Insulating Material

Abstract

This invention relates to self-extinguishing insulating compositions containing coolants which undergo endothermic decomposition when subjected to elevated temperature. The coolants are incorporated in various types of binder: One is combustible without leaving any solid residue. Another has the property of forming a foamed char to facilitate transpirational cooling at the heat-exposed surface. A third is incombustible. Various other substances, such as catalysts, oxidizers and plasticizers, may also be included.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 802,198 filed Feb. 25, 1969 now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to heat-insulating materials and more particularly to materials which decompose during the application of heat at elevated temperatures and which discontinue such decomposition immediately after the application of heat has been terminated. Considerable work has been performed to provide materials which are able to serve as heat insulators when subjected to elevated temperatures as high as 5,000.degree.F. In spite of such work, satisfactory materials have not been available. One difficulty has been that the materials continue to burn even after the application of heat has been terminated. Another difficulty in some uses has been that the materials liquify when subjected to heat or deposit undesirable residues upon the application of heat.

SUMMARY OF THE INVENTION

This invention provides materials which overcome the above disadvantages. The materials include a coolant, preferably ammonium oxalate, capable of endothermic decomposition at elevated temperatures to form gaseous products. The compositions of this invention are self-extinguishing, and the heat-exposed surfaces can be touched comfortably immediately or almost immediately after the application of heat has been terminated.

The compositions included in this invention have further advantages. For example, during exposure to heat at elevated temperatures certain of the materials included within this invention decompose and produce gases without becoming liquified. The gases serve as a heat barrier to minimize further exposure to heat. The gases also allow the passage of radio frequency signals. This is important when the compositions included in this invention provide insulation in or around electronic equipment.

The compositions of this invention have other important advantages. They can be formulated for paint consistency or with a consistency suitable for casting. Viscosity can also be increased so that they can be extruded, troweled, pressure-cast or molded.

In various embodiments of the invention, the coolants are uniformly dispersed in binders having different properties. One type of binder is combustible when subjected to heat, without leaving any solid residue. Another has the property of forming a porous char structure which permits passage of the gases resulting from the application of heat to provide a transpirational cooling. A third is incombustible.

Various substances can be included in the insulating compositions of this invention with the binders and the coolants. For example, catalysts or curatives are included to cure the binder. In the embodiments in which the binder is combustible without leaving a residue, a catalyst is preferably used which supplies oxygen to facilitate the combustion of the binder.

An oxidizer may also be included in the insulating composition, particularly when the binder is combustible without leaving any residue. A plasticizer may additionally be included to render the insulating composition flexible and to facilitate its combustion.

DETAILED DESCRIPTION OF THE INVENTION

In some embodiments of the invention, the binder is combustible at elevated temperatures, e.g., 3,000.degree.F. to 5,000.degree.F. to form gases without first liquifying and without producing any solid or liquid residue. A preferred binder is polysulfide resin.

The polysulfides, sometimes termed polyalkylene polysulfide prepolymers, are mercapto-terminated polymers of the general formula

HS(R--SS).sub.n RSH

where R is a polyvalent organic radical containing at least one methylene group and n is an integer of from about 3 to 100, and preferably from about 3 to 25. Preferred polysulfides include those in which R is

--C.sub.2 H.sub.4 OCH.sub.2 OC.sub.2 H.sub.4 --

The polysulfides may be prepared by condensation of an alkali metal polysulfide, e.g., sodium polysulfide, with an organic dihalide such as dichlorodiethyl formal, ethylene dichloride, or dichloroethyl ether, as described in Industrial and Engineering Chemistry, Volume 43, pp. 324-8 (1951). Small proportions, e.g., 0.5-2 percent, of trichloropropane or other polyhalides are often included with the dihalide. The polysulfides range in property from mobile to viscous liquids to solids at room temperature, depending on molecular weight. Those of liquid form are ordinarily preferred.

Other binders, including polyurethanes, polybutadienes and epoxide resins, can be used in place of or with the polysulfides. These binders are advantageous because they can be compounded in liquid form and cured to a solid matrix at relatively low temperatures below approximately 250.degree.F. In fact, any organic binder capable of being compounded as a liquid and cured to a solid at relatively low temperature can be used.

