US20050281968A1

US20050281968A1 - Energetic structural material

Info

Publication number: US20050281968A1
Application number: US10/870,889
Authority: US
Inventors: Carl Shanholtz; Scott Riley
Original assignee: Alliant Techsystems Inc
Current assignee: Northrop Grumman Innovation Systems LLC
Priority date: 2004-06-16
Filing date: 2004-06-16
Publication date: 2005-12-22

Abstract

A composite material including at least one energetic material and at least one filler, the composite material useful for the manufacture of structural components.

Description

FIELD OF THE INVENTION

The present invention relates generally to novel composite energetic materials which have sufficient structural integrity to allow manufacture of structural components. The material can be deflagrated or detonated upon proper initiation. The present invention further relates to methods of making and using the novel energetic material of the present invention.

BACKGROUND OF THE INVENTION

Structural composite materials which include an inert resin and a reinforcing fiber, typically fiber glass or carbon fiber, are well known. A commonly employed inert resin is an epoxy resin. Epoxide based composite materials are commonly employed in the manufacture of golf club shafts, boats, aircraft structure such as wings and fuselage, rocket motor cases and so forth. Epoxide based composite materials, while having excellent structural characteristics, do not contribute either to the propulsion of weaponry, or to the explosive power.
“Energetic” compounds, such as glycidyl azide polymers (GAPs), are used for a wide variety of formulations including explosive formulations, propellants, gas-generating compositions, and the like. It is generally preferred that such materials have a high energy content yet be relatively insensitive to impact, such that accidents are avoided and energy is released only when intended. However, such materials typically lack the integrity to be employed in the manufacture of structural composites.
There remains a need in the art for composite energetic materials which may be detonated or deflagrated upon proper initiation, and which have high structural integrity to allow them to be employed in the manufacture of structural components such as consumable rocket motor cases, rocket motor cases or unmanned aircraft that can be converted to an explosive device on demand, self-destructible componentry, and so forth.

SUMMARY OF THE INVENTION

The present invention relates to a composite energetic material which has high structural integrity and which can thus be employed in the manufacture of structural components, and which can be deflagrated or detonated upon proper initiation. The composite material includes an energetic resin and a reinforcement filler. The material can act as both a structural component as well as being the explosive device.
In some embodiments the energetic resin is a two-part thermosetting system in which a component A is reacted with a component B to form an energetic resin, and in some embodiments the energetic resin is a one part system.
One suitable class of energetic resins are those in which component A includes at least one polymer having two or more azide moieties and a component B includes at least one polyfunctional compound which has two or more carbon-carbon double or triple bonds adjacent to an activating moiety.
Another suitable class of resins include those formed by the reaction of component A which includes an energetically substituted alkyl diisocyanate such as those substituted with nitro- or nitraza groups and component B includes a polyol.
Suitable examples of substituted diisocyanates include, but are not limited to, 3,3,5,7,7-pentanitro-5-aza-1,9-nonane diisocyanate; 2-nitraza-1,4,butane-diisocyanate; 2,5-dinitraza-1,6-hexane diisocyanate; and so forth.
Another suitable class of energetic resins include those which are a one-part system which employs a free radical cured energetically substituted vinyl compound. Examples of such compounds include, but are not limited to nitroethyl methacrylate, dinitroporpyl acrylate, trinitroethyl acrylate, and so forth. Any suitable initiators known in the art such as peroxides, for example, may be employed. There are several categories of free radical initiators including thermal initiators, self initiation, redox initiators, photochemical initiators, ionizing radiation, and so forth. Very common thermal initiators include the peroxides and the azo compounds, for example. Photochemical initiators are often activated by UV light and include, for example, benzoin. These are only illustrations of some common free radical initiators and are not intended to limit the scope of the present invention. Such initiators are known to those of ordinary skill in the art.
In one embodiment, component A) includes at least one polymer which is a glycidyl azide polymer (GAP) and component B) includes at least one polyfunctional compound such as polyfunctional acrylates, polyvinyl ethers, polyallyls, polyacetylenic compounds and so forth. In one embodiment, component B) is a polyacrylate, i.e. a dienophile.
The GAP may further include additional functional moieties such as hydroxyl groups, for example. If the hydroxyl groups are terminal, the polymer may be referred to as a polyol.
The following is a structural representation of a GAP unit:
In one embodiment, the at least one polyfunctional olefin is an acrylate. Examples of suitable acrylates include, for example, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexane diol diacrylate, tripropylene glycol diacrylate, glycerol triacrylate, glycerol 1,3-diacrylate, trimethylol propane diacrylate, trimethylol propane triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, bisphenol-A diacrylate, alkoxylate acrylates such as ethoxylated and/or propoxylated bisphenol-A acrylates and ethoxylated and/or propoxylated trimethylol propane di- and tri-acrylates, acrylate terminated polyethers, acrylate terminated polyesters, urethane acrylates, epoxy acrylates and the like.
Another example of a class of polyfinctional olefins useful herein is the class of polyvinyl ethers.
Another example of a class of suitable polyfunctional olefins is the class of polyallyl compounds. One member of this group is glyoxal bis (diallyl acetal).
Another example of a class of suitable class of polyfunctional olefins is the class of polyacrylate compounds, one member of which is dipropargyl carbonate.
Other suitable polyfunctional compounds include, but are not limited to, propargyl ether, dipropargyl bisphenol A, tripropargyl 1,3,5 benzene tricarboxylate, pentaerythritol di tri and tetra-propiolates, hexanediol di-propiolate, pentaerythritol di, tri and tetra-3-butynates, hexanediol di-3-butynoate, pentaerythritol di, tri and tetra-4-pentynoates, teteaethylene glycol di-3-butynoate, ethylene glycol di-3-butynoate, neopentyl di-3-butynoate, diethylene glycol di-3-butynoate, trimethylol 4-pentynoate, hexanediol di-4-pentynoate, teteaethylene glycol di-4-pentynoate, ethylene glycol di-4-pentynoate, neopentyl di-4-pentynoate, diethylene glycol di-4-pentynoate, glyerol di and tri propiolates, glyerol di and tri-3-butynoates, glycerol di and tri-4-pentynoates, and so forth.
A reinforcing filler is employed in combination with the energetic resin. Suitable examples of reinforcing fillers include, but are not limited to, glass fibers, carbon fibers, polyaramid fibers, cellulosic fibers, paper, metal, wire, silica powders, carbon black and mixtures thereof.
The reinforcing filler may be incorporated with the energetic resin using any suitable means known in the art. One method is by a process commonly referred to in the art as “wet winding”. Using this process component A and component B of the energetic material are premixed, and the filler is then “wetted” with the premixture. The resins typically maintain a low viscosity liquid state for hours, and may require heat to build viscosity and solidify. While this is a typical procedure, the steps may be varied without departing from the scope of the present invention.
A wet winding machine, structurally similar to a lathe, rotates the mold tooling for the component or part which is being manufactured. The filler, typically in the form of a long fiber, is threaded onto a spool, the end of the fiber attached to the rotating mold tooling, and the mold tooling is rotated such that the fiber wraps around the tooling, thus forming a shell. The wet resin is held in a reservoir between the mold tooling and the spool on which the fiber is held. The fiber is threaded through a number of rollers and/or pivot points such that it is briefly submerged in the resin on its way to the mold tooling. Thus, the fiber being wrapped on the mold tooling is wetted with the resin.
A catalyst, as well as other optional ingredients may also be included in component A), component B) or both. Such optional ingredients include, for example, surfactants, energetic powders, antioxidants, plasticizers, and so forth.
The novel energetic composite material of the present invention allows structural components to be converted into useable energy upon proper initiation offers substantial advantage to a number of industries and in particular is advantageous for use in military applications. Such
The energetic structural material may further include an initiation system.
The composite energetic materials according to the invention are advantageous because they have both structural integrity, and are detonatable and/or deflagratable as well.
Thus, the composite materials according to the present invention may be employed in the manufacture of moldable compositions which may be employed in the manufacture of deflagratable and/or detonatable articles such as cartridge cases, mortar shell ends, detonator tubes, and so forth, which have a very high potential and thus contribute energy for propelling a self-propelled projectile of which the combustible article forms a part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the results of cure time at room temperature on Shore D Hardness on selected ratios of triacrylate to GAP mixtures.
FIG. 2 illustrates the burn rates of various GAP/acrylate compositions and further in combination with an energetic powder.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

