Effects of hydrophilic groups of curing agents on the properties of flame-retardant two-component waterborne coatings

A novel hydrophilic curing agent was prepared through hexamethylene diisocyanate trimer, polyethylene glycol monomethyl ether, and 2-((2-aminoethyl)amino)-ethanesulfonic acid monosodium salt. Then, flame-retardant two-component waterborne polyurethanes and their coatings were synthesized through adding the novel hydrophilic curing agent. Their properties and analysis were characterized through fourier-transformed infrared spectroscopy, differential scanning calorimeter, thermogravimetric, thermogravimetric infrared, limiting oxygen index, and UL-94. As a result, the −NCO content of novel hydrophilic curing agent was 16.4% and above 10.0% about 4 months. Besides, the novel hydrophilic curing agent dispersed well in two-component emulsions and improved themostability and compatibility of two-component flame-retardant waterborne polyurethanes. Meanwhile, the tensile strength of the novel film was 1.5 times than the previous one through adding novel hydrophilic curing agent at the same stoichiometric ratio of −NCO to −OH. What’s more, the best LOI and UL-94 of modified flame-retardant two-component waterborne polyurethane were 29.2% and V-0, respectively.