| Polyvinyl acetate (PVAc) emulsion, commonly known as white latex, is one of the important emulsion adhesives. It is widely used in coatings, fire retardant coatings, adhesives, etc. The emulsion possesses poor stability, poor water resistance, bad cold resistance, low strength of film and so on, which greatly affects its wide application. Therefore, the poly(vinyl acetate-butyl acrylate) emulsion was prepared by semi-continuous seed emulsion polymerization in this study, and the emulsion particle was designed as "core-double shell" structure by the "particle design" method. In order to improve the comprehensive performance of P(VAc-BA) emulsion and its films, some modification measures were executed, such as optimized the reaction conditions, studied the effect of crosslinker, modified the surface of emulsion particles and blended with nature rubber latex.At first, the latexes preparation conditions were optimized through the analysis of orthogonal experiment. Under the optimum conditions,the mechanical properties and water absorption of film were investigated systematically. FTIR, DSC and DMA were used to measure the construction and thermal behavior of film. The orthogonal analysis indicates that:the optimum synthesis condition was that the monomer ratio mVAc:mBA=3:1, the dosage of functional acrylic monomers was0.75%, the dosage of protective colloid PVA was2.0%, SDS:OP-10was1:3, the dosage of emulsifier was3%. When the drying temperature was about110℃, the overall performance of film was best.Secondly, Core-double Shell structure Poly(vinyl acetate-butyl acrylate) emulsion was prepared by semi-continuous emulsion polymerization, and the effects of ethyleneglycol dimethacrylate crosslinker (EGDMA) on the emulsion particle structure and film performance were studied systematically. The emulsion particles’structure was characterized by transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FT-IR), and the particle size and distribution were characterized by Zata Potential-Particle analyzer, as well as analysis of the film mechanical properties, water resistance, thermal properties and so on. The results shown that, when0.1%and0.5%EGDMA were added to the inner-shell and outer-shell reaction stage under the core-double shell P(VAc-BA) emulsion preparation process respectively, it led to a more clear core-double shell structure and a larger particle size (about500-800nm) of emulsion particles, and the comprehensive performance of the P(VAc-BA) emulsion showed better. This work provided some insight into modifying the surface properties of the emulsion particles, which may expand the application field of the emulsion.In addition, the Butyl Acryate(BA), Methyl Methacrylate(MMA), Vinyl Benzene(SM) and Acrylonitrile(AN) were used as the outer-shell monomer for the "core-double shell" model P(VAc-BA) emulsion particles respectively to modify the surface of emulsion particle and improve the water resistance of films. Meanwhile, the water resistance, the film-forming property and the thermal properties of films were studied. The results shown that, the BA monomer was the best to improve the water resistance, film-forming property and hardness in the four modified monomers.At last, the P(VAc-BA) emulsion was blended with nature rubber latex. The emulsion particles’structure and distribution were characterized by FT-IR and TEM, and the mechanical performances of hybrid film and prevulcanized latex were analyzed. As a result, the emulsion could obtain low viscosity, homogeneous particle distribution and better stability when the nature rubber latex about60%dry rubber content was blended with P(VAc-BA) emulsion about30%solid content. However, the mechanical property of hybrid latex decreased with the increase of nature rubber latex. |
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