Low Formaldehyde Emission Particleboard Bonded by UF-MDI Mixture Adhesive (Technical Note‪)‬

Abstract Chinese wood-based composite manufacturers are plagued with serious formaldehyde emission (F-emission) problems. Most products release formaldehyde between 35 and 60 mg per 100 g board. In this study, a particleboard with an emulsifiable diphenylmethane-4, 4'-diisocyanate (MDI)--urea-formaldehyde (UF) mixture adhesive was investigated in order to decrease F-emission to below 9 mg per 100 g board. Comparison of physical and mechanical properties of particleboard showed that the acidic agent N[H.sub.4]Cl did not improve the UF-MDI system curing, and it also affected the adhesive application method. When the two adhesives were mixed first, without adding N[H.sub.4]Cl, and then sprayed onto particles, properties were improved. Hot-press conditions that would optimize particleboard mechanical properties and ensure that F-emissions met El grade requirements were determined; hot-pressing at 175[degrees]C for 4.5 minutes might lower F-emissions to below 9 mg per 100 g particleboard.