Study On Synthesis And Properties Of Siloxane-modified Acrylate Copolymer Microemulsion

Siloxane-modified acrylate copolymer microemulsions were synthesized by seeding emulsion polymerization. They were transparent or translucent and bluish, and had good mechanical stability, chemical stability, freeze-thaw stability and storage stability. The diameter of modified microemulsion particles was controlled at the range of 20~80nm and the particle size distribution was relatively narrow. The siloxane-acrylate copolymer films were smooth and compact, possessed of good water-resistance and thermal-stability. There are wide foreground to apply the siloxane-modified acrylate microemulsion in many fields such as coatings of buildings, protecting coatings in industry, finishing coatings of leather and fabric.The acrylate copolymer microemulsions with mean diameter of about 40nm were synthesized by redox initiator systems. The better condition for the synthesis of acrylate copolymer microemulsion was the application of the seeding emulsion polymerization method and the composite surfactant of SDS/TS-02. The mean diameter of microemulsion initiated by APS/TMEDA was close to that of microemulsion initiated by APS/HSH, while the former easily induced gelaration.Based on the experimental experience of chapter 2, the synthesis of siloxane-modified acrylate copolymer microemulsions was completed by the thermal initiator of KPS and the choice of new siloxane monomer of C-1706. The effect of polymerization methods, the TS-02/SDS mass ratio and the content of siloxane on the polymerization and properties of microemulsion were investigated. The results indicated that the content could be up to 35% with mean particle size of 82.0nm at low composite surfactant concentration of 2.5% and 65~75℃Compared with thermal initiator, the mean particle size of the modified microemulsion initiated by redox system was smaller. It decreased with the increase of the amount of surfactant, monomer concentration and the VTIS/monomer ratio, but increased with the increase of the concentration of initiator. When the initiator concentration was 0.3~0.5%, theamount of composite surfactant was 2-4wt%, and the reactive temperature was 50℃, the solid content of the microemulsion could be up to 43.08% with small particle size of mean diameter <50 nm. Thermal properties of modified copolymeric films were tested by thermal analytic methods. The results showed that, when siloxane content increased from 0% to 15%, the Tg declined from 19.64℃ to 14.53℃ and the remainder increased from 0.16% to 9.67 at 400℃ The crosslinking degree of the films became high with the decrease of the volume of -OR groups, meanwhile, thermal stability of the film increased.