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.