Study On Optimization And Performance Of Components Used In Waterborne Polyurethane Coatings For Rail Vehicles

In order to achieve the water-based painting of rail transit,reduce the Volatile Organic Compounds(VOC)emission of middle-paint,and accomplish the aiming of energy-saving and emission-reduction,this paper uses two-component water-borne polyurethane paint formulated with hydroxyacrylic resin and polyisocyanate.The formula was confirmed finally,in accordance with the requirements of the CRRC of Qingdao Sifang Vehicle Company,combined with national standards and rail transportation industry standards for performance evaluation.Through experiments,it was confirmed that the coating performance was the best when the ratio of NCO/OH was 1.5 in the present system;three combinations satisfying the conditions were selected from different types of hydroxyacrylic resin and polyisocyanate,among which XP2655 and XP2457 had the best performance.The concentration of co-solvent,filler and functional additive was determined by experiments: 3% deionized water,2% dipropylene glycol dimethyl ether,5% propylene glycol methyl ether acetate;25% talcum powder,10 % heavy calcium;0.8% Thickener RM 8W,0.6% defoamer W 0506,1.0% leveling agent VXL 329,1.0% dispersing agent FN 265 were used in this formula.The intermediate paint were sented to China Railway Inspection and Certification Vehicle Inspection Station for testing.All technical indicators in the intermediate paint were qualified.Among them,the Cupping experiment results were 4.5 mm,better than the requirements of the technical specifications;The Two-component test period was 8 hours.It is 1 time of the standard value;the Outside dry time is 1.5 hours,2.6 times shorter than the standard value,and the Actual dry time is 5 hours,which is 2.8 times shorter than the standard value.The medium-coating paint was applied to the composite coating,that was sented to the China Railway Inspection and Certification Vehicle Inspection Station for testing.The technical indicators of the composite coating were all qualified.The chemical resistance was extended by 1 time and the salt spray resistance was extended by 3 times.The density is 1/5 of the standard value;in the toxic gas,the amount of CO is 1/60 of the standard value,the amount of CO2 is 1/70 of the standard value,and HF,HBr,HCl,NOx,SO2,and HCN are not detected.None detected.The VOC of this paint ≤110.0 g/L,which is less than the standard value of 150.0 g/L,which is only 20% of the average VOC emissions of conventional solvent-based coatings.