While this invention may be embodied in many different forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.
The energetic composite materials of the present invention include at one energetic resin and at least one reinforcing filler. The at least one energetic resin may be a two-part thermosetting system in which the energetic resin is the reaction product of component A and component B, or it may be a one part system.
One class of two-part thermosetting resins include that that are the reaction product of part A which includes at least one polymer having two or more azide moieties and part B which includes at least one compound having two or more carbon-carbon double or triple bonds. The polymers useful in this two-part thermosetting system include any polymers having two or more azide moieties. Specific examples of a polymer having multiple azide moieties is glycidyl azide polymer (GAP). This polymer may also be referred to as a polyol. The polymer may be a linear or branched polymer. Of course, more than one polymer having multiple azide moieties may be employed in part A as well.
GAP is an energetic material that will react via a 1,3 dipolar cyclo-addition to an activated olefin to form triazoline rings as shown represented by the chemical reactions in schemes 1 shown below. Scheme 1 illustrates the formation of a triazoline ring using GAP and a polyfinctional compound having vinyl groups.
Under certain conditions, the triazoline ring will rearrange to form a Schiff's base and nitrogen gas. The formation of the triazoline ring, and it subsequent decomposition to a Schiff s base is represented by the general chemical reactions is also shown in scheme 1 below.
Scheme 2 illustrates the formation of a triazole ring using GAP and a polyfunctional compound having acetylene groups. Such a compound shall be referred to herein as an as one having at least one acetylenic moiety. The triazole ring does not decompose like a triazoline ring does.
A polymer can be formed from GAP if it is crosslinked to another chain of GAP by a compound that has at least two activated olefin groups per molecule. Among the materials that will react with GAP are polyfinctional acrylates, vinyl ethers, allyls, acetylenic compounds and so forth. GAP cured in this manner can have crosslink densities which are similar to epoxy resins typically used in composites.
A glycidyl azide unit has the following general formula:
A glycidyl azide polymer may be represented by the following general formula:
Any molecule which contains multiple carbon-carbon bonds or which are suitable for a 1,3-dipolar cycloaddition reaction may be employed in curing polymer. The carbon-carbon double or triple bond may be positioned adjacent to an activating moiety such as, for example, carboxyl esters, ketones, aldehydes, halogens, aromatic rings, nitro or nitrile groups, and so forth.
One specific class of compounds useful for curing the azide containing polymer is the polyfunctional acrylates. Examples of suitable polyfunctional acrylates include the di- and triacrylates, for example. Specific examples include, but are not limited to, ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexane diol diacrylate, tripropylene glycol diacrylate, glycerol triacrylate, glycerol 1,3-diacrylate, trimethylol propane diacrylate, trimethylol propane triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, bisphenol-A diacrylate, alkoxylate acrylates such as ethoxylated and/or propoxylated bisphenol-A acrylates and ethoxylated and/or propoxylated trimethylol propane di- and tri-acrylates, acrylate terminated polyethers, acrylate terminated polyesters, urethane acrylates, epoxy acrylates and so forth. Mixtures of such materials find utility herein as well.
Other suitable polyfinctional compounds include, but are not limited to, propargyl ether, dipropargyl carbonate, tripropargyl 1,3,5 benzene tricarboxylate, pentaerythritol di, tri and tetra-propiolates, hexanediol di-propiolate, pentaerythritol di, tri and tetra 3-butynates, pentaerythritol di tri and tetra-4-pentynoates, dipropargyl bisphenol A, trimethylol 3-butyonates, trimethylol 4-pentynoates, hexanediol di-3-butynoate, hexanediol di-4-pentynoate, teteaethylene glycol di-4-butynoate, teteaethylene glycol di-4-pentynoate, ethylene glycol di-4-butynoate, ethylene glycol di-4-pentynoate, neopentyl di-3-butynoate, neopentyl di-4-pentynoate, diethylene glycol di-3-butynoate, diethylene glycol di-4-pentynoate, glyerol di and tri propiolates, glyerol di and tri-3-butynoates, glycerol di and tri-4-pentynoates, and so forth.
The reaction may be a crosslinking or curing reaction in which the azido group (—RN₃) of the GAP polymer reacts with the double bond of the acrylate or triple bond of an acetylenic group to from a triazoline or triazole ring, respectively.
Crosslinking may proceed according to the following general reaction:

