Ternary Synergistic Strengthening and Toughening of Bio-Inspired TEMPO-Oxidized Cellulose Nanofibers/Borax/Polyvinyl Alcohol Composite Film with High Transparency
E Songfeng, Doudou Ning, Yafang Wang, Jizhen Huang, Zhanfan Jin, Qin Ma, Kailun Yang, Zhaoqing Lu
Abstract
Utilizing and exploring degradable and renewable resources are of importance for environmental protection, and one efficient strategy is to use green cellulose-based materials as alternatives of eco-unfriendly polymers. However, compared to other polymeric and inorganic fibers, the cellulose-based materials show weak mechanical strength, which limits their applications in some extreme conditions. To obtain TEMPO-oxidized cellulose nanofiber (TOCN) films with high strength and toughness simultaneously, we prepared the ternary TOCN/borax/polyvinyl alcohol (PVA) composite films through a vacuum-assisted filtration method in this work. By controlling the additional contents of borax and PVA in the composites, the stress, elongation, and toughness of the TOCN/borax/PVA composites can be up to 226.53 MPa, 5.98%, and 9.84 MJ·m–3, which are 1.89, 2.51, and 6.39 times of a pure TOCN film, respectively. The outstanding mechanical behaviors of the TOCN/borax/PVA composites are attributed to the synergic strengthening effect of hydrogen and covalent bonding as well as the intrinsic and extrinsic toughening mechanisms. In addition, the TOCN/borax/PVA composites also maintain a high visible-light transparency of 83.36% at 800 nm, which has potential applications in solar cells, transparency electrodes, and flexible electric devices as substrates.