Preparation Of Nano-SiO₂/Wollastonite Composite Particles And Application In Polypropylene （PP）

Wollastonite is a new kind of industrial mineral materials. Wollastonite hasbeen widely used as fiber reinforcement in many industries such as rubber, plasticand papermaking, because of the special needle-like crystal formation. Themechanical properties of the wollastonite/PP have been restricted because the sharpcorners and smooth cleavage surfaces which are made inevitably by crashing thewollastonite.In this article, in order to utilize comprehensiviy characteristics of wollastoniteand nano-SiO₂and to improve the mechanical properties of composites, wollastonitewas coated by nano-SiO₂. In order to enhance compatibility of PP with wollastoniteand composite particles, they were organically modified. The effect of modifiedpowers on the toughening and reinforcing of the composites was studied, at the sametime to study on the Toughening and Strengthening Mechanisms. Through aboveresearches, some conclusions could be taken as follows:（1） The nano-SiO₂/wollastonite composite particles were prepared by thechemical precipitation. After a series of characteristics such as SEM, XRF and XRD,the results showed that the wollastonite had been coated by the nano-SiO₂, the sharpedges of the ordinary wollastonite were passivated and the slippy crystal surfaceswere rough.（2） The optimal technological parameters of the preparation of the compositeparticles were temperature-40℃、pH value-8.0、coating quantity-5%.（3） In order to enhance compatibility of PP with wollastonite, wollastonite andcomposite particles were organically modified through the Titanate coupling agentsTC-130. After a series of characteristics such as viscosity measurement、wettingangle and oil absorption, The results indicated that the optimum amounts of titanates coupling agent TC-130were0.8%and1.0%.（4） Wollastonite/PP composites with different interfacial textures were preparedby blending extrusion and the changes of mechanical properties of composite systemwith25%filler were studied. The result showed that, compared to wollastonite/PP,the tensile strengths of composite particles/PP and modified wollastonite/PP wereincreased12.6%and31.6%, at the same time the izod impact strengths wereincreased44%and58.4%.So the wollastonite which was coated by nanoSiO₂ormodified organically can improve the tensile property and impact toughness of thecomposites.（5） The tensile strength and the impact strength of the modified compositeparticles/PP were the greatest among the four composites, so the tensile property andimpact toughness of the composites can been enhanced greatly through adding theinorgano-organic modified wollastonite.