Study On The Preparaiton And Properities Of Organosilicone Modified WPU

Waterborne polyurethane(WPU) is widely applied in construction, textile, painting and transportationdue to its safe and environment-friendle properties.. However, the films of WPU always exhibit inferior properties such as low water resistance and thermal stability because of hydrophilic groups in its chain. Organosilicones which show excellent water and thermal stability and low surface free energy can enhance these defects of WPU, therefore the related work draw attention from researchers. The organosilicone modified WPU are mainly prepared by block polymerization with hydroxy silicone oil or end capped with silane coupling agent. But the low compatibility between hydroxy silicone oil and polyurethane and quantitative restrictions of isocyanate in prepolymers hinder the further development of organosilicone modified WPU. Given the above issues, we prepared a series of organosilicone modified WPU, the main content are as follows:1. Four kinds of polydimethylsiloxane(PDMS) with different structure are introduced into WPU chain by block polymerization in order to study the effect of PDMS on the properities of WPU. The properties of WPU emulsions and cured films were studied and the results show that dihydroxylalkyl-terminated polydimethylsiloxane(PDMS1;Mn=1000) exhibit better compatibility with polyurethane than the others, which can improve the water resistence, gloss and mechanical properities ignificantly as maintaining the high light transmittance of WPU films. Hydroxy silicone oil(PDMS2; M,=1000) and dihydroxylalkyl-terminated polydimethylsiloxane(PDMS3; Mn=2000) exhibit worse compatibility with polyurethane, so they lower the light transmittance and gloss dramaticly and improve the heat resistance and mechanical properities to some content. Polyether-terminated polydimethylsiloxane(PDMS4; M,,=2200) has little effect on the crystallinity while its modified samples possess high gloss and worst mechanical properities.2. The effect of the PDMS1loading on the properties of waterborne polyurethane emulsions and cast films are studied. The results indicate that the particle size of emulsions first increases and then decreases, and the viscosity of waterborne polyurethane shows reverse trend with the increase in the amount of PDMS1. The PDMS1loading enhance the tensile strength, hardness, water stability and gloss of the cast films. Meanwhile PDMS lower the crystallinity, thermal stability, elongation at break and light transmittance of films. When the weight ratio of PDMS is15-20wt%of soft segment, the synthesized waterborne polyurethane has the excellent overall performance.3. A kind of new silicone containing diol(HEA-Si) is synthesized by Michael addition between y-aminopropyltriethoxysilane(APTES) and hydroxyethyl acrylate(HEA). In order to investigate the effect of HEA-Si on the properities of WPU, a series of modified WPU is prepared by chain extender containing siloxane. The results indicate that HEA-Si increase the particle size, and decrease the viscosity and surface tension of WPU emlusions. The water resistance, thermal stability and water contact angle of WPU films are enhanced by introducing silicone in hard segment.4. WPU/nanosilica composites were prepared by HEA-Si and different amount of nanosilica. The crosslinking could be formed as the nanosilica are graft onto hard segment of WPU, which lead to the increase in the particle size and its distribution, decrease in the viscosity enhance their tensile strength, hardness, water contact angle and thermal stability of the composites films, but lower its elongation at break.