Crystallization kinetics of polypropylene under high pressure and steady shear flow

We investigate the simultaneous effect of pressure <f>P</f> 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 <f>1/t1/2</f> 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 <f>1/t1/2</f> can be expressed by a shifted degree of super-cooling <f>ΔT(P)</f> by pressure. We also find that <f>1/t1/2(T,P,γ˙)</f> under both pressure and shear flow can be described by a sum of <f>1/t1/2(T,P,γ˙=0)</f> under no shear and a linearly increasing term with shear rate <f>γ˙.</f> [Copyright &y& Elsevier]