| Styrene/acrylic emulsion has many advantages, such as environmental protection, better application performance and lower cost etc. However, it also has some disadvantages such as lower bursting strength and stiffness, poorer water resistance. Among the factors which affect the performance of emulsion, the main aspects are the selection and use of emulsifiers.In this study, used styrene and acrylate as main monomers, chosen a wide variety of emulsifiers, the styrene/acrylic emulsion used in auto-industry filter paper was prepared via emulsion copolymerization. The particle size, distribution and morphology of emulsion were characterized by laser granulometer and scanning electron microscopy. The application properties of the emulsion were analyzed by testing the stiffness, bursting strength, water resistance and permeability of filter paper. The effects of emulsifiers on the performance of emulsion were studied, the mechanisms of different emulsifiers were interpreted, and the pH regulation of emulsion and the stability of emulsion were discussed.Many emulsifier systems were selected according to the structural characteristics of emulsifiers and the HLB value of emulsion under certain experimental conditions. The optimal emulsifiers were as follows: OP-10/FR-1, OR-2/FR-1 and FOR-3/OF-40.In order to further improve the emulsion's properties, the effects of the dosage, ratio and adding method of emulsifiers on the emulsion properties were studied, and the emulsifier systems in emulsion copolymerization were optimized. The better emulsifier systems were showed that: (1) the dosage of OR-2/FR-1 is 3%, the weight ratio of OR-2/FR-1 is 2/1, and the adding method of OR-2/FR-1 is 3/2; (2) the dosage of OP-10/FR-1 is 2%, the weight ratio of OP-10/FR-1 is 2/1, and the adding method of OP-10/FR-1 is 2/1; (3) the dosage of FOR-3/OF-40 is 2%, the weight ratio of FOR-3/OF-40 is 2/1, and the adding method of OP-10/FR-1 is 3/2.Base on the above studies, in order to satisfy the requirement of practical application, the effects of pH-control on properties of styrene/acrylic emulsion was studied. The results showed that, the comprehensive properties of emulsion were encouraging and stable when ammonia water with concentration of 5.0% was used as pH regulator, and the system pH was able to be controlled at 8.0 in the process of polymerization, and after polymerization the pH was adjusted to 7.0～7.5.Study on the property stability of the emulsion synthesized by different emulsifiers. The results showed that, with the increase of the storage time, the stability of emulsion got better, and it had little or no effect on the viscosity and pH value of emulsion. The synthetic products were then characterized by laser granulometer and scanning electron microscopy, the particles in the latex were found to be uniformly-distributed and non-adhesive. It was found that the storage time has a little effect on the stiffness and bursting strength of filter paper, but it has serious impact on the water resistance of filter paper.
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