Wood-fiber and plastic extruded composites promise to expand beyond their current concentration in decking, researchers told delegates at the Progress in Woodfibre-Plastic Composites Conference 2002, held May 23-24 in Toronto.
Inroads have begun for other applications, thanks to higher wood-fiber loadings, improved strength, thicker constructions and new chemical additives, and the potential for improved distribution systems, they said. Lots of opportunity exists in residential siding, doors, window profiles and fencing. Industrial applications such as pallets and transportation infrastructure are potentially large markets.
Residential siding ``is on the radar screen'' for most major wood-composite producers, said Paul Smith, a professor at Penn State University's School of Forest Resources in State College, Pa. The total U.S. siding market was as much as $8 billion in 2000, half of which was vinyl, although fiber cement is gaining share rapidly.
Surveys of homeowners and builders indicate no current siding product is ideal, so wood-composite producers stand to gain by addressing issues such as ease of installation, aesthetics, durability and paintability.
Getting distribution systems in place will be key to developing new composite markets, Smith said. Decking's gains reflect its acceptance by big-box stores.
``Residential decking drives the industry in large part,'' Smith said. Rapid growth in composite decking has spawned about 15 major producers in North America, he estimated. Some speakers estimated decking accounts for about 70 percent of the wood/plastic composite market.
A possible side effect to mass-retailer involvement, however, could be pricing pressure in the future. Current wood/plastic composites, priced on the basis of low maintenance, are not very price sensitive.
New applications could arise from higher wood-fiber loadings, according to Daniel Beyts, head of the technical division of J. Rettenmaier USA LP of Schoolcraft, Mich. Conventional composites contain about 60 percent wood-fiber loadings, but Rettenmaier's system could go up to 90 percent, he claims. It relies on pure wood fibers supplied by Rettenmaier with lengths of 300-1,200 microns. Also key to the technology is a counter-rotating, conical twin-screw extruder and advanced dies.
Pulling a board through an orientation die improves strength properties useful to new applications, according to Frank Maine, principal with research company PSA Inc. of Guelph, Ontario. With polypropylene/wood-fiber composites, orientation by stretching decreases density as well, because the process introduces voids. Maine foresees new uses such as flooring and do-it-yourself furniture for such composites.
Bonding composite boards to create thicker constructions would be useful to replace timbers in uses such as docks, said Douglas Gardner, a professor at the University of Maine's Advanced Engineered Wood Composites Center in Orono, Maine. His studies show melt bonding could be viable at a processor's plant. Polyethylene-based composites are easier to bond than those based on PP, Gardner found.
Chemical additives also will help wood/plastic composites producers improve their products and gain new markets, predicted James Morton, principal with consulting firm Principia Partners of York, Pa. He predicts additives will help wood/plastic composite markets in North America grow from 850 million pounds in 2001 to more than 1.2 billion pounds by 2006.
Current health concerns about arsenic in pressure-treated wood could boost the demand for wood/plastic composites in the near term, Morton added. Wood companies will react quickly, however, and introduce substitutes for arsenic-based products, said Morton. In the long term, wood/plastic composites will not gain much market share from arsenic toxicity concerns, he said.
European markets for extruded wood/plastic composites have been slow to develop, according to David Plackett, a professor at the Danish Polymer Center at the Technical University of Denmark in Lyngby, Denmark. Only about 20 extrusion lines are installed in Europe to make such composites, although an equal number probably are planned, he said.
European efforts have focused on natural-fiber reinforcement of plastics for automotive uses, Plackett said. Hemp, flax, kenaf and sisal are among the fibers used to reinforce thermosets and thermoplastics.
Window profiles could be the most promising use for wood/plastic composites in Europe, but consumer attitudes are diverse on the continent. Scandinavians, for example, never embraced vinyl windows wholeheartedly, preferring wood products, Plackett noted.
Japan's wood/plastic composite market is growing and reached 44 million pounds in 2000, estimated Takeyasu Kikuchi, director for Ein Engineering Co. Ltd. of Tokyo. The country has about 30 producers, most of which license Ein technology. Lumber and building materials account for 70 percent of the Japanese market. Miscellaneous uses include novel, injection molded speaker boxes for Sony televisions.