GB2269379A - Pyrotechnic sheet metal - Google Patents
Pyrotechnic sheet metal Download PDFInfo
- Publication number
- GB2269379A GB2269379A GB9314576A GB9314576A GB2269379A GB 2269379 A GB2269379 A GB 2269379A GB 9314576 A GB9314576 A GB 9314576A GB 9314576 A GB9314576 A GB 9314576A GB 2269379 A GB2269379 A GB 2269379A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sheet material
- polymeric film
- pyrotechnic sheet
- pyrotechnic
- layer
- 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.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
- B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
- B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
- B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
- B60R21/264—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic
- B60R21/2644—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow using instantaneous generation of gas, e.g. pyrotechnic using only solid reacting substances, e.g. pellets, powder
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/14—Metallic material, boron or silicon
- C23C14/20—Metallic material, boron or silicon on organic substrates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
- B60R21/02—Occupant safety arrangements or fittings, e.g. crash pads
- B60R21/16—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
- B60R21/26—Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags characterised by the inflation fluid source or means to control inflation fluid flow
- B60R2021/26029—Ignitors
- B60R2021/26047—Ignitors of film shape
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Inorganic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Laminated Bodies (AREA)
Abstract
The material 10 comprises a substrate 11 of porous, vapourpermeable oxidizing polymeric film, for example a halogenopolymeric film eg. PTFE, having a layer 12, 13 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. Advantageously at least part of the oxidizing material is accommodated within the polymer pores. The pyrotechnic sheet material burns faster than material comprising solid polymeric film, owing to the increase surface area caused by the pores for contact of the substrate and the oxidisable material. Prior to coating of the substrate with the oxidisable material the pores may be partially filled with an incendiary material such as sodium azide. <IMAGE>
Description
PYROTECHNIC SHEET MATERIAL
This invention relates to pyrotechnic material in sheet form and to a method of manufacturing the said material. The material is useful in ignition systems in, for example, gas generators, rocket motors and shock wave transmission tubes and in heat generators of inflators for gas bags of vehicle occupant safety restraint systems.
Pyrotechnic sheet material consisting of one or more substrate layers of oxidizing polymeric film having a layer of oxidizable material 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.
Improved pyrotechnic sheet material having enhanced rate of flame propagation has been described in our co-pending United Kingdom patent application No 9304763.7.
The use of pyrotechnic sheet material to ignite a propellant charge has been described in our co-pending European patent application No 92300835-3 and hybrid inflators containing gas heating elements comprising pyrotechnic sheet material have been described in our co-pending United Kingdom patent application No 9302503.9.
Pyrotechnic sheet material for use in the gas-bag inflators of safety restraint systems are required to be very rapid acting and therefore the pyrotechnic material must have a high reaction rate.
An object of this invention is to provide a modified pyrotechnic sheet of the aforedescribed kind having an enhanced reaction rate and consequently enhanced rate and violence of burning and enhanced rate of energy release.
In accordance with this invention a pyrotechnic sheet material comprises a substrate of oxidizing polymeric film having at least a portion of a surface layer which 'is porous and a layer of oxidizable material on at least a porous portion of the said porous polymer layer, the polymeric film and the oxidizable material being conjointly capable of reacting together exothermically on ignition.
Preferably the porous polymer layer contains interconnected pores and advantageously it is vapour-permeable. Conveniently the total structure of the polymeric film is porous.
Porous polymeric film has lower density and higher surface to volume ratio than the solid polymeric film hitherto proposed for pyrotechnic sheet material. The oxidizable material can therefore be distributed over an increased surface area, so that, any desired ratio of oxidizable material to oxidizing polymer, usually preferably the stoichiometric ratio, can be achieved with a thinner layer of oxidizable material which will react faster.
The faster reaction rate is a consequence of the closer disposition of the reactant atoms in the pyrotechnic film, resulting in smaller diffusion distances to be traversed by reacting atoms.
In the polymeric sheet at least part of the oxidizable material is advantageously accommodated within the polymer pores but other materials such as modifying additives may, if desired, also be disposed in the pores. Thus in some cases an incendiary material such as, for example, a sodium azide composition may advantageously partially fill the pores in order to increase the energy of the pyrotechnic sheet material and/or to enhance the ease of ignition and the volume of gas produced by the material.
The porous polymer layer will generally have a porosity of 5 to 90%, preferably 70 to 90% and preferably has a specific surface at least 1.5 times and preferably more than 10 times that of solid polymeric film of the same dimensions. The polymeric film preferably has a 'microporous' structure with pores which are generally too small to be resolved by the naked eye.
