Study On The Environmental Waterborne Polyurethane

The synthesis and dilution of traditional polyurethane require a large amount of organic solvents, the remaining of which will cause great threat to the envirioment system and human health. Especially with the development of society and the improvement of people's environmental awareness, many coutries begin to set up envirment protection laws to restrict the content of volatile organic compounds in the producing and application processses of organic resins. In this situation, waterborne polyurethanes, which use water as an alternative dispersion medium with little or none use of organic solvents, have great environmental values and potential applications.Our research chose the low toxicity, high activity diphenylmethane diisocyanate and polyester glycol as the basic raw materials, chose dimethylol propionic acid as the hydrophilic chain extender, and the lowtoxicity and low cost acetone as the dilution to conduct the synthesize of waterborne polyurethane, based on the environmental raw materials and environmental producing process. The remaining number of NCO group was monitored by di-n-butylamine titration method and the results showed the reaction process of waterborne polyurethane. We discussed all the conditions that could affect the the producing process of waterborne polyurethane. And then the morphology of the polyurethane dispersion was characterized by TEM and the properties of the PU films were also tested. Through the control groups, we discussed all kinds of key factors that may affect the properties of waterborne polyurethanes emulsions and films.There exist many disadvantages of the single WPU emulsion, such as poor self-thickening, low solid content, weak water resistance, lower mechanical strength compared to acrylic resin and high cost. However, the property of polyacrylate (PA) emulsion and polyurethane emulsion could complement each other, which has great potential application. Organic silicone resin with low surface energy, good water resistance, fine weatherability and excellent air permeability has been widely used in polyurethane modification. The introduction of organic silicone groups into the chain of WPU could solve the problems mentioned above.A novel modification method, which introduces acrylic acid groups and organosilicon groups in to the WPU molecular chain, was adopted in the experiment. We first introduce the double bond utilizing the reaction between OH and NCO group in HEMA. Then free radical polymerization occurs between double bond and C=C double bond of vinyl siloxane, which results in the organosilicon and acrylic acid modification of WPU. Several characterization methods are took to evaluate the modification effect to the WPU dispersion systems and films.