Study On Preparation,Modification And Performance Of Waterborne Polyurethane By Mixing HMDI/IPDI And PCDL/PCL

With the increase of governments'supervision on the emission of VOC and HAP,the application of solvent polyurethane in coating and adhesive industry has been widely restricted.As a kind of green organic polymer material,waterborne polyurethane?WPU?is widely used in adhesive,coating and ink industry because of its advantages of environmental protection,non-toxic and safety.However,because most WPU have hydrophilic ionic groups on the main chain,the mechanical properties and water resistance of WPU when used in fields such as wood and ships are much lower than traditional solvent-based polyurethanes.In this paper,the mixed of HMDI/IPDI and PCDL/PCL was prepared by optimizing the formulation and preparation process of WPU;Then modify the mixing waterborne polyurethane by graphene oxide?GO?and hydrophobic fluorinated nano silica?F-SiO₂?to improve the WPU's mechanical properties and water resistance.The main work is as follows:1.The preparation and properties of waterborne polyurethane by mixing HMDI/IPDI and PCDL/PCLThe solvent-free aqueous polyurethane was prepared by mixing 4,4'-dicyclohexylmethane diisocyanate?HMDI?,isophorone diisocyanate?IPDI?,polycarbonate glycol?PCDL?,polycaprolactone glycol?PCL?,dimethylolpropionic acid?DMPA?and trimethylolpropane?TMP?.The influences of the ratio of OH/NCO?R?,the content of DMPA,the content of TMP,the molar ratio of HMDI/IPDI and the molar ratio of PCDL/PCL were studied by FTIR,SEM,laser particle sizer,contact angle analyzer and AFM.The results show that when the R is 1.35,the content of DMPA is 5.5%,the content of TMP is 2.5%,the molar ratio of HMDI/IPDI is 2:1,the molar ratio of PCDL/PCL is 2:1,the water absorption of WPU is 9.63%,contact angle is 118.04^o,hardness is H,and thermal stability is excellent.2.The preparation and properties of mixing waterborne polyurethane by modifying graphene oxideGO was prepared by Hummers method.Then,the mixed HMDI/IPDI and PCDL/PCL waterborne polyurethane were modified by GO through physical blending?GO/WPU?.The stability of GO/WPU emulsion and it's mechanical properties,thermal stability and friction properties were characterized,the effect of different content of GO on the properties of GO/WPU composite was studied.It is found that when w?GO?=1.5%,the WPU emulsion was stable,the particle size was 1.61?m,the hardness of the coating was 2 H,the tensile strength of the film reached 5.1 Mpa,and the addition of GO could improve the thermal stability of the coating and reduce the friction coefficient.3.The preparation and properties of mixing waterborne polyurethane by modifying hydrophobic nano F-SiO₂The hydrophobic nano F-SiO₂ was prepared by sol-gel method.Then,the mixed HMDI/IPDI and PCDL/PCL waterborne polyurethane were modified by hydrophobic nano F-SiO₂ through physical blending?F-SiO₂/WPU?.The stability of F-SiO₂/WPU emulsion and its mechanical properties,thermal stability and friction properties were characterized,the effect of different content of hydrophobic nano F-SiO₂ on the properties of F-SiO₂/WPU composite was studied.It is found that nano F-SiO₂ can improve the thermal stability,hydrophobicity and mechanical properties of WPU.The hardness of F-SiO₂/WPU can reach 2 H,the tensile strength is 5.7 Mpa,the contact angle can reach 141.15°and the maximum decomposition temperature in the first stage can be 50°C higher than that of pure WPU.In summary,the hardness of the hybrid waterborne polyurethane prepared at the optimal ratio is H and the contact angle is 118.04^o.Compared with pure WPU,the mechanical properties,water resistance and thermal stability of WPU modified by GO and hydrophobic nano F-SiO₂ are improved,such as hardness increased to 2 H,the maximum contact angle can reach 141.15°,the tensile strength is up to 5.7 Mpa,which makes WPU coatings widely used in wood and ships.