High‐strength unidirectional cellulose long filament‐reinforced polymer composite for structural engineering applications

Abstract Green polymer composites that are strong and stiff are desirable across various engineering fields to replace synthetic plastics, hence meeting the requirements for net zero demands. Nanocellulose, a natural and abundant biopolymer, is a promising candidate for the engineering and designing of novel composites with strengths surpassing petroleum‐based derivatives. In this work, we demonstrate the fabrication of a high‐strength, environmentally friendly and hydrophobic biocomposite using a lignin‐based resin and wet‐spun unidirectional cellulose long filaments (CLFs) as reinforcements. The wet‐spun CLFs were knit in the conformation of unidirectional mats and infused with the green hydrogen‐bonded lignin resin to form the prepreg. The unidirectional prepreg was densified using hot pressing whereby the synergistic effect of heat and pressure and the post‐curing process impacted the biocomposite with unique, fascinating features, including excellent flexural strength (389.9 MPa), modulus (38.5 GPa), hydrophobicity (101.0°), antioxidant properties (93.1%), and superior thermal stability. Our design strategy dispenses new insights into engineering lightweight and strong cellulosic materials that can substitute unsustainable plastics used across various engineering fields. Future aspects of this biocomposite include structural and automotive engineering. Highlights All‐green and sustainable unidirectional polymer biocomposite is fabricated. The biocomposite achieves higher strength and modulus than that of plastics. It has outstanding thermal stability, hydrophobicity, and antioxidant properties. The biocomposite is suitable for the replacement of synthetic plastics.