Research Of Organic Silicone Modified Waterborne Polyurethane

Waterborne Polyurethane(WPU) is a dispersible polymer in water medium. WPU posses characteristic as such good mechanical capability,high adhesion strength,good flexibility, noncombustible,non-pollution,easy processing,so it’s regarded as a kind of green and environment-friendly materials and widely used in many fields nowadays.However,WPU has poor capabilities in water resistance and solvent resistance,so,it must be modified for it’s application. Organic silicone possesses excellent properties such as low surface energy,thermal stability,oxidation resistance and biocompatibility. Through the modification,they can be combined and exhibited excellent overall performance, and it has broad prospects for development.Using stepwise polymerization and emulsion method,we first synthesized waterborne polyurethane prepolymer,and then, we used organic silicone to modify it on the base of this.1.We made a comprehensive study of the synthesis process of waterborne polyurethane,including the ratio of raw materials,the influence of the reaction temperature, reaction time,catalyst and chain extender,etc.The optimized conditions were:the reaction temperature in prepolymerization was75℃;the temperature of emulsification and chain extenders was40℃;reaction time was3-4h;the catalyst was dibutyl tin dilaurate,used in an amount of0.1%;the chain extender was ethylenediamine,used in an amount of1.0%.2.On the base of synthesized prepolymer before,we used hydroxy terminated siloxane to modify waterborne polyurethane prepolymer and investigated influence of organic silicone’s varieties and content on abrasion resistance,heat resistance,elongation at break,and the water absorption performance.The results showed that we could use the hydroxy terminal siloxane,whose average relative molecular weight was2000, and the content was13%,to modify the prepolymer before,thus we gained a new kind of waterborne polyurethane coating with excellent performance,whose abrasion resistance was40mg,heat resistance was above250℃,elongation at break was140.5%and water absorption was7.1%.3.We used infrared characterization and differential scanning calorimetry method to analysis and test molecular’s structure and heat resistance before and after modification.The results showed that organic silicone has been successfully embedded into the polyurethane,thermal decomposition temperature of the product was more than250℃,whose thermal stability was excellent.