Volatile acetic acid and formaldehyde emission from plywood treated with boron compound
Introduction
Over the past several decades, air pollution in homes and office buildings has become a matter of increasing concern. Formaldehyde emission has been the major concern associated with bonded wood products. Recently, interest has turned to other volatile organic chemicals (VOCs) [1]. Composite wood products such as particleboard, plywood and MDF are widely used in indoor products such as subflooring, door cores and furniture [2]. Emissions of VOCs potentially can arise from any of the materials that compose a panel; until recently attention has been on emissions of formaldehyde from UF adhesive [3]. It was concluded that the wood products were responsible for the elevated levels of terpenes, aldehydes, and acetic acid. Along with the air pollutant, volatile acids in woods are of great technical importance because of their corrosion of metals, iron–tannin discoloration of woods, influence on curing time of synthetic lacquers and glues and fixation of wood-preserving salts [4]. Air pollution is different from other contaminations in that air is freely exchanged among regions. Therefore, global solutions are required. Also, these chemicals have adverse health effects such as eye and respiratory irritation, irritability, inability to concentrate and sleepiness [5]. Because of increased emphasis on indoor air quality, accurate information is needed regarding the amounts and types of VOCs emitted from building materials or used in the indoor environment. On the other hand, many methods and chemicals have been devised to reduce some troublesome inherent properties (degradable by insect and fungi attack, flammable) of wood-based panel products. Boron compounds may be the most investigated preservatives for wood based panel products because of their beneficial effects such as preservative effectiveness, a broad spectrum of activity against insects and fungi and less impact on mechanical properties compared to other flame-retardant chemicals [6]. However, previous studies have not shown how formaldehyde and volatile acetic acid emissions of wood products are affected by these chemicals and preservation methods. Especially acetic acid emissions of treated plywood panels were investigated because of technological significance besides the other necessity mentioned above.
Section snippets
Material and method
In this experimental study, -thick rotary cut veneers were obtained from beech (steamed) and alder (non-steamed) logs at laboratory conditions. The veneers were then dried to 6–8% moisture content and weighed after dipping into 5% aqueous solution of preservative for . After impregnation, the veneers were subjected to a second drying process at industrial conditions, and then conditioned to 7% moisture content again and re-weighed. The net uptake of borax and boric acid was calculated
Results and discussion
The mean retentions of veneers were found for borax as (min. 11.4; max. 17.1) and (min. 8.8; max. 13.3), for boric acid as (min. 10.1; max. 18.3) and (min. 10.4; max. 14.7), beech and alder, respectively.
Conclusion
The formaldehyde emissions of plywood panels treated with boric acid increase. On the contrary, treatment with borax has a small decreasing effect for formaldehyde emission. The difference between formaldehyde emission values of the beech panels treated with boric acid and untreated beech panels was higher than that of the alder plywood panels. The increases in the amount of formaldehyde release from the panels produced by adding boric acid into the glue mixtures of UF1 and UF2 were 2.52 and
Acknowledgements
This study was financially supported by the research fund of Karadeniz Technical University. The authors express their gratitude for the financial support.
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