Investigating the extent of urea formaldehyde resin cure in medium density fibreboard: Characterisation of extractable resin components

Panel mass and nitrogen losses indicate medium density fibreboard (MDF) panels bonded with differing urea formaldehyde (UF) resins readily lose some 40–70% of resin components on exposure to cold water soaking. Analysis reveals these labile extractable resin components to be low molecular weight UF oligomers which were not present in such amounts in the original UF resins. Panel emissions appear linked to the relative proportions of these extractable UF resin condensation products. Furthermore, results indicate that when applying resin to fibre, resin components may chromatographically separate and become unavailable to cross-link into a fully cured resin matrix. Differences in wood fibre extractives, resin chemistry or application methodology gave minor differences in extractable resin components, but a greater resin loading contributed to lower relative resin extractability.