Fabrication of highly flame-retardant paper by in situ loading of magnesium hydroxide/basic magnesium chloride onto cellulose fibers

Magnesium hydroxide (MH) has attracted considerable attention as a green flame-retardant for cellulose paper. However, conventional MH-based flame-retardant paper exhibits relatively low flame retardancy due to the low loading amount and easy agglomeration of MH. Herein, a facile method was developed to prepare MH-based flame-retardant paper with a high level of flame retardancy based on the simple and simultaneous dispersion of MgCl 2 and CaO into water followed by mixing with cellulose fiber suspension before papermaking. By changing the reaction time, MH, basic magnesium chloride (BMC) or a mixture of the two can be uniformly loaded in situ onto cellulose fibers. The loaded MH, BMC or their mixture endows the cellulose paper with excellent thermal stability, flame retardancy and fire safety, especially paper loaded with a MH/BMC mixture. The excellent flame retardancy is attributed to the formation of a uniformly distributed protection layer composed of MH and BMC that acts as an endothermic flame-retardant before and after burning, which effectively blocks heat transfer and limits the release of combustible gas. This study provides a new approach for the preparation of paper with a high level of flame retardancy. Graphical abstract