MECHANISM OF FORMALDEHYDE EMISSION FROM W OOD SUBSTANCES AND REDUCINGEFFECT BY AMMONIA TREATMENT

A laboratory scale and quick testing method of formaldehyde emission f rom wood substances was established by applying a sensitive colorimetr ic analysis (chromotropic acid method) and the precise control of the temperature during test. The formaldehyde emission from both formaldeh yde-treated wood and particleboard decreased exponentially when they w ere kept at 35 to 80 degrees C. From the apparent activation energy, i t was speculated that the formaldehyde emission was controlled by the desorption of free formaldehyde molecules absorbed by wood or their di ffusion in the wood substance. The application of ammonia vapor to the reduction of formaldehyde emission was considered from the viewpoint of treatment conditions. Ammonia reacted quantitatively with free form aldehyde at room temperature, and formaldehyde emission decreased rema rkably in a short treatment time. However, even ii the ammonia was qua ntitatively sufficient, a lower limit level of concentration was obser ved. It was also supposed that the penetration of ammonia into wood wo uld be rate-determining. The ammonium carbamate was also effective bes ides an easy handling reagent for the reduction of formaldehyde emissi on.