Bright future for wood in plastics


Wood Plastics

Since the 1940s, forestry scientists at Scion have been trialling which pines grow the fastest and straightest. They were wildly successful with plantation forests – in future, they may be equally vital to the plastics industry.

Recent research at Crown Research Institute, Scion has focused on new uses for wood fibre beyond its traditional pulp and paper roles.

It was logical that when Scion began to develop composites based on thermoplastics, they almost immediately began introducing wood fibres into the mix using familiar technologies developed from their wood composites research.

The addition of wood fibres to create wood plastic composites has advantages over synthetic fibres (such as glass) in terms of lower cost, sustainability, end-of-life options, and relatively low density.

The addition of either wood flour or wood fibres reduces the cost of plastic, with wood flour resulting in the greater cost reduction.

“This lower cost has been one of the primary drivers for introducing wood flours into plastics since the 1970s. The addition of wood flours make plastic stiffer but not stronger, the addition of fibres achieves both, says business development manager in bio-based materials Jeremy Warnes.

To date, the difficulty of feeding and processing wood fibres in plastics processing machines such as extruders and injection moulders has held back the widespread inclusion of wood fibres in plastics.

“Wood fibres are difficult to handle since they are fluffy (like cotton wool) and wood chips are too coarse to be used in a plastics extruder”, explains Mr Warnes.

“Wood flour more-or-less fills a plastic whereas long, natural wood fibres reinforce the plastic giving it greater strength.”

Research done at Scion showed that wood flour could increase the maximum tensile stress of polypropylene by up to 45 percent. Scion’s wood fibre technology increased this same measure by 118 percent.

To enable the full reinforcement capacity of wood-based fibres, problems such as handling and feeding issues, insufficient fibre dispersion, adhesion to the plastic matrix and length retention during processing needed to be solved.

To overcome these problems, Scion researchers developed a thermoplastic binder which holds the wood fibres together in a pellet that can be poured in an extruder and then the reinforced compound fed into an injection moulding machine.

Scion has negotiated a licensing agreement with global wood manufacturer Sonae Indústria Group for the production and sale of the wood plastic pellet technology.

The licence gives Sonae Indústria Group an exclusive licence to commercialise the technology in Europe.

“Our successful trials with plastic processing operations have given us the confidence to introduce this new material to Europe,” says chief marketing and sales officer Christophe Chambonnet.

“As one of the world leaders in wood technology, with over 7 million tonnes of wood processed annually, Sonae Indústria needs to have an important role in the future of the wood sector. ihave no doubt that we are creating a new future by mixing wood fibres with thermoplastic polymers and a new perspective on the use of the wood fibre.”

Sonae Indústria has named the technology’s product “WoodForce”. While the first commercial applications of the technology are likely to appear in Europe, the intellectual property is retained in New Zealand with Scion having filed international patent applications for the technology.

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