Any porous oxidizing polymeric material may be used in this invention but a particularly advantageous form of porous polymeric film is that described in United Kingdom patent specification No 1,355,373. This material comprises a microstructure of interconnected nodes and fibrils of polymer produced by expanding a shaped polymeric article by stretching at an elevated temperature at a rate exceeding 10% per second of its original length. Polymeric sheet comprising such material is available under the registered trade mark GORE-TEX.
The preferred oxidizing polymeric film contains atoms chemically bound therein selected from the group consisting of halogens (especially fluorine), oxygen, sulphur, nitrogen and phosphorous. One preferred film layer comprises fluropolymer 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 of hexafluoropropylene and tetrafluoroethylene, copolymers of hexafluoropropylene and vinylidene fluoride, copolymers of tetrafluoroethylene and perfluoropropylene, copolymers of chlorotrifluoroethylene and vinylidene fluoride, homopolymers of perfluoropropylene, copolymers of perfluoropropylene and vinylidene fluoride, trichloroethylene homopolymers, copolymers of trichloroethylene and vinylidene fluoride, mixtures of two or more of such polymers or mixtures of any one or more of such polymers with PTFE.
The oxidizable material is advantageously vapour-deposited on the film layer and may suitably comprise a metal selected from the group consisting of lithium, sodium, magnesium, beryllium, calcium, strontium, barium, aluminium, titanium, zirconium, and alloys thereof. A most preferred metal is magnesium or an alloy thereof preferably coated on to a fluoropolymer substrate.
Preferably the ratio of oxidizable material to the substrate of oxidizing polymeric film is substantially stoichiometric at the location of the film underlying the metal. In this case the reaction between PTFE and magnesium can be represented as
(C2F4)n + 2nMg -- > 2nMgF2(g) + 2nC(s) + 5.98 MJ/Kg
The rate of energy release on ignition varies inversely with the thickness and porosity of the pyrotechnic sheet material and, accordingly, the thickness and porosity will be chosen to attain the desired energy release. Thus the preferred polymeric film will generally have an areal mass of 10 to 150 g/m2, typically 25-75 g/m2 and the total amount of the oxidizable material will be equivalent to a laminar thickness of 2 to 30 microns, typically 4 to 10 microns. The oxidizable material may be deposited on one or both sides of the oxidizing polymeric film.
The pyrotechnic sheet material of the invention may be used in any convenient shape or configuration, for example, in flat sheets, strips, tapes or discs or it may be folded, wrapped, wrinkled, pleated, corrugated, fluted or wrapped around a former such as a rod or tube.
If desired, for enhanced rate and violence of flame propagation, the sheet may be provided with spacer elements, for example protrusions formed on the surface, as described in our co-pending United Kingdom Patent Application No 9304763.7 These spacer elements are effective to prevent intimate contact of adjacent surfaces, for example of overlying sheets, and thus facilitate rapid combustion of the pyrotechnic material by allowing hot gas and flame to travel ahead of the burning face and initiate the material at downstream positions.
The invention also includes a method of manufacturing a pyrotechnic material which comprises depositing a surface layer of oxidizable material on at least a porous portion of a surface layer of oxidizing polymeric film having at least a portion of a surface layer which is porous, the oxidizable polymeric film and the oxidizable material being conjointly capable of reacting together. The oxidizable material is preferably vapour-deposited at low pressure (vacuum deposition) by direct evaporation or by magnetron sputtering. With this method the oxidizable material, for example magnesium, will penetrate, and lodge in, the pores of the polymer to a significant depth and possibly to the full depth of the porous layer.
The invention is further described by way of example only, with reference to the accompanying drawing which is a diagrammatic, perspective, part-sectional view of pyrotechnic sheet material of the invention.
Referring to the drawing, a pyrotechnic sheet material 10 consists of a substrate of a porous vapour-permeable oxidizing polymeric film tape 11 coated on both of its surfaces 12 and 13 with layers 14 and 15 respectively of oxidizable metal deposited by conventional vacuum-deposition techniques. The direction of the long axis of the tape 2 is indicated by an arrow. Each layer of metal 14 and 15 penetrates the adjacent surface of the porous tape 11 so that oxidizable metal permeates the pores of a surface layer of tape 11 adjacent to the surfaces 12 and 13.
As shown an edge portion of tape 11 has been left uncoated (to facilitate sealing) but this portion may also be coated with metal or trimmed off as desired.
Specific Examples of -a pyrotechnic sheet material of the invention are described in the following Examples.
Example 1
A pyrotechnic sheet material was prepared by vapourdepositing magnesium on each surface of a 75 micron thick substrate of microporous polytetrafluoroethylene (PTFE) film having porosity of 80%, the total amount of magnesium being stoichiometric with the PTFE. The magnesium coating was evenly distributed on each side of the film and penetrated the surface to a depth of 5 to 10 microns.
