Synthesis, Property And Polymerization Emchanism Of Emulsifier-Free Acrylic Resin/Nano-SiO₂ Composite Emulsion

Acrylic resin was widely used as the leather finishing materials. Recently,much better properties of acrylic resin, such as better water-resistance,solvent-resistance, hygiene properties and corium feeling, were desirable for theleather finish market. This thesis was mainly focused on the study of acrylicresin/nano-SiO₂ composite emulsion prepared via emulsifier-free emulsionpolymerization, based on the amphiphlic copolymer. Besides, acrylicresin/nano-SiO₂ composite emulsion with the excellent properties systhesized viain-situ emulsifier-free emulsion polymerization and sol-gel method in one step inorder to simplify the systhesis process.Poly(butyl acrylate/acrylic acid sodium)P(BA/AANa) and Poly(butylacrylate/vinyl acetate/acrylamide)P(BA/VAc/AM) were prepared at first. Thestructures of both amphiphlic copolymers were investigated by FourierTransform Infrared Spectroscopy(FTIR), Differential ScanningCalorimetry(DSC) and Transmission Electron Microscopy (TEM). Poly(methylmethacrylate/butyl acrylate/acrylic acid sodium)P(MMA/BA/AANa)/nano-SiO₂composite emulsion and Poly(methyl methacrylate/butyl acrylate/vinylacetate/acrylamide)P(MMA/BA/VAc/AM)/nano-SiO₂ composite emulsion weresynthesized via in-situ emulsifier-free emulsion polymerization, based onP(BA/AANa)and P(BA/VAc/AM) dividedly. P(MMA/BA/VAc/AM)/nano-SiO₂composite emulsion was obtained via both emulsifier-free emulsionpolymerization and sol-gel method in one step, on the basis of P(BA/VAc/AM). P(MMA/BA/AANa)/nano-SiO₂ composite, P(MMA/BA/VAc/AM)/nano-SiO₂composite and ES-P(MMA/BA/VAc/AM)/nano-SiO₂ composite werecharacterized via FTIR, DSC and TEM. The above three nanocompositeemulsions were applied in leather finish; then the applied properties of thefinished leather were determined in detail. At last, the influence of the syntheticconditions such as the reaction temperature, the monomer concentration and theinitiator concentration on the polymerization dynamics of ES-P(MMA/BA/VAc/AM)/nano-SiO₂ composite emulsion was investigated in detail.The polymerization mechanism of nanocomposite emulsion was also discussed.The best reaction conditions of P(BA/AANa) were: the use level of AA was5% and ammonium persulphate-sodium bisulfite of the initiator. The bestreaction conditions of P(BA/VAc/AM) were: the use level of AM was 14%,n(VAc): n(BA)=1:1, the reaction temperature was 90℃and the use level ofammonium persulphate-sodium bisulfite was 6%.The optimized synthesis processes of P(MMA/BA/AANa)/nano-SiO₂composite emulsion were: n(BA): n(MMA)=2:1,pH was 7, the use level of thepotassium persulfate(KPS) was 2%, the reaction temperature was 85℃and theuse level of nano-SiO₂ was 2%. The better properties of the leather finished byP(MMA/BA/AANa)/nano-SiO₂ composite emulsion in contrast to that byP(MMA/BA/AANa) were represented: increasing air permeability by 376.19%and water vapor permeability by 7.78%, decreasing water uptake by 16.31%;besides, wet rubbing fastness was 3class. Dry rubbing fastness was 4～5classand flex resistance was 20000 times.The best properties of P(MMA/BA/VAc/AM)/nano-SiO₂ compositeemulsion was obtained, when the dosage of nano-SiO₂ with the unsaturatedbonds was 1.5%. The better properties of the leather finished byP(MMA/BA/VAc/AM)/nano-SiO₂ composite emulsion in contrast to that by P(MMA/BA/VAc/AM) were represented: increasing air permeability by109.92% and water vapor permeability by 16.49%, decreasing water uptake by56.19%; besides, wet rubbing fastness was 2-3class. Dry rubbing fastness was4～5class and flex resistance was 50000 times.When the reaction temperature was 75℃, the reaction time was 2 hours, thedosage of KPS was 3%, the dosage of tetraethoxysilane(TEOS) was 5%, thedosage of vinyl trimethoxy silane was 4% and n(BA): n(MMA)=3: 2, the bestproperties of the emulsifier-free P(BA/VAc/AM)/nano-SiO₂ composite emulsionwas obtained.The better properties of the leather finished byES-P(MMA/BA/VAc/AM)/nano-SiO₂ composite emulsion in contrast toP(MMA/BA/VAc/AM) were represented: increasing air permeability by285.39% , water vapor permeability by 49.01% and dynamic waterproof by17.71%; besides, decreasing water uptake by 18.47%. Dry rubbing fastness was4～5class, wet rubbing fastness was 1 class and flex resistance was 100000 times.The solvent resistance and the fullness feeling of the leather finished byES-P(MMA/BA/VAc/AM)/nano-SiO₂ composite emulsion in contrast to that byacrylic resin in the factory were improved. In addition to, the softness andadhesion of finish were indistinguishableness.The reaction activity energy (E_a) of ES-P(MMA/BA/VAc/AM)/nano-SiO₂composite emulsion was 44.154kJ/mol and the polymerization reaction rate wasR_p∝[I]^1.716[m]^0.33. The polymerization mechanism of nanocomposite emulsion ofthe homogeneous nucleation was concluded.