Study On Modification For PVAc’s Water Resistance

Polyvinyl acetate emulsion has advantage of low cost, enviromental protection, high bonding strength, but disadvantage of poor water resistance. From emulsifier, protective colloid, the reasons for poor water resistance are analyzed. The methods of improving the water resistance of polyvinyl acetate are discussed, such as copolymerization with vinyl acetate, addition of compounding agent and emulsifier-free emulsion polymerization.Firstly, the paper studies the influence of PVA and different emulsifiers on polymerization and performance of polyvinyl acetate emulsion. Discuss the influence of emulsifier on particle size, water resistance and stability of polyvinyl acetate emulsion. The studies show the dosage of PVA is big the emulsion has good performance but disadvantage of water resistance. Using complex emulsifier the storage stability increased. As increasing complex emulsifier content particle size became smaller.Secondly, studies the influence of initiator dosage on performance of polyvinyl acetate emulsion. The studies show too little or too much initiator dosage disadvantage of reaction stability.Thirdly, seleceting three monmers as modifiers, the modification which was optimized with orthogonal design, lastly gained a emulsion with excellent water resistance and tensile strength.Fourthly, the copolymer of polyvinyl acetate was prepared by emulsifier-free emulsion process. As there is no emulsifier in the polymerization process, the stability of emulsion was poor. This chapter has described the soap-free copolymerization with vinyl acetate as basic monomer, maleic acid as modification functional monomer and butyl acrylate as modifier monomer, forming a stable, good water resistance emulsion.Finally, the copolymer of vinyl acetate and hydroxyethyl acrylate was synthesized by emulsion polymerization and then added the MDI. As the MDI can react with the hydroxyl groups of copolymers and the hydroxyl groups of polyvinyl alcohol, which made water resistance and tensile strength of the emulsion greatly improved.It was demonstrated that the properties of modified polyvinyl acetate had been improved greatly through the tests of particle size analyzer, tensile strength, FTIR, TEM, and so on.