Dissertations in Forestry and Natural Sciences

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Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on the Characteristics of Wood-Plastic Composites become stiffer after the distillate addition. Mathematically, the tensile modulus is the slope of the stress-strain curve. An increase in the slope means that more force is required to strain the material. The higher stiffness, which was also indicated by the decreased strain and bending with the higher distillate content, could be attributed to the capability of hardwood distillate to fill the gaps and pores in WPCs. This leads to restricted movement of the polymer chains within the material. The restricted movement of the polymer chains and the reduced ductility also explains the reduced Charpy’s impact strength. On the other hand, as the distillate fills the pores in WPC, this may increase the interfacial bonding between the polymer and wood fibers. Other studies have also revealed a correlation between material porosity and elastic modulus; as the material becomes less porous, elastic modulus increases (Patterson 2001, Bledzki et al. 2005b). The possible inclusion of distillates into the polymer-fiber interphase could also explain the improvements to the mechanical properties of the WPCs. The distillates are chemically hydrophobic but they may be able to bind to hydrophilic wood fibers through mechanical interlocking. On the other hand, the chemical similarity between the polymer matrix and the distillates could create a rather strong polymerdistillate interface. The molecular entanglement between the polymerized molecules in the distillates and the polymer chains may also account for the improved mechanical durability of the WPCs. Thus, the compositional differences between hardwood and softwood distillate may affect the compatibility characteristics and the interactions in the fiber-polymer interphase. When the distillate content was higher than 4 wt%, the excess distillate may have agglomerated or otherwise disrupted the interactions between the additives and other WPC constituents. Thus, there was a reduction of the strength of the WPCs. For more homogeneous distribution, the distillates may have to be added to the WPCs at the earlier stage of the production, which could also enhance the positive effect on the mechanical properties of the material. 100 Dissertations in Forestry and Natural Sciences No 222
Discussion Softwood distillate had distinct effects in comparison with hardwood distillate on the WPCs. The tensile strength of the WPC containing 2 wt% of softwood distillate was enhanced by over 5% compared to the unmodified WPC, and improvements in some other properties were also observed. One of the most clear distinctions between the WPCs with hardwood and softwood distillates was that the addition of hardwood distillate stiffened the composite whereas opposite effect was observed for the WPCs supplemented with softwood distillate. The improvement in mechanical strength at 2 wt% distillate content and a major increase in bending and strain at higher distillate contents (over 4 wt%) indicated that softwood distillate may improve the interfacial properties of the WPC constituents. However, it was possible that unlike the hardwood distillate, softwood distillate did not restrict the movement of polymer chains within the composite. The differences between the distillates can be attributed to their compositional differences; the softwood distillate was formed at lower temperatures (maximum temperature 215 °C) in ThermoWood ® process whereas hardwood distillate was obtained from a slow pyrolysis process where the maximum temperature was approximately 350 °C. The softwood distillate primarily consisted of hemicellulose degradation products whereas the hardwood distillate was a mixture of cellulose, hemicellulose, extractive and lignin degradation products. Moreover, the composition of the distillates was affected by the feedstock: softwood distillate was obtained primarily from pine whereas hardwood distillate was acquired from the slow pyrolysis of birch. In general, hardwoods contain more cellulose than softwoods, and the lignin content in softwoods is higher than in hardwoods. 8.3 WATER ABSORPTION The positive effects of hardwood and softwood distillates on water absorption of the WPCs were evident in studies III and IV. Dissertations in Forestry and Natural Sciences No 222 101
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PUBLICATIONS OF THE UNIVERSITY OF E
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Grano Oy Jyväskylä, 2016 Editors:
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ABSTRACT The use of raw materials d
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Universal Decimal Classification: 6
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Finally, I am grateful to my wife A
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TD-GC-FID/MS Thermal desorption/gas
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LIST OF ORIGINAL PUBLICATIONS This
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Contents 1 Introduction ...........
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1 Introduction The finiteness of cr
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Introduction A new and environmenta
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2 Wood-plastic composites By defini
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Wood-plastic composites additives u
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Wood-plastic composites Cellulose i
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Wood-plastic composites The propert
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Wood-plastic composites Figure 3. T
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Wood-plastic composites of lubrican
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Wood-plastic composites roughness a
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Wood-plastic composites Hosseinaei
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Wood-plastic composites the accessi
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Wood-plastic composites However, WP
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Wood-plastic composites A typical s
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Wood-plastic composites to fill the
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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
Page 115 and 116: 9 Summary and conclusions In the pr
Page 117 and 118: Bibliography Abdolvahaba E, Lashgar
Page 119 and 120: Bibliography Ayrilmis N, Jarusombut
Page 121 and 122: Bibliography Cernansky R. State-of-
Page 123 and 124: Bibliography polypropylene composit
Page 125 and 126: Bibliography with odor assessments
Page 127 and 128: Bibliography La Mantia FP, Morreale
Page 129 and 130: Bibliography Mohan D, Pittman CU, a
Page 131 and 132: Bibliography Rinne J, Taipale R, Ma
Page 133 and 134: Bibliography Stark NM and Rowlands
Page 135: Bibliography Yeh S and Gupta RK. Im
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Dissertations in Forestry and Natural Sciences

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