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

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