SIZE EFFECT OF COMPLIANT RUBBERY PARTICLES ON CRAZE PLASTICITY IN POLYSTYRENE

Blends of polystyrene containing concentric spherical shell particles produced from KRO-1 resin by means of a morphological transformation discussed earlier by Gebizlioglu et al.7 were disassembled to harvest the particles. These particles were in turn separated into two nearly nonoverlapping populations of average sizes of 0.32 and 2.3 μm and were subsequently reassembled by solvent blending into homo-PS to create two separate sets of heterogeneous polymers of large and small particles at particle weight fractions of 0.05 and 0.15, respectively. It was found that the craze flow stress increases systematically with decreasing particle volume fraction at constant particle size and that the blends with the small particles that are less potent craze initiators have substantially higher flow stresses than blends with the large particles. Definitive theoretical models for the cutoff particle size below which crazes cannot be initiated and for the craze flow stress are in substantial agreement not only with the results of the present study but also with particle size effects previously reported by us and other investigators. © 1990, American Chemical Society. All rights reserved.