Control Of VOC Emissions From Wood-based Panels: Principle, Method And Effect

Indoor air quality (IAQ) significantly influences people's comfort, health andproductivity, and volatile organic compounds (VOCs) emitted from wood-based panelsare recognized as one of the major causes resulting in poor IAQ. Since source control isthe best mean for improving IAQ, it is important to study the control principle andmethod of VOC emissions from wood-based panels, and subsequently developlow-emitting wood-based panels. For the previous studies on this problem, there aresome shortcomings:(1) it lacks VOC emission analysis at different stages ofwood-based panels during its manufacturing process, hence the influence of rawmaterials and manufacturing techniques on VOC emissions from wood-based panels isunclear;(2) it lacks effective method for selecting barrier layers on the surface ofwood-based panels; and (3) there is little research on optimizing the doping position ofadsorbents in wood-based panels. This thesis conducted research for theseaforementioned problems, and the main academic contributions are as follows:Firstly, the VOC species and emittable content at different manufacturing stages ofwood-based panels such as urea-formaldehyde resin, wood chip, wood fiber after resinapplication, medium density fiberboard and phenol-formaldehyde resin are determined.It is observed that the formaldehyde emission from wood-based panels is dominated bythe emittable formaldehyde content in adhesives, whereas the other VOCs emitted fromwood-based panels mainly come from wood chips; the drying and hot-pressingtechniques during manufacturing process are helpful in reducing the VOC species andemittable content in wood-based panels; the correlation between emittableformaldehyde content in adhesives and formaldehyde emission factor from wood-basedpanels is obtained, which provides guidance on predicting and controlling formaldehydeemission rate from wood-based panels during their manufacturing process.Secondly, a novel method, dynamic/static chamber method (DSC method) isproposed to measure the diffusion and partition coefficients of VOC in barrier layers onthe surface of wood-based panels. The method is time-saving and has high accuracy.Moreover, a group of dimensionless correlations for characterizing the effect ofbarrier layers on VOC emissions from wood-based panels is induced. They offer a technical tool to select barrier layers for lowering VOC emission rate fromwood-based panels.Thirdly, a simple closed chamber method is developed to choose adsorbents withexcellent adsorption performance for formaldehyde. Combining the mass transfer modelfor VOC emission from multi-layered materials, an optimization model for determiningthe optimum doping position of adsorbents in wood-based panels is established, andmethod for solving the optimization model is proposed. It is proved that the optimumdoping mode is placing the overall adsorbents into the top layer of wood-based panels,which provides theoretical basis to control VOC emission from wood-based panels.Finally, based on above analysis, a design method for low-emitting wood-basedpanels is put forward and then laboratory samples are prepared. Experimental resultsshow that the formaldehyde emission rate from wood-based panels can be reduced by75%.