Plastic deformation and cavitation in semicrystalline polymers studied by X-ray methods

Abstract

This paper is a literature review presenting the relation between the cavitation phenomenon and plastic deformation of polymers. The cavitation phenomenon, meaning the formation of numerous micro and nano size voids (cavities), is observed in many semicrystalline polymers deformed at temperatures above the glass transition. Cavitation occurs when crystals in the polymer are stronger than the amorphous phase. This means that the phenomenon may be controlled by applying an appropriate crystallization procedure. Thicker and less defected crystals usually grow when the time for crystallization is longer and it is easier to deform the amorphous phase with voiding. The cavitation process also depends on the deformation conditions. Faster stretching at lower temperatures is favorable for deformation with voiding. The cavities are observed only during tensile deformation as local triaxial straining is necessary for cavitation. Usually, cavities are formed when the strain is close to the yield point and voids have a nanometer size. Larger, micrometer cavities dominate at higher strains, near the end of the deformation process.