Applications of WPC Products

There are a variety of WPC products in the market These commerdal products could originate from virgin or recycled polymers and virgin or reclaimed wood. For instance, Andersen Windows Company utilizes waste PVC from their manufacturing plant in producing WPC window components. Certain Teed Company uses recycled fibers in their Boardwalk plastic composites. Some examples of WPC products and their major components are listed in Table 13.4, with a focus on the United States, which has the biggest WPC market for building applications. 

Wood-plastic composites was bom in Europe and experienced dramatic growth in North America in 1990s. In 1973, a company named SonessonPlast AB (Sweden) promoted a PVCAVF composite product with the trade name Sonwood . This was probably the first commercial WF/PVC composite in the world. Ten years later, in 1983, Woodstock appered in Italy, which consisted of 50 % WF and 50 % PP. WF and PP were extruded into a flat sheet that was then formed into different shapes. It was then applied in interior automotive paneling by Ford Motor Company, becoming the first major applications of WPCs in the United States. 

The expanding commercial production and marketing of WPCs for use in exterior applications has encouraged research on the durability and service life of WPCs. 

Shebani et al. [20] noted that removing extractives improved the thermal stability of different wood species. Therefore, using extracted wood for the production of wood-plastic composite (WPCs) would improve the thermal stability of WPCs. Because wood and other bio-fibres easily undergo thermal degradation beyond 200°C, thermoplastic matrix used in the composites is mainly limited to low-melting-temperature commodity thermoplastics like polyethylene (PE) and polypropylene (PP). However, the inherently unfavourable thermomechanical and creep properties of the polyolefin matrix limit some structural applications of the materials. 

The production of WPC by UF is today a well-established application in the food and dairy industry. WPC can be further fractionated in j3- and a-lactoglobulin fractions by properly selectingpH,ionicstrength and temperature (Zidney, 1998), or used for the manufacture of caseino-macropeptides with pharmotherapeutic value. 

The most common types of the new WPC are produced by mixing wood flour and plastics to produce a material that can be processed just like a plastic but has the best features of wood and plastics. The wood can be from sawdust and scrap wood products. This means that no additional wood resources are depleted in WPC, waste products that currently cost money for disposal are now a valuable resource - recycling can be both profitable and ethical. The plastic can be from recycled plastic bags and recycled battery case materials although in demanding applications, new plastics materials are used. Thus it is interesting to use materials recovered from short life cycle applications in long life cycle applications. The benefits of WPC combine the best features of wood and plastics. 

Because of their performance, easy installation, and cost-effectiveness, WPG products are being selected by homebuilders over other materials such as solid wood, concrete, clay, and aluminum, especially as biulding materials for applications like decking, siding, and window and door frames. WPCs are also used as molded panel components for automotive interiors. The market for these composites continues to expand in the United States and other parts of the world. In 1999, 460 million poimds of WPCs were produced in North America (56). In 2000, production of these composites increased to 760 million poimds and experts believe that the production of WPCs will continue to grow particularly because of their acceptance as a substitute for chromated copper arsenate pressme-treated lumber (57,58). 

The enthusiasm in this field is explained by the number of potential applications. For example wood-polymer composites (WPC), mostly manufactured through extmsion and injection moulding processes are used in automotive (dashboards or screen-doors of the vehicles) and construction applications (interior floor coverings, profiles for doors and windows, ornamental panels, external shutters, pavements, garage, or entrance doors). Replacement of wood products for building applications such as particleboard and fiberboard materials or injection mouldable wood is another area where natural fibers are generating increased interest. 

Wood plastic composites (WPCs) products have emerged as a new class of materials that can be used as alternative to solid pressure-treated wood in a variety of innovative applications, such as decking, docks, landscaping timbers, fencing, playground equipment, window and door frames, etc (1,2). 

Enhancing the drawbacks of WPCs (e.g., lower flexural strength and modulus) could not only improve their acceptance in load bearing structural applications but also open new applications for these products, thus expanding their market share. 

Whey may be substituted for starch by as much as 25% in extruded corn snacks, but the product does not puff as much as com alone, as the water-holding whey protein does not react with the starch matrix (Onwulata et al., 1998). WPCs or isolates can be added along with starch to create expanded snack foods with boosted nutritional content however, without texturization, whey proteins in amounts larger than 15% may interfere with expansion, making the products less crunchy. To counter this effect, whey proteins can be texturized with starch to improve their interaction with other food components in a formulation, principally to increase extmdate expansion. In one successful application, between 25% and 35% of the flour was replaced with whey protein (Onwulata et al., 2001a,b). 

Although heat-denatured whey protein, referred to as lactalbumin, has been available for many years for food applications, it was of little significance, mainly because the product is insoluble and therefore has limited functionality. The commercial production of functional whey protein became possible with the development of ultrafiltration in the 1960s. Whey protein concentrates (WPCs) produced by ultrafiltration are now of major commercial importance, with many specific food applications. Superior whey protein products (whey protein isolates, WPI) are being produced on a limited scale by chromatography, although their substantially higher cost has limited their production. 

Membrane processing. The use of ultrafiltration (UF) for the production of whey protein concentrates (WPCs) is now well established (p. 223). Obviously, UF or diafiltration (DF) can be used to prepare products enriched in total milk protein. Products with protein concentrations up to 85% have been produced and assessed for a range of functionalities and applications (Fox and Mulvihill, 1992). 

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