APPLICATIONS | WOOD PLASTIC COMPOSITES
which improves the sliding of the functionalised wood particles past each other,” according to the company.
Effect of Genioplast Additive for WPC on mechanical properties, moisture absorption and throughput in WPC production compared to typical stearate lubricant Source: Wacker
Better processing Wacker has developed processing aids designed specifically for WPC in collaboration with the Wood Competence Center, which is based at Linz in Austria, and introduced a first Genioplast Additive for WPC, based on a thermoplastic silicone elastomer, at K2016. The additive, which is sup- plied as a masterbatch, acts primarily as a lubricant to reduce the coefficient of the plastic component of the blend and thus reduce the internal and external friction during extrusion. Using the additive enables more stable processing with reduced energy input, allowing a higher through- put to be achieved. The company says that an additive addition of just 1% provides good lubrication, compared to 2-6% additions of conventional lubricants (typically stearates) to achieve the same effect. Tests also showed that in a mixture of 36-37% polypropylene and 60% wood flour, a 1% addition of the additive increased throughput by 65%. “The copolymer consists of a polar unit that
attaches to the wood particles via hydrogen bonds. The non-polar silicone chain projects outwards,
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In addition to improved processing, the Geni- oplast additive optimises dispersion of the wood or natural fibre in the polymer and improves compat- ibility between the fibre and the matrix polymer. These improvements enhance mechanical proper- ties such as impact strength and flexural toughness, the company says. Wacker says that the Genioplast WPC additives have also been shown to reduce water absorption, which improves long term weathering resistance. AFI Global, which does business as Addisperse, is developing a pelletised masterbatch containing a peroxide pre-dispersed in a polymer carrier that is intended to allow highly accurate feeding of peroxide for low-level controlled crosslinking. “Cross-linking creates better adhesion between the wood-fibre filler and the HDPE component of the composite. This improves flex strength, which can allow production of thinner boards,” says Paul Albee, Vice-President of Technology at the com- pany. He says that peroxide for crosslinking polymers may be provided as a liquid or as a crystal isolated on a powder, but that the pelletised form developed by Addisperse is easier to use in typical WPC processing. The product is currently in field testing.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.fiberondecking.com �
www.trex.com �
www.timbertech.com �
www.moistureshield.com �
www.americhem.com �
www.mitsui.com �
www.struktol.com �
www.lonza.com �
www.wacker.com �
www.afi-global.com
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