Wood-plastic composites (WPC) may be one of the most dynamic sectors of today’s plastics industry. Since my last article about Wood-Plastic Composites (WPC) in March 2004 a lot has happened:
- Figures have been released showing increased demand from US$ 750 million in 2002
to S$2.1billion by 2004 and predicting a demand of US$ 3.5 billion by 2009.
- Primary markets are for decking and railing but fencing is starting to be commercialisedto S$2.1billion by 2004 and predicting a demand of US$ 3.5 billion by 2009.
- Industry associations have been formed (NADRA, CFDA)
- Products are being marketed as "low maintenance" instead of "no maintenance"
- Entry of the "big boys" (Louisiana-Pacific (LP), Alcoa, Dow, Weyerhaeuser)
- Second-generation technology (oriented WPCs) is now commercial and rapid growth is
expected in the next few years
expected in the next few years
- Agricultural fibres (wheat straw, soy straw and corn stover) are new cellulosic fillers,
which will augment and/or replace the supply of wood fibres for WPCs.
which will augment and/or replace the supply of wood fibres for WPCs.
University researchers have taken keen interest to study WPC products. Results are often found in polymer/plastics related conferences1-3. The intent of this article is to update the readers on the market trends and the future of WPC technology.
Market Trends
Construction is the major market for WPCs, with decking and fencing accounting for 2/3 of the market. WPCs accounted for 25% of the $3 billion market in 2006 for North American sales of residential decking. And Wood still has 70% of the market, vinyl has only 4% and other plastics and metal contribute the remaining 1%.
In 2004, the main manufacturers of decking were Trex (34%), TimberTech (11%), LP (11%), AERT (6%), Fiberon (5%), and Epoch (5%). But at this time composites only provided about 10% (368 Million Lineal Feet) of the 3.5 billion lineal foot decking market. Decking has become so important in the market that it now boasts it own trade show (DeckExpo), magazine (Deck Builder) and trade association (NADRA – North American Deck & Railing Association).
Fencing is about to take off. The $5.5 billion North American market for fencing is dominated by chain link fence. WPC fencing is barely on the charts but several WPC manufacturers (Trex, Fiber Composites, TimberTech, AERT, Composatron, Royal, Heartland Biocomposites, and Woodguard) have announced fencing products – primarily residential privacy fencing which accounts for 80% of the residential fencing market. The American Fence Association (AFA) who runs the annual trade show FenceTech, have formed another trade association, CFDA (Composite, Fence & Deck Association) and published a new magazine Deck World.
The biggest change on the manufacturing scene is the addition of very large companies to the current list of about 50 manufacturers. The first was Louisiana-Pacific (LP) with their "Weatherbest", followed by Alcoa with their Alcoa Home Exteriors division (Oasis). A year ago, Dow chemical announced its arrival with the introduction of their "Symmatrix" decking line. In October 2006, Weyerhaeuser purchased PSA Composites LLC; the company that pioneered the second-generation oriented WPCs, and is planning to manufacture a low-density material, which is twice as strong, and half the weight of the first-generation WPCs.
The biggest change in advertising is the marketing of WPCs as "low maintenance" instead of a "no maintenance" material. To stop the growth of lichen or other microorganisms on WPCs, periodic washing is advised.
Doors, windows, siding, roofing, and trim are being developed for other residential construction markets. Doors and windows have been available for some time. The other products are in various stages of product development and market introduction.
Non-construction markets that are of growing importance are docks, landscape architecture and bridges. Everarch has recently made a major step forward with structural WPCs, building and installing several pedestrian bridges for walking trails, golf courses and municipal parks.
Government Interest
An indication of government interest in this area is provided by recent announcements:
- In the United States, an article reported that the U.S. Department of Agriculture and the U.S. Department of Energy have granted $790,000 to Louisiana State University at Baton Rouge, LA to make natural fiber-reinforced plastic composites. The LSU project, led by Dr. Qinglin Wu, will use recycled plastics and wood or other agricultural fibers. The market identified for the results of this work is the construction market.
- In the United Kingdom, the Department of Trade and Industry is providing £278,000 funding towards the £777,000 Combine project to develop plastics durable enough for car doors and boat-hulls which are light-weight, but environmentally friendly. The 2½ year project will develop prototypes using natural fibres and bio-plastics. The companies involved in the U.K. are NetComposites and Aptiform.
- In Canada, there is interest and support at both the federal and provincial government levels. At the federal level, Agriculture & Agri-Food Canada announced a new program to focus on commercialization of new agri-based products. The $134 million funding is to get ideas from the drawing board into the market. Bioproducts are especially identified.
- The Ontario government is funding Renewable Auto Technologies. The $5.9 million investment in the Ontario Bio-Car Initiative is a research project to turn Ontario’s harvest (wheat, corn, soybeans and forest biomass) into viable materials for the auto industry. Four Ontario universities involved in the research program (Guelph, Toronto, Waterloo and Windsor).
The Technology Evolution
Polyethylene is the dominant resin used in WPCs but PVC and polypropylene are used and are expected to become more important in the future.
The primary process technology for WPCs is extrusion using either single-screw or twin-screw extruders. The resulting WPC profile is typically a deck board (1" x 5 ½"), with a density of 1.1 to 1.2 g/cc, a flexural strength (MOR) of 3,000 to 3,700 psi. while a flexural modulus (MOE) of between 300,000 and 600,000 psi.
The use of Injection moulding to process WPCs is becoming more common. It is being used to make accessories like railing post caps and trim pieces. Injection molding uses WPC with a maximum content of 40% wood fibre whereas the extruded product can contain 50 to 60%.
