| Water-based, solvent-free and high solids molecular technology has become inevitable trend in the development of material production, because of environmental laws and regulations about coatings and adhesives enacted by each country. Conventional epoxy resin has excellent performance, which is only soluble in organic solvents insoluble in water and harmful to environment during applications. Therefore, water-borne epoxy has become a hot research, which inherits the advantages of epoxy resin and environmental friendly, but limits application because of brittleness, poor thermal stability. Polysilicone has advantages of temperature resistance, thermal stability, and excellent flexibility in main chain, so epoxy resin can be modified by silicone to increase flexibility and thermal stability.In this paper, using polyethylene glycol reacted with methyl tetrahydrophthalic anhydride(mole ratio 1:2.1) at 90 ℃ for 1.5h formed carboxyl terminated synthetic intermediates, then intermediate grafted on epoxy resin(mole ratio 1: 2.1) at 130℃for 4.5h, and obtained aqueous epoxy resin. Infrared spectroscopy were used to characterize the structure and indicated successful graft. Using acid value and epoxy value tracked reaction process and optimized synthetic conditions. Water-soluble, centrifugal stability and particle size of water-borne epoxy resin was characterized. The results showed that: water-borne epoxy resin had good water-soluble and stability, non-hierarchical during 3000r/min centrifugal process for 30 min, and particle size under 2.166μm made up 97% of the total.Polysiloxane A and B were synthesized by hydrolysis condensation reaction at 80℃ for 2.5h using dimethyl diethoxy silane, respectively γ-aminopropyl triethoxysilane, γ-(2,3-epoxypropoxy) propyl trimethoxysilane as raw materials. Structure was analyzed through FT-IR and 13 C NMR spectral, the results showed that the synthesis of polysiloxane A and B structure satisfied expected structure. Water soluble of polysiloxane A and B and the stability were characterized, the results indicated that polysiloxane A and B had solubility, good stability and can be stored more than six months.Polysiloxane, waterborne epoxy and curing agent were mixed homogeneously at proper ratio to form curing flim. Infrared spectra showed that both the cured films were cured completely, scanning electron microscopy showed that the polysilicone possesses perfect dispersity in water-borne epoxy resin. The flexibility of both type of cured film were raised to level 1. Two of the cured film coating hardness, adhesion, impact resistance, water absorption, water resistance and chemical resistance were tested and compared. With increasing polysilicone A content in reactive cured film, dry time shortened, pencil hardness increased, adhesion unchanged, the impact of height increased, water absorption increased, preferred water resistance in the content is 20%, and chemical reagents resistance increased. With increasing polysilicone B content in blended cured film, dry time lengthened, pencil hardness decreased, adhesion unchanged, the impact of height increased, water absorption unchanged, water resistance and chemical reagents resistance were good.Thermal stability of cured film were tested by thermal gravimetric analysis. With silicone content increasing, heat level of reactive cured film increased and the temperature at the maximum heat weight loss rate increased to 396.7℃, heat level and the temperature at the maximum heat weight loss rate of blended cured film were less affected. Comparative performance of the two modified cured film, found that the reactive film is better than blend films. |
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