Characterization of Functionally Graded Polyurethane Elastomers

Functionally graded polyurethane elastomers (FGPUEs) were prepared by poly(oxytretamythylene) glycol (PTMG) and 4,4’-diphenylmethane diisocyanate (MDI) with two molds fixed at different temperature. Effect of temperature gradient on the molecular aggregation state and mechanical properties were studied by differential scanning calorimetry (DSC), polarized optical microscope (POM), Fourier transform infrared spectroscopy (FT-IR) and pulsed nuclear magnetic resonance (NMR). Spherulite size of FGPUEs depended on the temperature gradient. Spherulite content of FGPUEs decreased from the low temperature side to the higher temperature side and spherulite size became greater toward the higher one. The glass transition increased from the lower temperature side to the higher temperature side. This was associated with the strong phase separation of the lower temperature side.