Flow-induced crystallization effect on polypropylene with respect to nucleating agents

Abstract

To study FIC on the laboratory scale, we used a parallel plate rheometer (PPR), which imparts shear rates of some order of magnitude. Applying shear in undercooling temperature (151 °C) conditions to induced crystallization, which was monitored by the increase in viscosity in the PPR following an established protocol that was stetted up to assess the conditions of the experiments. After annealing samples at 230 °C for 10 min to remove the melt memory effect, it was cooled to crystallization temperature (1510C) at the rate of -1.5 °C/min to undertake FIC and finally the sample was quenched by a cryo-freezer aerosol below 0 °C before being removed for characterization study. FIC involves the formation of the time and temperature-dependent relative crystallinity of a series of isotactic polypropylene (iPP) homopolymers. In this study, I selected iPP as a typical sample due to its simple formation conditions of polymorphic crystals and its unique properties of melting curves and crystalline morphology. In this research, the influence of some nucleating agents on the crystallization behavior of (iPP) Homopolymer has been investigated by OM (Optical Microscopy) and Transmission Electron Microscope (TEM) after undergoing FIC crystallization. The study of crystallization kinetics of iPP Homopolymer nucleated with (Talc, Na-Benzoate) and neat melt (Not nucleated-used as control) helped us to control the final morphologies and mechanical properties of semi-crystalline polymers. From the measured onset time of crystallization, it was possible to conclude that iPP containing Na- Benzoate as the nucleating agent was faster in crystallization.