Multifunctional Flame-Retardant, Hydrophobic, and Antifungal Boron-Silane Synergistic Coating for Archival Packaging...

Kraft paper, as a typical archival packaging material, is prone to microbial erosion, flammability, and moisture-induced degradation during long-term preservation. In this work, multifunctional archival packaging paper with integrated flame retardancy, antifungal activity, and hydrophobicity was successfully fabricated via the modification of boron-based flame retardants (borax, BX, and disodium octaborate tetrahydrate, DOT) and silane hydrophobic agent (octadecyltrimethoxysilane, ODTMS). The structure and performance of the modified kraft paper were systematically characterized by the limiting oxygen index (LOI), the vertical burning test, cone calorimetry (CCT), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), contact angle measurement, and the antifungal test. The optimized modified sample exhibited superior comprehensive properties. The LOI value increased from 20.6% for the original kraft paper to 37.5%. TGA revealed that the char residue of the optimized modified sample at 750 °C reached up to 55.35%, much higher than that of the original kraft paper, accompanied by marked decreases in the heat release rate, total heat release, and smoke production. Meanwhile, ODTMS endowed the modified sample with hydrophobic properties, with a water contact angle of approximately 130°. Antifungal tests demonstrated that the modified kraft paper displayed obvious inhibitory effects against eight fungal species, including Penicillium citrinum and Aspergillus flavus. Overall, the modification strategy proposed in this study is simple, eco-friendly, and low-cost, achieving multifunctional protection of archival packaging materials. This work is expected to provide novel materials and technical support for the long-term safe preservation of paper cultural relics and archives.