Abstract: This study reported an enhancement of crystallization capability for the βcrystalmodified polypropylene random copolymer (PPR) by incorporation of small amount of isotactic polypropylene (iPP). The investigations indicated that the relative content of βform crystals was increased to 92.4 % through an optimization of experimental conditions, and the βform crystallization capability also increased by 61.5 %. The investigation on crystal growth process indicated that iPP formed βcrystal nucleus at first and then induced the βform crystallization for PPR. The high content of βform crystals resulted in a significant great improvement in impact toughness. The impact strength obtained an increase from 22.8 to 45.9 kJ/m2 while the elongation at break increased to 574.4 %, which was almost by a factor of three compared with pure PPR. There is a synergistic effect between the rigidity of iPP and the high content of βform crystals, leading to little change in tensile strength of PPR/iPP compounds.

Key words: isotactic polypropylene, polypropylene random copolymer, β-modification, crystallization