Study On Silicone-Modified Acrylic Emulsion

Pure acrylic emulsion has the advantages of cheap and good performances so they are widely used in many regions, however, weatherability, water resistance and Ca2+ stability of the emulsion are unsatisfactory and there exists the phenomenon called "heat-adhesive and cold brittleness". Research on silicone-modified acrylic emulsion has become a hot topic because of the good weatherability and water resistance of the silicon-acrylic latex.In this thesis, the silicon-acrylic latex were prepared by semicontinuous seed emulsion polymerization using octamethylcyclotertrasiloxane(D4), vinyltriethoxysilane(A-151), methyl methacrylate(MMA) and acrylic butyl(BA) as main monomers, sodium dodecylbenzene sulfonate(SDBS) and octylphenol polyoxyethylene ether(OP-10) as compound emulsifier, potassium persulfate(KPS)as initiator. in addition, in order to avoid the other electrolyte ions existing in the emulsion, DBSA was used as catalyst, instead of inorganic acid catalyst, and the effects of different conditions on the emulsion were studied in details. The results illustrated that the seed emulsion should be synthesized when the pH is 3; when the pH is 9, reaction temperature is 80℃, the content of emulsifier is 4%(based on the total monomer mass), the KPS content is about 0.4% (based on the acrylic monomer mass) the quality of the emulsion is good, conversion and coagulum content is satisfying also. Orthogonal experiment was used to make further research about the effect of the ratio of SDBS to OP-10, the ratio of MMA to BA, the content of D4 and the initiator content on the emulsion.In the end of the thesis, the emulsion was characterized by infrared spectroscopy(IR), scanning electron microscopy(SEM), dfferential scanning calorimetry(DSC) and laser particle size analyzer, the results demonstrated that polysiloxane had been copolymerization with acrylic, particle size distribution of silicone-modified acrylic emulsion was narrow and particle size was small, besides, the glass transition temperature of the coating was proper.