Study on the structure, melting, and nonisothermal crystallization behaviors of isotactic polypropylene with nematic liquid crystalline polymer as a new β-nucleating agent

Abstract

Wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to evaluate the effect of nematic liquid crystalline polymer as a new β-nucleating agent (LCP-NA) on the structure, melting, and nonisothermal crystallization behaviors of isotactic polypropylene (iPP). A high content of β-crystal could be obtained by the combined effect of the optimum LCP-NA content and crystallization temperature and time. The relative content of β-crystal increased with increasing LCP-NA content, reached a maximum value of 59% when LCP-NA content was 1.0 wt % at 130°C for 1h, and then decreased with a further increase of LCP-NA content. Avrami, Jeziorny, Ozawa, and Mo methods were applied to describe the crystallization process. Jeziorny and Mo methods showed a good agreement in describing the nonisothermal crystallization behaviors of pure iPP and iPP blends with 1.0 wt % LCP-NA, but Ozawa method could not better describe these behaviors. The addition of LCP-NA could effectively increase the crystallization temperature and the crystallization rate, and induce heterogeneous nucleation with the nonisothermal tridimensional growth of the spherulite. Kissinger’s method indicated that the iPP blends with 1.0 wt % LCP-NA needed a higher energy for crystallization per mole than pure iPP.