Synergistic enhancement of UV-resistance and electrical conductivity of waterborne polyurethane composite with combination of functionalized 2D graphene oxide and 1D nanocellulose

Abstract In this work, a functionalized graphene oxide@functionalized nanocellulose (FGO@FNC) composite filler, that was firstly synthesized by using isocyanatopropyltriethoxysilane (IPTS) as a coupling agent through a sol-gel process, and subsequently incorporated into waterborne polyurethane (WPU) dispersion via a simple and scalable solution blending method to prepare WPU composite (WPU/FGO@FNC). It was found that for the as-prepared FGO@FNC filler, the urethane chains were covalently grafted onto the surface of 2D graphene oxide and 1D nanocellulose, as well as siloxane linkages were formed between FGO and FNC as a result of co-condensation. Notably, the inserted FGO@FNC filler, dispersing excellently within the WPU matrix, could reinforce mechanical properties, improve surface hydrophobicity and electrical conductivity of WPU/FGO@FNCs composites, and particularly enhance the UV-resistant performance. Furthermore, the most effective enhancement was acquired when 3 wt% of FGO@FNC was incorporated into the WPU matrix, i.e., the WPU/FGO@FNC3 composite, that showed surpassing mechanical properties (σb = 28.7 MPa, eb = 462.8 %), water contact angle (96.5°), and electrical conductivity (0.252 S/m); and more importantly, it retained considerably in physicochemical parameters nearly above 78 % after five days of UV exposure. This work offers a viable avenue for developing UV-resistant, electrical conductive, tough and hydrophobic multi-functional coatings.