WPC Products

The public view of WPCs is hard to evaluate more or less objectively. Many have never heard of WPCs. Many prefer real wood, and they are hard to blame. Wood is an excellent material, far exceeding WPC in many properties, first of all in strength and stiffness, in slip resistance, and in many types of wood—in fire resistance (except PVC-based wood composites). Common wood, however, is an inferior material compared to WPC with respect to water absorption, microbial degradation, and durability. There are exceptional types 

Overall, great many customers have gladly accepted the appearance of WPG in the market, though many are doubtful and many have rejected them outright. Nevertheless, WPC-based building products are capturing the market with pretty high speed for the last 10 years. 

It should be noticed here that bioresistance of WPG deck boards is diminished with the increase of wood fiber content (above 40%) and increased with mineral content (silica, calcium carbonate, talc, etc.). 

WPG decks require, though, normal washing, cleaning, and other care, as conventional wood decks do. It is obvious that a barbeque on a deck would unavoidably lead to grease and fat stains when potato salad is dropped upside down on a deck (and there is no other way for potato salad to drop, as everyone can testify), made of either wood or WPGs, leaves stains, which are not easy, though possible, to remove. In fact, it is much easier to remove grease from WPG deck than from a wood deck. 

Overall, a WPG deck is much more durable than a wooden deck and requires much less work in a long run. This is certainly attractive for some people. However, it requires a steep payment upfront. This is repulsive for other people. Both features of WPG affect the public acceptance, and both are considered as a practicality issue. 

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A modification of the swelling apparatus was used to evaluate WPC, peanut protein, single cell protein (SCP), and chicken preen gland protein. Chicken protein exhibited the highest swelling values followed in decreasing order by peanut, SCP, and WPC products (15). 

Whey protein concentrates (WPC) are produced by a variety of processing treatments to remove both lactose and minerals (20) as indicated in Figure 5. Even though it would be highly desireable to remove most of the lactose and minerals in these processes, it is not practical from an economic standpoint and thus most of these products only range in protein content from 35 to 50 %.The major objective of most of these processes is to produce a WPC with minimal protein denaturation in order to obtain a product with maximum protein solubility and functionality. However, from a practical consideration this objective is not readily obtainable, and thus most WPC products commercially available exhibit variable whey protein denaturation and functionality (20). 

Whey protein concentrates (WPC), which are relatively new forms of milk protein products available for emulsification uses, have also been studied (4,28,29). WPC products prepared by gel filtration, ultrafiltration, metaphosphate precipitation and carboxymethyl cellulose precipitation all exhibited inferior emulsification properties compared to caseinate, both in model systems and in a simulated whipped topping formulation (2. However, additional work is proceeding on this topic and it is expected that WPC will be found to be capable of providing reasonable functionality in the emulsification area, especially if proper processing conditions are followed to minimize protein denaturation during their production. Such adverse effects on the functionality of WPC are undoubtedly due to their Irreversible interaction during heating processes which impair their ability to dissociate and unfold at the emulsion interface in order to function as an emulsifier (22). 

As can be seen from Figure 19.27 skim milk can be fractionated by means of UTP MF (0.1 pm), in combination with an UF diafiltration step, in its two main protein fractions, i.e. native casein micelles and native whey proteins since no heat treatment step was required to separate the proteins. The MF permeate can be considered a sort of sweet whey, however, without containing the caseinomacropeptide (CMP). This MF permeate can be further concentrated to obtain a WPC product. The... 

Traditional composite panels are made from veneers and from mat-formed eomposites bonded by adhesive. More recently wood has also been combined (eompression moulded or extruded) with synthetic polymers, e.g. thermoplastic polymers, to make wood-polymer composites (WPC). WPC products have been growing very rapidly in the recent years, especially in the deeking market, where Woleott (2004) observed that their market share has grown from 2% in 1997 to 14% in 2003. Further, much research work has explored the use of fibre-reinforced polymers (FRP) to enhance the structural performance of engineered wood eomposites, ealled FRP-wood hybrid composites (Dagher et ai, 1998 Shi, 2002). 

WPC formulations that invite mold are those with a relatively high porosity (typically made using moist wood fiber) and, hence, having lower density that it might be in the final product. Particularly, it happens if the WPC profile is extruded in the absence or with not enough amounts of antioxidants. Typically, these WPC materials absorb more water than other WPC products in the market. Formulations that make mold on the deck is less likely, contain not only antioxidants but also minerals, which create a natural barrier for microbial degradation of WPC materials. Obviously, biocides and other antimicrobial agents in the formulation help to prevent or slow down mold on decks. 

