Preparation Of Pst/ba/aa Redispersible Polymer Powder

Along with coming of energy crisis and the increasing awareness of environmental protection, the construction energy conservation is taken more and more seriously. The outsite wall insulation is the widely used method of the construction wall energy saving at the present stage of our country, universally acknowledged one of which in the market is Exteral Thermal Insulation Composite Systems based on expanded polystyrene (ETICS). The Exteral Thermal Insulation mortar is used as bonding the expanded polystyrene board and wall., which is consist of cement, river or artificial sand, and imported polymer powder. It has certain advantages, such as high cohesional strength and convenience of operational construction. The goal of the experiment is to research and develop redispersible polymer powder that can be substituted for the imported one. Now the majority of redispersible polymer powder in the domestic market are series of polyvinyl acetate-ethylene (EVA), the drawback of which is weak water and alkaline resistance that more and more limits its further application. The water resistance and Cohesiveness of conventional Polystyrene/acrylate emulsion is better than EVA, however, it is expensive to be as mortar additive due to emulsifier additive.Based on this, selecting Styrene (ST) and Butyl Acrylate (BA) as major monomers which has favorable water and alkaline resistance, Acrylic Acid (AA) as function monomer, it prepared soap-free emulsion. Using spray drying, finally, it obtained the redispersible polymer powder. The result indicats that the powder can be well dispersible in water, which meets the requirements of application in the Exteral Thermal Insulation mortar. At the same time, it prepared the natural nanotubes grafted PST/BA/AA nanocomposite, and considered that the nanocomposite can enhance the thermal performance of redispersible polymer powder.Firstly, it prepared PST/BA/AA by soap-free emulsion polymerization and discussed the influence factors such as proportion of oil phase to water phase, percentage of AA and BA and heat preservation hour. The results are as follows. When the proportion of oil phase to water phase was a range of 30:100 to 40:100, the conversion rate, the viscosity and the solid content of PST/BA/AA were maximum, respectively 98%, 0.17Pa·s and 32%. When the percentage of AA was 13%, the conversion rate, the viscosity and the solid content of PST/BA/AA were maximum, respectively 93%, 0.2Pa·s and 34%. When proportion of soft monomer BA was 75%, the emulsion's viscosity and solid content were max, respectively 0.2Pa·s and 30.5%. When the heat preservation hour was 2h, the solid content of PST/BA/AA emulsion was 31%, which was max. Thus the optimality condition is 40:100 of proportion of oil phase to water phase, 13% of AA percentage, 75% of BA percentage, and 2h of heat preservation.The infrared spectrum and TEM have been employed to analyze the structure and morphology of the emulsion. The result indicates that the emulsion is PST/BA/AA, not the blend of PST, PBA and PAA, and the particle size of emulsion approximately is 0.2μm.In oder to obtain the redispersible polymer powder, it spray dried the PST/BA/AA emulsion. The parameter of spray drying is 200℃inlet temperature, 80℃outlet temperature, 800ml/h and 60s a time of pin unblocking. The powder can reform emulsion when it added to water. After testing by Laser Granularity Analyzer, it shows that the particle distribution of the reformed emulsion is 0-0.4μm, 90% particle sizes of which are 0.34μm .Then it also prepared nanocomposite of natural nanotube grfted PST/BA/AA by in situ polymerization. In order to cause natural nanotube to participate in the polyreaction, it has modified the amino and double bond onto nanotube. The performance of natural nanotube after modification by amino, double bond and polymerization were investigated by means of Fourier transform infrared (FT-IR) spectroscopy, ~1H NMR spectrum, transmission electron microscopy (TEM), specific surface area measurements (SSA) and thermogravimetry analysis (TGA). The result indicates that amino, double bond and PST/BA/AA do graft onto the natural nanotube, the grafting ratios of which respectively are 7.2%, 16.5% and 41.8%. Moreover, the emulsifier experiment indicates that after polymerizing, grafted natural nanotube can form emulsion in the water/oil system. Consequently, it can be used as inorganic emulsifier.