A Molecular Interpretation of the Toughness of Glassy Polymers

A model is proposed that describes the failure of glassy polymers in the crazing regime. This model is based on the realization that the cross-tie fibrils, which are known to exist between primary fibrils in all crazes, can have a profound effect on the failure mechanics of a craze as they can transfer stress between the broken and unbroken fibrils. A very simple model of crack tip stress amplification caused by the cross-ties is shown to work well in the prediction of the fracture toughness of a bulk, high molecular weight, glassy polymer. The toughness is shown to vary as the square of the breaking force of chain molecules and the square of the density of entangled strands at the interface. © 1991, American Chemical Society. All rights reserved.