Study On The Composites Of Rare Earth β-Nucleating Agent/Nano-CaCO₃/Polypropylene

In the study, a new rare-earthβ-nucleating agent (WBGⅡ) and nano-CaCO3 are used to modify ethylene-propylene random copolymer(PPR) and homopolymerization polypropylene (PPH) doubly. Meanwhile PP-g-MAH and POE-g-MAH are used as compatibilizer for PPR with nano-CaCO3 and PPH with nano-CaCO3 respectively. Also the effects of various components of WBGⅡ/nano-CaCO3/compatibilizer/PP composite system on the mechanical properties,crystallization properties and non-isothermal crystallization kinetics of the composites are studied .The results show that:The addition of proper amount ofβ-nucleating agent and nano-CaCO3 can improve the impact strength of PP effectively; the composites of modified PPR is 1.5 times higher than PPR, and modified PPH is 2.6 times higher than pure PPH; while the tensile and flexural properties do not decrease significantly, the comprehensive mechanical properties of the composites is improved obviously.During isothermal crystallization process, nano-CaCO3 can accelerate the crystallization rate of PP and make the spherulite size smaller; however rare-earthβnucleating agent can induceβcrystal modification in polypropylene, and the crystal morphology ofβ-PPR is acicular, butβ-PPH is petal shaped. In the composite system of PPR, there is a kind of exclusion effect between nano-CaCO3 andβ-nucleating agent, and it debases their nucleation activity.Nano-CaCO3 andβ-nucleating agent can all improve the melting temperature,initial crystallization temperature and crystallization temperature of PPH ,they also debase the supercooling degree of the composites and make the extension of the crystallization temperature broaden. However, During non-isothermal crystallization process, becauseβ-nucleating agent improve the crystallization temperature of the composites to high temperature region, so the crystallization of modified PPH is relatively difficult at the initial stage, and the crystallization rate slows down, the semi-crystalline time is prolonged.The non-isothermal crystallization kinetics of PPH and modified PPH fit to use the method of Jeziorny's method and Mozhishen's method .