VOC EMISSIONS FROM HEAT TREATED WOOD
P. Čech, D. Tesařová
3.2 Equipment for determination VOC emissions
Short path thermal desorption tube, Silco trated Thermal Desorption Tube 786090-100, inner diameter 4 mm, fill in with 100 mg of Tenax TA (Scientific Instrument Services company) for collection of VOCs emissions emitted from tested samples in to the air in chamber
Air sampler Gilian–LFS 113 SENSIDINE with air flow 6 l h-1 and 12 l h-1
Gas chromatograph Agilent GC 6890 with MS (mass spectrometer) detector 5973 with cryofocusation, thermal desorption and library of spectra NIS 05, column type HP – 5 (AGILENT USA)
VOC Emissions from Heat Treated Wood
VOC was tested in a small-space chamber with a volume of 1 m3. Air temperature: 23°C; relative humidity in the chamber: 50%; air changing rate: 1 m3 per 1 h; air speed over the tested samples: 0.1 to 0.3 m.s-1 3.3 Methods
Methods of VOC testing were set via standards:
ISO 16000: 2004 Indoor air
ISO 16000-1: 2004 General aspects of sampling strategy
ISO 16000-5: 2005 Measurement strategy for (VOCs) volatile organic compounds
ISO 16000-11: 2004 Determination of the emission of volatile organic compounds - sampling, storage of samples and preparation of test specimens
ISO 16000-6: 2005 Determination of volatile organic compounds indoor and test chamber air by active sampling on Tenax TA® sorbent, thermal desorption and chromatography using MS/FID
ISO 16000-9: 2004 Determination of the emission of volatile organic compounds - Emission test chamber method
4 RESULTS
Based on the obtained results (fig. 2, 3, 4) it is concluded that the heat-treatment of wood increases the quantity of VOC emissions emitted by tested samples. The main difference was found in the amount of emitted furfural and phenol in the blend of gaseous evaporated by heat-treated spruce in normal conditions. The temperature of heat-treatment has a great influence on the amount of emitted furfural by tested heat-treated wood.
That means the higher the temperature during the spruce heat-treatment the higher the furfural emissions. Furfural and phenol are typical chemicals, which are resulting in thermal degradation of wood components.
The finished surface by the water borne lacquer does not decrease the amount of emissions escaping from heat-treated spruce wood. Surprisingly, water borne lacquers even elevated the amount of VOCs.
Fig. 2 shows the influence of the temperature of the wood modification and of the time between the VOC measurement and wood modification on the amount of VOC emissions. The amount of VOC emissions decreases with the decreasing temperature of wood modification. The amount of emitted VOC declines with the increasing time between the modification of wood and the measurement of VOC emissions emitted by tested samples.
the temperature 200°C and 180°C and untreated wood in dependence on time. The highest concentration of TVOC was emitted by heat-treatment wood in temperature 200°C.
Figure 2: Amount of VOC emitted by heat-treated spruce wood after 3, 24, 72 and 672 h.
Figure 3: Comparison of TVOC emitted from thermally treated of Norway spruce, the temperature of thermally treated wood in the temperature 200°C
and 180°C and untreated wood.
VOC Emissions from Heat Treated Wood
Fig. 4 shows a comparison of VOC emissions from Norway spruce heat-treatment in 180°C and 200°C after finishing by water borne lacquer. We can see very high concentration of buthoxy ethanol, while this compound is obtained in water borne lacquer. Furfural and phenol are substances resulting from thermal decomposition of lignin. Concentration of furfural is moved in the hundreds of μg·m-3, while concentration of phenol is moved only to units of μg·m-3.
Figure 6: Comparison of VOC emissions from Norway spruce heat-treatment wood in 180°C and 200°C after finishing by water borne lacquer.
5 DISCUSSION
Main difference consists in the amount of emitted furfural and phenol in the blend of gaseous evaporated by heat-treatment Spruce in normal conditions.
The great influence of emitted furfural amount has the temperature of heat-treatment. The higher temperature during the spruce treatment means the
Furfural and phenol are typical chemicals, which are resulting in degradation of wood components. The finished surface by the water borne lacquer not only decreases the emissions escaping from heat-treatment Beech wood but even doesn’t increase the quantity of evaporated VOC emissions from these samples.
The next step of this research will investigate the influence of heat-treatment on the amount of VOC emissions emitted by different kinds of wood, and it will study the influence of heat-treatment on wood finished surfaces, especially to find the correlation between the kind of the surface finishing and VOC emissions. Eventually, the relation of the quality and quantity of VOC emitted by the heat-treated wood on the way of finishing of the heat-treated wood surfaces will be investigated.
6 CONCLUSION
Heat-treated wood from Norway spruce emitted more VOC components of furfural and phenol than untreated wood (natural wood).
Heat-treated wood form Norway spruce emitted more concentrations of furfural and phenol before finishing than after finishing.
Heat-treatment wood after the finishing (water born lacquer) emitted very high concentration of buthoxy-ethanol.
After finishing wood modified by heat treated process in 180°C emitted more concentration of VOC emissions than that processed in 200°C.
7 RECOMMENDATION
The modified - heat treated wood (spruce) is suitable for use in external environment (doors, floors, terraces). Heat-treated wood is not suitable for interior, especially from the perspective of the negative effect of chemicals on human health. This research has demonstrated the long-term effects of VOC emissions in the interior, so it is recommended that the heat-treated wood (furniture, floors, doors etc.) be exposed at least for six months after production and before its use in the interior.
ACKNOWLEDGMENTS
Supported by the European Social Fund and the state budget of the Czech Republic, project ‘The Establishment of an International Research Team for the Development of New Wood-based Materials’ reg. no.
CZ.1.07/2.3.00/20.0269.
VOC Emissions from Heat Treated Wood
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SESSION C Product Life-Cycle – from Concept to Market and Use