Nonisothermal Crystallization Kinetics and Microhardness of PP/CNT Composites

The nonisothermal crystallization kinetics and microhardness of nanocomposites consisting of a polypropylene matrix (PP) and carbon nanotube filler (CNT) have been investigated. Three types of PP matrixes have been used: two of them are nonfunctionalized PP that differ slightly in their melt flow index, whereas the third is grafted with maleic anhydride (MA). Ozawa formalism has been used to study the nonisothermal crystallization kinetics. The results show that the CNT filler has a nucleation role in the nonisothermal crystallization of PP. For all nanocomposites, the nonisothermal crystallization rate increases up to 4% CNT and then decreases slightly or remains almost constant at the higher filler content. This fact has been interpreted in terms of an aggregation of the particles at high filler concentration, which leads to a decrease of the nucleation ability of the filler because the number of heterogeneous nuclei decreases. The crystallization mechanism of the PP matrixes almost does not change in t...