THERMOMECHANICAL 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 degradati on processes of each polymer on the degradation of a 1:1 blend of thes e polymers, have been studied by using a conrotatory double-screw mixe r coupled to a torque rheometer. The products were characterized by Fo urier transform infra-red spectroscopy and thermogravimetry under iner t and oxidative atmospheres. Data for the blend were compared with cur ves simulated from a combination of the results for the single polymer s. LDPE is shown to form three to four times more carbonyl-containing products than IPP in the processing conditions used to prepare the ble nd. The main reason for this difference are the stabilizers added to I PP by the producer before its pelletization. Blending with LDPE stabil izes iPP, even at temperatures well above its melting point. (C) 1998 Elsevier Science Limited. All rights reserved.