| Polyurethane is widely used in coatings,adhesives,and other fields due to its excellent wear resistance,adhesion,processability,and high mechanical properties.In recent years,due to the increasing environmental awareness and the gradual improvement of related national regulations,the production and application of solvent-based polyurethane have been restricted,which has led to the attention of water-based polyurethane(WPU).WPU coatings are one of the most important applications of WPU resins,which have the characteristics of good wear resistance and high adhesion of solvent-based polyurethane.However,the introduction of a large number of hydrophilic groups inside WPU leads to a decrease in the material’s water resistance and heat resistance.In addition,WPU also has problems such as low solid content and long film-forming time.To solve these problems,this article proposes the following methods to improve the performance of WPU coatings:(1)The research aims to prepare WPU coatings using ethylenediamine and diethylenetriamine as chain extenders,in order to address the problems of excessive use of acetone during prepolymerization and poor mechanical properties after film formation.This method not only reduces the use of organic solvents in the WPU synthesis process,thereby reducing the cost of industrial production,but also produces WPU with improved wear resistance,mechanical properties,pencil hardness,and impact resistance.The experiment found that after using the amine compounds,the tensile stress increased from 15.3 MPa to 25.1 MPa,wear resistance decreased from 2.5%to 1.2%,pencil hardness increased from H to 2H,and impact resistance increased from 50 cm/kg to 70 cm/kg.(2)A study was conducted on the preparation of WPU coatings using star-shaped epoxyfunctionalized organosilicon and star-shaped amino-functionalized organosilicon via chemical copolymerization to improve the water resistance and heat resistance of the coatings.Organosilicon exhibits low surface tension,high surface migration capability,and good properties such as water and heat resistance,while star-shaped organosilicon simultaneously possesses the water resistance of polymeric organosilicon and the low viscosity of small molecule organosilicon.The experimental results showed that the copolymer WPU coating had superior comprehensive performance compared to pure WPU,with a decrease in surface tension,an increase in contact angle from 63.8° to 105.3°,a decrease in water absorption from 45.4%to 12.5%,and a significant improvement in salt spray resistance.Additionally,the introduction of organosilicon increased the initial decomposition temperature of the WPU film by about 20℃,thus improving the material’s heat resistance.(3)A study was conducted on the preparation of a new type of star-shaped organic silicon acrylate waterborne polyurethane(WPU)coating using acrylic acid ester-organic silicon composites.The introduction of acrylic acid ester compounds can fully utilize the advantages of polyacrylic acid(PA)and WPU,increase their solid content,and have relatively low costs,making them competitive in the market.In addition,the PA-WPU coating has good solvent resistance,with a acetone absorption rate of 90.2%.The mechanical properties of the PA-WPU film are good,with a significant increase in Young’s modulus and an initial decomposition temperature increased by about 25℃,thereby improving the heat resistance of the WPU coating.By introducing vinyltrimethoxysilane,it was found that its water absorption rate can be reduced to below 5%,and the acetone absorption rate is reduced to about 75%.After 720 hours of salt spray test,the coating still has corrosion resistance and can be used as a mechanical anticorrosion coating. |
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