Multiple interactions and micro/nano particles cooperation design of robust and hydrophobic cellulose nanofiber composite paper with superior flame resistance

Cellulose has gained popularity in the energy and chemical industries due to its abundant resources, low cost, and biodegradability. However, traditional cellulose paper exhibits deficiencies in strength, flame retardancy, and hydrophobicity, thereby limiting its application in packaging materials as well as posing safety hazards. In this work, multifunctional cellulose nanofiber composite papers (AS-LAB) were fabricated via a combination of charge difference design and vacuum filtration technology, followed by the double coating of mixed micro-scaled and nano-scaled particles. The strength of the AS-LAB composite paper was enhanced by 2.2 times compared to that of pure cellulose paper, attributed to the multiple interactions (including hydrogen bonding, covalent cross-linking, and electrostatic attraction) between the components and the perfect match of particles with different scales. Moreover, the simultaneous utilization of different ammonium polyphosphates with high and low polymerization degrees offers the AS-LAB composite paper with remarkable flame retardancy, and the rough surface in the sandwich structure caused by the multiscale particles renders the composite paper with desirable hydrophobicity (water contact angle 138.1°) and self-cleaning properties. Therefore, the design and fabrication of cellulose nanofiber composite paper shed light on the paper performance improvement and suggest its potential application in the packaging field.