occupant restraint safety systems the material may be 5 used advantageously in ignition elements for gas-generating compositions for gas-bag ("air bag") infiation and heating elements for heating stored gas in hybrid inflators. The invention also relates to the method of m~nllf~cturing said pyrotechnic sheet material.
Back~round of Invention Pyrotechnic sheet material consisting of one or more substrate layers of oxidizing polymeric film having a layer of oxidizable material, preferably metal, on at least a portion of at least one surface of the, or each, substrate layer, the polymeric film and the oxidizable material being conjointly capable of reacting together exothermically on ignition, has been described in PCT International Publications Nos WO 90/10611 and WO 90/10724.
15 Improved pyrotechnic sheet material having enhanced burning rate has been described in United Kingdom patent specification No. C~B 2,282,136A.
The use of the aforesaid pyrotechnic sheet material to ignite a gas-generating propellant charge for air bag inflation has been described in European patent publication no.
505024.
The pl~relled oxidizing polymeric film is halogenated film such as polytetrafiuoroethylene containing little if any hydrogen and the pl erell ed oxidizable material of the aforedescribed pyrotechnic sheet material comprises a metal selected from the group consisting of lithium, sodium, m~gn~ m, beryllium, calcium, strontium, barium, aluminium, titanium, zirconium, and alloys of any one or more thereof, the most preferred metal being magnesium. Advantageously the metal is vapour-deposited on the film by known methods, the amount of metal being preferably subst~nti~lly stoichiometric at the location of the film underlying the metal. On ignition this pyrotechnic sheet material produces substantially only solid products, any gases such as metal fluoride produced in the combustion zone 21~ 1279 inct~nt~neously ct nden.~ing to solid form. Such gasless material is advantageous in certain applications where blast effects must be avoided, but in applications where the material is primarily required to propagate ~ame to a further charge of combustible material the absence of gaseous products can be a disadvantage.
s Summary of Invention We have now found that the ease of igr~ition and flame tr~n.~mi~sion properties of the aforedescribed pyrotechnic sheet material can be enhanced by providing the sheet with a cont~ctin~: layer of gas-generating de~agrating material. The res-~ltin~ pyrotechnic sheet has the fast burning rate of the original material and also produces gas which rapidly travels to, 0 and penetrates, any ignitable gas-generating main charge in contact with the sheet material, thereby accelerating the ignition of the main charge. In addition to Pnh~ncin~ the flame tr~n~mi~ci~n capability, the layer of deflagrating material can also act as a protective barrier material to prevent or retard oxidation of a layer of oxitli7~ble material such as m~gnPsillm which oxidizes at a significant rate under normal atmospheric conditions. When Pnh~nced 5 ease of ignition only is required this effect can be achieved by the application of the deflagration material over a small portion of the pyrotechnic sheet material adjacent to an ignition point and the amount of deflagrating material need not be sufficient to produce a significant amount of gaseous products on combustion.
Thus, in accordance with this invention pyrotechnic sheet material comprises a substrate of 20 oxidizing m~tPri~l; a coating layer of oxidizable material on at least a portion of at least one surface of said substrate, the said substrate and the said layer of oxi(li7.~ble material being conjointly capable of reacting together exothermically on ignition; and a layer of gas-generating deflagrating material overlying at least a portion of the surface area of the substrate and/or the layer of oxidizable material, said deflagrating material being in ignition 25 ~l~n.~",;c~ion relationship with said substrate and oxidizable material. Deflagrating material in this context refers to material capable of sustained rapid burning without reaction with further oxidizing or red~lcing material.
The gas-generating deflagrating material may be applied as an adhering layer to the substrate and/or the layer of oxidizable material or it may be provided as a separate layer over 30 a free surface ofthe substrate and/or the oxi(li7~hle m~P.n~l, for example as a co-rolled sheet.
21fi 127~ -~_ 3 The substrate may advantageously be coated on both sides with oxidizable material and at least a portion of at least one of the layers of oxidizable material may advantageously be covered with a layer of gas-generating deflagrating material.
