Slipperiness is one of the biggest complaints consumers have about decks made from wood-plastic composites, according to a speaker at the International Conference on Biocomposites, held May 2-4 in Toronto.
Consumers can slip on wood-composite decks and injure themselves. Ironically, composites tend to be more slippery when dry than when wet, according to Anatole Klyosov, principal of consulting firm Mir International Inc. of Newton, Mass.
WPC is slipperier than wood, Klyosov told delegates.
He suggested wood-composite board manufacturers use a wire brush to finish the surface of their products, provide deep embossing or change the plastic in the matrix to one that is not so slippery.
Klyosov listed several other problem areas that cause complaints among consumers. The problems have led to five lawsuits against wood composite manufacturers and suppliers from 2004-10.
Rotting and splintering can occur after a manufacturer claims the product is maintenance-free. In an unspecified case in New Jersey, he said, a manufacturer had to pay $1.8 million in costs and lawyer fees after a complaint. The manufacturer had to replace the product and discontinue its claim that its product was maintenance-free.
Oxidative degradation leads to problems like crumbling or cracking that can be corrected by adding sufficient antioxidant compounds. In one case Klyosov cited, an Ohio lumber company spent more than $8 million to cover damages and a product recall for its composite deck boards. Defects were blamed on oxidative degradation. Some metal pigments and additives can also induce crumbling.
Excessive moisture content can lead to mold and mildew formation. Wood-composite materials typically have moisture content of 0.7 to 3 percent, but if a board is porous it can hold much more water in its interior. Claims of moisture resistance and low maintenance don't hold if porosity is excessive.
Porosity can hold water, Klyosov said. Minimize porosity by minimizing water content.
Porosity control can also be achieved by not exceeding desired processing temperature or line speed.
Shrinkage can occur if the manufacturing line is too fast or if cooling occurs too suddenly after manufacturing. Shrinkage of up to 0.5 percent is possible and can be a particular problem for hollow boards, Klyosov said.
Provide time to cool, relax and shrink the board at the manufacturing site, he told attendees.
Photo oxidation and fading can occur with excessive amounts of regrind or lack of inorganic pigments.
Other potential problems include strength issues, deflection, thermal expansion and contraction, termite resistance and flammability.
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