| Coatings were used more and more frequently in our social life, and it’s necessary in industrial procedure, civil architecture, anticorrosion field and so forth. Water-based coatings, which are environmentally friendly, are the future directions of coatings research and industrial production, and the solvent-based coatings must be replaced by water-based one. Water-based polyacrylate resins have been widely used because of its good film-forming ability, high glossiness, weather resistance ability and low cost of raw materials. However, properties such as hardness, water and solvent resistance, scratch resistance et al. are not as good as expected. The poor properties of polyacrylate resin will be improved via modification by nano silica with high hardness, abrasion and scratch resistance, and silica/polyacrylate composite with good properties will be obtained. In this paper, nano silica/MMA dispersion was modified by silcane coupling agent and then polymerized with acrylic monomers via free radical solution polymerization, and the water-soluble organic-inorganic hybrid acrylate resin was obtained after naturalization. The main influence factors of modifying silica/MMA dispersion and synthesizing hybrid resin, and properties of resin films were studied.In this paper, silcane coupling agent was dispersed in ethanol/water solution for modifying nano silica/MMA dispersion, influence of different silcane coupling agents and their amount, modification temperature and time, weight ratio of ethanol/water and pH were studied. The result showed that the optimal modification condition is as follows: silcane coupling agent KH570 was dispersed in ethanol/water solution with 9:1 weight ratio, and its weight is 10% of nano silica, the pH is 8-9, the modification temperature is 70℃, and the modification time is 12 h. The light blue and yellow nano silica/MMA dispersion modified by KH570 could keep stable over 3 months, its particle size, PDI and Zeta potential is 36.6nm, 0.327,-40.6 mV respectively. The FT-IR spectrum showed that silcane coupling agent was grafted and absorbed on silica successfully, The TEM images showed that both the dispersity of silica in MMA and stability of silica/MMA dispersion were enhanced after modification, the size distribution narrowed.Nano silica/polyacrylate hybrid water-soluble resin was synthesized via free radical solution copolymerization of silica/MMA dispersion modified by KH570 and acrylic monomers, influence factors of stability and properties on synthesizing hybrid resin were studied. The result showed that when hydrophilic monomers AA is 10% and HPA is 5% of total monomers weight, the acrylate resin obtained got good water dispersity and storage stability. Nano silica/polyacrylate hybrid water-soluble resin has good mechanical properties, stability and suitable viscosity with ethanol as solvent, silica content is 20% of total monomers. The FT-IR spectrum showed that copolymerization happened and the hybrid resin was obtained. The TEM image showed that silica particles were cladded and uniformly dispersed in polyacrylate resin. The TGA showed that extrapolated initial decomposition temperature of nano silica/polyacrylate hybrid water-soluble resin is 12.45℃ higher than that of acrylate resin, and thus thermal stability of hybrid resin enhanced.Film properties of nano silica/polyacrylate hybrid water-soluble resin were studied and compared with acrylate resin and organic silicon modified SiO2 sol/polyacrylate composite emulsion. The adhesion of hybrid resin is 0 grade, the hardness is 4H, the flexibility is 2mm, the glossiness is 81.2°, the film is still in good condition without blanching, bubble and abscission after immersion in water for 72 h. And the film also keeps good condition without abscission after wiping back and forth 50 times by methyl ethyl ketone. Comprehensive properties of hybrid resin are much better than acrylate resin and similar to composite emulsion. |
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