Impact of wetting and drying cycle treatment of intumescent coatings on the fire performance of thin painted red lauan (Parashorea sp.) plywood

Emulsion resins are widely used in wood-based materials for indoor furnishings. Previous studies have demonstrated that the ability of a material to retard flame arises from the interactions between four major components: i.e., binder resin (BR); carbonizing substrate (CS); foam-producing substance (FPS); and dehydrating agent (DA). Fire performance as influenced by wetting and drying cycle (WDC) treatment has not yet been reported. This study aimed to compare the fire performance of materials coated with EVAc (ethylene vinyl acetate copolymer) and PVAc (polyvinyl acetate copolymer) emulsion resins of differing BR/CS ratios, subjected to investigation by cone calorimeter. Intumescent formulation significantly enhanced the fire retardancy of painted plywood by exhibiting lower peak heat release rates (PHRR) and longer time to reach peak release rates. Additionally, lower BR content in the fire retardant systems further enhanced flame retardancy. The fire retardancy decreases with increasing the WDC treatment, caused by the weight loss of the coating materials. Infrared (FT-IR) analysis demonstrated that lower BR content extends the survival duration of the phosphorcarbonaceous structure of chars. The findings in this study enhance the state-of-the-art understanding of the effect of the intumescent.