Synthesis and characterization of multifunctional two-component waterborne polyurethane coatings: Fluorescence, thermostability and flame retardancy

Fluorescent and flame-retardant two-component waterborne polyurethane coatings were synthesized using 1,5-dihydroxy naphthalene, a halogen-free polyphosphate and a hydrophilic curing agent, and their properties were systematically characterized. The average particle sizes and zeta potential values were below 170 nm and -30 mV. Meanwhile, the multifunctional two-component waterborne polyurethane coatings had strong fluorescence intensities. When comparing with the coatings with 0.5 wt % 1,5-dihydroxy naphthalene, the coatings with 1.0 wt % 1,5-dihydroxy naphthalene had a stronger microphase separation. Interestingly, the thermostability of the multifunctional coatings was remarkably improved through 1.0 wt % 1,5-dihydroxy naphthalene, and besides it belonged to nonflammable materials. Additionally, all of the coating films passed the solvent resistance testing. These samples with different amounts of 1,5-dihydroxy naphthalene are environmental friendly, especially applications that require transparent and fluorescent coatings.