Solid explosive and propellant compositions containing a polyurethane polyacetal elastomer binder and method for the preparation thereof

Claim 1

A solid explosive or propellant composition characterized by low vulnerability to unplanned stimuli and having desired mechanical properties, including a desired degree of hardness, said composition comprising between 51 and 99 weight percent of a high energy material and between 1 and 50 weight percent of a binder, said binder being a chain-extended polyurethane polyacetal elastomer made by a process of: (a) reacting a dihydroxy-terminated polyacetal homopolymer with an alkylene diisocyanate in the presence of a urethane-forming catalyst in a reaction to produce an isocyanate-terminated prepolymer, said homopolymer having a weight average molecular weight of between about, 1,000 and about 60,000 as measured against a polystyrene standard by gel permeation chromatography and being produced by polymerizing a 4-lower alkyl substituted-1,3-dioxolane, said reaction employing between about 50 mole percent and about 70 mole percent of said alkylene diisocyanate based upon the total amount of said alkylene diisocyanate and said homopolymer employed, (b) reacting said isocyanate-terminated prepolymer with a dihydroxy-terminated polyacetal copolymer in the presence of a solvent and a urethane forming catalyst to provide a polyurethane polyacetal elastomer, said copolymer having a weight average molecular weight of between about 1,000 and about 200,000 as measured against a polystyrene standard by gel permeation chromatography and being the reaction product of a formaldehyde-providing compound and 1,3-dioxolane, said copolymer being employed in an amount of between about 30 and about 50 mole percent based upon the total amount of said copolymer and said isocyanate-terminated prepolymer employed, and (c) reacting said elastomer at an elevated temperature with an organic polyisocyanate to provide a chain-extended polyurethane polyacetal elastomer.