R₆is suitably organic, but may be inorganic as well. R₆may be polymeric or oligomeric as well.
It has been found that significant benefits can be achieved at ratios of about 0.5:1 acrylate to GAP to about 0.5:1.5. It is desirable to form one triazoline ring for each azide group in the GAP.
In one particular embodiment, a GAP/triacrylate combination exhibits satisfactory characteristics, cures rapidly to a hard resin at room temperature, and with rapid polymerization exhibits the potential to auto ignite. Such reaction can be mitigated by the addition of non-acrylate monomers to the system to control such rates. In one embodiment, this combination was employed with carbon fiber cloth. Such systems typically exhibit deflagration, but not necessarily detonation.
In another embodiment a GAP/GDBA system exhibits acceptable potlife at room temperature, satisfactory hardness when cured, but does not exhibit auto ignition. Such a system exhibits cure at 110° F. (43.3° C.) over 9 days to achieve a usable hardness without the formation of significant bubbles in the resin.
Another class of suitable polyfunctional compounds are the polyvinylethers.
Yet another class of polyfunctional compounds include the polyfunctional allyls. One example is glyoxal bis (diallyl acetal) (GBDA). It has been found that significant benefits can be achieved at ratios of about 0.3:1 to about 1.5:1 of the GBDA to the GAP.
Part A and part B of the two-part systems may be combined in any ratio which provides the desired degree of hardness. In a more broad sense, suitable ratios are, for example, from about 0.3:2.0 to about 2.0:1.0 on an equivalent weight basis, and more suitably, the ratio is about 0.5:1.0 to about 1.5:1.0 on an equivalent weight basis. Upon cure, the two part system transitions from a liquid state to a solid state. While curing will occur at ambient temperatures, the cure rate can be increased by raising the temperature at which the curing is accomplished.
It is believed that reaction occurs via a 1,3-dipolar cycloaddition reaction between the azide moiety and the carbon-carbon double bond resulting in a triazoline ring or triple bond resulting in a triazole ring.
A reinforcing filler is included in the energetic composite material in combination with the energetic resin. Such fillers are known in the art of structural materials and include, but are not limited to, glass fibers, carbon fibers, polyaramid fibers, cellulosic fibers, paper, metal, wire, silica powders, carbon black, and so forth. Mixtures of two or more such reinforcing fillers may be employed in the composite materials of the present invention.
Fiber fillers may be utilized as individual filaments (TOW), woven cloth, felt, chopped fiber, staples, and so forth.
Other optional ingredients in the energetic structural composites according to the invention including, but not limited to, energetic powders, surfactants, stabilizers, plasticizers and so forth. This list is intended for illustrative purposes only and is not exhaustive. Such ingredients are known to those of ordinary skill in the art.
Other energetic structural solid materials may be desirably incorporated into the energetic composite materials according to the present invention for additional energy and/or improved detonatability. Such additional solids are known to those of skill in the art and include, but are not limited, such compounds as solid nitramines, ammonium perchlorates, ammonium nitrates, and so forth. Examples of such nitramines include, but are not limited to, trimethylene trinitrarnine (RDX), tetramethylene tetranitramine or 1,3,5-trinitro-1,3,5-triazacyclohexane (HMX); 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0^5,9.0^3,11]-dodecane; 1,3,5,7-tetra-nitro-1,3,5,7-tetraazacyclooctane; 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0^5,9.0^3,11]dodecane (TEX); 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), triaminoguanidinium trinitrate (TAG nitrate), pentaerythritol tetranitrate (PETN); 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 1,3,3-trinitroazetidine (TNAZ); ammonium dinitramide (AND); 1,1-diamino-2,2-dinitro ethane (DADNE); and so forth and mixtures thereof. Those skilled in the art will appreciate that other known and novel high explosives not listed above may also be used in the present invention.
Other optional ingredients in the energetic structural composites according to the invention including, but not limited to, energetic powders, surfactants, stabilizers, plasticizers and so forth. This list is intended for illustrative purposes only and is not exhaustive. Such ingredients are known to those of ordinary skill in the art.
Energetic plasticizers may be optionally employed, although such plasticizers should be employed in amounts such that they are not detrimental to the cure time and hardness. Thus, for most applications, it may not be desirable to employ a plasticizer. Examples of such plasticizers include, but are not limited to, bis(2,2-dinitropropyl)acetal/bis(2,2-dinitropropyl)formal (BDNPF/BDNPA), trimethylolethanetrinitrate (TMETN), triethyleneglycoldinitrate (TEGDN), diethyleneglycoldinitrate (DEGDN), nitroglycerine (NG), 1,2,4-butanetrioltrinitrate (BTTN), alkyl nitratoethylnitramines (NENA's), or mixtures thereof.