The gas-generating deflagrating material may, for example, comprise any gas-5 generating propellant material. A nitrocellulose based propellant is advantageous andconvenient and may, for example, be applied to the film or oxidizable material as a separate sheet in laminar pyrotechnic sheet material of the invention, or as a solution in a solvent, for example ~cetonP, which is subsequently removed to leave an adherent layer of nitrocellulose propellant material on the film or oxidizable material. Other gas-generating propellant 0 materials which may be used include deflagrating materials such as black powder, sodium a_ide/oxidizer compositions, potassium perchlorate/~ minil~m compositions or other solid pyrotechnic gas-genel~Ling composition. These may be applied over the coated substrate as a solution or dispersion in a carrier liquid which can be removed, or in a curable liquid polymer or in a polymer solution, such as polymelhylLlin~loroethylene in acetone or 1S polyvinyl~cet~te in water, from which the solvent can subsequently be removed.
The layer of gas-genel~Ling de~agrating material is conveniently from 3-100 microns thick and preferably from 10-40 microns thick.
The plerelled oxi~i7.ing substrate comprises polymeric film preferably co~ g atoms chemically bound therein selected from the group con~i~ting of halogens (especially 20 fluorine), oxygen, sulphur, nitrogen and phosphorous. One prerel,ed film substrate comprises fluoropolymer such as polytetrafluoroethylene (PTFE) which produces a high energy pyrotechnic sheet, but other suitable polymeric films include those comprising polychlorotrifluoroethylene, polyhexafluoropropylene, copolymers of trifluoroethylene and hexafluoropropylene, copolymers of trifluoroethylene and tetrafluoroethylene, copolymers 25 of hexafluoropropylene and tetrafluoroethylene, copolymers of hexafluoropropylene and vinylidene fluoride, copolymers of tetrafluoroethylene and partially fluorinated propylene, copolymers of chlorotrifluoroethylene and vinylidene fluoride, homopolymers of partially fluorinated propylene, copolymers of partially fluorinated propylene and vinylidene fluoride, - ~`J.61279 trichloroethylene homopolymers, copolymers of trichloroethylene and vinylidene fluoride, mixtures oftwo or more of such polymers or mixtures of any one or more of such polymers with PTFE.
The polymeric film may optionally be a porous film, the pores advantageously occupying 6-95% of the film volume (i.e. porosity of 6-95%). Preferably the pores are interconnecting vapour-permeable pores having at least part of the oxitli7.~ble material vapour-deposited therein. Pyrotechnic sheet material comprising such porous film generally has faster burning rates than that cont~ining only solid polymeric film.
A preferred pyrotechnic sheet of the invention has discontinuous portions in the0 oxidizing substrate and/or the layer of oxidizable material, preferably in the oxidizable material, these portions having flame-permeable apertures through which the interface between the o~ in~ substrate and the oxidizable material is exposed as described in United Kingdom patent specific~tion no.GB 2,282,136A which is incorporated herein by reference.
Such exposure of portions of the interface enhances the ease of ignition and rate of combustion of the pyrotechnic sheet. In an especially ple~lled pyrotechnic sheet the substrate and the oxidizable material are permanently deformable and have di~lenl strains for rupture value thereby enabling one ofthe materials to be ruptured by stretching to expose flame-permeable apertures at the interface. The stretching may advantageously be effected by st~mping protrusions (embossing) on the contacting substrate and layer of oxidizable material, the protrusions subsequently serving as spacer elements to ~nh~nce the rate of combustion of the pyrotechnic sheet material.
The oxidizable material may advantageously comprise metal selected from the group consisting of lithium, sodium, magnesium, beryllium, calcium, strontium, barium, ~ minillm, titanium, zirconium and alloys thereof, which metal may be advantageously be vapour-2s deposited on the substrate. A metal layer is especially advantageous as it significantly enhances the dimensional stability of the pyrotechnic sheet and is easily ruptured. A most preferred metal for high heat generation is magnesium or an alloy thereof preferably coated on to a substrate film comprising fluoropolymer. Preferably the ratio of metal to the substrate of ~itli7in~ polymeric film is substantially stoichiometric or there is a small excess s of metal at the location of the film underlying the metal. The reaction between PT~E and magnesium can be represented empirically as (C2F4)n - 2nMg --> 2nMgFz + 2nC
This reaction releases 5.98 megajoules/kilogram of reactant pyrotechnic material.
s The rate of energy release on ignition varies inversely with the thickness and directly with the porosity of the pyrotechnic sheet material and, accordingly, the thickness and porosity will be chosen to attain the desired energy release. Thus the pr~rel,~;d polymeric film will generally have an areal mass of 10 to l50g/m2, typically 25-75g/m2 and the total amount ofthe oxidizable m~t~.ri~l will be equivalent to a laminar thickness of 2 to 30 microns, 0 typically 4 to l S microns.
