Study on the Crystallization Behavior of Polypropylene-graft-polydiphenylsiloxane Copolymer

The effects of polydiphenylsiloxane content on crystallization process, crystal transformation, and crystal morphology of polypropylene-graft-polydiphenylsiloxane (PP-g-PDPS) copolymers were investigated by differential scanning calorimetry and wide angle X-ray scattering. The experimental results show that the onset and peak temperature of the crystallization (Tconset and Tc) for PP-g-PDPS copolymer were slightly higher than those of PP. A small number of PDPS branches in PP-g-PDPS copolymer, acting as nuclei, increase the number of spherulite nuclei in a unit volume and lead to an increase of the degree of crystallinity. However, when the content of PDPS was over 4.8 wt%, the increase in PDPS branches in the PP-g-PDPS copolymers interfered with the crystallinization process of PP; the degree of crystallinity and crystal size of PP-g-PDPS copolymer decreased with increasing of the PDPS content. More and smaller spherulites, with less perfection, were observed in PP-g-PDPS copolymer than in the PP using polarized optical microscopy.