Synthesis And Characterization Of Starch Modifyied Polyvinyl Acetate Emulsion With Low Solid Content

Polyvinyl acetate emulsion which is non-toxic and environmentally friendly, has been widely used in various fields, such as wood processing, architecture, home decoration, textile, paper making and packaging and leather processing as adhesives and coatings. Currently, the production of polyvinyl acetate emulsion takes the first place in the industry of synthetic latex adhesive. In recent years, with the rising price and dwindling reserve of oil resource, the costs of polyvinyl acetate emulsion adhesive continue to increasing.In this thesis, polyvinyl acetate homopolymer emulsion and of PVAc/MAA copolymer emulsion with a low solid content (20%) had been synthesized by using semi-continuous seed emulsion polymerization. We also investigated the effects of the type, the amount and the ways to addition of polyvinyl alcohol and starch respectively on the properties of emulsion in two polymerization system. By characterizing the viscosity, conversion rate, aggregate stability, dilution stability, adhesive strength, particle size, rheological properties, the states of water and other properties of emulsion, we could obtain the following conclusions.The type and the amount of polyvinyl alcohol had great effects on the viscosity and stability of emulsion. With the increase of the amount of PVA, the viscosity increased and the dilution stability became better.The addition of MAA led to the improvement of the bonding strength while decreasing the particle sizes of the emulsion which became more uniform. The increase of MAA amount resulted in the increasing viscosity, slowing polymerization rate and the worse dilution stability. The appropriate amount of MAA was2%and it was better to add the MAA in the early stage.It was suitable to add the starch in the early stage. On the one hand, the starch could increase the viscosity and aggregate stability of the emulsion; on the other hand, it slowed down the rate of polymerization and weakened the bond strength of the emulsion. The particle sizes of emulsion increased by adding the raw starch, while the particle sizes decreased with addition of the oxidized starch.When the PVA217with the addition mount of3%and the homemade oxidized starch with the mount of12%were used in the synthesis of the emulsion, the better comprehensive performances and the better aggregate stability and dilution stability were obtained. The viscosity is13.8mPa.s, the average bond strength is10.66MPa, and the best bond strength is13.20Mpa.