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Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on the Characteristics of Wood-Plastic Composites Water absorption of WPCs can be reduced by modifying the wood fibers. For instance, Dányádi et al. (2010) showed that the benzylation of wood fibers resulted in decreased water absorption. The wood modifications conducted by Müller et al. (2012) had similar effects. Hosseinaei et al. (2012) extracted hemicelluloses from wood fibers, which also resulted in lower water absorption of their WPCs. Wei et al. (2013) modified poplar wood fibers chemically by esterification and noted that the esterified fibers were more hydrophobic than the unmodified fibers. Consequently, the compatibility between wood fibers and the plastic matrix increased, leading to lower water absorption. Thermal modification of wood also results in a considerably lower water absorption of WPCs (Ayrilmis et al. 2011, Butylina et al. 2011). 2.2.3 VOC emissions VOCs have a low boiling point and therefore, a high vapor pressure at room temperature, leading to the evaporation of a large number of molecules into the surrounding air. VOCs are abundantly present in nature, for example, they play an important role in the communication between plants (Ueda et al. 2012). However, some VOCs exert adverse effects on human health and may cause harm to the environment. Therefore, legislative efforts have been made to diminish the release of harmful VOCs from commercial products. The regulation of indoor VOC emissions aims to limit VOC emissions from commercial products into indoor air where concentrations are the highest. The major difficulty in the research of VOCs and their effects is that their concentrations are usually low and the symptoms and illnesses they evoke tend to develop very slowly. The VOC emission characteristics of WPCs have not been extensively studied because these materials are generally used outdoors. Nevertheless, WPCs are increasingly being used indoors (Kim and Pal 2010). Therefore, their effects on indoor air quality are becoming more relevant. As WPCs consist mainly of wood and plastics, it is often presumed that their VOC emissions are dominated by these two major constituents. 40 Dissertations in Forestry and Natural Sciences No 222
Wood-plastic composites However, WPCs have usually been processed at high temperatures, which may change the VOC emission characteristics of the material. Furthermore, the incorporation of additives exert effects on the VOCs. Schwarzinger et al. (2008) conducted an elemental analysis of different WPCs by two-stage pyrolysis-GC/MS (gas chromatography-mass spectrometry). In addition to the identification of marker compounds for different wood types, they identified pyrolysis products from polymers (PE, PP, and PVC), which is important with respect to VOCs. Furthermore, their analysis of WPCs with various lignocelluloses provided further insights into the fundamental differences between WPCs with different reinforcements. Félix et al. (2013) examined the release of VOCs from WPCs made from landfill-derived plastic and sawdust. Their findings were in accordance with those of Schwarzinger et al. (2008); the key markers for WPCs were phenols and aldehydes. In general, the profile of VOCs displayed alkanes, alkenes, phenols, aldehydes, aromatic hydrocarbons, terpenes, carboxylic acids, esters, nitrogen compounds, ketones, and alcohols. The most abundant VOCs in WPCs were furfural, -pinene, 2-ethyl-1- hexanol, 2-methoxyphenol, N-methylphthalimide, butylated hydroxytoluene, 2,4-di-tert-butylphenol, and diethylphthalate. In addition, Félix et al. (2013) demonstrated that the incorporation of additives increased the release of certain VOCs. Another important finding was that WPCs have the potential to emit off-odor compounds that cannot be completely masked by odorizing agents. The identified off-odor compounds in WPCs included acetylfuran, hexanal, 4-vinylguaiacol, acetic acid, and 2-methoxyphenol. One way to control VOC emissions from WPCs is to incorporate odorants into the composites to mask at least part of the off-odor compounds (Félix et al. 2013). Moreover, the addition of other types of additives capable of affecting the odor characteristics along with the other properties of WPCs could provide a simple solution. Another approach, proposed by Yeh et al. (2009), is to cover the composite with a thin layer of virgin Dissertations in Forestry and Natural Sciences No 222 41
Page 1: PUBLICATIONS OF THE UNIVERSITY OF E
Page 4 and 5: Grano Oy Jyväskylä, 2016 Editors:
Page 7 and 8: ABSTRACT The use of raw materials d
Page 9: Universal Decimal Classification: 6
Page 12 and 13: Finally, I am grateful to my wife A
Page 14 and 15: TD-GC-FID/MS Thermal desorption/gas
Page 17 and 18: LIST OF ORIGINAL PUBLICATIONS This
Page 19 and 20: Contents 1 Introduction ...........
Page 21 and 22: 1 Introduction The finiteness of cr
Page 23 and 24: Introduction A new and environmenta
Page 25 and 26: 2 Wood-plastic composites By defini
Page 27 and 28: Wood-plastic composites additives u
Page 29 and 30: Wood-plastic composites Cellulose i
Page 31 and 32: Wood-plastic composites The propert
Page 33 and 34: Wood-plastic composites Figure 3. T
Page 35 and 36: Wood-plastic composites of lubrican
Page 37 and 38: Wood-plastic composites roughness a
Page 39 and 40: Wood-plastic composites Hosseinaei
Page 41: Wood-plastic composites the accessi
Page 45 and 46: Wood-plastic composites A typical s
Page 47 and 48: Wood-plastic composites to fill the
Page 49: Wood-plastic composites absorption.
Page 52 and 53: Taneli Väisänen: Effects of Therm
Page 63 and 64: 4 Thermal processing of wood Therma
Page 65 and 66: Thermal processing of wood Figure 9
Page 67 and 68: Thermal processing of wood counterp
Page 69 and 70: Thermal processing of wood and the
Page 71 and 72: Thermal processing of wood and Miet
Page 73 and 74: 5 Aims and significance Despite the
Page 75 and 76: 6 Materials and methods Two types o
Page 77 and 78: Materials and methods heat energy f
Page 79 and 80: Materials and methods with the untr
Page 81 and 82: Materials and methods 6.2.1 Tensile
Page 83 and 84: Materials and methods 6.3 WATER ABS
Page 85 and 86: Materials and methods The emissions
Page 87: Materials and methods where Evoc is
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Taneli Väisänen: Effects of Therm
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9 Summary and conclusions In the pr
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Bibliography Abdolvahaba E, Lashgar
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Bibliography Ayrilmis N, Jarusombut
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Bibliography Cernansky R. State-of-
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Bibliography polypropylene composit
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Bibliography with odor assessments
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Bibliography La Mantia FP, Morreale
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Bibliography Mohan D, Pittman CU, a
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Bibliography Rinne J, Taipale R, Ma
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Bibliography Stark NM and Rowlands
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Bibliography Yeh S and Gupta RK. Im
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