Ultrastrong, Fire-Resistant, and Sustainable Phosphorylated Cellulose Microfibers Hot-Pressing Structural Material

The widespread use of petrochemical-based plastics has led to significant environmental concerns. Cellulose fiber structural materials were widely used in automotive manufacturing and construction industries and have emerged as a potential solution to this issue. However, interfacial bonding issues between cellulose fibers hinder further material development. In particular, cellulose microfibers exhibit even more challenging interfacial bonding, greatly limiting the enhancement of the mechanical properties. Herein, a bottom-up approach was used to prepare phosphorylated cellulose microfibers hydrogels strengthened by externally induced Ca2+ cross-linking. Phosphorylated cellulose microfiber hot-pressed structural materials (PMHM) were then fabricated under the combined influence of temperature and pressure. The results indicate that the strength of PMHM is 273 MPa and that its modulus is 16 GPa. Its mechanical properties are significantly higher than those of commercially available petrochemical-based plastics and are comparable to those of nanocellulose-assembled materials. Additionally, the limiting oxygen index of PMHM is 41.13%, which classifies it as a flame-retardant material. Its coefficient of thermal expansion is 7 × 10–6 K–1, and it remains stable at temperatures up to 200 °C. Notably, PMHM undergoes significant degradation when exposed to the natural environment for 70 days and can be molded into materials for various industrial parts. Given its excellent mechanical properties, flame retardancy, degradability, and processability, PMHM has considerable application potential in fields such as automotive manufacturing and construction.