Properties of Crazes and Deformation Zones in Glassy Polymers

摘要

New experimental methods, holographic interferometry and quantitative transmission electron microscopy, have been developed to investigate the microstructure, mechanical properties and failure of crazes and deformation zones DZ's in glassy polymers. Plasticizaton by the environment is found to be the major factor in environmental crazing and cracking. Air crazing, and the transition to more ductile DZ behavior, is controlled largely by the entanglement density of the polymer glass. Low entanglement density polymer craze readily and the craze fibrils break down rapidly to form cracks. High entanglement density polymers preferentially form non-fibrillated DZ's; crazes when formed are more resistant to craze breakdown in these polymers. A comprehensive model of these entanglement effects has been developed which explain the natural extension ratios of crazes and DZ's, the craze to DZ transition and the craze fibril stability.