MECHANISMS OF CAVITATION OVER A RANGE OF TEMPERATURES IN RUBBER-TOUGHENED PSAN MODIFIED WITH 3-STAGE CORE-SHELL PARTICLES

In situ straining on a transmission electron microscope (TEM) stage ha s been used to study deformation mechanisms in a blend of poly(styrene -co-acrylonitrile) (PSAN) with PMMA/acrylate-rubber/PMMA core-shell pa rticles, over a range of temperatures. Thin sections were tested at - 20, 23 and 60 degrees C at a constant tensile strain rate of 0.05% s(- 1) Cavitation was observed at all three temperatures. At - 20 degrees C, the main deformation mechanisms were crazing of the PSAN matrix and fibrillation of the acrylate rubber. At 23 degrees C, crazing and she ar yielding of the PSAN occurred simultaneously, with more extensive f ibrillation of the rubber particles and drawing of material from the P MMA cores. This disruption of thermoplastic core material indicates th at high stresses are generated within the modifier particles. At 60 de grees C, crazing could no longer be detected: shear yielding of the ma trix and cavitation of the rubber particles were the main mechanisms o f deformation.