Paper packaging materials like cardboards are widely used to protect archives which are a major kind of cultural relics. Unfortunately, paper is a combustible material, and thus exploring environment-friendly flame retardant for paper-based archive packaging material plays an important role. Herein, boric acid, borax and disodium octaborate are used to modify the craft paper-based packaging materials for archive conservation to improve fire safety. The modified craft paper exhibits much higher flame retardancy than the pristine one dose based on vertical burning tests, without much influence on mechanical properties such as tensile strength and elongation at break. Thermogravimetric analysis (TGA), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS) reveal that porous glass structure is formed during the combustion, because thermal decomposition of boric acid, borax and disodium octaborate will produce porous glassy matter as B₂O₃. The porous glass covers the paper surface as an insulating layer which retards the further pyrolysis and combustion, resulting in a denser carbon layer. Our study provides a robust way to reduce the fire hazard of the archive packaging material by applying environment-friendly boron-based fire retardants.

Paper packaging materials; archive conservation; flame retardant