Microstructural and molecular dependence of the work of fracture parameters in semicrystalline and amorphous polymer systems

Abstract

The influence of microstructural, morphological and molecular variables on the fracture behavior of polymers and related composites by using the essential work of fracture (EWF) concept has been surveyed in this article. It was postulated that a clear distinction between crack initiation and growth is the essential prerequisite to differentiate between effects of the initial structure and its alteration due to mechanical loading. Strong structural anisotropy in polymers and composites may obstruct the use of the EWF method. It was concluded that the specific essential work of fracture (w e ) in amorphous polymers is controlled by the molecular entanglement. In semicrystalline polymers w e can hardly be correlated with a single parameter of the crystalline or molecular structure. This is owing to a strong interrelation between structural and molecular variables. Results on blends and filled polymeric systems suggest that the essential (resistance to crack initiation) and the non-essential or plastic work (resistance to crack propagation) can hardly be improved simultaneously. This article points out several topics worth of investigations by adopting the EWF method.