MECHANICAL-PROPERTIES OF HTPB-IPDI-BASED ELASTOMERS

A polyurethane elastomer having mechanical and adhesive properties sui table for liner applications in solid rocket propellants was developed using HTPB as the prepolymer and IPDI as the curing agent. The effect s of the NCO/OH ratio (R value) and the triol/diol ratio on the mechan ical properties of the polyurethane matrix were investigated. The reac tion of HTPB and IPDI is followed by monitoring the changes in the IR absorption bands of the NCO stretching at 2255 cm(-1) and the CO stret ching at 1730 cm(-1). It was found that the rate of the polyurethane f ormation obeys an overall second-order kinetics. At an R value of 1.15 , the elastomer shows the maximum tensile strength and 200% elongation at break. The hardness, elongation, and the tensile strength reach a steady value around the same R value. The elastomers having a triol/di ol ratio less than 0.03 show a decrease in the tensile strength and mo dulus with a concomitant increase in elongation. At a triol/diol ratio greater than 0.05, the tensile strength increases to about the same v alue for the liner composition without any triol component. The elonga tion reaches a steady level at a triol/diol ratio of 0.10 and one obse rves a steady increase in hardness up to about 0.5. The modulus for th e compositions having a triol/diol ratio greater than 0.1 is about 50% higher than that for the composition without triol. (C) 1997 John Wil ey & Sons, Inc.