Study On Synthesis And Properties Of Waterborne Polyurethane Adhesive

Water is the dispersion medium for the waterborne polyurethane. Because water has a higher latent heat of volatilization than other solvents, the drying time of waterborne polyurethane is thus longer. The self-emulsion waterborne polyurethane contains hydrophilic groups, which reduces water resistance. Most waterborne polyurethanes are linear polymers, which put limits the adhesion performance and heat resistance.In order to address the problems mentioned above, waterborne polyurethane dispersion was synthesized using Polybutyleneglycol adipate (PBA2000), toluene 2,4-diisocyanate(TDI), dimethylol propionic acid(DMPA), and Diethylene glycol(DEG). The factors (molar ratio, reaction condition, etc.) affecting the properties of waterborne polyurethane film were discussed. The result shows that waterborne polyurethane demonstrated good performance when the following condition are met:the initial molar ratio of -NCO/-OH is to 3.2, the content of hydrophilic groups is 1.8, nutralization degree is 100-110% at 30-40℃, and the nutralization reaction time is around 3-5min.In order to further improve the adhesive strength and the heat resistance, a dual crosslinkable waterborne polyurethane was synthesized through blocking the isocyanate groups and introduction of ambient cross-linking silane coupling agent. By studying the blocking reaction and silane coupling agent modification reaction, the optimum amount of blocking agent, silane coupling agents, and reaction temperature were obtained. The incorporation of silane coupling agents was confirmed by FTIR. The resultant adhesive shows better adhesion strength and the boiling resistance.