A typical pyrotechnic sheet comprises a film of halogenopolymer 3 to S0 microns,(preferably 10 - 30 microns) thick having on each side a vapour-deposited layer of magnesium 2 to 40 microns (preferably 4 - 15 microns) thick each m~gnesi~lm layer being overlaid with a cont~cting layer of gas-ge~ li"g defiagrating material 10 - 40 microns thick.
The invention also includes a method of m~nl-f~cturing a pyrotechnic sheet material which comprises depositing a layer of oxidizable material on at least a portion of at least one surface of a substrate of oxidizing material, the substrate and the oxidizable material being conjointly capable of reacting together exothermically on ignition, and applying to at least a portion of the surface of the oxidizable material and/or the substrate an overlying layer of gas-generating deflagrating material in ignition tr~n~mi~sion relationship with said substrate and oxidizable material.
Ple~l~bly the o~i~li7~ble material is vapour-deposited at low pressure on the polymer substrate by direct evaporation or magnetron sputtering.
Brief description of the drawing The invention is further described by way of example only with reference to the accompanying drawing which is a diagrammatic perspective, part-sectional view ofpyrotechnic sheet material of the invention.
~Z1612~ -Detailed description of the drawin~
Referring to the drawing, pyrotechnic sheet material design~ted generally by thenumber 10 consists of a substrate 11 of oxidizing polymeric film, for example ofpolytetrafiuoroethylene, coated on each side with a vapour-deposited layer of oxidizable 5 metal for example magnesium 12. Each layer of oxidizable metal is coated with a layer of gas-generating deflagrating material 13 .
Specific Examples The m~nl-f~ctllre of the pyrotechnic sheet material of the invention is further described in the following specific Examples wherein parts and percentages are given by 0 weight.
Example 1 A 25 micron thick solid sheet of P lF~ was coated on each side with an 8.5 micron thick vapour-deposited layer of m~gn~.~illm (appluxil"ately stoichiometric proportions). The coated sheet was embossed with regular rows of dimples by passing the sheet between a 15 patterned metal roll and a plain rubber roll. The dimples were spaced at 3rnm centres in each direction and each dimple was approximately 0.75mm square at the base, O.5mm square at the top, and 0.25mm high. The upper layer of magnesium was thereby ruptured around the periphery of the top of the dimples to expose the oxidizing polymeric film at the m~gnesillm/PTFE upper interface, the width ofthe exposed areas being up to 10 microns.
A sample portion of the embossed sheet having an area of 164 cm2 was coated witha solution in acetone of nitrocellulose, having a nitrogen content of 12.2%, and the acetone was evaporated offto leave a continuous contacting film of nitrocellulose over the layers of m~gnesium.
2s The sample was rolled into a helically wound charge assembly by winding around a central tubular phenolic resin former having an internal diameter of 6mm and 6mm wall thickness. Three longi~l~in~l slits e~P.n~ing to within lOmm from each end of the charge were cut through the spiral section of the pyrotechnic sheet. The assembled charge was ignited by a squib in a combustion test vessel (ballistic bomb) having a volume of 3 Scc.
21612~9 The pressure in the vessel after ignition was recorded. A sample coated with 0. lg nitrocellulose gave a maximum pressure of 22.1MPa in 2.02 milliseconds and a sample coated with 0.21g nitrocellulose gave a maximum pressure of 27.9MPa after 1.84 milliseconds. In a compa,~live test a sample without a nitrocellulose coating gave a s maximum pressure of 20MPa after 2.03 milliseconds.
These results clearly demonstrate the improved pressure (gas production) obtained with the nitrocellulose coated material.
