Since the energy crisis in the early 1970s, there has been a decided trend towards tightly constructed buildings that conserve energy and reduce costs. The downside of these well-intended efforts has been the lowering of interior air exchange rates, to the extent that many chemical contaminants are now being trapped indoors where people spend most of their lives. These contaminants may include volatile organic compounds (VOCs), such as formaldehyde, that have been suggested by some to be among the factors responsible for this air quality deterioration. Wood composite panels, which contain formaldehyde such as particleboard and medium density fiberboard (MDF) are often targeted for strict emission regulations or prohibited altogether, despite the fact that this industry has reduced formaldehyde emissions of raw panels by more than 80% over the past twenty years, thereby actually minimizing indoor air contaminants. Moreover, most consumer products made with composite panels are not used in a raw form, but instead have some type of surface finish over the substrate, that generally acts as a barrier to off-gassing, and subsequently reduces emissions.
In this year’s research, ten commonly used finishes were evaluated for their effectiveness as emissions barriers for formaldehyde and total volatile organic compounds (TVOC). It appeared that the powder coating is among the most effective barriers for both formaldehyde and VOCs, with more than 90% emission reduction when applied to MDF. A similar efficiency was observed with phenolic, vinyl, melamine paper, aluminium oxide overlay, Syn Décor laminates, thermofoil 12mil, and 2 mils Natural vinyl applied on particleboard panels. Some finishing material such as birch veneer showed excellent efficiency towards formaldehyde reduction with, however, a lower VOC emission reduction. Results also suggested further evaluation of other combinations of substrate and finish need to be considered (powder coatings on particleboard, clear coating or vinyl laminate on MDF) to more fully evaluate the impact of the substrate, if any, on emission characteristics of these surface treatments. The evaluation of the other finishing materials which showed an excellent efficiency on a particular type of product such as particleboard also need to be evaluated on the other product, in this case MDF in order to complete the evaluation of the effectiveness of any given barrier. The paper finish, water based topcoat, and the multiple (3) topcoat wet process appeared to be the less efficient barriers to either formaldehyde and/or VOCs with, 41% and 28% formaldehyde emission reduction respectively and an increase of VOC emissions by 79% and 57% respectively, suggesting that these barriers may have high solvent contents. A limitation of this first study was that the formaldehyde and VOC contribution of the surface coating or laminate were not tested by themselves without a substrate. The very limited number of tests conducted for any individual barriers suggests that these preliminary results should be viewed with caution and that more sampling is necessary to ensure completeness as well as confidence in the data. The next phase of this study will include an inter-laboratory comparison study, further evaluation of the finishes and the effect of sample aging as it relates to emissions.
A very good correlation between ASTM D 5116 and ASTM D 6007 has been established by comparing formaldehyde emission results from the two methods. An R² of 0.94 has been obtained and could be improved by expanding the database.