Semicrystalline Polymers

Abstract

Understanding the correlation between morphology andmicromechanical processes of deformation and fracture of semicrystalline polymers is essential for material development, modification, and failure analysis. Since semicrystalline polymers exhibit a hierarchical morphology with structures ranging from the nanometre to the millimetre scale, various electron microscopic techniques are applied to image typical structural units such as crystalline blocks, lamellae, spherulites, and fibrils. In this chapter, a general survey of methods of morphological and micromechanical analysis is first provided, with examples given for the most significant semicrystalline polymers, polyethylene (PE) and polypropylene (PP). The chapter presents methods for enhancing contrast by chemical staining and etching, the application of electron diffraction contrast, electron beam irradiation effects, studies of crystallisation and melting phenomena, as well as typical micromechanical phenomena that can be related to brittle, ductile, or high-strength behaviour, such as crazing, chevron formation, fibrillation, and others. Additional examples of semicrystalline polymers, such as polyamides, fluoropolymers, polyurethanes, biomedical polyesters, etc., are then given.