Abstract: The crystallization behavior of and the mechanical properties of long chain branching polypropylene(LCBPP-g-VS/St) grafted by vinyl silane and styrene were investigated in this paper. The results indicated that the crystallization peak temperature and the melting peak temperature of PP-g-VS/St increased 10℃ and 2℃ respectively, and the spherulite size of PP-g-VS/St dramatically decreased based on neat LCBPP. Furthermore, the crystallites of PP-g-VS/St composed of γ and α forms when the cooling rate was 10℃/min，while the crystal of PP-g-VS/St composed of α and β form when the polymer crystallized on the injection-molding condition. The non-isothermal crystallization kinetics of PP-g-VS/St indicated that the LCB structure acted as a heterogeneous nucleating agent at the beginning of crystallization and hindered the crystal growth in the latter stage. Compared to virgin iPP, the tensile strength, flexural modulus and impact strength of PP-g-VS/St increased by 28%, 40% and 453%, respectively.

Key words: polypropylene, vinyl silane, styrene, grafting, mechanical property, crystallization