Microstructural Processes in the Deformation and Fracture of Polymers

摘要

Fracture of shear bands in polystyrene at intersections, by tension and crazing, by shear, and by tensile fracture was studied. The fibrous material in the shear band was elongated and deformed during tensile fracture. They were completely recovered after annealing. The propagation of shear bands was observed by high speed (6000 frames/sec) cinematography. Three different obstacles were introduced, an existing shear band, a fully recovered thick band, and a region dispersed with 2-6 micrometer rubber particles (a strip of HIPS). Except for the second one which behaved as though it was not there, the other two obstacles effectively reduced the speed of propagation of the shear band packet and changed their mode of operation. Transport of methanol in deformed and undeformed PMMA was compared. Transport rate was enhanced by deformation and obeyed Case I behavior while that of undeformed PMMA obeyed Case II. Desorption and resorption kinetics were all Fickian in the beginning regardless of the mechanical history before sorption. (Author)