The epoxides, also referred to as glycidyl polyether resins, are epoxy-terminated polymers of the general formula

where R' is the divalent organic radical of a dihydric alcohol or a dihydric phenol and n usually has a value of from about 1 to 20.

Preferred epoxides include those in which R' is ##SPC1##

The epoxides may be prepared by condensation of epichlorhydrin in alkaline medium with a dihydric alcohol or a dihydric phenol such as Bisphenol A. The epoxides range in property from viscous liquids to low melting solids, depending on molecular weight or degree of condensation. The degree of condensation is indicated by the epoxide equivalent, defined as the grams of resin per one gram equivalent of epoxy. Epoxides are prepared with epoxide equivalents ranging from about 140 to 4000, but those of about 185 to about 300 are usually preferred since these are in liquid form at room temperature.

A catalyst is generally included to cure the binder. For example, lead peroxide (PbO.sub.2) may be used as a catalyst when the binder is a polysulfide. This catalyst is preferably employed at a level of approximately seven per cent by weight of the binder, and may be used in a range of approximately six to ten per cent by weight of the binder. In addition to serving as a curing agent, a catalyst such as lead peroxide also furnishes oxygen to facilitate the combustion of the binder.

Paraquinonedioxime (HON:C.sub.6 H.sub.4 :NOH) may be used as a catalyst instead of lead oxide when the binder is polysulfide. Paraquinonedioxime is advantageous because it decomposes completely into gaseous products.

When polyurethane constitutes the binder, glycerine or other hydroxyl-containing substances can serve as catalyst or curative. The hydroxyl groups react with the isocyanate groups of the polyurethane to cure the binder. Castor oil and amines are other examples of curing agents used with polyurethane binders. Alternatively, a polyol binder containing free hydroxyl groups can be condensed with an isocyanate such as tolylene diisocyanate to form the polyurethane.

When epoxide resins are employed as binders, either alone or in combination with polysulfides, appropriate accelerators are the aliphatic and aromatic primary, secondary and tertiary amines, generally employed at levels up to about 15 parts per 100 parts epoxide. Preferred polyfunctional amines include 2,4,6-tri(dimethylaminomethyl)phenol, diethylenetriamine, and dimethylaminopropylamine. Other suitable amines include dimethylaminomethyl phenol and benzyldimethylamine. Polyamide curing agents may also be employed with the epoxides. Preferred polyamides are the reaction products of polymeric fatty acids with polyamines. The polymeric fatty acids may, for example, be dimerized and trimerized unsaturated fatty acids derived from drying oils such as soybean oil, linseed oil, tung oil and the like. The polyamines employed for the preparation of polyamide curatives include ethylenediamine, diethylenetriamine and the like.

A coolant, preferably ammonium oxalate (NH.sub.4).sub.2 C.sub.2 O.sub.4.sup.. H.sub.2 O, is included in the insulating composition in all embodiments and is one of the principal features of the invention. The ammonium oxalate may be anhydrous or hydrated. The coolant is capable of undergoing endothermic decomposition to form gases at the elevated temperatures so that it absorbs heat in such decomposition. For example, when ammonium oxalate is used as the coolant, it decomposes with the absorption of approximately 73 kilocalories per mole:

(NH.sub.4).sub.2 C.sub.2 O.sub.4.sup. . H.sub.2 O.fwdarw. 2NH.sub.3 + 2CO.sub.2 + H.sub.2 O + H.sub.2

When ammonium oxalate is used as the coolant, it is preferably employed at a level of approximately three parts by weight to each part by weight of binder, particularly when the binder is polysulfide. The relative proportion of the coolant can range from approximately one half to four parts by weight for each part by weight of binder. Although various ammonium salts have been known as coolants, ammonium oxalate has apparently not been known as a coolant, as may be seen from an article entitled "Sublimation Pressures and Latent Heats of Ammonium Salts" by N.W. Luft in the October, 1955 issue of "The Industrial Chemist".

