Urethane-silica functionalized graphene oxide for enhancing mechanical property and fire safety of waterborne polyurethane composites

Herein, we first prepared urethane-silica functionalized graphene oxide (FGO) via in-situ method, and then physically incorporated FGO with waterborne polyurethane (WPU) matrix to fabricate composites. It was found that large amounts of urethane-silica components were covalently attached onto the FGO sheets. Moreover, the FGO exhibited spatial distribution in the WPU matrix, leading to excellent dispersibility and compatibility with WPU. Interestingly, the flexible urethane-silica components on the FGO sheets could not only modulate the mechanical properties of WPU/FGOs composites, but also reinforce the carbonaceous block with rigid silicon layer, and thus contributing to the fire safety. The most balanced enhancements in mechanical and flame retardant properties were achieved when 2 wt% FGO was incorporated into the WPU matrix, resulting in a significant increase in tensile strength, elongation at break, and limiting oxygen index (17.1 MPa, 925.0%, and 23.1%, respectively) as compared to the neat WPU. In addition, the WPU/FGOs composites possessed improved water resistance, which maybe potentially favor to the wet rub resistance and self-protective applications. This work provides a potential avenue for designing graphene-based composite and makes it promising application in multifunctional coatings.