FRACTURE-TOUGHNESS AND FRACTURE MECHANISMS OF PBT PC IM BLEND .2. TOUGHENING MECHANISMS

Scanning electron microscopy (SEM) and transmission electron microscop y (TEM) techniques were employed in the morphology and fracture mechan isms studies on a commercial polybutylene terephthalate/polycarbonate/ impact modifier (PBT/PC/IM) blend. The fracture mechanisms involved at different temperatures under both impact and static loading were reve aled. It was found that massive plastic deformation of the matrix mate rial occurred after rubber particle cavitation; and it was this plasti c deformation that was responsible for the drastic enhancement in frac ture toughness although the widespread cavitation did absorb a conside rable amount of energy as well. The major source of toughness was the same for both impact and static fracture tests, but the toughening pro cesses became effective at a much lower temperature under static than impact conditions. The sequence of toughening events was also observed using TEM.