TVOC and formaldehyde emission behaviors from flooring materials bonded with environmental-friendly MF/PVAc hybrid resins

Abstract

Polyvinyl acetate (PVAc) was added as a replacement for melamine-formaldehyde (MF) resin in the formaldehyde-based resin system to reduce formaldehyde and volatile organic compound (VOC) emissions from the adhesives used between plywoods and fancy veneers. A variety of techniques, including 20-l chamber, field and laboratory emission cell (FLEC), VOC analyzer and standard formaldehyde emission test (desiccator method), were used to determine the formaldehyde and VOC emissions from engineered flooring bonded with five different MF resin and PVAc blends at MF/PVAc ratios of 100:0, 70:30, 50:50, 30:70 and 0:100. Although urea-formaldehyde (UF) resin had the highest formaldehyde emission, the emission as determined by desiccator method was reduced by exchanging with MF resin. Furthermore, the formaldehyde emission level was decreased with increasing addition of PVAc as the replacement for MF resin. UF resin in the case of beech was over 5.0 mg/l, which exceeded E-2 (1.5-5.0 mg/l) grade. However, MF30:PVAc70 was <= E-1 (below 1.5 mg/l) grade. Because formaldehyde emission is caused by formaldehyde-based resin, the engineered floorings bonded with PVAc only had emissions of just 0.25 mg/l. The results of formaldehyde emission by the 20-l small-chamber and FLEC methods showed a similar tendency with those from the desiccator method. After the replacement of UF resin by MF resin, PVAc addition further reduced formaldehyde emission. With increasing installation time, formaldehyde emission factors (EFs) were decreased. Furthermore, the results of the desiccator method correlated with those of the 20-l chamber and FLEC methods. VOC emission results by 20-l small-chamber and FLEC methods were similar to the formaldehyde and aldehyde emission results. VOCs were calculated between C-6 and C-16 as total VOC (TVOC). The TVOC EF results by 20-l small-chamber and FLEC methods were comparable with that of formaldehyde emission by FLEC. Although the major emitted harmful gas from wood-based composites was formaldehyde, it was followed by VOC emission. Although it was hard to compare directly the 20-l chamber and FLEC results because the data were based on the sum of only four VOC compounds, the VOC analyzer can be applied as a pre-test method for TVOC emission test. The TVOC emission results were also similar to the FLEC results. Due to its good correlation with the TVOC emission levels obtained from the standard desiccator, FLEC and 20-l chamber methods, the VOC analyzer can be successfully applied to the measurement of TVOC emissions from adhesives used in building materials.