Preparation And Characterization Of Epoxy Resin/Acrylic Composite Latex

Epoxy resin at first was dissolved in acrylic monomers mixture (acrylic acid, butyl acrylate and methyl methacrylate), then epoxy resin / acrylic composite latexes were prepared by emulsion polymerization, in which potassium persulfate was used as initiator, the mixture of polymeric surfactant, sodium dodecyl sulfate and polyoxyethylene alkylphenyl ether (n=10) as emulsifiers. The polymeric surfactant was block copolymers with end epoxy groups, which were synthesized by poly(ethylene glycol) and epoxy resin. In emulsion polymerization, the chemical reactions include the hydrolysis of epoxy groups and the esterification between the carboxyl and epoxy groups. The influence of the amount of emulsifiers, epoxy resin and initiator on the polymerization conversion was investigated. The.effects of the amount of emulsifiers and epoxy resin on the stability of composite latex and the water absorption of the latex film were studied also. At the same time, the influence of the condition of pre-emulsification on the stability of acrylic latex and the water absorption of the latex film were measured, and the particle size distribution of the epoxy resin / acrylic composite latexes was characterized.For the composite emulsion polymerization, in which prescriptions contain with or without acrylic acid, the changes in the percentage of epoxy were compared. It was shown from these changes that the chemical reactions of epoxy groups were took place. If the latex films were inserted in acetone solvent, it was found that the latex film with the acrylic acid component was partially dissolved, but without theacrylic acid component was full dissolved. These results demonstrated that the epoxy groups took place the hydrolysis and the ester linkage with carboxyl group was formed in emulsion polymerization. The results of the particle size distribution showed that the mean particle size of the composite latex with acrylic acid was bigger than that of the composite latex without acrylic acid.The acrylic acid latexes were prepared by polymeric surfactant as the emulsifier. The influence of the molecular weight and the amount of polymeric emulsifier on the stability of acrylic latexes and water absorption of latex films were studied. It was shown that the polymerization stability of the latex prepared by polymeric emulsifier was lower than that of the latexes prepared by low molecular emulsifier. The storage stabilities of both latexes were very good. The water absorption of latex films decreased with the increasing of the amount of polymeric emulsifier because of the linkage reaction between the epoxy and carboxyl. At the same time, the molecular weight of polymeric emulsifier also affected the water absorption of latex film. The influence of the amounts of epoxy resin on the stability epoxy resin/acrylic composite latexes and the water absorption of the latex films were studied. It was shown that the water absorption of the latex films decreased with increasing the amount of epoxy resin owning to the ester linkage reaction. The polymerization and storage stability of the composite latexes were very good.The influence of the amount of epoxy resin > initiator polymeric emulsifier and low-molecular weight emulsifier on polymerization conversion rate were studied. It was shown that the induction period of initiator was prolonged and the rate of monomer fractional conversion was slowed while polymeric emulsifier and epoxy resin were increased. The results demonstrated that the epoxy resin and polymeric emulsifier were inhibitors. The induction period of initiator was shortened and the rate of monomer fractional conversion was improved with the initiator or the amount of low-molecular weight emulsifier increasing.The effects of the amount of polymeric and low-molecular weight emulsifiers, stir time and speed in the emulsification on the stability of the epoxy resin / acrylic composite latex and the water absorption of the latex film were studied. It was shownthat the stability was improved with increasing the amount of emulsifiers, but a little effect on the water absorption of the latex films was observed. The stability of the composite latex was enhanced while the stir time was prolonged and the stir speed was raised in pre-emulsification. It was shown from experimental results of the composite latexes that all the amount of emulsifier, the stir time and speed of emulsification affected their particle size and distribution.