Although ammonium oxalate is the preferred coolant, other materials may be and have been used. For example, oxalic acid (C.sub.2 H.sub.2 O.sub.4) and fumaric acid (C.sub.4 H.sub.4 O.sub.4) have been used as coolants and are effective. However, they are more difficult to handle than ammonium oxalate since they constitute acids, and as such, should be used over an acid-resistant primer or base. The acid resistant furan resins are suitable binders for use with these coolants. The furan resins are formed by the acid-catalyzed condensation of furfuryl alcohol. The condensation is halted at an intermediate stage by neutralization, and curing of the resultant prepolymer may be completed by addition of a strong acid catalyst after the coolant and any other desired ingredients have been incorporated. The unsaturated polyester resins are also appropriate binders for use with these coolants. The polyesters are prepared by the condensation of a glycol, such as ethylene or propylene glycol, with an unsaturated dicarboxylic acid such as fumaric acid or maleic anhydride. Physical properties may be varied as desired by employing a proportion of saturated dicarboxylic acid or aromatic dicarboxylic acid, e.g., adipic acid or phthalic anhydride, along with the unsaturated acid, for example, by employing a 50:50 mole proportion of saturated and unsaturated acid. The polyesters are generally blended with about 10 to 40 per cent by weight of low molecular weight monomer, e.g., styrene, and cured to solid products by addition of about 0.5 to 5 percent of an organic peroxide catalyst, e.g., benzoyl peroxide, ter. butyl peroxide, or methyl ethyl ketone peroxide.

Oxamide (CONH.sub.2).sub.2 and carbamide (urea) (NH.sub.2 (CONH.sub.2) are also theoretically advantageous as coolants because they decompose endothermically. However, the gases produced are combustible to generate heat, which neutralizes the endothermic effect of the decomposition in some applications. Urea oxalate (2CO(NH.sub.2).sub.2.sup.. C.sub.2 H.sub.2 O.sub.4) is also theoretically advantageous, as are hydrazine compounds such as hydrazine formate (N.sub.2 H.sub.4.sup.. 2HCO.sub.2 H).

A coolant such as ammonium oxalate has been used in a binder such as polysulfide or a polyurethane without any additional material other than a catalyst such as lead oxide for curing the binder. In such materials, a portion of the binder may remain as a liquid film when subjected to heat at temperatures as high as 5000.degree.F. This is not objectionable in some applications, such as aerodynamic heat shields, where the liquid film is swept away by aerodynamic flow.

In some applications a completely gaseous end product is desired. For example, in the insulation of combustion chambers of gas generators, hot gas ducts or hot gas holding chambers, it is preferable that the insulating material, particularly the binder, produce no solid char or liquid products which might interfere with the functioning of valves or control devices. A completely gaseous end product also provides increased working fluid, enabling the gas generator system to work at increased efficiency. Similarly, in rocket motors, the gases produced from the insulating material facilitate the production of increased thrust.

Where it is desired to insure that the binder will be completely converted to gases, a limited amount of an oxidizing compound capable of decomposition at elevated temperature is preferably incorporated in the insulating composition. This oxidizer is preferably ammonium perchlorate (NH.sub.4 ClO.sub.4), usually employed at a level of approximately one part by weight to each part by weight of binder. The proportion of oxidizer may range from zero up to approximately 1.5 parts by weight to each part by weight of binder. If the proportion of oxidizer exceeds about 1.5 parts by weight, the material no longer serves as efficiently as an insulator.

Oxidizers other than ammonium perchlorate may also be used. Ammonium nitrate (NH.sub.4 NO.sub.3), for example, has also been found to be advantageous. In fact, almost any chlorate, perchlorate or nitrate may be used, urea nitrate and hydrazine nitrate being other examples. It is preferable to use chlorates, perchlorates, or nitrates which are free of metal cations where no residue is desired upon decomposition.

