Eco-friendly flame-retardant Xuan paper via layer-by-layer assembly organic/inorganic composite coating on pulp fiber

Abstract

Positively charged chitosan (CS) and negatively charged montmorillonite (MMT) were layer-by-layer (LBL) assembled on Xuan paper pulp fiber to fabricate an organic/inorganic flame-retardant coating. The Xuan paper achieved a limiting oxygen index (LOI) value of 24.6% when the pulp fiber was treated by 20 bilayers (BLs) of CS/MMT coating, and its vertical flame properties also improved with less after-flame and after-glow times compared to the untreated one. These results demonstrated that the flame retardancy of Xuan paper could be enhanced by this organic/inorganic composite coating. Thermogravimetric (TG) analysis results revealed that LBL assembly of CS/MMT coating on pulp fiber improved the thermal stability at higher temperature and promoted char formation, showing the obvious condensed phase flame retardant action. Scanning electron microscopy results further confirmed that the treated Xuan paper by CS/MMT coating on pulp fiber promoted the char formation and formed the stable covering layer. The ink wetting property of Xuan paper was not influenced through the LBL assembly flame-retardant treatment of the pulp fibers by CS and MMT. This research provides a new approach for flame-retardant Xuan paper without influencing its ink wetting property using the eco-friendly organic/inorganic composite flame-retardant system.