A NEW CRITERION FOR BRITTLE-DUCTILE TRANSITION OF POLYMER BLENDS

The T(c) criterion was first used by S. Wu for characterizing the brittle-ductile (B-D) transition of N6/EPDM blends. But in this paper, a new criterion which is based on the stress analysis of blends is proposed to characterize the B-D transitions of blends, namely, A criterion A = V(fc)2/d(c) = constant. V(fc) and d(c) are the critical volume fractions and particle size of dispersed particles in blends, respectively. For given blends, A is independent of the morphology of dispersed phase and is only the characteristic parameter of matrix. The B-D transitions of different blends, including polar N6/EPDM blends, nonpolar PP/EPDM blends and PE/CaCO3 composites, were manipulated with A criterion and satisfactory results were obtained. In addition, a new master curve for the impact strength of PP/EPDM blends versus V(f)2/d was obtained. The results showed that A criterion is more suitable than T(c) criterion for characterizing the B-D transition of blends.