Non-isothermal crystallization kinetics of montmorillonite filled β-isotactic polypropylene nanocomposites

Montmorillonite filled isotactic polypropylene nanocomposites (iPP/MMT) generally form alpha-modification due to the heterogeneous alpha-nucleation of MMT for iPP crystallization. To obtain MMT filled beta-iPP nanocomposites, MMT with beta-nucleating surface (beta-MMT) was prepared by supporting calcium pimelate (CaPA) as beta-nucleator on the surface of MMT particles. The crystallization behavior, melting characteristics, and non-isothermal crystallization kinetics and crystallization activation energies of MMT and beta-MMT filled iPP nanocomposites were studied by differential scanning calorimetry. It is found that the crystallization peak temperatures of beta-MMT filled iPP nanocomposites were higher than those of beta-iPP and MMT filled iPP nanocomposites, which indicated that the heterogeneous nucleation of beta-MMT is stronger than that of MMT. Jeziorny and Mo methods were applicable to study the non-isothermal crystallization kinetics of iPP and its nanocomposites. Addition of CaPA, MMT and beta-MMT can increase the crystallization rate. The crystallization activation energies were calculated by Friedman methods, and nucleating activities were calculated by Dobreva methods. It is indicated that beta-nucleation decreased the crystallization activation energy of iPP, and the nucleating activity of beta-MMT is higher than that of CaPA and MMT.