The Preparation Of Redispersible Polymer Powder And Its Application Performance

Dry mix mortar, which has the characteristics of stable and uniform quality, good performance in application, multi function, easy application and environment friendly, has been widely used in various construction areas. Redispersible polymer powder, as one important additive in dry mix mortar, thus attracts more attention. Especially when the development of dry mix mortar is still on the initial stage in our country and most redispersible polymer powders depend on import, self-developing redispersible polymer powder is becoming one key point for the development of dry mix mortar.In this paper, the preparation of the original emulsion is discussed. We synthesize one kind emulsion based on acrylic monomer which is spray dried. Through spray drying several emulsions, three kind redispersible polymer powder (vinyl acetate / ethylene, vinyl acetate/ ethylene/ Ac, and vinyl acetate/ ethylene/VeoVa) are produced. The determining factors in the process are discussed. The application performance in mortar of the resultant redispersible polymer powders are tested, which is also compared with the performance of some imported powders.The results indicate that the synthesized emulsion can be spray dried. According to the preparation process of redispersible polymer powder, we conclude that whether one emulsion can be spray dried largely depends on the range between T_g and T_f, and also is concerned with the speed of forming film when the temperature is above minimum film forming temperature (MFT). What's more, the emulsions with less surface tension have advantage in the progress of spray drying. In addition, the re-emulsion ability of resultant powder is mainly determined by the conglomeration state of powders. Through the research of the function of inorganic auxiliary agent, it proves that the way of adding it during spray drying has better effect.The resultant powders' performance in mortar are tested. The results indicate that the resultant powders almost have the same performance as original emulsions. The IR and ~1H-NMR analysis show that the resultant powders have almost the same composition and structure as original emulsion. In comparison with some imported powders in modifying cement mortars, they also have good performance, such as comparable or even better adhesive strength, higher impact resistance, and lower water absorption etc.