Volatile organic compound emissions arising from the hot-pressing of mixed-hardwood particleboard

This study investigated the effects of adhesive type and press variables on the volatile organic compound (VOC) emissions arising from hot-pressing mixed-hardwood particleboard. Three adhesive types, urea-formaldehyde resin (UF), phenol-formaldehyde resin (PF), and polymeric methylene diisocyanate resin (pMDI), were evaluated in this study. A 2(5-1) fractional factorial design was used to evaluate the primary effect of five press variables (press temperature, press time, mat resin content, mat moisture content, and board density) and their interactions. A total of 27 chemical compounds were identified and quantified in the VOC emissions using four analytical techniques. Formaldehyde, methanol, acetic acid, and HMw VOCs with hexanal being the predominant chemical were the major compounds comprising the VOC emissions. The results revealed that formaldehyde and methanol emissions from UF particleboard, as well as the methanol emissions from PF particleboard were the most abundant components of the VOC emissions, and they contributed about 92 and 72 percent of the total identified VOCs, respectively. Lower levels of formaldehyde and acetic acid were released during the hot-pressing of PF particleboard. Acetic acid and HMw VOC emissions were the most abundant components of the VOC emissions arising from pMDI-bonded particleboard. pMDI significantly reduced the methanol emissions from the mixed-hardwood particleboard. The most significant press variables controlling VOC emissions were press time, mat resin content, press temperature, and interactions among these three variables. These press variables had different effects on the individually identified compounds based on the adhesive type used. In general, formaldehyde emissions arising from hardwood particleboard hot-pressing were significantly lower than those from softwood particleboard. However, formaldehyde emissions from UF-bonded hardwood particleboard were significantly higher than from the softwood UF-bonded particleboard.