a new approach for improving fire resistance of cellulosic materials is provided , especially when the cellulosic material is to be used in polymer composites . cellulosic material is treated with an aqueous mixture of alkali metal or ammonium hydroxide and alkaline earth or aluminum metal salt simultaneously with or within a short period of time of preparing the mixture . the treated cellulosic material becomes self - extinguishing and may also have improved thermal stability , improved interfacial thermal resistance , improved resistance to damage by oxidants and other chemical agents , improved resistance to biological agents and / or improved resistance to damage by ultra - violet light .