Thermo-mechanical degradation of polypropylene, low-density polyethylene and their 1:1 blend

Thermo-mechanical degradation of isotactic polypropylene (iPP) and low-density polyethylene (LDPE), and the effect of the specific degradation processes of each polymer on the degradation of a 1:1 blend of these polymers, have been studied by using a conrotatory double-screw mixer coupled to a torque rheometer. The products were characterized by Fourier transform infra-red spectroscopy and thermogravimetry under inert and oxidative atmospheres. Data for the blend were compared with curves simulated from a combination of the results for the single polymers. LDPE is shown to form three to four times more carbonyl-containing products than IPP in the processing conditions used to prepare the blend. The main reason for this difference are the stabilizers added to IPP by the producer before its pelletization. Blending with LDPE stabilizes iPP, even at temperatures well above its melting point. (C) 1998 Elsevier Science Limited. All rights reserved.