Synthesis And Application Of Large-particle Polysiloxane-acrylate With Core-shell Structure

Polysiloxane has the advantages of small polarity,good flexibility,high temperature resistance and oxidation resistance;Polyacrylate has a strong interaction with polar polymer and widely used as impact modifier for thermoplastic resins and their alloys.Polysiloxane and polyacrylate can be combined by emulsion polymerization to prepare a kind of impact modifier with better impact resistance.But the particle size of polysiloxane-acrylate latex prepared by emulsion polymerization method is mostly below 200 nm.The polysiloxane-acrylate latex of core-shell structure with a particle size of 300 nm can be more useful in the process of impact modification of thermoplastic resins such as polycarbonate(PC).Therefore,it is of great significance to develop the technology for preparing a large-particle polysiloxane-acrylate with core-shell structure.In this paper,a traditional emulsion polymerization method had been used to synthesis the polysiloxane core latex with the choice of three siloxane monomers octamethylcyclotetrasiloxane(D4),methacryloxy propyl trimethoxyl silane(KH-570)and hexamethyl disiloxane(MM).After the grafted of N-butyl acrylate(BA),the rubber latex had been agglomerated by agglomerating agent of polyacrylate polymers.Methyl methacylate(MMA)and(St)as the shell monomers had been grafted to prepare the large-particle polysiloxane-acrylate with core-shell structure.This composite latex were synthesized via multi-stage emulsion polymerization which the mean particle diameter was 400 nm and has a higher solid content of 32.2%.After the process of demulsification,curing,vacuum filtering,washing and drying,the final product polysiloxane-acrylate elastomer present a kind of white solid particles.The structure of the polysiloxane-acrylate and the morphologies of the latex particles were characterized by the FT-IR,DSC,TEM and laser grain-size analyzer.Each reaction time of three stages which include the synthesize of polysiloxane core latex and the graft of BA and MMA/St had been confirmed via testing the solid content and monomer conversation.The effects of the emulsifier concentration,water-solubleinitiator amounts and polymerization temperature on the state of the polysiloxane-acrylate latex and particle diameters were also studied.The elastomer of large-particle polysiloxane-acrylate with core-shell structure was used for PC toughening modification.The low-temperature toughness of PC could significantly improved with the addition of elastomer.The PC blend possessed the high impact strength(69.6 kJ/m2)at-40 ? when the addition of elastomer is 9wt%,and this impact strength value is close to that(77.1kJ/m2)at normal atmospheric temperature.By comparing with the elastomer which particle size is 200 nm,the improve of low-temperature toughness with the large-particle polysiloxane-acrylate elastomer on PC was more obvious.