A plasticizer may also be included in the insulating material constituting this invention to render the material pliable. Glycerol triacetate C.sub.3 H.sub.5 (OCOCH.sub.3).sub.3, commonly designated as triacetin, is a preferred plasticizer when the binder is a polysulfide. Glycerol triacetate is advantageous since it contains a high proportion of oxygen relative to carbon. Furthermore, it reduces viscosity so that higher coolant levels can be incorporated in the compositions. When subjected to heat, glycerol triacetate is combustible to form gases in substantially the same manner as the binder. The combustion of the glycerol triacetate is facilitated by the oxygen resulting from the decomposition of the ammonium perchlorate. The plasticizer is usually employed at levels of up to approximately thirty per cent by weight based on the binder. Glycerol triacetate levels of approximately twenty per cent by weight are preferred.

Other plasticizers may be used in place of glycerol triacetate. For example, dibutyl phthalate may also be used. This material is advantageous for substantially the same reasons as glycerol triacetate, since its high oxygen content facilitates combustion, although glycerol triacetate has the higher oxygen content. Other plasticizers, such as high boiling esters of polyfunctional alcohols, may be also used.

The insulating compositions constituting this invention are formed by first combining all ingredients except the catalyst or curative. When it is desired to form the insulating material, the curative is added to the mixture, whereupon the composition cures to a solid in approximately one to twelve hours. Curing can occur at ambient temperature when the preferred binder, catalyst, coolant, oxidizer and plasticizer specified above are employed. Alternatively, the coolant may be mixed initially with the catalyst and oxidizer, since they are usually all in the form of solids. This mixture may then be added to the liquid binder or binder-plasticizer mixture when it is desired to produce the insulating composition. Whichever method is used, the mixtures produced prior to the mixing of the binder and the catalyst may be stored for indefinite periods without affecting the characteristics of the insulating material produced.

The insulating compositions included within this invention have important advantages. When heat is applied, as from an acetylene torch at a temperature of approximately 5,000.degree.F., various decomposition and combustion reactions ensure such that the net effect is endothermic. In effect, the decomposition of the coolant, binder, plasticizer and catalyst acts as a heat sponge which more than offsets the heat released by the combustion. Tests have shown that the insulating material absorbs approximately 5,000 BTU per pound. This is comparable to the material used for the Gemini re-entry heat shield.

The compositions are self-extinguishing immediately after the heat is removed from the surface of the insulating material, at which time the temperature of this surface is sufficiently low that it can be touched without discomfort, indicating that relatively little heat is passing through the insulating material. In this way, members insulated by the compositions constituting this invention are protected against substantial rise in temperature.

In view of these properties, the insulating compositions can be used with a pulsed source of heat to control the combustion and decomposition of the insulating material. They can also be used with a pyrotechnic heat source which does not produce any gas in itself, particularly since the insulating compositions produce gases when subjected to heat.

The insulating compositions constituting this invention have other important advantages. For example, when used in a gas generator, they add to efficiency by producing gases as the insulating material is consumed. This property is especially important in rocket motors since the gases generated from the insulating material impart additional thrust.

Since the compositions of the invention are consumed in providing the insulating action, a somewhat greater thickness may be applied initially than the average thickness which may be desired. This is particularly appropriate when the insulating material is used as the external skin on rocket engines and missiles, where it provides a cool external layer as it is consumed, causing the weight of the rocket engine or missile to decrease.

The insulating compositions constituting this invention are further advantageous in that the gaseous decomposition products produced are incombustible without additional oxygen. This may be seen from the fact that, when the flame from an air-acetylene torch is applied to the insulating material, the torch must be disposed up-wind of the effluent gases or they will extinguish the torch. If the gases were combustible, the endothermic effect would be at least partially offset by the combustion of the gases.

The insulating materials constituting this invention can be advantageously used as a coolant around hot gases. The gases produced from the insulating material are relatively cool in view of the essentially endothermic nature of reaction, and they mix with the gases to be cooled and receive heat from such gases.