Example 2 0 A pyrotechnic sheet comprising 25 micron thick PT~E film coated on each side with an 8.5 micron thick vapour-deposited layer of m~gn~.sjllm was prepa~ed and embossed as described in Example 1. A 10.61g sample of the embossed sheet was cut to the shape of a trapesium with opposite parallel sides having respective lengths of 150mm and 118mm and a length of 0.8 metres between opposite equal sides. The sample was coated on each side with a slurry co~ i";,lg 4 parts sodium azide, 0.065 parts carbon black, 1.81 parts vinylidene fluoridefhPx~fl-lolopl~ylene copolymer (binder and oxidizer for the sodium azide) available under the registered trade mark ~ITON and 8.37 parts ethyl acetate. The ethyl acetate was removed by evaporation leaving 3.09g of residual coating material. The sample was wound around a 12mm .I;~ ler tubular phenolic resin former with the shorter parallel edge on the side and inserted into a 28mm tli~met~.r x 11.7mm long thin steel tube leaving about 15mm at each end of the sample protruding beyond the steel tube. Each protruding end was 'petalled' by making 6 equally spaced longit~l~in~l cuts around the circumference, each cut extending to lcm from the end for a length of 15mm.
Two such wound samples were placed in proxi"Ji~y in a ballistic bomb having a volume of 7100 cc and ignited .~imlllt~neously at the end of one sample. A m~im~lm pressure of 1.6MPa was reached in 81.7 milliseconds.
In a comparative test two 16.51g samples of the uncoated pyrotechnic sheet generated a pressure of 1.4MPa in 103 milliseconds.
Claims (15)
1. Pyrotechnic sheet material comprising a substrate of oxidizing material;
a coating layer of oxidizable material on at least a portion of at least one surface of said substrate, the said substrate and the said layer of oxidizable material being conjointly capable of reacting together exothermically on ignition; and a layer of gas-generating deflagrating material overlying at least a portion of the combined surface area of said substrate and/or said layer of oxidizable material, said deflagration material being ignitable by the burning of the said substrate and oxidizable material.
a coating layer of oxidizable material on at least a portion of at least one surface of said substrate, the said substrate and the said layer of oxidizable material being conjointly capable of reacting together exothermically on ignition; and a layer of gas-generating deflagrating material overlying at least a portion of the combined surface area of said substrate and/or said layer of oxidizable material, said deflagration material being ignitable by the burning of the said substrate and oxidizable material.
2. Pyrotechnic sheet material as claimed in claim 1, wherein said substrate is coated on both sides with oxidizable material and at least a portion of at least one of the layers of oxidizable material is covered with a layer of gas-generating deflagrating material.
3. Pyrotechnic sheet material as claimed in claim 1, wherein the gas-generating material is selected from the group consisting of nitrocellulose-based propellant material, black powder, sodium azide/oxidizer composition and potassium perchlorate/aluminium composition.
4. Pyrotechnic sheet material as claimed in claim 1, wherein the said layer of gas-generating material is from 3-100 microns thick.
5. Pyrotechnic sheet material as claimed in claim 1, wherein said oxidizing substrate comprises polymeric film containing atoms chemically bound therein selected fromthe group consisting of halogens, oxygen, sulphur, nitrogen and phosphorous and the oxidizable material comprises metal selected from the group consisting of lithium, sodium, magnesium, beryllium, calcium, strontium, barium, aluminium, titanium, zirconium and alloys thereof.
6. Pyrotechnic sheet material as claimed in claim 5, wherein the said polymeric film comprises interconnecting vapour-permeable pores having at least part of the oxidizable material vapour-deposited therein.
7. Pyrotechnic sheet material as claimed in claim 1, wherein the oxidizing substrate and/or the layer of oxidizable material has discontinuous portions having lame permeable apertures through which the interface between the oxidizing substrate and the oxidizable material is exposed.
8. Pyrotechnic sheet material as claimed in claim 7, wherein the said oxidizing substrate and said layer of oxidizable material are permanently deformable and have different strain-for-rupture values, the said flame-permeable apertures being stretch-ruptures in said substrate or said layers of oxidizable material.
9. Pyrotechnic sheet material as claimed in claim 1, having spacer elements formed on the surface of the substrate and/or the layer of oxidizable material.
10. A method of manufacturing pyrotechnic sheet material which comprises:
depositing a layer of oxidizable material on at least a portion of at least one surface of a substrate of oxidizing material, said substrate and said oxidizable material being conjointly capable of reacting together exothermically on ignition; and applying to at least a portion of the surface of the oxidizable material and/or the substrate an overlying layer of gas-generating deflagrating material in ignition transmissionrelationship with said substrate and oxidizable material.
depositing a layer of oxidizable material on at least a portion of at least one surface of a substrate of oxidizing material, said substrate and said oxidizable material being conjointly capable of reacting together exothermically on ignition; and applying to at least a portion of the surface of the oxidizable material and/or the substrate an overlying layer of gas-generating deflagrating material in ignition transmissionrelationship with said substrate and oxidizable material.
