RUBBER TOUGHENING OF PLASTICS .8. EFFECTS OF GLASS-BEADS ON THE KINETICS OF CREEP IN ABS

Creep measurements were made on a series of six ABS blends containing 0 to 20 vol% of 80 mu m glass beads. At small strains, the beads raised the modulus of the ABS. However, debonding of the polymer from the glass resulted in a rapid drop in modulus with increasing strain epsilon and bead content phi , and at strains above 1. 0% the order of stiffnesses was reversed. Debonding resulted in an increase in creep rate with phi , as measured by the time tau to reach 1% volume strain. Plots of In tau ** minus **1 against applied stress were linear, in accordance with the Eyring equation, and provided data for comparing stress concentration factors gamma . The relationship between gamma and phi fitted approximately to the Ishai-Cohen effective area model. It is concluded that debonded glass beads accelerate multiple crazing by increasing average stresses in the ABS matrix, and in that respect resemble rubber particles. However, unlike rubber particles, debonded beads drastically reduce notched Charpy impact strength.