The reinforcing filler may be incorporated with the energetic resin using any suitable means known in the art. One method is by a process commonly referred to in the industry as “wet winding”. Using this process if the energetic resin is a two component system, for example, then component A and component B of the energetic material are premixed, and the filler is then “wetted” with the premixture. The resins typically maintain a low viscosity liquid state for hours, and may require heat to build viscosity and solidify. While this is a typical procedure, the steps may be varied without departing from the scope of the present invention.
Once the reinforcing filler has been wetted with the premix, then the two-part system is allowed to cure. The cure may proceed at ambient temperatures, but it can be accelerated through the use of a catalyst system, and can be accelerated such as by elevating the temperature of the mixture.
If a one part system such as the free radical system described above, is employed, an appropriate initiator may be added to the system. Any suitable initiator may be employed. Such initiators are known in the art. Suitable examples include, but are not limited to,
A wet winding machine, structurally similar to a lathe, rotates the mold tooling for the component or part which is being manufactured. The filler, typically in the form of a long fiber, is threaded onto a spool, the end of the fiber attached to the rotating mold tooling, and the mold tooling is rotated such that the fiber wraps around the tooling, thus forming a shell. The wet resin is held in a reservoir between the mold tooling and the spool on which the fiber is held. The fiber is threaded through a number of rollers and/or pivot points such that it is briefly submerged in the resin on its way to the mold tooling. Thus, the fiber being wrapped on the mold tooling is wetted with the resin.
A process known as “wet layups” may also be followed in which a cloth woven from the reinforcing filler, for example, carbon or glass fiber, is wetted with the energetic resin as described above and placed as desired. This process is commonly employed in the manufacture of structural bodies and is known in the art.
Yet another method is to use what is known in the art as a “pre-preg”. Using this method, the fiber is wetted with the energetic resin and is placed on a spool or formed into a cloth. The material is referred to as the “pre-preg”.
The resultant cured resin is a highly combustible solid. Therefore, advantageously, it can be detonated or deflagrated upon proper initiation. Thus, an initiation system may be desirably incorporated into the resultant article of manufacture such as a fuzzing system.
In one particular embodiment of the present invention, a GAP/poly-acrylate system was employed in combination with RDX filler. This combination was found to be easily applied to carbon fiber cloth, even when mixed with significant amounts of RDX. This system generates sufficient amounts of heat, i.e. energy, during its rapid polymerization that if a critical mass is prepared, the resin autoignites.
In another embodiment, a combination of GAP/glyoxyl bis(diallyl acetal)(GBDA), a tetrallyl compound, may polymerize more slowly with GAP at elevated temperatures of greater than about 38° C. (greater than about 100° F.) than a GAP/acrylate system. Such a combination of GAP/GBDA can produce a resin that has desirable properties for composite resins, but that does not exhibit the extreme autoignition that may happen with a GAP/acrylate system.
The composite material of the present invention is advantageously employed in explosive devices because it can be detonated to provide blast energy while having enough structural integrity to be used in making the structural components of the explosive device itself, for example.
The composite material of the present invention may also be deflagrated to provide heat or propulsive gases, or can be employed to destroy the structural component in a rapid manner.
Due to having properties which allow it to be detonated as well as to be able to employ the material in the manufacture of structural components, the present invention finds utility in military applications.
The present invention may be employed in the manufacture of aircraft bodies such as drone aircraft which can be directed to a target and detonated, combustible gun projectile sabots which can detonated en route to produce a traveling charge resulting in improved gun ballistic performance, combustible rocket motor cases which provide added thrust during sustained phase flight or which consume the case to reduce drag, components for reconnaissance equipment that can be rapidly destroyed to prevent capture, and so forth. Other applications may include rockets and missiles and components thereof, and casings for cartridges, and so forth.
The following non-limiting examples further illustrative embodiments of the present invention.

