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 and cellulose. Lignin is covalently linked to hemicellulose molecules, increasing the mechanical strength of the cell wall. Lignin is a non-polar hydrophobic polymer whereas cellulose and hemicelluloses are hydrophilic (Thomas et al. 2011). In the pulp industry, lignin is normally removed from the pulp (chemical pulp) when manufacturing bleached writing paper, because lignin is responsible for the yellowing of paper with age (Ek et al. 2009). Since lignin yields a considerable amount of energy when burned, it is considered as a potential alternative to fuels derived from non-renewable sources. In addition, the pyrolysis of lignin yields chemical compounds that are thought to be potentially useful in many fields of applications (Lora and Glasser 2002). For instance, guaiacol, which is a thermal degradation product of lignin, has smoky sensory notes and it can be used as a flavorant (Goldstein 2002, Dorfner et al. 2003). In addition to lignocellulose, wood contains small amounts (3–10%) of other organic components (Pettersen 1984, Rowell et al. 2013, Stokke et al. 2014). Wood extractives include simple sugars, fats, waxes, resins, proteins, terpenes, and gums. The extractive compounds are crucial components of the defense system of the tree, but they also act as energy reserves and support tree metabolism (Clemons 2008). There are also trace amounts (about 1%) of inorganic ash in wood (Rowell et al. 2013). 2.1.2 Polymers A variety of thermoplastic or thermosetting polymers can be used as the matrix material in WPCs (Clemons 2008). However, the low thermal stability of wood limits the polymers to those that have adequately low processing temperatures. The thermal degradation of wood components begins at approximately 120 °C, and major changes take place at over 200 °C. Thus, polymers which have a processing temperature lower than 200 °C need to be used in WPCs (Godavarti 2005). The most common polymers include PE, PP, and PVC that are thermoplastics. 28 Dissertations in Forestry and Natural Sciences No 222
Wood-plastic composites The properties of a polymer are primarily defined by its molecular structure. Homopolymers contain only one type of monomer whereas copolymers or terpolymers consist of several kinds of monomers. The branching of polymer chains has multiple effects on the polymer. For example, the highly branched low-density polyethylene (LDPE) is softer and has a lower density and poorer tensile strength than the more linear high-density polyethylene (HDPE). (Clemons et al. 2013) The properties of polymers also depend on its tacticity – the arrangement of monomers along the polymer backbone. Polymer tacticity can be divided into three classes: an isotactic polymer has all of its substituents on the same side of the backbone, and polymers with alternating placements of substituents along the backbone are called syndiotactic. Atactic polymers lack any consistent arrangement in their substituents. (Clemons et al. 2013) The monomers of a copolymer can also be organized in a variety of ways (Clemons 2008). An alternating copolymer consists of two different monomers arranged in an alternating sequence within the chain of the molecule (ABABAB…). The organization of monomers in random copolymers is not defined (ABAABBBA…). Statistical copolymers have monomers arranged according to a known statistical rule. Block copolymers are made up of polymerized monomer blocks. If a copolymer contains side chains that have a different composition compared with the main chain, the polymer is termed as a graft copolymer. The crystallinity of the polymer affects its thermal and physical properties because the crystalline regions inside the polymer structure increase the interactions between the polymer chains. When the structure of the polymer is highly ordered, there are fewer possibilities for the polymer chains to move relative to one another. Thus, more energy is required to transform the polymer into an unordered fluid state, meaning that polymers with high crystallinity have higher melting points in comparison with their more amorphous counterparts. (Beyler and Hirschler 2001) High crystallinity also means that the Dissertations in Forestry and Natural Sciences No 222 29
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: Wood-plastic composites Cellulose i
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
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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.
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Page 63 and 64: 4 Thermal processing of wood Therma
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Page 73 and 74: 5 Aims and significance Despite the
Page 75 and 76: 6 Materials and methods Two types o
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Materials and methods 6.2.1 Tensile
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Materials and methods 6.3 WATER ABS
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Materials and methods The emissions
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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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