Comparative Bench Scale Evaluation of Flame Exposure Behavior of Plywood and MDF Coated with Fire-Retardant Paint

Wood-based panel boards are widely used in construction and interior applications for their low cost and favorable mechanical properties, yet their flammability remains a major safety concern. This study evaluates the effectiveness of commercial fire-retardant (FR) coatings on plywood and medium-density fiberboard (MDF). The coatings were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Fluorescence (XRF), while fire performance was assessed through a bench-scale vertical flame exposure setup developed for comparative evaluation of ignition behavior under localized flame exposure, combined with infrared thermography to monitor surface temperature evolution. FTIR revealed functional groups such as phosphate, melamine, and hydroxyls, while XRF confirmed phosphorus, aluminum, and silicon, all contributing to char formation and flame inhibition. Fire tests showed that FR-coated panels delayed ignition, lowered peak surface temperatures, and in some cases achieved partial self-extinction compared with uncoated or primer-coated boards. Plywood retained structural integrity after exposure, whereas MDF became brittle and flaky, highlighting the role of substrate type in thermal response under localized flame exposure. Overall, FR coatings demonstrated improved resistance to ignition and early-stage thermal development by extending ignition time, reducing heat transfer, and preserving stability. These findings emphasize the value of passive fire protection strategies in delaying ignition onset and reducing early-stage thermal development under localized flame exposure and reducing early-stage thermal degradation in wood-based panel applications and furnishing applications.