Crazing in Glassy Polymers

This lecture explores the phenomenon of crazing in glassy polymers, which are fine crack-like striations that can withstand significant stress loads and are precursors to failure. The microstructure of crazes, nucleation, propagation mechanisms, and the competition between crazing and necking are discussed. The lecture also covers the relationship between crazing and entanglement effects, the effect of molecular weight on craze formation, and strategies to reduce brittle behavior through rubber toughening. The importance of multiple crazes in dissipating energy and improving resistance to failure is highlighted, along with the role of elastomer particles in nucleating crazes. The lecture concludes by emphasizing the impact of entanglement density on craze strength and fracture resistance.