Fatigue Fracture Surface Micromorphology in Poly(vinyl chloride)

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Abstract
The fatigue fracture surface micromorphology of poly(vinyl chloride) (PVC) was studied as a function of molecular weight (M), plasticizer content, and residual orientation, with particular attention given to how these variables affect the formation of discontinuous growth bands (DGBs). Discontinuous growth bands, which form on a number of polymeric solids under cyclic loading, represent successive increments of crack extension through a craze zone. As expected, DGB width showed little change in size over the molecular weight range or specimen orientations examined and increased in size with increasing plasticizer content. On the other hand, the cyclic stability of these bands increased markedly with an increase in molecular weight, but to a lesser extent with additions of a plasticizer. The internal structure of the bands became more ragged with increasing M, whereas the addition of a plasticizer reestablished the crisp and well-defined micromorphology associated with DGBs in low-M polymers.