11. A method as claimed in claim 10 wherein the layer of gas-generating deflagrating material is applied as a layer adhering to the substrate and/or the layer of oxidizable material.
12. A method as claimed in claim 11, wherein the gas-generating deflagrating material is applied as a solution or dispersion in a carrier liquid which is subsequentlyremoved.
13. A method as claimed in claim 11, wherein the gas-generating deflagrating material is applied as a solution or dispersion in a curable liquid polymer or in a polymer solution from which the solvent is subsequently removed.
14. A method as claimed in claim 10, wherein the layer of gas-generating material is applied as a layer separate from the substrate and/or the layer of oxidizable material.
15. A method as claimed in claim 14, wherein the layer of gas-generating material is applied by co-rolling with the substrate and/or the layer of oxidizable material.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9422402.9 | 1994-11-07 | ||
| GB9422402A GB9422402D0 (en) | 1994-11-07 | 1994-11-07 | Pyrotechnic sheet material |
| GB9423445A GB9423445D0 (en) | 1994-11-21 | 1994-11-21 | Pyrotechnic sheet material |
| GB9423445.7 | 1994-11-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2161279A1 true CA2161279A1 (en) | 1996-05-08 |
Family
ID=26305939
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002161279A Abandoned CA2161279A1 (en) | 1994-11-07 | 1995-10-24 | Pyrotechnic sheet material |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0710637A1 (en) |
| JP (1) | JPH08217588A (en) |
| KR (1) | KR960017594A (en) |
| AU (1) | AU3663795A (en) |
| CA (1) | CA2161279A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2312492A (en) * | 1996-04-26 | 1997-10-29 | Ici Canada | Hybrid inflatator for an air bag |
| US5704640A (en) * | 1996-05-01 | 1998-01-06 | Morton International, Inc. | Bondable autoignition foil |
| US6170398B1 (en) * | 1997-08-29 | 2001-01-09 | The Ensign-Bickford Company | Signal transmission fuse |
| US6527297B1 (en) | 2000-08-30 | 2003-03-04 | Autoliv Asp, Inc. | Inflator device ignition of gas generant |
| AU2003304422A1 (en) * | 2002-07-12 | 2005-03-07 | The Regents Of The University Of California | Nano-laminate-based ignitors |
| US7951247B2 (en) | 2002-10-01 | 2011-05-31 | Lawrence Livermore National Security, Llc | Nano-laminate-based ignitors |
| US20090078345A1 (en) * | 2007-09-25 | 2009-03-26 | Ensign-Bickford Aerospace & Defense Company | Heat generating structures |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3213793A (en) * | 1961-07-24 | 1965-10-26 | Kimberly Clark Co | Manufacture of cellulosic propellant |
| US3549436A (en) * | 1967-12-13 | 1970-12-22 | Gen Electric | Layered propellant composition consisting of an electrical conductor and an insulator |
| GB8905747D0 (en) | 1989-03-13 | 1989-04-26 | Secr Defence | Pyrotechnic material |
| GB2269380B (en) * | 1992-08-04 | 1995-11-22 | Ici Plc | Pyrotechnic sheet material |
| GB2269379A (en) * | 1992-08-06 | 1994-02-09 | Ici Plc | Pyrotechnic sheet metal |
| GB9319886D0 (en) | 1993-09-27 | 1993-12-15 | Ici Plc | Pyrotechnic material |
-
1995
- 1995-10-09 EP EP95307127A patent/EP0710637A1/en not_active Ceased
- 1995-10-24 CA CA002161279A patent/CA2161279A1/en not_active Abandoned
- 1995-11-03 AU AU36637/95A patent/AU3663795A/en not_active Abandoned
- 1995-11-06 KR KR1019950039860A patent/KR960017594A/en not_active IP Right Cessation
- 1995-11-07 JP JP7288765A patent/JPH08217588A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08217588A (en) | 1996-08-27 |
| EP0710637A1 (en) | 1996-05-08 |
| KR960017594A (en) | 1996-06-17 |
| AU3663795A (en) | 1996-05-30 |
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