Influence of Adjustable Grafted Side Chains on the Non-Isothermal Crystallisation of a Ternary-Monomer Solid Phase Graft Copolymer of Polypropylene

Abstract

A solid phase graft copolymer with an adjustable structure was prepared by grafting maleic anhydride, methyl methacrylate and butyl acrylate onto polypropylene (PP). How the grafted side chains affected the crystallisation of the graft copolymer was studied by differential scanning calorimetry and polarised optical micrographs. Results show that the grafted side chains not only promoted heterogeneous nucleation but also hindered the whole crystal growth of the copolymers. The Jeziorny method and Mo method were successful in describing the non-isothermal crystallisation kinetics. The Jeziorny method showed that the Avrami exponent ranged from 2 to 3, indicating that the crystal tended to grow in a three-dimensional mode. The Mo method showed that the graft copolymer (known here as PPTM) needed a lower crystallisation rate than PP to attain the same crystallinity at unit time, due to the hetero-nucleation of the grafted side chains. Meanwhile, the hetero-nucleation of the grafted side chains caused a decrease in the crystallisation half-time and in the spherulite size of PPTM. Hindrance of the grafted side chains was shown by the incomplete crystallisation images and by the increase in the non-isothermal crystallisation activation energy of PPTM.