| On nano-Si02surface grafting process, emulsifiers instead of alcohol in order to reduce the silane coupling agent KH-570hydrolysis rate to reduce the KH-570between the self-clustering, improved the surface grafting nano-SiO2. Nano-SiO2and acrylic monomers in situ polymerization to form the seed emulsion. Using Silane coupling agent (KH-570), Methyl methacrylate (MMA) and Butyl acrylate (BA) as monomer, we have prepared the pre-emulsion. Using core-shell emulsion polymerization, we have prepared a core-shell structure of SiO2/acrylate hybrid emulsions. Adding amino resin in the emulsion system to prepare an thermal crosslinking acrylic emulsion. The test results show that:(1). According to the data analysis of Organic process of modification of the experiment, we use emulsifier to replace organic alcohols to control the rate of hydrolysis of the KH-570, and discussed the effect of the type and the dosage of emulsifier on the modification. The modified process conditions: use anionic emulsifier SDS and its amounts account for4%of the total amount of the SiO2, and reacted at25℃under12h.(2). In situ seed emulsion polymerization, the emulsion stability increase with the increase of the content of SDS, when the feeding amount of MMA, BA, and a modified sol is unchanged. In seed emulsion polymerization process, when the monomer feeding amount is unchanged, the film hardness and temperature resistance were improved with the increase of the modified nano-SiO2addition. When modified nano-SiO2addition is unchanged, with the increase in the amount of KH-570addition, the coating temperature resistance and water resistance were improved.(3). By adopting the way of Core-shell emulsion polymerization, discussed the effect of the technology, amount and ratio of emulsion, added amount of the nano-SiO2, distribution and dosage of the initiator and added amount and distribution of hard and soft monomers on the rate of emulsion gel, particle size, appearance and water resistance of the coating film, heat resistance, hardness, and the contact angle in the polymerization process of seed and shell emulsion. The experimental data show that:the shell emulsion emulsifier is selected as complex of anionic emulsifier CO-436with the use of non-ionic emulsifier CO-897. Its compounding ratio is2.5:1, and addition in an amount account for the total amount of monomers of5to6%; The addition of nano-SiO2account for8.3%of the total monomers; initiator ratio is1:2, and the total addition of initiator account for0.7to0.9%of the total amount of monomers; In the process of seed emulsion polymerization, hard and soft monomer ratio is1:3, and in the overall emulsion polymerization, the soft and hard monomer ratio is from1:1to1:2; When functional monomer is added in an amount of13.3%of the total amount of monomers, and the addition amount of nano-SiO2is of8.3%of the total amount of monomers, and the ratio of the composite emulsion with amino resin is3:50, the prepared emulsion coating film has good water resistance, decay resistance and hardness.(4). Using amino resins and composite emulsion manufacture paint by mechanical blending. And water resistance, heat resistance and hardness of the coating film have a great improvement.(5). By using the TEM, thermal gravimetric analysis and FTIR to characterize the modified effect of modified nano-SiO2and emulsion:modified nano-SiO2has a good dispersion and weakened the effect of nano-SiO2"second reunion", nano-SiO2particles which was coated by composite latex particles have a core-shell structure; Increasing the thermal decomposition temperature of emulsion improve the heat resistance of the coating film. |
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