Crystallization kinetics of polypropylene under high pressure and steady shear flow

We investigate the simultaneous effect of pressure P and shear flow on the crystallization process of polypropylene using a modified pressure–volume–temperature measurement system that has been developed in our laboratory. We focus on the inverse of half-conversion time 1/t1/2 that is defined by the inverse of the time when the relative crystallinity of system reaches to one half. It is found that the pressure dependence of the quantity 1/t1/2 can be expressed by a shifted degree of super-cooling ΔT(P) by pressure. We also find that 1/t1/2(T,P,γ̇) under both pressure and shear flow can be described by a sum of 1/t1/2(T,P,γ̇=0) under no shear and a linearly increasing term with shear rate γ̇.