Mechanical properties of bimodal polyurethane cross-linking systems

Using hydroxyl-terminated polybutadien(HTPB), oxide/tetrahydrofuran copolyether(PET) and glycidyl azide polymer(GAP) as binders, polyisocyanates(N100) and isophorone diisocyanate(IPDI) as curing agents, trimethylolpropan(TMP) as crossing agent, four types of bimodal polyurethane cross-linking systems including PET_s/PET_L/N100, GAP/PET_L/N100, GAP/PET/IPDI/TMP and GAP/HTPB/IPDI/TMP were prepared. The effect of the bimodal network on the mechanical properties of polyurethane elastomer was investigated. The results show that the mechanical properties of bimodal systems are better than that of short-chain monomodal system. The improvement of mechanical properties of bimodal polyurethane cross-linking systems may be explained by nonaffine deformation, and the degree of nonaffine deformation in these bimodal systems may be influenced by the different degree of the hydrogen bonding. The mechanical properties of bimodal systems may be significantly affected by the difference of the curing rate between monomodal systems.