Wood-Plastics composites

The plastic fraction used in WPC is usually recycled PE, PP, PET, PVC PS, or a mix of these. Wood fiber as well as other natural lignoceUulosic fibers can be used as the filler the characteristics of fibers that are good candidates are shown in Table 5.9. Being of natural origin, a given type of fiber can have a large variation in properties (Kouini and Serier, 2012). The use of compatibilizers or pretreatment of the wood fraction is often employed to ensure good dispersion of filler in the plastic matrix. 

WPC does not outperform wood in most environmental attributes. For instance, a recent (Bohn and Smith, 2011) cradle-to-grave LCA was carried out on the environmental merits of WPC based on recycled plastics and those of treated wood, for deck con-stmction (Clanons, 2002). In every category, the treated wood (with copper oxide and dodecyl dimethyl ammonium chloride) outperformed WPC material. The energy cost of WPC was 8.5 times that of treated wood. But when compared to plastic building materials, WPC nearly always turns out to be better from an enviromnental standpoint, based on in several LCA studies (Corbiere-NicoUier et al., 2001 Wotzel et al., 1999). 

FIGURE 5.5 A deck made of wood-plastic composites. TABLE 5.9 Candidate Wood Fibers For Wood-plastic Composites 

Source Reproduced with permission from Pritchard (2007). 

The authors found that the depression of glass transition temperature (Tg) due to the addition of plasticiser is substantially reduced by the loading of wood flour. In addition, various wood-plastic composites were compounded into different colours, and several pairs of the compounds with different rheological properties were extruded in single and twin-screw extruders to see whether any wood-patterns are developed. When the differences in the shear viscosity and the Tg of the two compounds were too large, the incomplete plasticisation of the higher viscosity component was observed due to the lower viscosity component. It was found also that distinct wood-patterns were only developed both inside and on the snrface of the extruded prodncts for the pairs of the composites with optimal differences in both viscosity and plasticiser content. 

The effects of wood flour, acrylic impact modifier, and plasticiser on the rheology of PVC based wood-plastic composites have been presented. The anthors tried to determine an optimal pair of wood-plastic composites that would exhibit substantially different rheological characteristics at high shear so that patterns similar to the grain of wood can be developed inside and on the surface of the product if two composites with different colours are extruded at once. 

The shear thinning, and the shear viscosity were increased as the wood flour content was increased and they decreased with increasing temperature. Also, plasticiser significantly reduces the viscosity of PVC, while the addition of impact modifier to PVC yielded little 

It was also found that when the wood flour content was high, the addition of a large amount of impact modifier increased the viscosity of the composites. The depression of the Tg due to the addition of plasticiser can substantially be reduced by the loading of wood flour. 

The production of WPC typically uses a fine wood waste (sawdust in the 40 to 60 mesh range) mixed with various plastics. The powder is extruded to a dough-like consistency and the profile is then extruded through a single-step die with no additional calibration and only a simple water bath for cooling. 

WPC have successfully proven their application in various fields, including lumber, decking and railing, window profiles, wall studs, door frames, furniture, pallets, fencing, docks, siding, architectural profiles, boat hulls and automotive components. The market for WPC has been experiencing growth both in North America and Europe [52]. 

The advantages of WPC include increased bending strength, stiffness (flexural and tensile modulus), reduced thermal expansion and cost. Mechanical properties such as creep resistance, modulus and strength are usually lower than those of solid wood. WPC are not being nsed in applications that require considerable structural performance [53], although in early 1984, cellulose flour was used to reinforce PA to give PA 12 [54]. 

Thermoset composites are mainly considered due to their intrinsic fire resistance. They provide low flame spread and very low smoke emissions without any addition of halogenated fire retardants or higher loading of filler or reinforcing materials. Phenol-formaldehyde and urea-formaldehyde are the most common thermosetting resins used as adhesives for wood composite products, including plywood, particleboard, fibreboard and oriented strand board [66-69]. 

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The improved physical and mechanical properties of the wood-plastic composites lead to a diversity of applications, e.g., automotive parts, furniture, construction (e.g., building panel, flooring veneers), toys, cutlery handles, industrial pattern, sports equipment, musical... 

TIR tooling indicator runout wpc wood-plastic composite... 

Hill, C.A.S. (2000). Wood-plastic composites strategies for compatibiUsing the phases. Journal of the Institute of Wood Science, 15(3), 140-146. 

Synthetic wood or wood-plastic composites (WPC) made from rigid PVC heavily filled with wood flour, extruded in wood-like profiles that can be sawn, nailed and screwed just like natural wood. .. 

Apart from PVC and other commodity plastics, engineering plastics and wood-plastic composites are used for specific advantages corresponding to specific applications. 

Wood-plastic composites based on 30% to 70% natural fibre-filled polypropylene, polyethylene, polystyrene and PVC. 

Wood-plastic composites (WPC) are used as building material for decking, fencing, siding. .. for the low maintenance constraints. US demand is forecast at 2.5 billion through 2008. 

In addition, ABS that has been recovered can be recycled into high value composites without separation from impurities. This has been exemplified with wood-plastic composites that contain ABS as matrix polymer. Both virgin ABS and recycled ABS were used and the properties of the materials were compared (126). In order to increase the performance, coupling agents were used, all based on grafted maleic anhydride. 

S.-K. Yeh, S. Agarwal, and R.K. Gupta, Wood-plastic composites formulated with virgin and recycled abs, Compos. Sci. Technol., 69(13) 2225-2230, October 2009. 

