| Redispersible emulsion powder has the characteristics of green environmental protection and zero pollution, therefore it has been widely used in many building materials field. With the development of society and the more rigorously demand of people for the qualities of architecture material, the requirement of high-performance redispersible powder became more and more. Therefore, further in-depth study of preparation of redispersible emulsion powder with good performance has wide market prospects.Firstly, The styrene-acrylic emulsion was synthesized with the configuration of a “soft-core and hard-shell”. Secondly, the redispersible emulsion powder was prepared using the spray drying method. Lastly, the influencing factors on the powder’s redispersibility and stabilization mechanism of reconstituted emulsion were investigated. The performance of emulsion and emulsion powder were characterized by fourier transform infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry, nano-laser particle analyzer, UV-visible spectrometer and scanning electron microscopy.Seeded emulsion polymerization process was used to produce a kind of styrene-acrylate emulsion with “soft-core and hard-shell” structure and good performance. The effects of some factors, including of emulsifier, initiator and mass ratio of core to shell, on properties of styrene-acrylate emulsion were mainly discussed. The results showed that when the content of emulsifier was 1%, the content of initiator was 0.5% and the mass ratio of core to shell was 2:1, the styrene-acrylate emulsion was prepared with a narrow size distribution. The average size of emulsion particle was 110.5 nm. The emulsion particles have a clear core-shell configuration and two Tgs(-23℃, 75℃). The acrylate has good film forming properties. The water content and residual content of emulsion powders is low. The emulsion with good performance was suitable for spray-drying.The redispersible emulsion powder was prepared by spray drying. The influence of the p H value, the content of protective colloid, drying temperature and atomizer speed on redispersible emulsion powders properties were mainly discussed. The redispersible emulsion powders properties were including of protective colloid, on water content, residual content, redispersibility and film forming ability. The optimized pretreatment parameters and spray drying parameters were established. The result showed that when the p H value was 9, the content of PVA was between 7% and 8%, the drying temperature was 130℃ nearly, the atomizer speed was 24000 r·min-1, the styrene-acrylate redispersible powders could be prepared with good redispersibility and good film forming ability. The particle size of reconstituted emulsion was 157.7nm, with a narrow size distribution. The molecular configuration of redispersible emulsion powders does not change. All of the analyses show that after the powder is dispersed in water, it can return to its orginal conditions.The influence of the p H value, the dosage of Methacrylic Acid and the content of protective colloid on emulsion powder dispersion performance were mainly discussed. The experimental result indicated that when MAA’s dosage is 4~5%(wt) and the p H value above 9, the carboxyl group distributed on the surface of the particles was transformed into carboxylic ions in order to protect these groups during spray drying. In this way, the powder has good redispersiblity. The particle also has a high zeta potential, which Boosting the electrostatic repulsion between particles. In this way, the reconstituted emulsion has good stability. when PVA’s dosage is 7~8%(wt), on the one hand, the emulsion particle surface hydrophilic group increased, which make the emulsion powder have good redispersiblity. On the other hand, PVA’s long chain poly-ethylene groups were absorbed on the surface of particles, which provide enormous steric force and help to prevent particles aggregation. In this way, the reconstituted emulsion has good stability.In this paper, the styrene-acrylic emulsion powder with excellent properties was prepared. The influence factors of styrene acrylic emulsion powder’s redispersibility were analyzed comprehensively and a kind of dispersion stability mechanism was proposed. This issue has important practical value and theoretical significance... |
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