The influence of liquid crystalline copolysiloxane (LCP-O2) as a new nucleator on crystallization structure and morphology of isotactic polypropylene (PP) has been investigated by means of wide angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The experimental results showed that LCP-O2 with low concentration in PP played a role in the heterogeneous nucleation effect, enhanced the crystallization velocity, and the spherulites became smaller and more homogeneous. Moreover, β-phase was induced in PP. The nucleating activity of LCP-O2 mainly depended on its concentration, molecular structure of liquid crystalline, and thermal history of processing. The relative content of β-form (K_β) increased with increasing crystallization temperature or LCP-O2 concentration, reached a maximum value, and then decreased as the temperature or LCP-O2 concentration further increased. K_β was 58% when the mass fraction of LCP-O2 was 1.0%, and the crystalline temperature and time were 130 ℃ and 1 h, respectively. The trigonal β spherulite with the sheaflike grain growth is bright and colorful compared with the black and white monoclinic α one with the cross-hatched radial grain growth. In addition, the rotundity of α-spherulites was clear, while that of β-spherulites was relative obscure. With increasing temperature, the morphology of β and α spherulite disappeared at 157 and 171 ℃, respectively.

Key words: liquid crystalline copolymer, β-form nucleator, isotactic polypropylene, crystallization structure and morphology, blend