Effect of nanoclay on the nucleation, crystallization and melting behaviour of polypropylene: A study on non-isothermal crystallization kinetics

Non-isothermal crystallization kinetics of virgin polypropylene (PP) and its nanocomposites have been evaluated using differential scanning calorimetric technique. The nanocomposites were prepared using melt intercalation method. It is observed that the crystallization peak temperature of nanocomposite is marginally higher than virgin PP at various cooling rates. The non-isothermal crystallization melt data were analysed using Avrami, Ozawa and Mos models. The half-time for crystallization decreased with incorporation of clay nanoparticles. The values of crystallization rate constant and cooling rate at unit crystallization time showed that the crystallization rate increased with the increasing of cooling rates for virgin PP and nanocomposite, but the crystallization rate of nanocomposite was faster than that of PP at a given cooling rate. The activation energy for non-isothermal crystallization of virgin polymer and nanocomposites based on Kissinger method has been determined to be 186 and 196 kJ mol(-1), respectively. The polarized micrographs showed that the number of effective nuclei increased in the PP-clay nanocomposite, where the clay acts as a heterogeneous nucleating agent during the crystallization of the nanocomposite.