Niska / Sain Wood-Polymer Composites

1. Auflage 2008
ISBN: 978-1-84569-457-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 384 Seiten

Reihe: Woodhead Publishing Series in Composites Science and Engineering

Wood-polymer composites (WPC) are materials in which wood is impregnated with monomers that are then polymerised in the wood to tailor the material for special applications. The resulting properties of these materials, from lightness and enhanced mechanical properties to greater sustainability, has meant a growing number of applications in such areas as building, construction and automotive engineering. This important book reviews the manufacture of wood-polymer composites, how their properties can be assessed and improved and their range of uses.After an introductory chapter, the book reviews key aspects of manufacture, including raw materials, manufacturing technologies and interactions between wood and synthetic polymers. Building on this foundation, the following group of chapters discusses mechanical and other properties such as durability, creep behaviour and processing performance. The book concludes by looking at orientated wood-polymer composites, wood-polymer composite foams, at ways of assessing performance and at the range of current and future applications.With its distinguished editors and international team of contributors, Wood-polymer composites is a valuable reference for all those using and studying these important materials. - Provides a comprehensive survey of major new developments in wood-polymer composites - Reviews the key aspects of manufacture, including raw materials and manufacturing technologies - Discusses properties such as durability, creep behaviour and processing performance

Autoren/Hrsg.

Niska, K O

Sain, M.

Leseproben

2 Additives for wood–polymer composites
D V SATOV,     Canada Colors and Chemicals Limited, Canada Publisher Summary
This chapter presents that the process of bringing any product to market is initiated when the sponsors of the venture agree that there is an identified market need and profit can be generated upon commercialization. Additive selection is just as important to the success of the venture as the choice of processing equipment and raw materials for the final product. The additives play two roles in contributing to the success of the venture. The role seen by the marketplace is that of effecting end product performance attributes to meet consumer expectations, regulatory requirements, and the marketing objectives of the manufacturer. The role internal to the business enterprise is that of affecting the manufacturing process to minimize the unit cost of finished goods for greater profitability. Additives can be used wisely and cost effectively to optimize performance and profit. Due diligence is required with an understanding of all the parameters. The catch is that for any one objective, there is often more than one solution available; one must identify the option that provides the best overall answer, after considering all the possible ripple effects of any option. 2.1 Introduction
The process of bringing any product to market is initiated when the sponsors of the venture agree there is an identified market need and, upon commercialization, profit can be generated. Additive selection is just as important to the success of the venture as the choice of processing equipment and raw materials for the final product. Additives play two roles in contributing to the success of the venture. The role seen by the marketplace is that of effecting end product performance attributes to meet consumer expectations, regulatory requirements, and the marketing objectives of the manufacturer. The role internal to the business enterprise is that of effecting the manufacturing process to minimize the unit cost of finished goods for greater profitability. Having had the opportunity to spend years both as a user of chemicals as additives and modifiers in manufacturing, as well as promoting them to industry, I have developed the perspective that it is important to minimize the number and total volume of additives used in a product. Rarely is additive selection a major consideration from the start of a venture. More often additives and modifiers are included based on typical formulas and industrial norms, and are fine-tuned only after inadequacies have been identified. The single greatest reason industry uses more additives than necessary is that there is a lack of adequate development in coordinating or matching the finished product requirements with the particulars of the process technology and the primary material components; in the case of composites these primary materials being resin and natural fiber. Industry tends to use additives to make up for process deficiencies, a boon to the chemical industry. This is because process equipment is the primary initial investment and is an obvious cost to contain from the start, regardless of the fact that a capital cost can be amortized and written down. Subsequently any process inadequacy is addressed with additives, resulting in an operational cost that will continue until the process is upgraded. It is the author’s opinion that choosing which resin and fiber to use must be an integral part of the initial strategy. Considerations are: suitability for application, availability and cost of raw materials from chosen source, reliability of supply especially assuming demand will grow, and/or potential for alternative sources, and how choice fits into the marketing plan (such as environmental marketing). The equipment must be suitable for processing of the designated materials to make a part cost effectively. Considerations include the base process being considered, design features such as screw configuration, output potential, both as weight per unit time and for a given die, length per unit time, overall energy consumption, having adequate cooling capacity which takes account of projected growth, and other downstream equipment parameters such as specifications on the hauler, saw-speed, and packing. In approaching optimized additive use, it is essential first to establish the part to be made, the required product attributes, the primary material components, and the process technology, and then design the additive package to ensure performance requirements are met and unit costs are optimized. Tables 2.1–2.3 summarize the functions, materials and dosages for polyethylene-, polypropylene-, and polyvinyl chloride-based composites. Table 2.1 Polyethylene (PE)-based composite Function Material Dosage range (%) Matrix component Polyethylene resin Difference from total of other components to 100% Matrix component Natural fiber 30–60 Coupling agent Maleated polyolefin 2–5 Lubricant(s) Stearates/esters/EBS/other 3–8 Antioxidants Phenolics/phosphites 0–1 Acid scavengers Stearates/hydrotalcites 0–1 UV protection HALS/benzophenones/benzotriazoles 0–1 Mineral filler Talc 0–10 Biocide Zinc borate 0–2 Density reduction Microspheres/chemical or physical blowing agent 0–5 UV protection/aesthetics Pigments As required Flame retardants/smoke suppressants Various As required Table 2.2 Polypropylene (PP)-based composite Function Material Dosage range (%) Matrix component Polypropylene resin Difference from total of other components to 100% Natural fiber 30–60 Lubricant(s) Stearates/esters/EBS/other 3–8 Antioxidants Phenolics/phosphites 0–1 Acid scavengers Stearates/hydrotalcites 0–1 UV protection HALS/benzophenones/benzotriazoles 0–1 Mineral filler Talc 0–10 Biocide Zinc borate 0–2 Density reduction Microspheres/chemical or physical blowing agent 0–5 UV protection/aesthetics Pigments As required Flame retardants/smoke suppressants Various As required Table 2.3 Polyvinyl chloride (PVC)-based composite Function Material Dosage range (%) Matrix component Vinyl Difference from total of other components to 100% Natural fiber 30–40 Heat stabilizer Various 1–3 Lubricant(s) Stearates/paraffin/esters/OPE/EBS/other 3–8 Acid scavengers Stearates/hydrotalcites 0–1 UV protection HALS/benzophenones/benzotriazoles 0–1 Mineral filler Carbon filler 0–10 Biocide Zinc borate 0–2 Co-stabilizer Zeolite 0–3 Density reduction Microspheres/chemical or physical blowing agent 0–5 UV protection/aesthetics Pigments As required Flame retardants/smoke suppressants Various As required This table does not take into account most PVC processors use PHR versus %. 2.2 Lubricants and rheology control additives for thermoplastic composites
‘Lubricant’ is a generic term for many different chemicals that affect the rheology of molten thermoplastics, whether or not they contain fibers. The rheological effect of additives intended for other functions can be seen in unfilled thermoplastics and is even more pronounced in highly filled thermoplastic composites. Lubricants are used to improve the rheology of the total formula so it will process as required. Rheology refers to how the melt...