STUDIES ON TOUGHNESS OF POLYOLEFIN RESINS .4. EFFECT OF CRYSTALLINITYON BRITTLE-DUCTILE TRANSITION IN POLYETHYLENE

The brittle-ductile transition temperature (BDTT) of polyethylene was evaluated using the Charpy impact test. The effect of the crystallinit y on BDTT was the main concern in this study. Higher density resins re vealed lower BDTT. On the other hand, whitening of the deformed region during the tensile test and craze-like failure during the tensile tes t with a notch increased for higher density resins more than for lower density resins. Therefore, a crack shielding effect by microvoid form ation at yielding zone near the notch is proposed as the toughening me chanism on Charpy impact test for higher density resins.