Brittle-ductile transition of incompatible low-concentration blends containing recycled polypropylene

For the recycling of plastic parts of scrapped cars, an expensive separation process is needed. To lower these costs, it is necessary to recycle blended polymers. This study concerns blends consisting of polypropylene and a small amount of polyamide, which can be considered as an impurity. When this amount is lower than 5 vol%, tensile properties are not affected. The methods formerly used have been adapted to other blends of similar compositions. The amount of 5 vol% is critical. whatever pollution is added to polypropylene (mineral or organic). This critical amount marks a brittle-ductile transition. The facts that the mechanical properties are particularly sensitive around this amount, that ambient temperature is close to the glass transition temperature of polypropylene and that molecular mobility has changed can explain the strange elongation observed at break values, (C) 2000 Elsevier Science Ltd. All rights reserved.