Dunbar of Ontario, Canada and the Wee Piper of Vermont are producing bagpipes and chanters from catalyst-heat wood-plastics supplied by Wing Archery. The wood-plastic composite has replaced the black African wood usually used for bagpipes. Pipers claim that the tone of the new wood-plastic chanter is more mellow. Traditionally, bagpipe parts of ebony wood are black and this intense black has not been duplicated in wood-plastics. Generally, wood-plastic bagpipe parts are made in the natural maple color or dyed a deep brown. 

Kelly Putters of Oregon produces a variety of putters made from catalyst-heat wood-plastics using myrtle wood and broad leaf maple which is native to the state. The light and dark wavy grains of these two woods are enhanced by the plastic treatment and have a three dimensional depth in their natural color. Several other golf club manufacturers have made small quantities of wood-plastic laminated birch and solid persimmon drivers for market studies. The dimensional stability of the wood-plastic composite is important during the manufacturing when the various face and base plates are inserted. 

Fifteen years ago, when wood-plastic composites were first introduced many people predicted that this process would solve the problem of wood dimensional stability and great claims were made for its future use. Now that the physical properties of wood-polymer composites are better understood, specific commercial products are being produced which take advantage of the desirable aesthetic appearance, the high compression strength, increased hardness and abrasion resistance and improved dimensional stability. Future use of wood-polymer composites will depend upon the imagination of the producer and the market place. 

It is significant that in the excellent and detailed book by Hebeish and Guthrie (4) only 16 out of 342 pages are devoted to this subject. Of these, 7 are on wood-plastic composites which are mainly in-situs polymerized monomers and only partially grafted. Nevertheless, they are closely related and with worldwide industrial applications. Details of these have been discussed not only in the above references but numerous other reviews and reports (37,38). These should be consulted for further details. 

In 75% of the cases, wood fibres are the preferred filler for thermoplastic matrices. Their high availability may account for this. The resulting composite material is internationally known as WPC, which stands for wood plastic composite. They have been produced industrially since 1980 and the market has gradually increased in the last 10 years, especially in the United States, reaching 700 000 metric tons with an 11% increase rate per annum. In Europe, the WPC market is considered to be emerging. At the best estimations, it reached only 100 000 metric tons in 2005 (Anonymous, 2006) and in lapan the market is even smaller. In America, more than 50% of the WPC is used for parquets and decking made with polyethylene. In Europe, it is the automobile sector that is preponderant with polypropylene-based composites. 

Anonymous. Wood-plastic composite growth taking off in Europe... while strong WPC growth continues in the USA.. Additives for Polymers (5) 9—11 (2006). 

Wood Plastic Composites (WPC) In WPC applications, it was claimed that the addition of organic phosphate, zinc borate/boric acid, sodium silicate, or ATH to milled rice straw with a resin binder can produce a fire-resistant board.65... 

Figure 14.22 Example of a line for the manufacturing wood-plastic composites...

Wood-plastic composites offer a number of benefits ... 

This research project represents initial studies into a new approach to blending thermoplastic materials like polystyrene with wood materials, leading to a new class of wood-plastic composites. Traditional wood-plastic composites have involved the impregnation and subsequent in situ polymerization of vinyl monomers. This procedure has been adopted for selected products for which improved physical properties justify increased production costs. While producing mixtures or blends of wood and plastics, these types of composites do not demonstrate significant chemical bonding between the wood and plastic components. 

When wood meals are kneaded with synthetic thermoplastic resins, the mixture shows hot-melting behavior as these plastics act as external plasticizers [20]. However, such wood plastic composites lack a fibrous construction and do not show the excellent properties of solid wood such as beautiful grain and color, tactility, or insulation. 

Wood-plastic composite specimens (WPG) were prepared by impregnating the oven-dry specimens with a solution of methyl methacrylate containing 1 % a,a -azobisisobutyronitrile as a catalyst, wrapping the specimens in aluminum foil, and curing the polymer at 80°C for 3 h. The structure of pattern (A-5) and (A-6) + (B-6) and (B-9) can be obtained under experimental conditions, but pattern (A-2) and (A-3) + (B-1) can be expected in industrial practice. 

Other important products include radiation cross-linked foamed polyethylene which is used for thermal insulation, floor mats, crash padding, floating jackets, and wood/plastic composites cured by gamma irradiation. These have been used successfully for flooring in places such as department stores, airports, hotels, and churches where their excellent abrasion resistance, the beauty of the natural grain, and low maintenance costs are important. This latter technique is also being used in the conservation of objects made of stone and wood of interest to our cultural heritage. 

Clemons C (2002) Wood plastic composites in the United States the interfacing of two indastnes. Forest Products Journal, 52(6) 10-8 Clifton NC (1978) Sprinkler storage of windblow proves effective and economic. Wood World, 79(12) 26-7... 

Wolcott MP and Englund K (1996) A technical review of wood-plastic composites. In Maloney T (ed) Proceedings of the 33rd Washington State University Particleboard Symposium, Pullman, Washington, 117-43... 

Wolcott MP (2004) Engineered wood-plastic composites. Conference on Wood Utilization Solutions to Hazardous Fuels. December 14-15. Spokane, WA Wood JR and Goring DAI (1973) The distribution of lignin in fibres produced by kraft and acid sulphite pulping of spruce wood. Pulp and Paper Magazine of Canada, 74(9), 117-21 (T309-13)... 

Wood plastics composites (WPC) - Anti rot, smface growth and anti-algal products for wood plastics composites (the growth of wood rot fungi on WPC is seen in Figure 6). 

CZVTKOVSKY, TIBOR. Radiation Processing of Wood Plastic Composites. Radiation Processing of Polymers. Hanser Publishers, New York (1992) 121-148. 

CZVIKOVSZKY T., Radiation processing of wood-plastic composites, in Radiation Processing of Polymers, (eds A. SINGH, J. SILVERMAN), Hanser - Oxford Univ.Press, Munich, NewYork, 1992. 

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