Bioinspired High-Strength Borate Cross-Linked Microfibrillated Cellulose Composite Laminate with Self-Extinguishing Flame Retardance and Superhydrophobicity for Self-Cleaning.

Abstract

The cross-linking of borates enhances the intercellular structural connection, resulting in the creation of a mechanically superior structural material composed of lignocellulose and borate. This is accomplished by employing a mechanical pretreatment procedure and a binder-free hot-pressing method. Nevertheless, these materials frequently encounter constraints in humid environments, making it challenging to simultaneously achieve the desired performance objectives. Here, the prepressed bulk of microfibrillated cellulose is modified and subjected to hot pressing, while ensuring that the enhanced physical and mechanical properties of lignocellulosic recombinant materials are maintained. This modified material is termed the microfibrillated cellulose composite laminate (MCCL). These findings indicate that the application of compression, shear, and friction forces during hot-pressing results in the formation of a compact laminated structure using pine lignocellulose. The self-cleaning MCCL exhibits significantly improved mechanical properties compared with untreated lignocellulose materials (ULM). Specifically, the flexural strength (MOR), modulus of elasticity (MOE), and internal bonding strength (IB) of self-cleaning MCCL are found to be 5 times, 2.5 times, and 4.1 times higher, respectively, than those of ULM. This improvement in the pine lignocellulose can be attributed to the enhanced layering and branching that occurs during mechanical milling. This results in a higher proportion of ester and hydrogen bonds, as well as an increased exposure of hydroxyl groups. As a result, the modified MCCL exhibits self-cleaning properties, as evidenced by its surface water contact angle (WCA) of 152°. The rolling/jumping water droplets, which contain pollutants, effectively remove graphite powder from the surface, leaving it clean. Moreover, MCCL demonstrates exceptional dimensional stability and flame-retardant self-extinguishing properties, making it highly promising as a structural material in engineering technology.