The insulating compositions constituting this invention have another important advantage, viz. they allow communication at radio frequencies through the gases which are produced and which envelop the insulating material. This is important when the insulating materials are used to protect electronic systems from heat near rocket engines and within missiles. The gases produced from other insulating materials create impenetrable barriers to the passage of energy at radio frequencies. For example, energy at radio frequencies is generally blocked by insulators which carbonize or char or which decompose into metal ions. The radio frequency transparency of the insulating materials constituting this invention has been proven in flight tests of Loki darts containing a transponder and coated with a preferred embodiment of the insulating material in a thickness of approximately 0.030 inches. This coating was consumed by aerodynamic heating during the first 30 seconds of the flight. During this period of time, communications were maintained at radio frequencies with the transponder.

The materials constituting this invention can be formulated with a paint consistency or with suitable consistency for casting operations. Viscosity can also be increased so that the materials may be extruded, troweled, pressure-cast or molded.

A coolant such as ammonium oxalate may be used with a binder such as a polyurethane to produce an insulating material which produces an intumescent or foaming char. For example, sugar or aluminum hydroxide (Al(OH).sub.3) may be used as a catalyst to cure the polyurethane binder at somewhat elevated temperature on the order of approximately 200.degree.F. The hydroxide may be included in the insulating materials in a ratio of approximately five to 25 parts by weight per hundred parts by weight of binder, and preferably in a ratio of approximately ten parts by weight per hundred parts by weight of binder. In addition to aluminum hydroxide, the hydroxides of other metals such as iron (ferric and ferrous), chromium (chromic and chromous), calcium, zirconium, platinum and magnesium may be used.

The insulating compositions described in the previous paragraph have foaming characteristics that are produced as the binder and catalysts react, yielding carbon dioxide as a by-product which creates an insulation having pores. When such compositions are subjected to heat, the gases produced by decomposition and combustion move through the porous char structure to produce a transpirational cooling of the insulating material. The movement of the gases through the char structure facilitates the production of a gaseous interface between the char and the heat source. The ratio of binder to coolant can be varied to provide any desired combination of char strength and density and cooling gases for a given application.

Insulating materials with foaming characteristics have relatively low density, and they have good resistance to vibration and withstand physical loads well. The amount of material required to fill a given space is also minimized. The aluminum hydroxide or other hydroxide may deposit a residue of metal oxide, a possible disadvantage in certain applications. However, for ablative coatings, such metal oxides will contribute to the char structure.

Insulating compositions having foaming characteristics have been provided with flexible as well as rigid properties. In these, the binders have included polyurethanes and the preferred coolant has been ammonium oxalate. When insulating materials having flexible properties and foaming characteristics have been produced, a preferred mixture has been formed from 2,4- and 2,6- tolylene diisocyanates, in approximately 80/20 ratio by weight, and polyhydroxyl compounds. The polyhydroxyl compounds may be polyether or polyester polyols, or a combination of polyether and polyester polyols.

When the insulating materials have been provided with foaming characteristics and rigid properties, polyethers have been used which are primarily propylene oxide adducts of such substances as sorbitol, sucrose, pentaeythritol, methyl glucoside and diamines. These materials have ranged in functionality from triols to octols and in equivalent weight from 75 to 160.

Coolants, and particularly ammonium oxalate, have also been incorporated into incombustible binders such as asbestos, Portland cement and plaster of Paris. With such insulating compositions, the back surface opposite the heat-exposed surface has been maintained at a temperature below the decomposition temperature of the ammonium oxalate until the insulating composition has been completely consumed by the application of heat.

EXAMPLES 1-3

Parts by Weight 1 2 3 32.0 20.75 19.0 liquid polysulfide resin (binder) (a) 8.0 5.19 4.7 dibutyl phthalate (plasticizer) 2.2 1.56 1.3 lead dioxide (curing agent) 19.3 23.5 24.0 ammonium perchlorate, 200 micron (oxidizer) 38.5 49.0 51.0 ammonium oxalate (coolant) (a) Thiokol LP-2, dithiol of molecular weight 4000, derived from 98 mol % dichloroethyl formal and 2 mol % trichloroprop ane (Ind. Eng. Chem. Vol. 43, p. 324, 1951)

Formulations 2 and 3 are relatively stiff in compounding; formulation 1 is more readily workable and is compounded with greater ease. The cured coatings are exposed 3 inches from an acetylene torch at an oxygen pressure of 5 pounds per square inch. Under these conditions, formulation 1 exhibits an ablation rate of approximately 0.0024 inches per second. Ablation rates of about 0.0020 and 0.0018 inches per second are obtained with formulations 2 and 3, respectively.

