ENHANCED POLYCARBONATE TOUGHNESS .2. MECHANISMS

Glassy shell-rubbery core polymer particles, 0.1 to 0.2 mum in diamete r, increase the plane strain J(IC) values of 3.175 mm thick polycarbon ate from 3.05 kJ/m2 (no particles) to 9.5 kJ/m2 (7.5 phr particles) at 23-degrees-C. Some modest decreases in these values are caused by tes ts at -20-degrees-C in samples 9.525 and 3.175 mm thick. If only the p article concentration is varied, J(IC) increases monotonically to 7.5 phr (by wt), then levels off or decreases slightly at 10.0 phr. The to tal volume of 1 to 2 mum diameter cavities formed in the matrix by the apparently unbonded particles behaves similarly; cavity volume and J( IC) are directly related. With increasing particle concentration the t ensile modulus is unchanged, the yield stress and strain decrease mode stly, the strain at fracture decreases appreciably, and the heat recov erable orientation in the fractured samples decreases. Few cavities ar e formed. The particles reduce the extent of shear deformation in the tensile samples.