Research Of Styrene-acrylic Emulsion For Polymer Cement Waterproof Coating And Its Application

Polymer cement waterproof coating has some advantages such as general applicability, airtightness and environmental friendness etc. So it is deemed to be one of the most promising waterproofing materials. But problems are also existed, for example low compatibility with cement and poor mechanical properties of waterproof coating film. To overcome these weaknesses, seed semi-continuous emulsion polymerization was applied to prepare modified styrene-acrylic emulsion, and synthesize high performance polymer modified cement waterproofing coating.The theoretical glass transition temperature( Tg) of polymer was set to-10℃, so hard and soft monomer’s ratio( BA: St) was determined as 56:39. To enhance the dispersibility of emulsion to cement, nonionic emulsifier OP-20 were selected from nonylphenol polyoxyethylene ether. Otherwise, OP-20 and anionic emulsifier sodium dodecyl sulfate( SDS) were adopted as composed emulsifier. When the emulsifier proportion( OP-20 : SDS=10 : 2) became 3.5%( relate to the monomer total mass, same below), the synthesized emulsion appeared fine and smooth,, the compatibility of latex and cement and the polymerization stability were also best. In order to improve the affinity between polymer film and hydratable silicate gelation system, the functional monomer dibutyl maleate( DBM) and methacryloxy propyl trimethoxyl silane( A-174) was incorporated. The results showed that when the dosage of DBM and A-174 were 1.7%, 4.5%, respectively, the mechanical property of waterproof coating film became best.The emulsions films were measured by Infrared spectroscopic( FTIR), Differential Scanning Calorimeter( DSC) and DLS etc. FTIR revealed that A-174 has reacted with styrene or acrylic monomers. DSC results suggested that Tg of unmodified, modified with DBM, modified with DBM and A-174 were-2.53℃,-11.87℃,-16.12℃, respectively. DLS showed the average particle size was 210 nm, the distribution was narrow correspondingly.Herein the preparation modified styrene-acrylic emulsion was applied for polymer cement water proof coating. The factors of coating recipe such as ratio of polymer to cement( P/C), coalescing agents, defoamingagents were studied. The results showed that when P/C was 1, the dosage of coalescing agents was 1%, the one of defoamingagents was 0.45%, the performance of waterproof coating film was best. SEM characterization was carried out for comparing with the other commercial coating, it was found that film was more compact than commercial one. It also proved that the waterproof coating prepared in this study has better comprehensive properties r than commercial waterproof coating according to the national standards.