The following coating compositions upon curing exhibit comparable insulating and ablation properties.

EXAMPLE 4

100 p. by wt. Liquid polysulfide resin (a) 25 Dibutyl phthalate (plasticizer) 7.5 Lead dioxide (curing agent) 50 Ammonium oxalate (coolant) 0-0.3 aluminum distearate (retarder)

EXAMPLE 5

100 p. by wt. Liquid polyurethane (b) 7.3 Amine curing agent (c) 13.2 Amine curing agent (d) 100. Ammonium oxalate, through 60 mesh (b) Thiokol Solithane 113 tolylene diisocyanate-urethane prepolymer having an equivalent weight of 389-404 and an isocyanate content of 10.6% (c) Thiokol C-113-300 (d) Thiokol C-113-328

examples 6-9

parts by Weight 6 7 8 9 100 100 100 100 Liquid polyurethane (b) 50 Castor Oil (curing agent) 6.5 Aluminum hydroxide (curing agent) 9.5 Calcium hydroxide (curing agent) 7.25 Magnesium hydroxide (curing agent 150 50 50 50 Ammonium oxalate (coolant)

EXAMPLES 10-11

Parts by Weight 10 11 100 Epoxide resin (e) 100 Epoxide resin (f) 10 10 2,4,6-tri(dimethyl- aminomethyl)phenol (g) 100 100 Ammonium oxalate (e) Shell Epon 828, the condensation product of epichlorhydrin and bisphenol A, having a molecular weight of 350, an epoxy value of 0.5 equivalent per 100 grams, a hydroxyl value of 0.1 equivalent per 100 g., and an epoxide equivalent of 190-210 grams per gram mole of epoxide. (f) Ciba Araldite 6020 resin, having an epoxy equivalent of 208 grams per gram mole of epoxide (g) Rohm & Haas DMP-30 (curing agent)

EXAMPLE 12

Parts by Wt. 60 Liquid polysulfide resin (h) 40 Epoxy resin (f) 4 2,4,6-tri(dimethyl- aminomethyl)phenol (g) 200 Ammonium oxalate (h) Thiokol LP-33, dithiol of molecular weight 1000, derived from 99.5 mol % dichloroethyl formal and 0.5 mol % trichloropropane (Ind. Eng. Chem. Vol. 43, p. 324, 1951)

EXAMPLE 13

100 Parts by Wt. Furan resin (j) 1.0 Acid catalyst (k) 150 Oxalic acid (j) Resin X-2, a room-setting furfuryl alcohol condensation polymer available from Furane Plastics Inc., of Glendale, California. (k) Z-1A, available from Furane Plastics Inc.

EXAMPLE 14

Parts by Wt. 100 Unsaturated polyester casting resin (l) 1.0 Methyl ethyl ketone peroxide 105 Fumaric acid (l) Copolymer of styrene and propylene glycol maleate-phthalate

Although this invention has been disclosed and illustrated with reference to particular applications, the principles involved are susceptible of numerous other applications which will be apparent to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Claims

What is claimed is:

1. An insulating composition constituting a polymerizable liquid capable of being cured to form a solid matrix and comprising a binder having uniformly dispersed therein a coolant substance capable of substantially complete endothermic decomposition at elevated temperatures above room temperatures to form gaseous products.

2. The composition of claim 1 wherein said binder is combustible to form gaseous products.

3. The composition of claim 1 additionally containing an oxidizing agent capable of decomposition at elevated temperatures above room temperatures to facilitate the oxidation of said binder.

4. The composition of claim 1 additionally containing a plasticizer for said binder, said plasticizer being combustible to form gaseous products.

5. The composition of claim 1 wherein said binder is a polymerizable liquid capable of being cured to form a solid matrix.

6. The composition of claim 5 wherein the content of said coolant substance is in the range of above 0.5 to 4 parts by weight to 1 part by weight of said binder.

