| Acrylic emulsion polymerization is an important way of industrial production, the polymer prepared by using this method has a little amount of VOC, and it has been a relative mature technology to use butyl acrylate and methyl methacrylate as a monomer of emulsion polymerization. Although such polymer has advantages of water resistance, alkali resistance and acid resistance, it has poor water resistance, and its damping is not significant in the low temperature and high temperature regions. The present paper firstly studies the formulation design of the acrylate emulsion, and then introduces organic silicon groups into acrylic polymer to improve its property and obtain silicone acrylic emulsion with stable and good performance.The silicone acrylic emulsion is used to prepare water-based damping coatings, and the formulation design of the damping coatings that is suitable for automobile is determined by analyzing and comparing affections of fillers and additives on the performance of the coatings, and the physical performance, heat resistance and chemical resistance of the coating are detected and compared with that of class-A coatings. By studying the affections of polymerization process on the particle size of the emulsion, it can be determined that the emulsion obtained by semi-continuous’feed-starving’method has a good stability, wherein the latex particles have a size of 3～5μm and are narrowly and uniformly distributed. The ratio of soft and hard monomer polymers is studied by using FOX formula, when the ratio of soft and hard monomer polymers is 1.25:1, and glass-transition temperature is-4.48℃, the coating has a good elongation rate. At the same time, the amount of emulsifier and initiator in the system are described, and it is finally determined that when the proportion of amount of the emulsifier is 4 wt.% and the proportion of amount of the initiator is 0.375 wt.%, the gel rate of the emulsion is less than 1%, and the conversion rate of monomers is larger than 95%. The acrylic emulsion is added with organic siloxane, it is determined that the loss factor of the coating is larger than 0.3, the temperature is between a range of-30℃-50℃ by dynamic mechanical properties analysis.The prepared water-based emulsion paint uses water as a solvent, so it saves cost and protects environment. The experiment studies affections of the particle size and dosage of mica powder on dynamic mechanical properties of the coating, and the DMA result indicates that 400 mush of the mica facilitates to slip lamellar structures; when the peak value of tan 5 is 0.62, and the proportion of amount of mica is 40 wt.%, the friction between the lamellar structures of mica is increased, the damping temperature range is-20～40℃. This experiment further adds spherical glass beads to increase the value of tanδ from 0.62 to 0.71. Since there are a various of additives that can be added in the coating, the experiment mainly selects wetting agent, dispersing agent and antifoaming agents which have a significant influence, and selects proper types and dosage. The prepared coating is tested and the result indicated that its performance completely meets the standard, and it is better than that of class-A coating in adhesion, heat resistance, water resistance and so on. |
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