Alliant Techsystems Inc.

Thiokol Corporation

David G Guillot

Albert R Harvey

Himansu M Gajiwala

This method permits manufacturing EPDM rocket motor insulation in which carbon fibers are dispersed and immobilized in the EPDM polymeric matrix but are not excessively fractured or fragmentized, i.e., broken into smaller fragments, when encountering degrees of shear necessary to homogeneously or otherwise distribute or disperse the carbon fibers in the EPDM polymeric matrix. The method is substantially solvent free and is performed via distributive/reduced shear mixing to distribute the fragile carbon fibers into a rubber matrix without excessive damage. According to one embodiment, at least about 50% of the elastomer composition introduced into the mixing apparatus is liquid EPDM terpolymer having sufficiently low molecular weight and high diene content to permit dispersion of the carbon fibers in the EPDM without substantial fragmentation of the fibers. According to another embodiment, mixing takes place in a kneader capable of rotating a screw having a discontinuous screw thread about the screw axis while superimposing an axially reciprocating stroke to the screw. The kneader imparts low shear distributive mixing of the carbon fibers in the EPDM terpolymer.

Method of insulating a case of a solid propellant rocket motor

A novel and improved EPDM formulation for a solid propellant rocket motor is described wherein hexadiene EPDM monomer components are replaced by alkylidene norbornene components, and, with appropriate adjustment of curing and other additives, functionally required rheological and physical characteristics are achieved with the desired compatibility with any one of a plurality of solid filler materials, e.g., powder silica, carbon fibers or aramid fibers, and with appropriate adhesion and extended storage or shelf-life characteristics.

EPDM rocket motor insulation

An insulation composition that comprises at least one nitrile butadiene rubber ('NBR') having an acrylonitrile content that ranges from approximately 26% by weight to approximately 35% by weight and polybenzoxazole ('PBO') fibers. The NBR may be a copolymer of acrylonitrile and butadiene and may be present in the insulation composition in a range of from approximately 45% by weight to approximately 56% by weight of a total weight of the insulation composition. The PBO fibers may be present in a range of from approximately 3% by weight to approximately 10% by weight of a total weight of the insulation composition. A rocket motor including the insulation composition and a method of insulating a rocket motor are also disclosed.

Polybenzoxazole-filled nitrile butadiene rubber compositions

A novel and improved EPDM formulation for a solid propellant rocket motor is described wherein hexadiene EPDM monomer components are replaced by alkylidene norbornene components and with appropriate adjustment of curing and other additives functionally-required rheological and physical characteristics are achieved with the desired compatibility with any one of a plurality of solid filler materials, e.g. powder silica, carbon fibers or aramid fibers, and with appropriate adhesion and extended storage or shelf life characteristics.

A low shear modulus vulcanizate for construction of flexible bearings, particularly for rocket motors, consisting essentially of a mixture of two natural or synthetic rubber copolymers, the first having about 92% cis-1,4-polyisoprene and about 8% trans-1,4-polyisoprene moieties and the second having about 98% by weight cis-1,4-polyisoprene and about 2% by weight trans-1,4-polyisoprene moieties. The composition is lightly filled and contains a low proportion of sulfur, so the vulcanizate has the required low shear modulus, low rate of thermal crystallization at low temperatures, and an acceptably high shear strength.

Crystallization resistant, low modulus elastomer for flexible bearings

Thermoplastic elastomeric ablative insulation having low density are disclosed. The ablative insulation is based upon a thermoplastic elastomeric polymer resin containing a polyamide polymer and a maleic anhydride modified EPDM polymer. The ratio of polyamide polymer to maleic anhydride modified EPDM is in the range from about 20:80 to about 40:60. Carefully selected fillers provide suitable charring and ablative insulation performance without unduly increasing the insulation density. Typical fillers include an phosphorus containing compound, such as ammonium polyphosphate, a polyhydric alcohol present, such as pentaerythritol, silicone resin, chopped fibers, an antioxidant, a butadiene polymer, and a peroxide.

Low density thermoplastic elastomeric insulation for rocket motors

Thermoplastic elastomeric ablative insulation having good mechanical properties at extremely low temperatures are disclosed. The insulation is based upon a polyamide-ether resin and includes carefully selected fillers to possess good low temperature mechanical properties and still provide suitable charring and ablative insulation performance at low temperatures (-65.degree. F.). A typical insulation within the scope of the present invention includes a polyamide-ether thermoplastic elastomeric polymer resin, an inorganic phosphorus containing compound, such as ammonium polyphosphate, present in the insulation from about 5 to about 60 phr, and a polyhydric alcohol present, such as pentaerythritol, in the insulation from about 1 to about 30 phr. The insulation compositions within the scope of the present invention optionally include silicone resin present in the insulation in range from about 0 to 15 phr. Chopped fiber filler may also be present in the insulation in range from about 0 to 100 phr.

Thermoplastic elastomeric internal insulation for rocket motors for low

Rocket motor insulation compositions are provided. An important component of such insulation compositions is a thermoplastic liquid crystal polymer. Such a polymer provides an ablative insulation which has good performance characteristics during operation of the rocket motor. One such thermoplastic liquid crystal polymer is a wholly aromatic polyester known as VECTRA.RTM.. The insulation may also include fillers such as fibrous fillers and particulate fillers. Typical fibrous fillers include glass or carbon fibers. Typical particulate fillers include materials such as silica, alumina, powdered coal, and the like.

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Tremonton, UT, United States of America

David G Guillot