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Turning Debris into Dollars

Scientists at Forest Research are looking to improve the dimensional stability of medium-density fibreboard (MDF) with the aim of expanding its applications.

"Dimensional instability in MDF is seen in cases when the product is used in environments where there are considerable moisture changes," says programme leader Dr Rick Ede. "This shows as thickness changes of the panel, or changes in gaps along the edges of panels -- linear expansion.

"It also prevents MDF being used in very high moisture environments, or as an exterior cladding."

Opportunities for improving the stability of the panels have been found, he says. "One of these, involving a new treatment that modifies the fibre, is showing particular promise as a general method for improving MDF dimensional stability."

Medium-density fibreboard is made by combining glue with wood fibres produced from residues such as wood chips, and sometimes, sawdust. The resulting composite panel products are presently used mainly in furniture, such as computer desks, and in kitchens, such as cupboards and benchtops with hard-wearing overlays.

Raw wood residue costing $40 a tonne is converted into products that sell for between $400 and $1000 a tonne. The value-added products made from this low-value forest residue earn New Zealand about $300 million a year from exports.

The country's four fibreboard makers account for almost five percent of world production, and New Zealanders' use of the product per capita is the highest in the world.

New Zealand's medium-density fibreboard is good quality because of the radiata fibre used and the standard of processing, Ede says. MDF has several attributes that make it the material of choice for a whole range of products.

But Forest Research has been working alongside the New Zealand MDF industry on how fibreboard can be extended into new applications and better products. Constant product improvement is needed to keep pace with international competitors.

"This is being achieved by better understanding MDF fibre; what influences its chemical and physical properties, and how these properties influence the performance of the panel products" Ede says. "As well, we manipulate these properties to fit specific purposes, modify the adhesive binding the fibre, and combine MDF with other fibres and plastics to produce new products."