INFLUENCE OF MORPHOLOGY ON THE TOUGHENING MECHANISMS OF POLYPROPYLENEMODIFIED WITH CORE-SHELL PARTICLES DERIVED FROM THERMOPLASTIC ELASTOMERS

The micromechanical deformation processes of impact-modified polypropy lene (PP) with core- shell particles derived from PP/EPR (ethylene- pr opylene- rubber) block copolymers and PP/PA/SEBS-g-MA thene-co-but-1-e ne)-block-polystyrene-graft-maleic anhydride) graft copolymers have be en investigated by in-situ tensile tests in high-voltage electron micr oscopy. Morphology studies in transmission electron microscopy show th at the morphology of modifier particles is drastically affected by the ir concentration I was found that the driving mechanism for the initia tion of plastic deformation is a controlled microvoid formation, which is caused by cavitation in the stretched rubber shell under mechanica l lending. According to the inherent properties and phase structures o f modifier particles, a single or multiple cavitation appears with or without fibril formation at the interface between the modifier particl es and the matrix. The Predominant mechanism for the improvement of to ughness is the shear yielding of the ligaments of matrix material indu ced by local stress concentration by the microvoids. (C) 1998 John Wil ey & Sons, Ltd.