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 in a co-extrusion process. This layer should be able to delay the release of VOCs and therefore, alter the odor profiles of WPCs. 2.3 MANUFACTURING TECHNOLOGIES There are several alternative methods for manufacturing WPCs. Compounding is a process in which filler and additives are added to the molten polymer. The compounded material can be formed into pellets or granules prior to future processing, or they can be immediately shaped into the final product (in-line processing) (Clemons et al. 2013). The processability of WPCs is similar to plastics, which is an advantage since WPCs are can typically be processed with the same machinery. Extruders are the most commonly used systems for WPC compounding. Hotcold mixers are also used but mainly for the processing of PVCbased WPCs (Schwendemann 2008). The product manufacturing technologies for WPCs include sheet or profile extrusion, injection molding, and compression molding (Stokke et al. 2014). Profile extrusion is the most commonly used manufacturing method for a WPC, and it is used to produce composites with a continuous profile of the desired shape (Gonçalves et al. 2014). WPC panels can be produced by sheet extrusion. Injection and compression molding produce non-continuous pieces with a more complicated shape. 2.3.1 Extrusion Extrusion produces continuous linear profiles by forcing a melted WPC through a die. Different types of extruders and processing strategies have been used to produce WPCs. For example, some processors manufacture WPCs in one step, using twin-screw extruders whereas some prefer to adopt several extruders in tandem to compound and finally form the desired profile of the WPC. (Clemons et al. 2013) 42 Dissertations in Forestry and Natural Sciences No 222
Wood-plastic composites A typical screw extruder consists of feeders, modular barrels, screws, a gearbox, a heating, and cooling unit (Figure 5), and a centralized control unit to adjust the extrusion speed, feeding rate, temperature, and other process parameters (Schwendemann 2008). The extruding screw system, consisting of screws and barrels, mixes, devolatilizes, and performs the reactions for multiple applications. Figure 5. The basic structure of an extruder. The screws mix the components in order to produce a homogeneous blending fluid in the barrel. The screws are usually made up of three zones: the feeding, melting, and melt pumping zone. In the feeding zone, the raw materials for WPC are usually solid, but when they move to the melting zone, most polymers have melted while fillers and additives remain in a solid state. The melt pumping zone forms a continuous fiberpolymer blend, which is finally pumped to the pelletizer after cooling or extruded through the die. (Stokke et al. 2014) A typical barrel-length-to-diameter (L/D) ratio of a singlescrew extruder varies from 20 to 30. The screw builds up high pressure in the composite melt so that it can be extruded through the die. Even though the single-screw extruders are less expensive than those with twin-screw systems, they suffer from a limited mixing and self-cleaning ability as well as from the selective material intake. The twin-screw extruders, whether corotating or counter-rotating according to the screw rotation Dissertations in Forestry and Natural Sciences No 222 43
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 and 42: Wood-plastic composites the accessi
Page 43: Wood-plastic composites However, WP
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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