7. A self-extinguishing insulating composition, comprising an initially liquid polymerizable binder capable of being cured to form a solid matrix, a curing agent to polymerize said binder to the solid state, and a coolant substance capable of substantially complete endothermic decomposition at elevated temperatures above room temperatures to form gaseous products, said binder being combustible to form gaseous products without leaving a residue.

8. The composition of claim 7 wherein the content of said coolant substance is in the range of from about 0.5 to 4 parts per part by weight of said binder.

9. The composition of claim 7 wherein said coolant substance is selected from the group consisting of ammonium oxalate, oxalic acid and fumaric acid.

10. The composition of claim 9 wherein said binder is selected from the group consisting of polysulfides, polyurethanes and epoxide resins.

11. A self-extinguishing insulating composition comprising a combustible binder constituting a polymerizable liquid capable of being cured to form a solid matrix and having ammonium oxalate uniformly dispersed therein at a level of from about 0.5 to 4 parts per part by weight of said binder.

12. The composition of claim 11 additionally containing a plasticizer for said binder, said plasticizer being combustible to form gaseous products without leaving a residue.

13. The composition of claim 11 wherein said binder is selected from the group consisting of polysulfides, polyurethanes and epoxide resins.

14. The composition of claim 13 additionally containing ammonium perchlorate to facilitate the oxidation of said binder.

15. An insulator, including the following substances:

a binder having properties of combusting at elevated temperatures and forming gases and constituting a polymerizable liquid capable of being cured to form a solid matrix;

a plasticizer having properties of combusting at elevated temperatures above room temperatures and forming gases;

a catalyst having properties of facilitating the curing of the binder and the combustion of the binder and the plasticizer; and

a coolant capable of substantially complete decomposition at elevated temperatures above room temperatures into gases in endothermic reaction when subjected to heat.

16. The insulator set forth in claim 15 wherein the coolant decomposes into gases which remain at the surface of the insulator to prevent the binder and the plasticizer from combusting after the application of heat to the insulator.

17. The insulator set forth in claim 16, further including an oxidizer having properties of decomposing to provide an oxidation of the binder and the plasticizer and to form gases in providing such decomposing.

18. An insulator including the following substances:

a binder constituting a polymerizable liquid and having a hydrocarbon chain and capable of being processed as a liquid and of being cured to form a solid and having properties of combusting at elevated temperatures without providing any residue;

a plasticizer constituting an ester and having properties of combusting at elevated temperatures above room temperatures without providing any residue;

a catalyst having properties of facilitating the curing of the binder and the oxidation of the binder and the plasticizer at the elevated temperatures; and

a coolant capable of substantially complete decomposition at the elevated temperatures above room temperatures and of providing endothermic reactions in such decomposition.

19. An insulator as set forth in claim 18, further including an oxidizer having properties of decomposing at the elevated temperatures to provide an oxidation of the binder and the plasticizer and to form gases in providing such decomposing.

20. The insulator set forth in claim 18 wherein

the binder constitutes a material formed from a group consisting of polysulfides, polyurethanes, polybutadienes, polyester resins, and epoxides;

the plasticizer constitutes a material formed from a group consisting of triacetin, dibutyl phthalate, and high-boiling esters of polyfunctional alcohols; and

the coolant is formed from chemical groups consisting of oxalates, oxalic acid, fumaric acid, oxamide, carbamide and hydrazine compounds and carbamates.

21. An insulator including the following substances:

a binder constituting a polymerizable liquid and having a hydrocarbon chain and capable of being processed as a liquid and of being cured to form a solid and of combusting at elevated temperatures above room temperatures without providing any residue;

an oxidizer having properties of substantially complete decomposition at the elevated temperatures to provide an oxidation of the binder and to form gases in providing such decomposing; and

a coolant dispersed in the binder and capable of substantially complete decomposition at the elevated temperatures and of providing endothermic reactions in such decomposition.