EXAMPLES

Example 1

The autoignition temperature of several resins formed through the thermosetting reaction of glycidyl azide polymers (GAPs) with various acrylates was tested using differential scanning calorimetry (DSC). The results are shown in the table below.

TABLE 1


			Autoignition Temp
Formula	Part A	Part B	(° C.)

1	GAP polyol	—	226
2	GAP polyol	1,6-hexanediol	130
		diacrylate
3	GAP polyol	Tetraethylene glycol	130
		diacrylate
4	GAP polyol	Polyethylene glycol	125
		(400) diacrylate
5	GAP polyol	Trimethyleneolpropane	137
		triacrylate
6	GAP polyol	Pentaerythritol	130
		triacrylate
7	GAP polyol	Pentaerythritol	128
		tetraacrylate

Example 2

A variety of GAP/polyacrylate and GAP/GBDA systems were tested for mechanical and thermal characteristics, interaction/adhesion with various types of fiber cloth, and ignitability/sensitivity. These compounds are shown in table 2 below.

TABLE 2


	Commercial	Equivalent	Functional
Compound	Name	Weight (g)	Groups

Glycidyl Azide Polymer	GAP	99	Azide/
(Polyol)			Alcohol
Glyoxal bis (diallyl		63.6	Tetraallyl
acetal) (GBDA)
Tris[(4-vinyloxy)butyl]	Vectomer ®	180.2	Trivinyl
trimelliate	5015		ether
Bis[(4-vinyloxy)butyl]	Vectomer ®	181	Divinyl
isophthalate	4010		ether
Proprietary Composition	Vectomer ®	376.6	Poly vinyl
	1312		ether
Pentaerythritol triallyl		85.5	Triallyl
ether			ether
Triallyl amine		63.5	Triallyl
Divinyl triethyleneglycol		101	Divinylether
Bisphenol A divinyl ether			Divinyl ether
Diallyl Maleate		65.4	Diallyl/vinyl
			diacid
Allylmethacrylate		63.1	Allyl/
			acrylate
1,6 Hexanediol Diacrylate	Sartomer ® SR-	113	Diacrylate
	238
Tetraethylene Glycol	Sartomer ® SR-	151	Diacrylate
Diacrylate	268
Polyethylene Glycol (400)	Sartomer ® SR-	254	Diacrylate
Diacrylate	344
Trimethylolpropane	Sartomer ® SR-	98.6	Triacrylate
Triacetate	351
Pentaerythritol	Sartomer ® SR-	99.3	Triacrylate
triacrylate	444
Pentaerythritol	Sartomer SR-	88	Tetra
Tetraacrylate esters	295		Acrylate
W/Pentaerythritol
Triacrylate esters

Mixtures employing the various polyacrylates and GAP demonstrated that these materials will polymerize at room temperature without a catalyst in less than 24 hours. The resulting polymers had physical characteristics ranging from rubbery to glassy depending on the functionality of the acrylate, and the ratio of GAP to the polyacrylate in the polymer. The GAP/acrylate systems will also autoignite in small amounts, e.g. less than 10 g, of freshly mixed GAP/acrylate if placed in an oven at 140° F. (60° C.), or a GAP/acrylate system was found to autoignite at room temperature when sufficient amounts were present in a container that prevented sufficient heat exchange with the surrounding environment, e.g. 70 g in a small cup.

Example 3

A series of polymers were prepared using GAP polyol and the above list of polyfunctional acrylates. The polymers were analyzed by differential scanning calorimetry (DSC):

1) the acrylate neat as received;
2) immediately after mixing with GAP; and
3) after 24 hours curing.

The auto ignition temperature of GAP was determined to be 226° C. as shown in Table 3 below while the single exotherms reported for the neat acrylates indicates the auto polymerization temperature of the acrylate monomers (167-212° C.). The initial exotherm (56° C.-68° C.) observed in the freshly mixed samples is the result of polymerization between GAP and the polyfunctional acrylate. The second exotherm (128° C.-135° C.) is the auto ignition temperature of the mixture. Exotherms in the cured EA polymers are due to the auto ignition of the polymer. DSC also determined that GAP/pentaerythritol tetraacrylate could be held at 97° C. for two hours with no auto ignition.

