Indentation creep in polymers and polymer nanocomposites

Abstract

Abstract Creep refers to the capacity of a material to bear load and it represents a fundamental property for material design. Indentation appears as a most convenient tool for the study of creep behavior in polymers. The present work gathers information on the indentation creep response of a wide variety of polymers, taken from different sources, and offers a comprehensive overview of the factors that can influence creep. It is shown that viscoplastic behavior assessed by the traditional technique is influenced by the internal polymer characteristics and also by external factors. As a general rule, chain stiffness, chain branching, crystallinity, physical ageing and rigid-filler addition promote creep resistance. The advent of modern instrumented indenters allowed analysis of viscoelastic flow. Interestingly, it is found that the creep parameters obtained from traditional and instrumented testing are in close agreement provided the viscoplastic regime prevails. Graphene-polymer nanocomposites are used to illustrate the reduced creep rate, creep extent and strain rate sensitivity found upon addition of the rigid filler to a number of thermoplastic matrices.