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 polymer will be strong but brittle, which accounts for the high modulus and low impact resistance (Galeski 2003). Semicrystalline polymers have both crystalline and amorphous regions, i.e., these polymers combine the high strength of crystalline polymers with the flexibility of the amorphous types (Callister 2005). In composite materials, semicrystalline polymers are typically more efficiently reinforced by fibers than amorphous ones because the fibers act as nucleation sites for the crystallization process with the fiber becoming surrounded by a finely divided microcrystalline structure, which improves the modulus, especially the flexural modulus (Quan et al. 2005). At the moment, PEs are the most commonly used plastics because they are easy to produce and modify. PE (Figure 2) is a semicrystalline polymer. The polymer chains in PE can branch in a different manner, resulting in polymers with different properties. HDPE has a variety of applications because of its excellent barrier properties and resistance to different solvents. LDPE is commonly used in containers, bottles, films, and plastic bags because it is a flexible and tough polymer with a good resistance to chemicals. In addition, LDPE has good electrical properties. (Klyosov 2007, Kim and Pal 2010) Figure 2. The chemical structure of PE. The properties of PP resemble those of PE. PP is a semicrystalline polymer with a methyl group (CH3) attached to the polymer backbone (Figure 3), meaning that PP can be either isotactic, atactic or syndiotactic. However, over 90% of produced PP is isotactic. Like PE, PP finds its applications in packaging, containers and films. Furthermore, PP is used in the automotive industry and can be found in laboratory equipment and textiles. (Kim and Pal 2010) 30 Dissertations in Forestry and Natural Sciences No 222
Wood-plastic composites Figure 3. The chemical structure of isotactic PP. PVC (Figure 4) is commonly used in construction, packaging, and insulation because it has an excellent weather resistance and electrical properties. Additionally, PVC has good mechanical properties. However, the processing of PVC is problematic because it releases a toxic compound, hydrochloric acid (HCl), when burned or melted. Furthermore, the thermal stability of PVC is very poor but can be improved by adding heat stabilizers during processing. The presence of a chlorine group in PVC means that the polymer may have different tacticity. Unlike PP, PVC has mainly an atactic stereochemistry. (Klyosov 2007, Kim and Pal 2010) Figure 4. The chemical structure of atactic PVC. 2.1.3 Additives Additives are introduced into a polymer to alter its processability or performance (Clemons 2008). When a polymeric material contains additives, it is usually referred to as a “plastic”. Examples of additives are plasticizers, pigments, biocides, UV stabilizers, and antioxidants. The additive content is usually low because these materials are often rather expensive. Moreover, an excessive amount of the additive may deteriorate the properties of the material (Clemons et al. 2013). In WPCs, additives are used to improve the processability of the composites and especially to enhance the coupling between chemically different wood fibers and plastics. Furthermore, Dissertations in Forestry and Natural Sciences No 222 31
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: Wood-plastic composites The propert
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
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Page 77 and 78: Materials and methods heat energy f
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Page 81 and 82: 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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