INVESTIGATION OF VARIABLES AFFECTING HOT-PRESS FORMALDEHYDE AND METHANOL EMISSIONS DURING LABORATORY PRODUCTION OF UREA-FORMALDEHYDE-BONDEDPARTICLEBOARD

An extensive research project has been under-taken to investigate vari ables that affect hot-press formaldehyde and methanol emissions from p articleboard bonded with urea-formaldehyde resin. A system has been de veloped to collect hot-press emissions from particleboard made in the laboratory (1). The system consists of an aluminum caul plate that is sealed when the press is closed, but has an inlet and outlet to allow air to be drawn through the air space immediately surrounding the boar d during pressing. The emissions are trapped with a series of liquid-f illed scrubbers in an ice bath. The scrubber contents are then analyze d for formaldehyde using the chromotropic acid method. Some of the sam ples were analyzed for methanol using gas chromatography. The results from a number of studies demonstrate that several variables affect hot -press formaldehyde and methanol emissions. Formaldehyde emissions inc reased with increasing press time, platen temperature, moisture conten t, resin level, and formaldehyde-to-urea (F/U) mole ratio. Formaldehyd e emissions decreased with increasing board thickness, but were not af fected by wood particle size and degas time. Formaldehyde emissions we re also affected by the type of chemically bound formaldehyde present, i.e., methylol groups emitted much more formaldehyde than methylene g roups. Methanol emissions increased with increasing press time, moistu re content, and decreasing wood particle size. Degas time did not affe ct the methanol emissions. There was a close relationship between the emissions and the moisture movement out of the panel.