	TABLE 3


	DSC Exotherms

		Auto Ignition	Auto
Neat	Polymer-	(Freshly	Ignition
(° C.)	ization	Mixed)	Cured

GAP	226
1,6 hexanediol	167	68	135	130
diacrylate
Tetraethylene	172	66	129	130
Glycol diacrylate
Polyethylene	174	66	128	125
Glycol (400)
Diacrylate
Trimethylolpropane	212	63	134	137
triacrylate
Pentaerythritol	206	59	136	130
triacrylate
Pentaerythritol	201	56	132	128
tetraacryalte

It was determined that GAP/acrylate mixtures would wet (soak into) both fiberglass and graphite fibers cloths. Also, both fiber glass or carbon fiber cloth sections, when assembled wet with GAP/acrylate and cured as a unit, would adhere to each other, thereby producing a composite material.
Cubes of carbon fiber cloth (2×2×2 inches) that were saturated with a mixture of GAP/pentaerythritol triacrylate and cured, were found to deflagrate when subjected to initiation by a no. 8 blasting cap. Two other cubes of similar construction were prepared using a GAP/diacrylate adhesive (80%) and RDX (20%). These cubes were found to deflagrate with considerable yellow smoke when initiated with a no. 8 blasting cup.
Strands of cured GAP/polyacrylate impregnated fiber glass cloth were prepared for burn rate determination in both single and double ply configurations. It was found that neither the single nor double ply strands would burn using the standard techniques. Observations of these two composite materials included 1) that the two ply material was more rigid that the single ply, 2) that it was difficult to separate the two layers after cure and 3) the single ply was easy to cut with scissors.
A third and fourth set of strands were made using a single ply of carbon fiber cloth soaked in two GAP/acrylate energetic resins which were subsequently cured. One set of strands was made using the fiber cloth along with a solution made from a GAP/diacrylate and 0.5% acetone. The second set was made from the fiber cloth and GAP/diacrylate, trimethylene trinitramine (RDX) (20%) in acetone (0.5%). Each strand was coated in plasti-dip after curing. The samples made with only GAP/diacrylate were found to burn only as far as the coating on the strand, while strands which additionally had RDX were determined to burn at an approximate rate of 0.18 ips at 500 psi.
Sensitivity of the cured GAP/polyacrylate systems was tested by impact (100 cm drop.). Samples were prepared from GAP/diacrylate/acetone solutions containing 0%, 5%, 10%, 15% and 20% RDX and cured at room temperature. It was found that only 20% of the samples containing 15% RDX deflagrated while approximately 80% of the samples containing 20% RDX deflagrated. None of the samples detonated under this stimulus.

Example 4

In a system of GAP and a polyfinctional crosslinker the ratio of 1:1 functional equivalents will produce the maximum number of triazoline rings in a fully cured polymer. It may be desirable from an energetic standpoint to have a low ratio of crosslinking monomer to GAP so as to leave some azide groups intact in the finished polymer. In other cases it might be desirable to insure minimum sensitivity by using a greater than 1:1 ratio of GAP and crosslinking monomer.
A series of samples were prepared having a range of ratios of GBDA to GAP between 0.3 GBDA to 1 GAP to 1.5 GBDA to 1 GAP. A second series of samples using mixtures of GAP/triacrylate were prepared at the same functional ratios for comparison. GBDA/GAP samples were cured at 150 F while the GAP/triacrylate samples were cured at room temperature. The samples were tested for hardness at 24, 48, 72 and 96 hours. The GBDA/GAP samples tested at 24 hours were found to be too soft to measure. Hardness tests were performed with a Shore D Durometer.
As can be seen from the data in FIG. 1 that the GAP/triacrylate samples with a triacrylate to GAP ratio of >0.5:1 were found to reach maximum hardness by 48 hours. Samples with a >0.7:1 reached maximum hardness at 24 hours. It can also be seen that increasing the ratio of triacrylate to GAP to 1.5:1 did not effect the hardness of the cured resin.
With regards to GAP/DPC resins, it can be seen from FIG. 2 that the burn rate of the resin is dependant on not only the ratio of GAP to DPC but also on the concentration of RDX in the resin. The highest burn rate was achieved with 20% RDX in a resin with a GAP/DPC ration of 6:1.

Examples 5, 6 and 7

Example 5 was prepared using GAP/dipropargyl carbonate (DPC) at a ratio of 1:1. The longitudinal tensile strength was determined using ASTM D-3039 and the energetic composite. The results are shown in the following table.

Maximum Stress Maximum Failure Modulus

psi (kPa) Strain % Strain % psi (kPa)

Example 5 276,281 4.84 4.94 7,816,429

(1,904,890) (53,892,381)
The values obtained for the maximum stress and strain, failure strain and modulus indicate an energetic composite product which has suitable strength and integrity for use in the industry.
Examples 6 and 7 were prepared using GAP/DPC at ratios of 6:1 and 3:1. Also, energetic powder, RDX, was added at concentrations of 20%, 40% and 60%. These compositions, along with example 5, were tested for resin burn rates. The mixed resins were fed as a slurry into a soda straw which was 0.25″ (6.35 mm) in diameter and burned in a standard strand bomb. The results are shown in FIG. 2. As can be seen from FIG. 2, the burn rates are faster at higher ratios of GAP to DPC and also when the concentration of RDX is increase.
The above disclosure is intended for illustrative purposes only and is not exhaustive. The embodiments described therein will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.

Claims

1. An energetic composite material comprising at least one energetic resin and at least one reinforcing filler.

2. The energetic composite material of claim 1 wherein said energetic resin is a two-part thermosetting composition.

3. The energetic composite material of claim 1 wherein said at least one energetic resin is selected from the group consisting of:

a) a two part composition wherein part A comprises at least one polymer having two or more azide moieties and part B comprises at least one polyfunctional compound having two or more carbon-carbon double bonds positioned next to an activating moiety; at least one compound having at least one allyl moiety, at least one compound having at least one acetylenic moiety, or mixtures thereof;

b) a two part composition wherein part A comprises at least one energetically substituted alkyl diisocyanate and part B comprises at least one polyol; or

c) at least one free radical cured energetically substituted vinyl compound.

