Study On Polypropylene Composites Toughened And Reinforced By Elastomer And Inorganic Filler

Preparation of polymer composites is one of the important methods to realize high performance of polymer materials. In this paper, a newly developed ethylene-octene copolymer (EOC), catalyzed by metallocene catalysts, was used as an impact modifier for PP instead of traditional modifier (EPDM). The relationship between the structure and properties of polypropylene composites toughened and reinforced by EOC and CaCOs respectively or together was studied systematically. Deep investigation and analysis on high performance, application and theory of polypropylene composites were carried out. A lot of valuable information was obtained that can be used for development of polypropylene composites. The main works and conclusions were listed as following:1. The theological and crystallization behaviors of PP/EOC blends showed that increasing octene content in EOC elastomer resulted in a decrease of EOC fluidity, an increase of the adhesive fracture energy with PP (that is compatibility with PP) and of hindering PP crystallization.2. Effect of the viscosity ratio, mterfacial adhesion, processing conditions and composition on the dispersing morphology and properties of PP/EOC blends was investigated. Low viscosity ratio and high shear rate during processing were found to produce fine and uniform dispersion of EOC in PP matrix, while low viscosity ratio, high interfacial interaction, good fluidity of elastomer and high shear rate in molding process resulted in fibril dispersion, which afford a guide for controlling the morphology of PP/EOC blends. Soft fibril formation of EOC in PP did not improvethe tensile and flexural properties, and restrained the improvement of the impact strength. The results showed that fine, uniform dispersion of elastomer with low degree of orientation in PP was better for the improvement of toughness, and optimal toughness was obtained in blends with a certain size of elastomer region.3. By compounding CaCO3 with PP, the effect of CaCO3 content, diameter and shape on the crystallization, dispersion morphology and properties of PP/CaCO3 composites was investigated. The results showed that addition of CaCO3 into PP decreased the apparent crystal size in perpendicular direction to the (110), (040) and (130) crystallographic planes of PPa crystal, and with similar uniform dispersion of CaCO3, the dominant factor influencing toughness is the diameter of CaCO3 particles, but not the decrease of PP crystal size. The toughening effectiveness of nano CaCO3 is obviously better than that of micron CaCO3.4. The impact behaviors of PP/EOC and PP/CaCO3 were compared. The toughening mechanisms of PP/EOC and PP/CaCO3 systems are firstly proved to agree well with Wu's percolation theory. The essential condition occurring brittle-tough transition in two binary systems is that the matrix ligament thickness (L) is lower than the critical matrix ligament thickness (Lc) which is approximate to 0.095?m. It was revealed that elastomer or filler had its strong point as modifier of PP. At the same matrix ligament thickness L , improvement of toughness by elastomer was obviously higher than that of CaCO3, while adding CaCO3 increased the modulus, hardness and heat deflection temperature of PP.5. Toughening mechanism of polymer/elastomer/filler composites was limited to qualitative explanation without quantitative analysis in the past. EOC and CaCO3 were combined to toughen and reinforce PP to study the effect of factors such as the composition, the diameter and shape of filler, the nature of elastomer, dispersing morphology and matrix type on the properties of PP/EOC/CaCO3 composites. The results revealed that the essential condition occurring brittle-tough transition in such ternary system was L?LC (?0.095?m) , and the effect of above factors on the impact behavior followed percolation mechanism which indicated that it was some reasonable using Lc as single parameter criterion of brittle-tough transition ofPP/EOC/CaCO3 composites. The micro-deformation model at different dispersing morphology was th...