Effects of injection moulding induced morphology on the fracture behaviour of virgin and recycled polypropylene

The effect of injection moulding induced morphology on the fracture behaviour of virgin and recycled polypropylene (PP) has been studied. Skin-core morphology has been analysed by microhardness measurements, since the microhardness and the degree of crystallinity are directly related. Virgin PP has shown higher nticrohardness values and bigger plastically deformed zone at the crack tip than recycled one. These two differences are due to the higher crystallinity of the recycled PP. Other-wise, in both materials, skin layer has shown lower microhardness values and smaller plastic zone extension than the core region. The former phenomenon is suggested to be governed by the different degrees of crystallinity between both regions, whereas the latter is related to the stress-state (triaxial stress-state) rather than to morphological parameters. (C) 2003 Published by Elsevier Ltd.