Abstract
An iPP-g-St graft copolymer synthesized by free-radical initiated solidstate grafting polymerization of styrene in nascent spherical iPP granules was effectively fractionated by temperature gradient extraction fractionation (TGEF) into fractions of different styrene content. The fractions were characterized by FTIR, 1H-NMR, DSC, PLM and WAXD. The fraction extracted at room temperature (25 0C) is homopolymer of styrene, and the fractions collected at 70, 90, and 105 0C are iPP-g-St graft copolymer with decreasing degree of grafting. All the fractions of the grafting product contain a certain amount of styrene, meaning that almost all the iPP chains in the granules are accessible to the grafting monomer. The internal morphology of the iPP granules is highly porous, which enables the grafting monomer and the radicals to reach at each iPP chain during the polymerization. As styrene content of the iPP-g-St fraction increases, its crystallinity decreases, the size of iPP lamella decreases, and the crystalline morphology becomes more irregular.
© 2013 by Walter de Gruyter GmbH & Co.