Increasing the tensile strength of HTPB with different isocyanates and chain extenders

The influence of the diols 1,4-butanediol, BDO, and 1,4-cyclohexane dimethanol, CHDM, on the mechanical properties of HTPB, cured with the diisocyanates, IPDI, HDI and H12MDI, was investigated. The highest tensile strength was obtained by using H12MDI and BDO. When adding the diols the tensile strength increases strongly up to 2 mol of diols per mote of HTPB. Above that point the effect is moderate. The ultimate elongation of the materials has a maximum between 1 and 2 mol of diols per mole of HTPB. If more than 1 mole diol per mole of HTPB is added, all the examined materials begin to strain crystallise and the initial modulus of elasticity increase linearly with increasing amount of diol. (C) 2002 Elsevier Science Ltd. All rights reserved.