The ageing of modified glass-reinforced polypropylene in air and in antifreeze

The comparative behaviour of modified and unmodified glass-reinforced polypropylene during ageing in air (135 degrees C) and in antifreeze (115 degrees C) with exposure up to 80 days was investigated. Approaches to thermostabilization of the composites are proposed. Mechanical properties (tensile strength, flexural strength, impact strength) and melt flow have been measured for original and aged samples. According to Hg-porosimetry data, the unmodified composite has a loose macroporous structure. Ageing leads to progressive phase separation. In contrast, the original modified composite is characterised by a dense structure; ageing leads to the structure compacting, and pore size decreases. The unmodified composite displays a drastic failure of mechanical properties after 10 days of heating. Modified thermostabilized glass-filled polypropylene reatins its thermooxidative stability during ageing in air as well as in antifreeze, its molecular weight characteristics remain practically constant. (C) 2000 Elsevier Science Ltd. All rights reserved.