Ethylene-propylene diene terpolymer (EPDM)-based insulation system is being globally used for case-bonded solid rocket motors. A study was undertaken using EPDM as base polymer, blended with hypalon and liquid EPDM and filled with fibrous and non-fibrous fillers. These formulations were evaluated as rocket motor insulation system. The basic objective of the study was to develop an insulation system based on EPDM for case-bonded applications. A series of rocket motor insulator compositions based on EPDM, filled with particulate and fibrous fillers like precipitated silica, fumed silica, aramid, and carbon fibres have been studied for mechanical, rheological, thermal, and interface properties. Compositions based on particulate fillers were optimised for the filler content. Comparatively, fumed silica was found to be superior as filler in terms of mechanical and interface properties. Addition of fibrous filler (5 parts) improved the peel strength, and reduced the thermal conductivity and erosion rate. All the compositions were evaluated for sulphur and peroxide curing. Superior mechanical properties were achieved for sulphur-cured products, whereas peroxide-cured products exhibited an excellent ageing resistance. Rocket motors were insulated with optimised composition and propellant cast, and the motors were evaluated by conducting static test in end-burning mode.
EPDM elastomer, thermal insulation, solid rocket motor insulators, erosion rate, interface properties, ethylene-propylene diene terpolymer insulation system
