The Rheology of Crystallizing Polymers: Towards a Universal Description

A longstanding goal in polymer rheology is to develop a physical picture that relates the growth of mechanical moduli during polymer crystallization to that of structure. We have recently shown that the rheology is dominated by the formation and growth of the spherulitic superstructures. Here, we aim to develop a universal description of the process by exploring the roles of temperature, surface and bulk nucleation densities, and gap thickness. We study the model system of isotactic polypropylene (iPP) through simultaneous mechanical rheology and optical microscopy, with augmentation by deterministic reconstruction and stochastic simulations. We collapse the variable space by considering two scaled parameters; one related to bulk nucleation density and the other to surface.