Thermal Degradation of Thermoplastic Polyurethane Modified with Polycarbonate

Thermal degradation of thermoplastic polyurethane modified polycarbonate has been investigated by means of DSC, GPC and FT-IR techniques. The polyurethanes used in this study are TPU-35 and TPU-53 containing 35.5 and 53.4 wt % of hard segments, respectively. The more content of hard segment, the higher the glass transition temperature (T{sub g}) of TPU was observed. On the other hand, the T{sub g} of the TPU modified PC decreased with the content of TPU and the annealing temperature regardless of the hard segment contents. The latter behavior may arise from the thermal degradation of TPU upon annealing process: the observed thermal degradation temperatures were at 240 and 250 deg. C D for the PC/TPU-35 and PC/TPU-53, respectively. The molecular weight, molecular weight distribution and viscosity agree well with the DSC measurement, which implicates a thermal degradation of TPU. In addition, thermal stability of the TPU modified PC linearly decreased with an incorporation of TPU. Transesterification or any interaction was not observed using FT-IR: the evidence was no frequency shift or any variance between the carbonyl stretching and NH group. For the specimens prepared below the degradation temperature, the enhancement of the thickness dependent impact strength of the PC/TPU blend was observes, and the morphology of the two blends was compared. (author). 19 refs., 2 tabs., 12 figs.