Study On Properties Of Silicone Modified Waterborne Polyurethane And Preparation Of Coating Containing Silicone

Waterborne polyurethane(WPU)coating,as a friendly polymer material,provides several green characteristics such as environmental protection,low toxicity and health.WPU polymers have a variety of morphological structures which can be customized,and superior appearance characteristics.Therefore,it is widely used in various industrial finishes including automobiles,buildings,wood furniture,transportation tracks,metal instruments and other fields.In recent years,silicone modification of waterborne polyurethane has become the key exploration direction of researchers at home and abroad.With the excellent physical and chemical properties of silicone and the characteristics of low surface energy,it has greatly improved the water resistance,thermal stability and weather resistance of polyurethane,and widened the application field of waterborne polyurethane.Therefore,it is of great significance to prepare silicone modified waterborne polyurethane coatings with excellent properties.In this paper,silicone modifiers such as reactive silicone emulsion DRI,non-reactive silicone emulsion 9608,silicone modified acrylic emulsion 4866,and water-soluble silicone modified hydroxy acrylic resin 1023 were respectively blended with hydroxy acrylic dispersion as a resin component,introduced into a two-component waterborne polyurethane(2k-WPU)system.In addition,silicone modified polyisocyanate 9025 was selected to blend with polyisocyanate curing agent OS-9018 as a hardener component and introduced into2k-WPU coating system.The compatibility between silicone modifiers and 2k-WPU system was studied,and the effects of the introduction angle of silicone modifiers on the water resistance,high temperature resistance and weather resistance of the coating were investigated.The results show that the self-emulsifiable silicone modifiers(1023 and 9025)showed better compatibility with 2K WPU system.When silicone is introduced into the coating from the perspective of resin,the siloxane segments is easy to migrate and accumulate on the surface of the coating film,which significantly improves the high temperature resistance and weather resistance of the coating film.However,when silicone is introduced into the coating from the perspective of curing agent,the siloxane segments are evenly distributed in the coating,and the water resistance and high temperature resistance of the film are significantly improved.The silicone modifiers 1023 and 9025 with excellent compatibility and good performance were selected to investigate the effects of silicone compound modification on the water resistance,high temperature resistance and weather resistance of 2K WPU coating.The results show that the water resistance,thermal stability and weather resistance of 2K WPU can be improved by silicone compound modification.When the isocyanate index R = 1.5,9025 is as the curing agent component and the addition amount of 1023 resin is 20%(accounting for the main resin,wt.%),the application performance of the film is good and the resistance is basically the best.At this time,The water contact angle of the film is 89.2 °,and the water absorption is only 1.7%,which is 0.76 times lower than that of the coating before modification with 1023 resin(Si WPU-9025(1))and 9.5 times lower than that of2k-WPU;The water boiling resistance of the film is up to 5 h,which is 3.2 times higher than that of Si WPU-9025(1)and more than 10 times higher than that of unmodified 2k-WPU;The yellowing degree of the coating at 250 ℃ for 4 h is the lightest;The photodegradation rate of1000 h artificial accelerated aging is 28.7%.The light retention of the film is 9.4% higher than Si WPU-9025(1)and 15.6% higher than 2k-WPU.The film is only slightly yellowing and the improvement of weather resistance is close to saturation.Finally,silicone modified waterborne polyurethane with excellent properties was used as the main system,and the coating interface was adjusted by selecting appropriate coating additives to improve the appearance quality and interface performance of the coating.When the amount of mixed film-forming aids composed of C1+C2+C3 is 9%,W2 substrate wetting agent 0.1%,L1 leveling agent 0.3% or L2 leveling agent 0.6%,D2 defoamer 0.3%,PUR-62 rheology additive 0.1% and AMP-95 neutralizer 0.1%,a coating film with excellent appearance and good interface performance can be obtained.SEM and AFM show that the coating film is dense and smooth as a mirror.