Preparation Of Functional Waterborne Polyurethane And Coating Properties

In recent years,waterborne polyurethane(WPU)has been widely used in coatings,adhesives,synthetic leather and other fields due to its excellent low-temperature flexibility,excellent mechanical properties,bonding properties,environment-friendlly and non-toxic characteristics.In this paper,polycaprolactone polyol,toluene diisocyanate and dimethylolpropionic acid(DMPA)are used as basic raw materials to design the molecular structure of WPU and synthesize WPU prepolymers.Combined with a variety of modification methods,the multi-component composite modification is carried out,aiming at improving the corrosion resistance and wear resistance of WPU coating.In the research of WPU anti-corrosion,WPU prepolymer is prepared,then butyl acrylate(BA)and styrene(St)are used for preliminary acrylate modification.The results show that when the R value is 1.3,the DMPA content is 5.5wt%,the neutralization degree is 100%,and the PU/BA/St ratio is 60/20/20,the comprehensive performance of the preliminary acrylic modified WPU(WPUA)emulsion meets the requirements.On the basis of this WPUA emulsion,glycidyl methacrylate(GMA)is introduced for further internal crosslinking modification,and dodecafluoroheptyl methacrylate(DFMA)is introduced for organic fluorine modification to obtain crosslinked fluorine-modified waterborne polyurethane(CFWPUA)emulsion.It is found that when the GMA content is 5wt%and the DFMA content is 7.5wt%,the inside of the CFWPUA material is a double crosslinked system with high crosslinking density,and the outside is a hydrophobic surface formed by the migration of long fluorine side-chains.At this time,the water absorption rate of CFWPUA film is 7.91%,and the gel content is 91.5%;the water contact angle of the CFWPUA coating is 102.5°;in the polarization curve test,corrosion current density of CFWPUA coating is 1.881×10^-7 A·cm^-2,and its protection efficiency for the metal substrate is 98.12%;in the electrochemical impedance spectroscopy test,the initial corrosion resistance of the CFWPUA coating reaches2.124×10⁷?·cm²,and CFWPUA coating could also provides excellent protection for metal substrates within a certain period of time,showing corrosion resistance comparable to commercial waterborne fluorocarbon coatings.In the prepolymer synthesis stage of WPU wear-resistant research,DMPA ratio of5.5wt%and neutralization degree of 100%are used.Cross-linking agent A,cross-linking agent B and castor oil are respectively introduced into the system to construct cross-linking structure while completely capping the WPU prepolymer,then three kinds of modified WPU(CWPU)emulsions with different cross-linking systems are prepared.The results show that the comprehensive properties of the three CWPU materials are relatively excellent.Among them,the KCWPU2 membrane has a water absorption of 10.35%and a gel content of 73.6%.The water absorption of TCWPU2 membrane is 13.14%and the gel content is 56.6%.The water absorption of CCWPU2 membrane is 8.16%and the gel content is 52.4%.In the wear test,the mass loss of most CWPU wear-resistant coatings is about 8mg,and the mass loss of KCWPU2 wear-resistant coatings is only 4.7mg,reaching the level of high-quality commercial wear-resistant coatings,showing superior wear resistance.