Study on nonisothermal crystallization of maleic anhydride grafted polypropylene/montmorillonite nanocomposite

Abstract

This paper studies the nonisothermal crystallization behavior of maleic anhydride grafted polypropylene/montmorillonite nanocomposite by differential scanning calorimetry (DSC) in comparison with the maleic anhydride grafted polypropylene matrix (PP-g-MAH). The nanocomposite was prepared by melt-intercalation, and its microstructure was characterized by wide angle X-ray diffraction and transmission electron microscopy. The DSC results show that the presence of MMT resulted in the increase of crystallization rate and the decrease of supercooling degree required for crystallizing nucleation. The Avrami analysis shows that the nonisothermal crystallization process of PP-g-MAH and the hybrid at an early stage followed the Avrami equation with Avrami exponent value of about 2.5. The activation energy for the transport of the macromolecular segments to the growing surface was determined by using the Kissinger method. The calculated activation energy was 162.0 kJ/mol for PP-g-MAH and 193.2 kJ/mol for the nanocomposite. The activity of nucleation of MMT was calculated with the value of 0.84 by using Dobreva’s method. It indicates that the silicate layers of MMT are active substrates for the heterogeneous nucleation, which results in the increase of the crystallization rate and the decrease of the degree of surpercooling required for crystallizing nucleation.