Studies of thermal oxidative degradation of polypropylene impact copolymer using the temperature rising elution fractionation method

Thermal oxidative degradation of polypropylene impact copolymer has been studied with its fractions obtained using the temperature rising elution fractionation method. The fractions were analyzed using 13C NMR, Fourier transform infrared and differential scanning calorimetry measurements, and the chemical structure, isotacticity, conformation and melting point were investigated. It is found that these fractions are composed of a homopolymer or a polymer blend of polypropylene, polyethylene and ethylene–propylene copolymer. The thermal oxidative degradation of each fraction was carried out at 130 °C, and the degradation progress was estimated by the change of molecular weight distribution (from gel permeation chromatography curves). The rate of degradation is found to be dominated by the content of tertiary CH bonds (propylene unit) and the existence of 31 helix conformation corresponding to a crystalline polypropylene part in each fraction. The latter is more evident leading to the degradation reaction path with a lower activation energy. Copyright © 2007 Society of Chemical Industry