Flow-induced crystallization of polymer: theory and experiments

In this work we analyze the crystallization kinetics under steady shear flow conditions of different samples obtained by blending two isotactic poly(1-butene)s with different average molecular weights. It is observed that the addition of a small amount of high MW-polymer (<10 wt%) to a low MWsample does not produce any appreciable effect upon the crystallization kinetics under both quiescent and shear flow conditions. This behavior can be attributed to constraint release of high MW chains due to the relaxation of the shorter chains and can be described by the double reptation theory, which coupled with classical nucleation models allows for good quantitative predictions of the experimental results by using the relaxation times of the two blend components as the only fitting parameters.