Evaluation of glue joint parameters between wood cellular material and magnesium oxide sheet

The increasing demand for lightweight, durable, and fire-resistant construction materials has led to the development of hybrid composites combining wood-based cores with mineral- nonorganic skin sheets. This study evaluates the performance of adhesive joints between wood cellular materials and magnesium oxide (MgO) sheets under elevated temperature exposure. Four industrial adhesive systems: polyvinyl acetate (PVA), melamine-urea-formaldehyde (MUF), emulsion polymer isocyanate (EPI), and polyurethane reactive (PUR) were tested to determine their fire resistance and thermal stability. A custom-built small-scale fire testing chamber, designed to approximate the ISO 834 standard time-temperature curve, was employed to assess joint integrity and panel performance.Results showed that MUF adhesives failed within the first 5 minutes, while PVA exhibited highly variable results due to its thermoplastic nature. PUR and EPI adhesives demonstrated significantly better performance, maintaining structural integrity up to 18 and 21 minutes, respectively, under equivalent thermal exposure. Larger-scale composite panel tests confirmed that relocating the MgO-wood adhesive interface toward the panel center improved cohesion and delayed delamination, achieving sustained integrity for up to 39 minutes. The findings highlight the importance of adhesive type, joint placement, and controlled testing environments in optimizing the fire performance of wood-MgO composites. The research provides practical insights for developing lightweight, fire-resistant panels suitable for doors, partitions, and other interior structural applications.