WOOD FIBRE-REINFORCED PLASTIC

This chapter first gives an overview of cellulose raw materials and their molecular and supermolecular structures. The principles of shaping cellulose into fibres, films, and nonwovens by means of solution techniques are then outlined followed by a section on properties and market applications of these materials. Derivatives of cellulose are presented with special emphasis on thermoplastic cellulose esters, typical plasticizers, and promising reinforcing materials. Finally, recent developments and future prospects of cellulose materials are reviewed as far as the above applications are concerned. This book does not cover the important applications of cellulose and ligno cellulose fibres for reinforcing thermoplastics, like wood plastic composites (WPC) and natural fibre reinforced plastics (NFRP), since in these cases cellulose does not substitute a thermoplastic. 

Thus, substrates such as aluminium and its alloys, alloys of titanium, low- and high-carbon steels, nickel, copper, fibre-reinforced plastics (containing both thermoplastic and thermosetting matrices - in the latter case, the matrix might well also be a formnlated epoxy-based system), glass, concrete and wood are all encountered. This means that they can be, and indeed are, widely used in construction, aerospace, automotive (both original equipment and aftermarket), electrical and electronics, furnimre, foundry, consumer and abrasives applications. 

Window frames and doors PVC, foamed PVC (wood substitute), ABS (coextruded with vinyl modified ASA or polyolefins modified styrene acrylonitrile copolymer (SAN) -glass-fibre reinforced plastic (GFRP), composite based, ABS (thermoformed panels for high quality doors and window profiles)... 

With adhesive bonding, a large variety of substrates can be joined, such as glass, ceramics, plastics, fibre-reinforced plastics, metals and wood. Many more substrates and combinations are possible and each can have significantly different properties, in particular mechanical properties and surface conditions. 

Typical Use Automotive indusby Glass fibre reinforced plastics, e.g. Typical Use Highly stressed wrapping of PVC profiles. Wood wrapping ... 

Although aircraft structures comprise thousands of components produced from a myriad of basic materials, the most common substrates for structural adhesive bonding are wood, aluminium, titanium, stainless steel and the composite materials such as bonded sandwich structures, fibre reinforced plastic (FRP) laminates and fibre-metal laminates (FML) where the metal is usually aluminium. 

Structure - The material used for the construction of a fishing vessel include wood, aluminium, fibre-reinforced plastics, high tensile steel and ferro - cement. The arrangements of aluminium and steel structures normally consist of shell plating supported by longitudinal members and, in turn by transverse frames. The structure must withstand the envisage forces imposed, such as sea forces, dead loads and cyclic forces. 

Chtourou, H., Riedl, B. and Ait-Kadi, A. (1992). Reinforcement of recycled polyolefins with wood fibres. Journal of Reinforced Plastic and Composites, 11, 372-394. 

Since the early 2000s, plant-derived biobased fibrous fillers have been frequently used for the reinforcement of PLA-based materials. A well known and frequently used plant-derived fibrous filler is kenaf. Like the case of pollen as an additive, the wettability between PLLA and kenaf should be improved by the addition of a compatibilizer. Other fibrous materials are cellulose fibrous materials or fibres [383,384], cellulose whiskers [385], recycled cellulose fibre [386], cotton fibre [387], sugar beet pulp [388], flax [389], bamboo fibre [390], kenaf [391-393], papyrus [394], hemp fibre [395], cuphea and lesquerella [396], ramie [397], rice straw fibre [398], red algae fibre [399], miscanthus fibre [400], abaca fibre [401], milkweed [402], wood fibre [403] and recycled newspaper fibre [404], Poly(L-lactic acid) fibre can also be used to reinforce soft plastics such as PCL [405],... 

Rubber from trees has been used in both solid and latex form, and also converted further into isomerized and chlorinated polymers of very different properties and uses. Wood from trees is used directly for plywood, composition board, and wood-flour reinforcement of phenolic resins. The cellulose from wood is purified and used for laminates and for regenerated cellulose products such as cellophane, viscose rayon, and vulcanized fibre. The lignin from wood has been explored for use in plastics, but never carried through to complete commercial success. 

