Structure/property relationships in highly crosslinked polyurethanes. Part I. Synthesis, characterization and tensile behaviour

Highly crosslinked polyurethanes based on 4,4′-diphenylmethane diisocyanate (MDI), polyol LHT-112 and trimethylol propane (TMP) were synthesized with various ratios of polyol to TMP, and their dynamic mechanical properties were analysed by using torsion pendulum and dynamic mechanical thermal analysis (DMTA) methods. The crosslink densities were estimated from the moduli above the glass transition temperature, T_g. The Young's modulus and the tensile stress-strain behaviour of the materials were measured as a function of the variation of [polyol]/[TMP] and the cure time. It was found that the T_g, Young's modulus and fracture stress decrease with an increasing amount of polyol in the polyurethane.