Study On Waterborne Hydroxyl Acrylic Resin For Automotive Interior Coatings

Two component waterborne polyurethane is becoming more and more attractive among researchers because of combining the excellent properties of waterborne coatings and conventional solvent-based polyurethane coatings.It exhibits excellent mechanical properties,room temperature cure characteristics and environmental protection characteristics and has been widely utilized in automotive,wood,plastic,leather and other coatings.Two component waterborne polyurethane consists of waterborne hydroxyl component and hydrophilic modified polyisocyanate.As the hydroxyl component,waterborne hydroxyl acrylic resin has the characteristics of molecular tenability,small particle size,low cost and good film appearance.It has a significant effect on properties of 2K-WPU.As the main oligomer with hydroxyl groups in two component coatings,the crosslinking density of curing process can be increased and the comprehensive properties of coatings can be enhanced because of the hydroxyl groups can be designed on their macromolecular chains.The waterborne hydroxyl acrylic resins were prepared by optimization of the ratios of raw materials and polymerization reaction parameters,in which used methyl methacrylate,butyl acrylate,hydroxypropyl acrylate and triethylamine as experimental materials.We studied the effects of the initiator types and contents,reaction times,hydroxyl group types and contents,neutralization degrees and other factors on the properties of the oligomers and two component waterborne acrylic polyurethane coating films.The oligomers and two component films were characterized by Fourier transform infrared spectroscopy,Malvern nanoparticle size analyzer,termogravimetric analyzer and differential scanning calorimeter,respectively.The results showed that when the initiator BPO content was 3%,the reaction time was 3 h,the hydroxyl monomer was HPA,the hydroxyl content was 3%,and the neutralization degree was 100%,the properties of the waterborne hydroxyl acrylic resins and films were the best.The film pencil hardness was 2B,adhesion was 0 degree,gloss was higher than 95,the water absorption of the film was 8.88%and the gel rate was 96.48%.Particle size analysis showed that the resin average particle size was about 81.46 nm;TG analysis showed that the film had good thermal stability.Studies on the kinetics of crosslinking reactions showed that the apparent activation energy Ea=52040 KJ.mol^-1.In order to improve the comprehensive performance of the film,the waterborne hydroxyl acrylic resin was modified with epoxy resin by the free radical grafting copolymerization.The influence of the epoxy resin types and contents on the properties of the product and films were studied.It was found that epoxy resin can improve the hardness,water resistance and solvent resistance of films.When the epoxy resin was E-20 and the content was 8%¹0%,the comprehensive performance was the best.TG analysis results showed that the thermal stability of the resin was improved.The results of particle size analysis showed that the average particle size of the modified resin was 105.7 nm,indicating that the average particle size of resin increased.The Zeta potential analysis results showed that the absolute value of Zeta potential dispersed in water increased from 41 mv to 52.6 mv,which showed that the dispersion stability of the resin in the water was improved after the modification of epoxy resin.The performance test results of automotive interior coatings met the requirements.