4. The energetic composite material of claim 3 wherein said at least one energetically substituted alkyl diisocyanate comprises at least one nitro group or at least one nitraza group.

5. The energetic composite material of claim 4 wherein said at least one energetically substituted alkyl diisocyanate is selected from the group consisting of 3,3,5,7,7-pentanitro-5-aza-1,9-nonane diisocyanate; 2-nitraza-1,4-butane diisocyanate; 2,5-dinitraza-1,6-hexane diisocyanate; and mixtures thereof.

6. The energetic composite material of claim 5 wherein said free radical cured energetically substituted vinyl compound is selected from the group consisting of nitroethyl methacrylate, dinitropropyl acrylate, trinitroethyl acrylate, and mixtures thereof.

7. The energetic composite material of claim 1 wherein said energetic resin is a two part resin having a component A and a component B, and said energetic composite material is formed by premixing A and B and wetting said reinforcing filler with the premix.

8. The energetic composite material of claim 3 wherein said activating moiety is selected from the group consisting of carboxyls, carboxyl esters, ketones, aldehydes, halogens, aromatic rings, nitro groups, nitrile groups and mixtures thereof.

9. The energetic composite material of claim 3 wherein said at least one polyfunctional compound is an acrylate.

10. The energetic composite material of claim 9 wherein said at least one polyfunctional compound is selected from the group consisting of diacrylates, triacrylates and mixtures thereof.

11. The energetic composite material of claim 9 further comprising a non-acrylate.

12. The energetic composite material of claim 9 wherein said acrylate is selected from the group consisting of 1,6-hexanediol diacrylate, hexanediol dipropriolate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate and mixtures thereof.

13. The energetic composite material of claim 3 wherein said at least one polyfunctional compound is a polyolefin.

14. The energetic composite material of claim 3 wherein said at least one polyfunctional compound is glyoxal bis (diallyal acetal).

15. The energetic composite material of claim 3 wherein said at least one polymer is a glycidyl azide polyol.

16. The energetic composite material of claim 15 wherein said at least one polyfunctional compound is glyoxal bis (diallyl acetal) and said at least one polymer is glycidyl azide polyol.

17. The energetic composite material of claim 16 wherein said ratio of glyoxyl bis (diallyl acetal) to said glycidyl azide polyol is about 0.3:1.0 about 1.5:1.

18. The energetic composite material of claim 15 wherein said at least one polymer is glycidyl azide polyol and said polyfunctional compound is a polyfunctional acrylate.

19. The energetic composite material of claim 18 wherein the ratio of polyfunctional acrylate to in the acrylate cured GAP is in the range of about 0.5:1 to about 0.5:1.5 polyfunctional acrylate to GAP.

20. The energetic composite material of claim 3 wherein said at least one polyfunctional compound is selected from the group consisting of propargyl ether, dipropargyl carbonate, tripropargyl 1,3,5 benzene tricarboxylate, pentaerythritol di-3-butynate, pentaerythritol tri-3-butynate, pentaerythritol tetra-3-butynoate, pentaerythritol di-4-pentynoate, pentaerythritol tri-4-pentynoate, pentaerythritol tetra-4-pentynoate, dipropargyl bisphenol A, trimethylol 3-butyonates, trimethylol 4-pentynoates, hexanediol di-3-butynoate, hexanediol di-4-pentynoate, teteaethylene glycol di-3-butynoate, teteaethylene glycol di-4-pentynoate, ethylene glycol di-3-butynoate, ethylene glycol di-4-pentynoate, neopentyl di-3-butynoate, neopentyl di-4-pentynoate, diethylene glycol di-3-butynoate, diethylene glycol di-4-pentynoate, glyerol di and tri-3-butynoates, glycerol di and tri-4-pentynoates, and mixtures thereof.

21. The energetic composite material of claim 1 wherein said at least one reinforcing filler is a member selected from the group consisting of glass fibers, carbon fibers, polyaramid fibers, cellulosic fibers, paper, metal, wire, silica powders, carbon black and mixtures thereof.

22. The energetic composite material of claim 1 further comprising at least one member selected from the group consisting of surfactants, energetic powders, antioxidants and mixtures thereof.

23. The energetic composite material of claim 1 further comprising at least one member selected from the group consisting of nitramines, ammonium perchlorates, ammonium nitrates and mixtures thereof.

24. The energetic composite material of claim 23 further comprising at least one nitramine selected from the group consisting of trimethylene trinitramine, tetramethylene tetranitramine, and mixtures thereof.

25. The energetic composite material of claim 1 further comprising an initiation system.

26. A combustible article formed from an energetic composite material, said energetic composite material comprising:

A) at least one reinforcing filler; and

B) at least one energetic resin selected from the group consisting of:

i) an energetic two part resin which is the reaction product of at least one polymer having two or more azide moieties and at least one polyfunctional compound having two or more carbon-carbon double bonds which are adjacent to an activating moiety, at least one compound having at least one allyl moiety, at least one compound having at least one acetylenic moiety, or mixtures thereof;

ii) an energetic two part resin which is the reaction product of at least one energetically substituted alkyl diisocyanate and at least one polyol;

iii) a free radical cured energetically substituted vinyl compound;

and mixtures thereof.

