Bio-production of fire retardant and hydrophobic packaging paperboard with enhanced tensile strength through coating with modified cellulose nanofiber

The challenge of creating cellulose-based materials resistant to fire, water, and are eco-friendly has surged in various industries. Innovative bio-based cellulose substances, especially those with robust fire and humidity resistance, are pivotal for high-quality cellulose-based packaging. This study focuses on TEMPO-oxidized cellulose nanofibers at concentrations of 2, 2.5, and 3wt%, modified using three chemical combinations: "ammonium dihydrogen phosphate + albumin", "silica + methyltrimethoxysilane", and a mixture of all four ingredients. Each combination, with a constant level of 14% and a coat weight of 3.5 g.m⁻², was applied to the surface of the produced paperboards. Flame retardancy analysis results indicate that modified TEMPO-oxidized CNF at 3wt%, employing the quadruple combination, offers suitable fire properties in the prepared paperboard, mainly due to intumescent phosphorus-based flame retardants. These retardants reduce the peak heat release rate as a function of the heat release temperature. Furthermore, silicon groups by blocking functional hydroxyl groups, induced hydrophobicity in cellulose nanofibers, as indicated by contact angle and water uptake measurements. Tensile strength significantly improved after incorporating wettable bio-retardants into cellulose nanofibers and coating them onto the cellulose matrix. Also, the roughness and homogeneity of the surface of the paperboard increased when the solid of CNF increased from 2 to 2.5, and 3wt%, respectively according to the FESEM analysis. This modification system offers potential as a foundational substrate for high-quality pharmaceutical and hygienic packaging, providing degradable alternatives to non-recyclable plastics and achieving eco-friendly advantages.