Dissertations in Forestry and Natural Sciences

More documents

Recommendations

Info

Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on the Characteristics of Wood-Plastic Composites additives provide WPCs with a better surface appearance and long-term durability (Sherman 2004). Coupling agents are additives that improve the adhesion between wood and plastics, and their content in WPCs is typically less than 5%. Coupling agents can be classified into the surface-active agents and functional modifiers. Surface-active agents do not form covalent bonds with either the polymer matrix or the wood fiber; instead, they increase the interfacial adhesion of these constituents by acting as a solid surfactant. MAPP is one of the most commonly used coupling agents; its anhydride part forms ester bonds with wood’s hydroxyl groups and the long hydrophobic polymer incorporates into the polymer network. MAPP is therefore a functional modifier. Consequently, the wood fibers and the polymer matrix become bonded together, resulting in enhanced mechanical properties and reduced moisture absorption. Organosilanes, acrylic-modified polytetrafluoro-ethylene (PTFE), epoxides, isocyanates, organic acids, inorganic agents, and titanates are some other examples of the coupling agents used in WPCs (Lu et al. 2000, Godavarti 2005). Mineral additives are another major group of additives used in WPCs. They include talc (Mg3Si4O10(OH)2), calcium carbonate (CaCO3), kaolin clay (Al2Si2O5(OH)4), and silica sand (SiO2). In particular, talc and calcium carbonate are commonly utilized in WPCs because they are abundantly available, inexpensive, and they clearly enhance mechanical properties of the composite. In addition, talc has a natural affinity to oil, making it a good filler and lubricant for the mineral oil derived plastics (Klyosov 2007). Due to its hydrophobicity and ability to close the pathways for water in the composite, the addition of talc into WPCs results in reduced moisture absorption and less swelling liability. (Huuhilo et al. 2010) The processability and surface appearance of WPCs can be improved using lubricants, such as zinc stearate, paraffin waxes, oxidized PE, and ethylene-bis-stearamide (EBS). However, the use of metal stearates together with maleated coupling agents can nullify the effects of both additives. Typically, the amount 32 Dissertations in Forestry and Natural Sciences No 222
Wood-plastic composites of lubricants in WPCs is less than 5%, but it is also dependent on the type of the polymer matrix. For example, the lubricant content level for a HDPE-wood composite (wood content 50–60%) is usually 4–5% whereas a similar composite composed of PP as a polymer matrix instead of HDPE is typically manufactured with 1–2% of lubricant. (Sherman 2004) Light stabilizers and colorants (pigments) are also added to WPCs to improve the resistance against color fade and UV degradation, and to provide the desired appearance (Sherman 2004, Clemons et al. 2013). The amount of pigments in WPCs must be 1–3% or even higher to avoid color staining from the wood. Biocides, such as zinc borate, protect composites against fungal and microbial attacks and maintain their surface appearance. They also reduce the moisture absorption. Flame retardants suppress the production of flames and therefore, prevent the spread of fire. 2.2 PROPERTIES There are two common reasons to add wood to polymers: 1) to lower the price of the final product and 2) to reduce the dependency on mineral oil based products (Kim and Pal 2010). This, however, means a compromise as the properties of wood and plastics are altered, i.e., WPCs possess rather different characteristics. For example, WPCs absorb less water than wood but have higher tensile strength than plastics. WPCs have therefore found use in multiple applications. The low density and good processability of WPCs are favored in automobile industry, for instance. On the other hand, WPCs are widely used in building products, such as siding and decking because of their low water absorption and good creep performance. However, the properties of WPCs are highly dependent on the product formulation, manufacturing, and the quality of the raw materials. Dissertations in Forestry and Natural Sciences No 222 33
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: Wood-plastic composites Figure 3. T
Page 37 and 38: Wood-plastic composites roughness a
Page 39 and 40: Wood-plastic composites Hosseinaei
Page 41 and 42: Wood-plastic composites the accessi
Page 43 and 44: Wood-plastic composites However, WP
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
Page 90 and 91:
Taneli Väisänen: Effects of Therm
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
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
show all

Dissertations in Forestry and Natural Sciences

Create successful ePaper yourself

Delete template?

Save as template?