27. The article of claim 26 wherein said reinforcing filler is wetted with i), ii) or iii) or mixtures thereof.

28. The combustible article of claim 26 further comprising at least one member selected from the group consisting of nitramines, ammonium perchlorates, ammonium nitrates, and mixtures thereof.

29. The deflagratable and/or detonatable article of claim 26 wherein said at least one polyfunctional compound is an acrylate.

30. The deflagratable and/or detonatable article of claim 29 wherein said acrylate is a member selected from the group consisting of hexanediol diacrylate, hexanediol dipropriolate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylporpane triacrylate and mixtures thereof.

31. The deflagratable and/or detonatable article of claim 26 wherein said at least one polymer is a glycidyl azide polyol.

32. The deflagratable and/or detonatable article of claim 26 wherein said at least one energetic resin is formed from a two part composition which is the reaction product of a polyfunctional acrylate and GAP wherein the ratio of polyfunctional acrylate to GAP is in the range of about 0.5:1 to about 0.5:1.5 polyfinctional acrylate to GAP.

33. The deflagratable and/or detonatable article of claim 26 wherein said activating moiety is selected from the group consisting of carboxyls, carboxyl esters, ketones, aldehydes, halogens, aromatic rings, nitro groups, nitrile groups and mixtures thereof.

34. The deflagratable and/or detonatable article of claim 26 wherein said least one energetically substituted alkyl diisocyanate is selected from the group consisting of 3,3,5,7,7-pentanitro-5-aza-1,9-nonane diisocyanate; 2-nitraza-1,4-butane diisocyanate; 2,5-dinitraza-1,6-hexane diisocyanate; and mixtures thereof.

35. The deflagratable and/or detonatable article of claim 26 wherein said free radical cured energetically substituted vinyl compound is selected from the group consisting of nitroethyl methacrylate, dinitropropyl acrylate, trinitroethyl acrylate, and mixtures thereof.

36. The deflagratable and/or detonatable article of claim 26 wherein said at least one reinforcing filler includes at least one member selected from the group consisting of glass fibers, carbon fibers, polyaramid fibers, cellulosic fibers, paper, metal, wire, silica powders, carbon black and mixtures thereof.

37. The deflagratable and/or detonatable article of claim 26 further comprising at least one member selected from the group consisting of surfactants, energetic powders, antioxidants and mixtures thereof.

38. The deflagratable and/or detonatable article of claim 26 wherein said article is a cartridge casing, a rocket motor case, an aircraft body, a gun projectile sabot, or a component for reconnassaince equipment.

39. The deflagratable and/or detonatable article of claim 26 wherein said at least one energetic resin is a two part composition formed from the reaction of at least one polyfunctional acrylate and glycidyl azide polyol.

40. The deflagratable and/or detonatable article of claim 39 wherein said ration of polyfunctional acrylate to GAP is about 0.5:1 to about 0.5:1.5.

41. The deflagratable and/or detonatable article of claim 39 further comprising a non-acrylate.

42. The deflagratable and/or detonatable article of claim 26 wherein said at least one energetic resin is a two part composition formed from the reaction of at least one glyoxal bis (diallyl acetal) and at least one glycidyl azide polyol.

43. The deflagratable and/or detonatable article of claim 42 wherein the ratio of said at least one glyoxal bis (diallyl acetal) to at least one glycidyl azide polyol is about 0.3:1 to about 1.5:1.0.

44. The deflagratable and/or detonatable article of claim 26 wherein said at least one polyfinctional compound is selected from the group consisting of propargyl ether, dipropargyl carbonate, tripropargyl 1,3,5 benzene tricarboxylate, pentaerythritol di-3-butynate, pentaerythritol tri-3-butynate, pentaerythritol tetra-3-butynoate, pentaerythritol di-4-pentynoate, pentaerythritol tri-4-pentynoate, pentaerythritol tetra-4-pentynoate, dipropargyl bisphenol A, trimethylol 3-butyonates, trimethylol 4-pentynoates, hexanediol di-3-butynoate, hexanediol di-4-pentynoate, teteaethylene glycol di-3-butynoate, teteaethylene glycol di-4-pentynoate, ethylene glycol di-3-butynoate, ethylene glycol di-4-pentynoate, neopentyl di-3-butynoate, neopentyl di-4-pentynoate, diethylene glycol di-3-butynoate, diethylene glycol di-4-pentynoate, glyerol di and tri-3-butynoates, glycerol di and tri-4-pentynoates.

45. The deflagratable and/or detonatable article of claim 26 further comprising an initiation system.

46. A method of making a structural article or a component of an article which is detonatable, deflagratable or both, the method comprising the steps of:

a) providing a premix of a component A and component B of a two-part energetic resin in liquid form or a one-part energetic resin in liquid form;

b) providing a reinforcing filler;

c) wetting the reinforcing filler with the liquid of a); and

d) allowing c) to solidify.

47. The method of claim 46 wherein said article is a cartridge casing, an aircraft body, a gun projectile sabot or a component for reconnaissance equipment.

48. The method of claim 46 wherein said article or component of said article further comprises an initiation system.