Modelling Viscoelastic Response in Semicrystalline Polymer Fibers*

Polymer fibers are ubiquitous in Nature and find widespread applications in industry. Fiber mechanical properties are critical to their application and to product quality. Models for the mechanical properties of fibers that can capture their behavior in different deformation experiments, over a wide range of temperatures and that relate these properties to the fiber microstructure are currently lacking in the literature. We present a model that can accurately capture the mechanical behavior of semicrystalline fibers. We demonstrate that the moduli from model fits compare well with the crystalline and amorphous phase moduli from WAXD and vary with temperature in a physically realistic manner. The model relaxation timescales for semicrystalline/glassy fibers follow the TNM-KAHR temperature dependence. Our findings indicate that the qualitative features of the fiber mechanical properties are independent of microstructural details, and only require crystal/amorphous coexistence. Our model is also able to capture the mechanical response of several other non-equilibrium systems including biological cells, microgel pastes etc.