Study On Silicone Rubber/Silicone Resin Complex Particles

Double bonds were introduced into the polysiloxane chain by the copolymerization of octamethylcyclotetrasiloxane(D4) and tetravinyltetramethylcycoltetrasiloxane(Vi-D4). When these double bonds were initiated by potassium persulfate(KPS), silicone particles with certain degree of cross linking were gained. To be a second monomer, methyltrimethoxysilane(MTMS) came into being a shell which enwrap the silicone particle. The mechanical property of epoxy resin modified with silicone particles and core-shell particles was also studied.The polysiloxane emulsion of D₄ and Vi-D4 was prepared using sodium dodecyl benzene sulfonate as an emulsifier and sulfuric acid as a catalyst. The effect of ultrasonic and string emulsification method on the monomer drops diameter, copolymerization and latex particles diameter were compared. It was found that two kinds of nucleation mechanism, monomer drop nucleation and micelle nucleation, existed in the copolymerization emulsified by ultrasonic method. Compared with stirring emulsification, by ultrasonic method the stability of latex emulsified was stronger, and the conversion was higher. The effects of the monomer ratio, temperature, catalyst and emulsifier concentration on the conversation and latex particles diameter were also studied. The reactivity ratios of D4 andVi-D4 were calculate with analyzing by chromatogram( rD₄ = 1.3572; rVi-D₄ = 0.3583). The trend of copolymer composition changing with conversion was predicted.The effect of the Vi-D4 fraction in pre-polymer, reaction temperature, and the feeding mode of initiator on crosslink of polysiloxane were studied. The gel fraction of silicone rubber increases with the increasing of Vi-D4 ration and temperature. The gel fraction of silicone will decrease if KPS feeds with H2SO4.The effect of the technics on forming of core-shell particles was studied. We found that the sol-gel reaction of MTMS is more peaceable in neutrality or weakly acidic and alkalinity. When the fraction of MTMS is large, the emulsion particles will accumulate easily. Thedifference of mean particles between prediction value and core-shell particles prepared by the method of pre-swelling is bigger than by the method of semi-continuous method.The mechanical properties of modified epoxy resin show that the flexural modulus, flexural strength and elongation at break is lower than that of pure epoxy resin, and it decreases with the increasing of rubber fraction. The impact strength of both modified epoxy resin is better than the pure epoxy resin, and it would appear peak value when silicone rubber fraction arrive 10%. The mechanical properties of modified epoxy resin increase with the enhancing of gel fraction. It show that the fracture surface of pure epoxy resin appears brittle fracture, but the modified epoxy resin appears gliding fracture. The dispersibility in epoxy resin of core-shell particles is better than that of silicone particles, and it would become more remarkable when the rubber fraction increases.