22. An insulator including the following substances and having properties of decomposing and combusting only during the application of heat to the insulator;

a binder having a hydrocarbon chain and capable of being processed as a liquid and of being cured to form a solid and of combusting at elevated temperatures without providing any residue;

an oxidizer having properties of decomposing at the elevated temperatures to provide an oxidation of the binder and to form gases in providing such decomposing; and

a coolant dispersed in the binder and having properties of decomposing at the elevated temperatures and of providing endothermic reactions in such decomposition, the binder being a polysulfide, the oxidizer being ammonium perchlorate and the coolant being ammonium oxalate.

23. The insulator set forth in claim 22 wherein the polysulfide, the ammonium perchlorate and the ammonium oxalate respectively have approximate relative parts by weight of 1, one-half and 3.

24. The insulator set forth in claim 22 wherein the ammonium perchlorate has a range up to approximately 4 parts by weight to 1 part by weight of binder and the ammonium oxalate has a range of approximately one-half to 4 parts by weight to 1 part by weight of binder.

25. An insulator, including the following substances:

a binder constituting a polymerizable liquid and having properties of becoming cured from a liquid to a solid and of combusting at elevated temperatures above room temperatures without forming a liquid; and

a coolant dispersed in the binder and capable of substantially complete decomposition into gases at the elevated temperatures in an endothermic reaction.

26. The insulator set forth in claim 25, including, a curing agent for the binder.

27. The insulator set forth in claim 25, further including an oxidizer capable of substantially complete decomposition at the elevated temperatures above room temperatures to provide an oxidation of the binder and to form gases in such decomposition.

28. The insulator set forth in claim 25 wherein the binder constitutes a material formed from a group consisting of polysulfides, polyurethanes, polybutadienes and epoxides;

the coolant is formed from chemical groups consisting of oxalates, oxamide, oxalic acid, fumaric acid, carbamide and hydrazine compounds and carbamates.

29. The insulator set forth in claim 28 wherein oxidizer formed from a group consisting of perchlorates and nitrates is included in the insulator and is provided with properties of substantially complete decomposition at the elevated temperatures to provide an oxidation of the binder and to form gases in such decomposition.

30. An insulator for materials including the following substances;

a binder formed from a polymerizable liquid group consisting of polysulfides, polyurethanes, polybutadienes, polyester resins, and epoxides and having properties of combusting at elevated temperatures above room temperatures without forming any residues, the binder constituting approximately one (1) part by weight;

an oxidizer formed from a group consisting of chlorates, perchlorates, and nitrates and having properties of substantially complete decomposition at the elevated temperatures to provide an oxidizing of the binder and to form gases in providing such decomposing, the oxidizer constituting up to approximately four (4) parts by weight;

a coolant formed from a group consisting of oxalates, oxamides, oxalic acid, fumaric acid, carbamide and hydrazine compounds and carbamates and capable of substantially complete decomposition at the elevated temperatures and of providing endothermic reactions in such decomposition, the coolant constituting approximately one-half to four parts by weight; and

a plasticizer formed from a group consisting of triacetin, dibutyl phthalate, and high boiling esters of polyhydric alcohols and having a weight up to approximately 30 percent of the binder by weight.

31. In an insulator including the following substances:

a binder formed from a polymerizable liquid group consisting of polysulfides, polyurethanes, polybutadienes, polyester resins, and epoxides having properties of combusting at elevated temperatures above room temperatures without forming any residues, the binder constituting approximately one (1) part by weight;

a coolant formed from a group consisting of ammonium oxalates, oxamides, carbamates, oxalic acid, fumaric acid, carbamide and hydrazine compounds and capable of substantially complete decomposition at the elevated temperatures above room temperatures and of providing endothermic reactions in such decomposition, the coolant constituting approximately three (3) parts by weight; and

a plasticizer formed from a group consisting of triacetin, dibutyl phthalate, and high boiling esters of polyhydric alcohols and having a weight up to approximately thirty percent (30%) of the binder by weight.

32. In the insulator set forth in claim 31, an oxidizer formed from a group consisting of chlorates, perchlorates and nitrates and having properties of substantially complete decomposition at the elevated temperatures above room temperatures to provide an oxidizing of the binder and to form gases in providing such decomposing, the oxidizer constituting approximately one part by weight.