Specialised equipment has been recently been developed to process WPCs, since the available process equipment had its limitations. B&P Process Equipment of Saginaw, MI have made a major step forward in extrusion technology with the development of a twin-screw co-rotating extruder that produces pressure without the need for a secondary device such as a single-screw extruder or a gear pump. Cincinnati Milacron is marketing this TE series of extruders. Krauss-Maffei, have recently introduced an injection moulding compounder, with a twin-screw extruder mounted on an injection-molding machine that ram injects the output of the extrusion compounder. This development is illustrated with a WPC injection molded pallet. More about extrusion machine and its manufacturers have been described elsewhere4.
Second-generation WPC technology
In this new development, orientation is used to increase the thermoplastic polymer's properties enormously, in a similar way to that achieved in a one dimensionally oriented monofilament fishing line, biaxially oriented polypropylene film, or natural products such as wood, where uniaxial-oriented, bulk orientation gives greater physical properties in the direction of the grain than across the grain.
Second generation WPC products include oriented polypropylene that has a draw ratio of 12:1 providing a flexural strength increase from 7,000 p.s.i. to 40,000 p.s.i. – 6 times increase; and a flexural modulus increase from 270,000 p.s.i. to 1,100,000 p.s.i. – a four-fold increase.
PSA Composites developed this technology and Green Forest Engineered Products (GFEP) in Nevada, MO was the first licensee. GFEP now manufactures a line of products, specialising in fence posts used for electric fences for rotational grazing. Instead of becoming the second licensee, Weyerhaeuser, the forest products giant, purchased PSAC and in the near future is planning to manufacture low-density composites, that are twice as strong and half the weight of first-generation WPCs.
Manufacturing with other processes
While the orientation process has not yet been commercially applied to processes other than thermoplastics extrusion, a number of applications are under development
· A new company, MKM AutoTech, has been formed in Canada based in Guelph, Ontario with the explicit purpose of developing and commercializing injection moulding of oriented thermoplastics. The company is currently working with three injection moulding manufacturing companies and plan to work with several companies who are injection moulding automotive parts. The company will also be taking advantage of funding from the Ontario Government as well as newly formed Ontario BioAuto Council.
· A sheet of low-density embossed WPC sheet (12" x 5 ½" x ¼") has been thermoformed into a tray with the retention of the low-density and the embossed wood grain. This demonstration shows that thermoforming is possible. Efforts are currently underway to obtain support from commercial thermoforming processors to make demonstration parts for the automotive and packaging industries.
· Hydroforming is a steel-forming process where high-pressure water is used to form steel pipes into automotive parts such a car and truck chassis. Recently work at McMaster University under the direction of Dr. Mukesh Jain, has progressed to show that hydroforming of oriented thermoplastics, has reached “Proof of Concept”. The next stage will involve making automotive parts to show that this technology is practical and economic.
The Challenges and the Future of WPCs
Wood K Plus provided a world market overview of the production of WPC in 2005 at the Bordeaux WPC conference in March 2007. It showed North America produced 700,000 tons of which WPC, 80% was growth from the last 5 years. Europe was next with 100,000 tons all of which 100% was growth from the last 5 years. Similarly with neither China (50,000 tons) nor Japan (40,000 tons) produced any WPC 5 years ago. Obviously, the availability of fibre for WPCs is a major issue.
The question of fiber availability was addressed by a report sponsored by the U.S. government entitled "Forest and Agricultural fiber resource availability", (April 2005).
This report estimates that the total resource potential is1366 million dry tons per year. Of this, the forest resources are 368 (roughly 1/3) and the agricultural resources 998 (roughly 2/3). Agricultural fibres should be a major raw material in the future because agricultural fibre sources can provide comparable physical properties and they are usually closer to the market than forestry fibre sources and transportation costs are a major part of the cost of this raw material for the WPC manufacturers and poses additional challenge. Rice hulls are already being used as a substitute for wood fibre in WPCs currently being manufactured. Heartland Biocomposites have recently announced the first commercial use of APCs (Agricultural fibre/Plastic Composites). The company is using wheat straw and recycled plastics in their production plant in Torrington, WY for the production of fencing, decking and sheet products.
Among others current development activities include the use of nano-fillers, bio-resins and thermosetting systems. These works are in the early stages of commercialization. From this short update, it should be evident that orientation of thermoplastics will be a major element in the ongoing dramatic growth of thermoplastic composites as illustrated by WPCs and APCs. These will be described at a later date. Keep tuned.
References
- S-K Yeh, K-J. Kim, and R.K. Gupta; Cincinnati, ANTEC 2007, p. 2235
- L.M. Matuana and O. Faruk; Cincinnati, ANTEC 2007, p. 1248
- J. Muzzy, X. Xu, and A. Ragauskas; Cincinnati, ANTEC 2007, p. 2240
- R. Stewart; Plastics Engineering, 63 (2), pp.22-26 (2007)
Frank Maine,
Frank Maine Consulting Ltd., 71 Sherwood Drive, Guelph, Ontario N1E 6E8 Canada
Dr. Maine is an organic chemist with a B.Sc. and an M.Sc. in Engineering Chemistry from Queen's University and a Ph.D. in organic chemistry from Cambridge University. He held various positions in government laboratories and in industry in various areas of plastics engineering. He was Manager of Research and Development at Fiberglas Canada.
Dr. Maine is actively involved in the commercialization of oriented plastics. Currently, he is working with a group of companies that are developing and commercializing oriented thermoplastic and composite products including woodfibre/plastic composites. He has given numerous presentations and is often sought speaker in WPC technology including being Conference Chair of the Executive Conference Management Annual Conference on WPCs.
Previously, he was the Member of Parliament (Canada) for the Guelph riding of Wellington from 1974 to 1979.