Natural fibres possess sufficient strength and stiffiiess but are difficult to use in load bearing applications by themselves because of their fibrous structure. Most plastics themselves are not suitable for load bearing applications due to their lack of sufficient strength, stiffness and dimensional stability [51]. In natural fibre reinforced composites, the fibres serve as reinforcement by giving strength and stiffness to the structure while the plastic matrix serve as the adhesive to hold the fibres in place so that suitable structural components can be made. The matrix for the natural fibres includes thermosets, thermoplastics and mbber. Different plant fibres and wood fibres are fotmd to be interesting reinforcements for rubber, thermoplastics and thermosets [52-58]. 

Chemical compounds which contain reactive groups such as the methanol group (-CH2OH) as in methanolamine compounds are able to form stable, covalent bonds with cellulose fibres. This treatment decreases the moisture pick-up and increases the wet strength of reinforced plastics. Isocyanates are also suitable to modify the chemical structure via its reaction with the OH groups of cellulose. The mechanical properties of composites reinforced with wood-fibre and PVC or PS can be improved by an isocyanate treatment of those cellulose fibres or the polymer matrix. The improvement of the properties of the composites can be explained by the reduction in the number of OH groups responsible for moisture uptake and consequently the increase in the hydrophobicity of the fibre s surface... 

For obtaining a low -weight, high-bending-stiffness structure, sandwich constructions are a conunon choice for composite components. To make a sandwich, low-density materials are inserted as sandwich cores between two faces of the structural material itself (so in this case between two stacks of prepreg plies). Commonly used core materials are plastic foams (for example, made from PVC, PS, or PET) and balsa wood. Examples of core materials for more sophisticated, structured sandwich cores are honeycombs (made from aluminium, or resin-impregnated paper sheets), or fibre-reinforced foams. 

Lee KY, Bharadia P, Blaker JJ, Bismarck A (2012c) Short sisal fibre reinforced bacterial cellulose polylactide nanocomposites using hairy sisal fibres as reinforcement. Compos A 43 2065-2074 Lei Y, Wu Q (2010) Wood plastic composites based on microfibrillar blends of high density polyethylene/poly(ethylene terephthalate). Bioresour Technol 101 3665-3671 Liu D, Zhong T, Chang PR, Li K, Wu Q (2010) Starch composites reinforced by bamboo cellulosic crystals. Bioresour Technol 101 2529-2536 Liu H, Xie F, Yu L, Chen L, Li L (2009) Thermal processing of starch-based polymers. Prog Polym Sci 34 1348-1368... 

Virgin carbon fibre reinforced polymer Virgin polyethylene terephthalate Wide-angle X-ray scattering Wood-plastic composite(s)... 

Bonding of plastic retainers to wood-fibre panels, fixing air vents beneath instrument panels or reinforcing door panels with side-impact-protection parts also requires the fast-setting and durable properties with high resistance to mechanical stress and heat of PUR adhesives. 

The last two items of the earlier list involve the behaviour of primers, in part chemical, in part physical, as forms of adhesives sticking the bulk adhesive to the actual metal, wood or other adherend. When dissimilar materials are to be joined, an adhesive suitable for one may not be so for the other. In these circumstances a primer for one of the substrates is chosen to be both suitable for it and compatible with the adhesive. Phenol-formaldehyde condensation products are often thus used particularly when the adhesive itself contains such material dispersed in another polymer, e.g. Redux775 (Bonded Structures, Ltd) or various epoxy-phenolic or nitrile-phenolic adhesives. Most important members of the class of coupling agents are the reactive silanes (siloxanes) and titanates. These materials have achieved their main use in the treatment of glass fibres for the manufacture of glass reinforced plastics. 

The most important thing is to get the microspheres evenly distributed in the polymer matrix. It is therfore recommended to vibrate fluid compositions in the mold, especially in the case of large articles 2). Since molding compositions do not easily fill the molds, tamping and low pressures (0.5-2 MPa) are used for small, simple objects, while the molds for large or complicated objects are filled layer by layer1). The molds are made from plastic, reinforced with metal, wood or fibre their surfaces are degreased or covered with a separation layer. 

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