On ignition the pyrotechnic sheet burned faster and more violently than a corresponding pyrotechnic sheet comprising solid
PTFE film having the magnesium all disposed in solid layers on the surface of the PTFE film. Thus in a closed vessel ballistic test the vivacity of the pyrotechnic sheet material of this
Example was measured as 6.5 x 1011 pascals/second whereas in the same test the viscosity of the same mass of a similar pyrotechnic sheet wherein the substrate was 25 micron thick non-porous PTFE was 1.8 x 1011 pascals/second.
Example 2
The pyrotechnic sheet material of this example was the same as that of Example 1 except that, before the vapour-deposition of the magnesium coating, the microporous PTFE film was soaked in a saturated aqueous solution of sodium azide and subsequently dried, thereby reducing the porosity to 40% i.e. filling 50% of the pore space with solid sodium azide.
The pyrotechnic sheet of this example had higher energy, was easier to ignite and produced more gas than the pyrotechnic material of Example 1.
Claims (25)
1. A pyrotechnic sheet material comprising a substrate of
oxidizing polymeric film having at least a portion of a
surface layer which is porous and having a layer of
oxidizable material on at least a porous portion of the
said porous polymer layer, the polymeric film and the
oxidizable material being conjointly capable of reacting
together exothermically on ignition.
2. A pyrotechnic sheet material as claimed in claim 1 wherein
the said porous polymer layer comprises interconnecting
pores.
3. A pyrotechnic sheet material as claimed in claim 1 or claim
2 wherein the said porous polymer layer is
vapour-permeable.
4. A pyrotechnic sheet material as claimed in any one of
claims -1 to 3 wherein at least part of the oxidizable
material is accommodated within the pores of the polymeric
film.
5. A pyrotechnic sheet material as claimed in any one of
claims 1 to 4 wherein the pores of the polymeric film are
partially filled with incendiary material.
6. A pyrotechnic sheet material as claimed in claim 5 wherein
the incendiary material comprises sodium azide.
7. A pyrotechnic sheet material as claimed in any one of
claims 1 to 6 wherein the said layer of oxidizing polymeric
film has a porosity of 5 to 90%.
8. A pyrotechnic material as claimed in claim 7 wherein the
said layer of oxidizing polymeric film has a porosity of
70% to 90%.
9. A pyrotechnic sheet material as claimed in any one of
claims 1 to 8 wherein the specific surface of the said
porous layer of oxidizing polymeric film is at least 1.5
times that of solid polymeric film of the same dimensions.
10. A pyrotechnic sheet material as claimed in claim 9 wherein
the specific surface of the said porous layer of oxidizing
polymeric film is more than 10 times that of solid
polymeric film of the same dimensions.
11. A pyrotechnic sheet material as claimed in any one of
claims 1 to 10 wherein the porous layer of oxidizing
polymeric film has a microporous structure.
12. A pyrotechnic sheet material as claimed in claim 11 wherein
the porous layer of oxidizing polymeric film comprises a
microstructure of interconnected nodes and fibrils of
polymer.
13. Pyrotechnic sheet material as claimed in any one of claims
1 to 12 wherein the oxidizing polymeric film contains atoms
chemically bound therein, said atoms being selected from
the group consisting of halogens, oxygen, sulphur, nitrogen
and phosphorous.
14. Pyrotechnic sheet material as claimed in claim 13 wherein
the oxidizing polymeric film comprises fluoropolymer
selected from the group consisting of
polytetrafluoroethylene (PTFE),
polychlorotrifluoroethylene, polyhexafluoropropylene,
copolymers of trifluoroethylene and hexafluoropropylene,
copolymers of trifluoroethylene and tetrafluoroethylene,
copolymers of hexafluoropropylene and tetrafluoroethylene,
copolymers of hexafluoropropylene and vinylidene fluoride,
copolymers of tetrafluoroethylene and perfluoropropylene,
copolymers of chlorotrifluoroethylene and vinylidene
fluoride, homopolymers of perfluoropropylene, copolymers of
perfluoropropylene and vinylidene fluoride,
trichloroethylene homopolymers, copolymers of
trichloroethylene and vinylidene fluoride, and mixtures of
two or more of such polymers.
15. Pyrotechnic sheet material as claimed in any one of claims
1 to 14 wherein the oxidizable material is vapour-deposited
on the polymeric film.
16. Pyrotechnic sheet material as claimed in any one of claims
1 to 15 wherein the layer of oxidizable material comprises a metal selected from the group consisting of lithium,
sodium, magnesium, beryllium, calcium, strontium, barium,
aluminium, titanium, zirconium, and alloys consisting of
any two or more thereof.
17. Pyrotechnic sheet material as claimed in claim 16 wherein
the oxidizable material comprises magnesium or an alloy
thereof and the substrate comprises fluoropolymer.
