| Polyurethane?PU?has been widely used in artificial leather,adhesives,coatings and other fields.However,most traditional PUs are prepared from volatile organic reagents,which causes pollution to the environment and endangers human health.In recent years,due to the emphasis on environmental protection at home and abroad,the traditional solvent-based PU has gradually been transformed into water-based,and the preparation of multi-functional water-based polyurethane?WPU?materials has become a hot research topic.Compared with solvent-based PU,WPU lacks in weather resistance and water resistance.For this reason,various methods have been explored to modify WPU to improve WPU performance.This paper mainly studies the synthesis of TDI/IPDI type WPU and the WPU modified by nano oxide and epoxy resin.The research content is as follows:?1?Preparation and performance study of TDI/IPDI WPU.Toluene diisocyanate?TDI?and isophorone diisocyanate?IPDI?were used to synthesize TDI/IPDI type WPU.The hardness,heat resistance and water resistance of the coating film were studied.Among them,the hardness of the TDI/IPDI WPU coating film is increased from HB to H compared to the IPDI WPU coating film,the heat resistance is not much different,and the water resistance is weakened as the DMPA content increases.The optimal synthesis conditions were determined:TDI/IPDI molar ratio=3:7,R=4.0?4.5,DMPA content was 5.1?5.8%.?2?Preparation and properties of nano-Si O2 modified WPU.Nano-Si O2-modified WPU?TDI–Si O2/WPU?was obtained by in-situ polymerization.The optimized conditions for synthesizing TDI–Si O2/WPU emulsion are determined as R=4.5,DMPA content is 6.5%,and the optimal addition ratio of Si O2 is 0.75%.Compared with the pure WPU coating film,the hardness of the coating film is increased from H to 2H,the heat resistance is increased by a maximum of 45.91?,the water absorption rate is reduced from 28.32%to 18.86%,and the anticorrosion performance is 4.04×105?compared to the pure WPU coating film increased to8.79×105?,Ecorr increased from-0.498 V to-0.399 V,and Icorr decreased from1.032×10-6A/cm2 to 2.558×10-7A/cm2.?3?Preparation and properties of nano-Zn O modified WPU.In the emulsification stage,physical mixing modification method was used to prepare nano-Zn O modified waterborne polyurethane?Zn O/WPU?.The optimal addition ratio of nano-Zn O is 0.5%.Compared with the pure WPU coating,the hardness of the prepared coating is increased to 2H,the water absorption is reduced to 16.52%,and the heat resistance is relatively close.In terms of anti-corrosion performance,the modified film impedance modulus reaches 1.42×106?.?4?Preparation and properties of nano-Zn O/epoxy resin modified waterborne polyurethane.Epoxy resin modified waterborne polyurethane?EWPU?was prepared by graft copolymerization.Nano-Zn O/epoxy resin mixed modified waterborne polyurethane?Zn O/EWPU?was prepared by physical mixing method in EWPU synthetic emulsification stage.The experiment found that the optimal addition ratio of epoxy resin was 8%,the optimal addition amount of nano-Zn O was 0.5%,the water absorption rate of the modified coating film was reduced to 14.82%,the hardness was2H?3H,and the impedance modulus was 4.07×106?. |
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