Boron nitride nanosheets reinforced waterborne polyurethane coatings for improving corrosion resistance and antifriction properties

Effective corrosion resistance and antifriction properties can prolong the durability of coatings. We demonstrate that hexagonal boron nitride (BN) nanosheets can be employed as the reinforcement in waterborne polyurethane (PU)-matrix composite coatings and lead to a significant improvement in their corrosion protection properties. The impedance modulus at 0.1 Hz dropped from 109 Ω·cm2 to 108 Ω·cm2 for 2% BN/PU coatings after 114 h immersion in 3.5 wt% NaCl electrolyte, while it dropped from 108 Ω·cm2 to 5 × 106 Ω·cm2 for neat PU coatings. The dynamic friction coefficient was decreased for 22.6% with the addition of 2 wt% BN in the PU composite coatings at 100 °C. The morphologies of the coating surfaces showed less abrasion than neat PU after the test. The major challenge of preparing BN/PU composite coatings was the dispersion of BN nanosheets in the waterborne polymer, which was solved by functionalization of BN nanosheets with hydroxyl groups.