18. Pyrotechnic sheet material as claimed in any one of claims
1 to 17 wherein the ratio of oxidizable material to the
substrate of oxidizing polymeric film is substantially
stoichiometric.
19. Pyrotechnic sheet material as claimed in any one of claims
1 to 18 comprising a substrate film of oxidizing polymer
having an areal mass of 10 to 150 g/m2 having deposited on
the surface thereof an amount of oxidizable material
equivalent to a laminar thickness of 2 to 30 microns.
20. Pyrotechnic sheet material as claimed in any one of claims
1 to 19 provided with spacer elements effective to prevent
intimate contact of overlying sheets.
21. A method of manufacturing a pyrotechnic sheet material
which comprises depositing a layer of oxidizable material
on at least a porous portion of a surface layer of
oxidizing polymeric film having at least a portion of a
surface layer which is porous, the polymeric film and the
oxidizable material being conjointly capable of reacting
together exothermically on ignition.
22. A pyrotechnic sheet material substantially as described
herein and illustrated in the accompanying drawing.
23. A method of manufacturing a pyrotechnic sheet material
substantially as described herein with reference to the
Example.
24. A pyrotechnic sheet material whenever prepared by a method
as described in claim 21 or claim 23.
25. An inflator for a vehicle occupant safety restraint
system comprising pyrotechnic sheet material as
claimed in any one of claims 1 to 20, 22 or 24.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9314576A GB2269379A (en) | 1992-08-06 | 1993-07-14 | Pyrotechnic sheet metal |
| MX9304751A MX9304751A (en) | 1992-08-06 | 1993-08-05 | PYROTECHNICAL LEAF MATERIAL. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB929216720A GB9216720D0 (en) | 1992-08-06 | 1992-08-06 | Pyrotechnic sheet material |
| GB9314576A GB2269379A (en) | 1992-08-06 | 1993-07-14 | Pyrotechnic sheet metal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9314576D0 GB9314576D0 (en) | 1993-08-25 |
| GB2269379A true GB2269379A (en) | 1994-02-09 |
Family
ID=26301380
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9314576A Withdrawn GB2269379A (en) | 1992-08-06 | 1993-07-14 | Pyrotechnic sheet metal |
Country Status (2)
| Country | Link |
|---|---|
| GB (1) | GB2269379A (en) |
| MX (1) | MX9304751A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2282136A (en) * | 1993-09-27 | 1995-03-29 | Ici Plc | Pyrotechnic material |
| EP0710637A1 (en) * | 1994-11-07 | 1996-05-08 | Imperial Chemical Industries Plc | Pyrotechnic sheet material |
| EP0692411A3 (en) * | 1994-07-12 | 1997-08-06 | Morton Int Inc | Pyrotechnic inflator for an air bag |
| GB2312496A (en) * | 1996-04-26 | 1997-10-29 | Ici Canada | Pressure vessel assembly |
| GB2312492A (en) * | 1996-04-26 | 1997-10-29 | Ici Canada | Hybrid inflatator for an air bag |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2508896A1 (en) * | 1981-07-02 | 1983-01-07 | France Etat | Cellular pyrotechnic material with controlled porosity - comprising binder, oxidn.-redn. couple and micro-cavities, useful smoke producing, incendiary, heat vaporising or fuel compsns. |
-
1993
- 1993-07-14 GB GB9314576A patent/GB2269379A/en not_active Withdrawn
- 1993-08-05 MX MX9304751A patent/MX9304751A/en not_active IP Right Cessation
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2508896A1 (en) * | 1981-07-02 | 1983-01-07 | France Etat | Cellular pyrotechnic material with controlled porosity - comprising binder, oxidn.-redn. couple and micro-cavities, useful smoke producing, incendiary, heat vaporising or fuel compsns. |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2282136A (en) * | 1993-09-27 | 1995-03-29 | Ici Plc | Pyrotechnic material |
| GB2282136B (en) * | 1993-09-27 | 1998-04-29 | Ici Plc | Pyrotechnic material |
| EP0692411A3 (en) * | 1994-07-12 | 1997-08-06 | Morton Int Inc | Pyrotechnic inflator for an air bag |
| EP0710637A1 (en) * | 1994-11-07 | 1996-05-08 | Imperial Chemical Industries Plc | Pyrotechnic sheet material |
| GB2312496A (en) * | 1996-04-26 | 1997-10-29 | Ici Canada | Pressure vessel assembly |
| GB2312492A (en) * | 1996-04-26 | 1997-10-29 | Ici Canada | Hybrid inflatator for an air bag |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9314576D0 (en) | 1993-08-25 |
| MX9304751A (en) | 1994-05-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |