Characterisation of thermally treated and untreated polyethylene- polypropylene blends using DSC, TGA and IR techniques

The thermal characteristics of thermally treated and untreated very low density polyethylene, isotactic polypropylene and their blends were investigated. Injection moulded blends containing five different weight percentages of VLDPE/iPP were prepared and thermally treated at 100°C for 2, 4, 7 and 14 days. Differential scanning calorimetry, thermogravimetry and infrared spectral analysis techniques were used to study the effect of thermal treatment and blending ratio on the thermal and chemical stability. The addition of PE had caused the T^m, heat of fusion and percentage crystallinity of PP main melting peak to decrease, indicating that both polymers are partially miscible. T^m has been found to increase with aging time, however, the heat of fusion is not significantly affected. The initial and final decomposition temperatures, maximum decomposition rate temperature, order of decomposition reaction, activation energy and activation enthalpy were calculated, in a dynamic nitrogen atmosphere, and discussed in terms of blending ratios and aging times. The IR spectra of all blends at different aging times do not show any degradation products.