Effect of selective localization of carbon nanotubes in pa6 dispersed phase of PP/PA6 blends on the morphology evolution with time, part 2: Relaxation of deformed droplets after cessation of flow

Abstract

The relaxation of carbon nanotube (CNT)‐filled PA6 droplets in PP matrix was studied after cessation of simple shear flows. The morphology evolutions of blends with various CNT contents in PA6 were probed by optical microcopy over time. It was shown that the retraction of deformed droplets accelerates with increasing CNT content in PA6. As evidenced by linear rheological measurements, gradual formation of elastic structures within the droplets was found responsible for such observations. The pre‐shearing flow was varied to investigate the effects of different flow histories on the kinetics of relaxation. By increasing the shear‐rate of the flow prior to relaxation, the relaxation kinetics slowed down to some extent. The slowed‐down kinetics was attributed to the partial rupture of the elastic structures within PA6. This idea was evidenced by performing the startup of steady shear flow experiments on PA6/CNT nanocomposites. The final morphology of the blends after the melt blending process was analyzed. The average droplet size was found to increase with increasing the CNT content. Also, the distribution of the droplet sizes became broader as a result of the increased viscosity and elasticity ratios. POLYM. ENG. SCI., 56:51–60, 2016. © 2015 Society of Plastics Engineers