Preparation And Properties Of Waterborne Polyurethane Emulsion Modified By Internal Crosslinking

The industrial production of waterborne polyurethane has been realized in China in the 1980s,but the annual output of waterborne polyurethane only accounts for 2%of the polyurethane industry after 30 years.Although waterborne polyurethane has the advantage of low volatile organic compounds and accords with the concept of environmental protection and health pursued by modern people,the disadvantages of traditional waterborne polyurethane,such as poor water resistance and heat resistance,which cannot be ignored.These factors are also the main obstacles encountered in the promotion and application of waterborne polyurethane.In this paper,some modification studies on waterborne polyurethane emulsion were carried out towards these drawbacks and a series of interlinked waterborne polyurethane emulsion were prepared.The specific work is as follows:Polyester polyol?PE3020?and hexamethylene diisocyanate?HDI?,dimethylol propionic acid?DMPA?were used as main raw materials,and tricarboxylic castor oil?MACO?,which was modified by maleic anhydride modified castor oil,was used as crosslinking modifier.The modified castor oil waterborne polyurethane emulsion?MACO-WPU?was synthesized by prepolymerization.The MACO-WPU emulsion and film were characterized by FT-IR,TG,SEM,XRD,universal material testing machine and laser particle size analyzer.The effects of R value,DMPA content and MACO content on the stability and particle size of MACO-WPU emulsion and thermal stability,water resistance and mechanical properties of the films were investigated.The results show that when the dosage of MACO is increased from 0 to 3%,the tensile strength of the WPU adhesive film is increased from 2.43 MPa to 13.15 MPa,the growth rate is 4.41 times,the elongation at break is reduced from 537%to 195%,the water absorption rate is reduced from 15.32%to 6.77%,the thermal stability is improved,and the crystallinity is also obviously reduced.Therefore,when the R=1.2,w?DMPA?=5%,w?MACO?=3%,the product with stable emulsion,complete adhesive film and excellent water resistance and mechanical properties can be obtained.Polyester polyol?PE3020?,hexamethylene diisocyanate?HDI?and dimethylol propionic acid?DMPA?as main raw materials,and introducing a polymurmuid resin?HK-6?as a cross-linking agent,The inorganic nano-SiO₂ was uniformly dispersed into the HK-WPU system by the ultrasonic method,and the composite emulsion of SiO₂/HK-WPU was synthesized.SiO₂/HK-WPU by means of FT-IR,TG,SEM,XRD,universal material testing machine and contact angle tester U composite emulsion and its film were characterized.The effects of HK-6and SiO₂ content on the stability and particle size of SiO₂/HK-WPU emulsion and thermal stability,water resistance and mechanical properties of the films were investigated.The results showed that when the content of HK-6,nano-SiO₂ was 6%and 1.5%respectively,the water contact angle of SiO₂/HK-WPU film was 45%higher than that of unmodified WPU film,and 45%higher than that of HK-6modified WPU film.The results showed that the cross linking between furan rings increased the cross linking density of polyurethane chain segments,and the water resistance of modified film was obviously enhanced,and the force of the film was also made.The mechanical properties and thermal stability were improved.Polyester polyol?PE3020?,hexamethylene diisocyanate?HDI?,dimethylol propionic acid?DMPA?was used as raw material,epoxy resin?E51?and amino silane coupling agent?KH550?were used as modifiers.KH550/E51-WPU was synthesizedbyprepolymerization.Thentrimethylpropanetrimethacrylate?TMPTMA?,hexafluorobutyl acrylate?HFA?,methyl methacrylate?MMA?was added to the modified waterborne polyurethane composite emulsion.Fluorinated acrylate modified waterborne polyurethane emulsion was prepared by free radical solution polymerization and semicontinuous addition with azodiisobutyric cyanide?AIBN?as initiator.The synthetic emulsion and film were characterized and analyzed by FT-IR,TG,SEM,XRD,universal material test.The effects of E51content and KH550 content on the properties of modified waterborne polyurethane emulsion and its film were investigated.The effects of three monomer ratios of TMPTMA/HFA/MMA on the properties of WPUA emulsion its film were investigated.The results showed that the tensile strength of WPU film was increased more than 2 times as much as that of unmodified WPU by the grafting of KH550 and E51.The test of TG,XRD showed that the tensile strength of WPU film was increased more than 2 times than that of unmodified WPU.The thermal stability and crystallization properties of WPUA were improved,and the tensile strength of WPUA film was increased by more than 5 times than that of unmodified WPU due to the increase of crosslinking density in WPUA,and the surface energy of WPUA film was enhanced by the dispersion of fluorine-containing branched chains on the surface of the polymer.The water contact angle reaches 99.5°,and the hydrophobicity is obviously improved.