How to reduce density of WPC products in controlled way, without the presence of moisture in raw materials... 

Simple ways to measure rheology of WPC hot melts to characterize and predict performance of WPC products... 

The above examples show some empirical data. In the absence of truly systematic studies in the area, it is rather risky to draw some general conclusions. However, even those scattered data provide some guidelines in further experimenting and justify certain anticipations in behavior of filled WPC products. 

The reason for the adapted ASTM procedure is that plastic lumber (and WPC products) is generally nonuniform through the cross section, and small cut specimens sometimes give large variations in compressive (and other) properties. 

M. Manning. Creating value in WPC products with anti-microbials and stain resistant additives. In WPC Conference 2004, Baltimore, MD, Principia Partners, Cleveland, OH, October 11-12, 2004. 

Photooxidation of plastics and wood-plastic composites (WPCs) was described in principal detail in the preceding Chapter 15. It was emphasized that photooxidation acts in a synergism with thermooxidation of the materials, speeding up an oxidative degradation of WPC products, particularly being exposed to direct sunlight. 

By far, wood particles are the major raw material source used for manufacturing WPCs. Wood particles can originate from sawdust, planer shavings, short solid pieces of lumber, conventional wood composite scrap [6], and scrap pallets [12], Both softwoods and hardwoods can be used for WPC production. Currently, most WPCs using softwoods are made with southern yellow pine, while WPCs produced with hardwoods are made with oak, maple, or aspen. The anatomical features as well as physical, mechanical, and chemical properties of softwoods and hardwoods differ considerably among species, and may affect the wood-polymer interface, and, as a consequence, the composite s properties and performance. 

A variety of wood particle sizes are used to produce WPCs depending on the type of product. The dimensions of wood particles are usually measured in mesh size as the particles resulting from passing through a mesh with a given number of mesh squares in a square inch. The wood used in WPCs is most often in particulate form (wood flour) or very short fibers rather than longer individual fibers. Commonly, mesh sizes 20, 40, 60, and 80 are used in WPC production. 

WPC is claimed to be superior to natural wood in several ways. Its main features can be summarized as follows (1) the thermoplastic polymer component resists rot and insects, thus providing an inherently longer product life and less maintenance requirement than wood alone (2) the cellulosic fiber content provides reinforcement, increases the rigidity of the product compared to the polymer component (3)WPC products can be worked like wood using current tools and fastening techniques (4) WPC... 

Ponderosa pine, a common species used extensively in window and door manufacture and routinely made into wood floor, is a good overall performer. Other species, such as maple, oak, and many other hardwoods and softwoods can be successfully used. The density of hardwoods can be almost twice that of softwoods and so will result is a heavier product. Moreover, some wood fibers are more durable than others depending on the environmental conditions (wet or dry). Also the modulus is generally higher for hardwoods resulting in a stiffer WPC product. 

Some of the most common sources of recyclate wood feedstocks suitable for composites include [269] (a) primary wood wastes (such as wood wastes from sawmills (b) secondary wood wastes (generated when wood products, such as furniture, cabinets and doors are made) and (c) postconsumer wood wastes (which can include anything from construction and demolition debris to packaging, crates and pallets. Primary and secondary wood wastes are the key materials used for WPC production in the U.S.A. 

The processes that can be used for the manufacture of WPC products are compounding, extrusion, injection molding and pultrusion. Drying ofwood is an important prerequisite of WPC production since... 

In order to produce a WPC product by the extrusion process, it is required to first melt the polymer, then mix the molten polymer with the dried wood fiber such that a homogeneous melt is achieved and any remaining moisture can be removed by vacuum venting. The extruder then compresses the homogeneous blend to pass through the die. Various extrusion configurations have been developed for WPC product manufacture [274], some of which are described below. 

After the introduction of processing facilities for wood-plastic composites (WPC) by extrusion and later by injection moulding techniques, WPC production and its use increased almost exponentially. 

In the United States, approximately 75% of the WPCs are used in the building sector and approximately 50% of the entire market volume is used for terraces and patios. In the year 2003, the market share of WPC products for exterior use was 14%, comprising a financial volume of approximately 3.5 billion US. These so-called deckings consist of polyethylene with a wood percentage of 50-70%. 

In principle, WPC products are recyclable. They are melted down and processed into granules. A second extrusion or injection moulding is technically feasible. However, the quality of recycled WPCs and the reaetion of the wood component is still unelear. Furthermore, the blending of various plastie eomponents often makes the recycling even more complex. ... 

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