Formaldehyde busting minerals

Wood Focus magazine
24 Apr 2011
The structured model of a mineral with the dispersed pollutant molecule. Image courtesy of Fraunhofer Institute for Silicate Research.

Formaldehyde emissions from particleboard can be reduced using modified minerals called zeolites, say researchers at the Fraunhofer Institute for Wood Research in Braunschweig, Germany.

Tightly restricted by EU and USA legislation, formaldehyde is a toxic chemical widely used in urea-formaldehyde based adhesives in particleboards because ‘alternative adhesives for many applications are too expensive’, says Dr Jan Gunschera, from the Department of Material Analysis and Indoor Chemistry at Fraunhofer.

However, Gunschera’s team has found a way of adding minerals to wood-based panels during production, effectively countering the vapours, rather than removing the formaldehyde itself. The method entails using ‘modified zeolites’ – aluminosilicate minerals which are mined from volcanic rock and chemically treated to perform a certain function, in this case to bind formaldehyde.

The zeolites function as a sort of ‘molecular sieve’, inhibiting pollutants through a combination of adsorption and chemical binding. ‘Pores in the zeolites are of comparable size to the molecule diameter of formaldehyde,’ says Gunschera.

The team has found that the zeolites caused a 70% boost in the adsorption rate, after formaldehyde was added to processed material in the measuring chambers and five per cent weight of zeolite powder was put directly into sample particleboards made of spruce roundwood. The result was that formaldehyde emissions from the board dropped by 40%.

The best adsorption properties have been measured in synthetic zeolite Y, which the experts modified with amino groups. Mechanical tests are claimed to have proved that the minerals have no negative impact on the board’s properties.

Zeolites are widespread minerals, used in many applications such as cleaning and separation processes as well as catalysis. ‘There are natural and artificial zeolites,’ explains Gunschera. ‘The modified ones we have used have been specially made.’ However, he added that to have an impact on industry, the modified zeolites would have to be produced on a large scale by the chemical industry and delivered to wood-based panel manufacturers.

‘The tests until now have been performed at lab scale. Enlargement of the amounts and optimisation towards economic efficiency have to be [achieved] in the future, [as] production is not profitable.’

The next steps will be ‘feasibility tests with some industrial partners,’ notes Gunschera.

John Hanan, Technical Development Superintendent at MDF manufacturers Medite, based in County Tipperary, Ireland, says that, ‘It may well work in terms of capturing formaldehyde, but any mineral in there may affect tool wear. It is interesting work and there may well be some mileage in it, but as soon as I see chemically modified zeolites, I think, “that is going to jump the cost up”.’

Geoff Rhodes, Marketing and Business Development Director at Coillte Panel Products, adds, ‘Over the years there has been a continuing process to reduce formaldehyde emissions in not just wood but all products. I think the wood-based industry is a good example of using different technologies to do this, and it has been very successful and continues to be. This is in an interesting piece of further research that continues that theme.’

Rhodes also warns that the dangers of formaldehyde should not be taken out of context. ‘I am standing on a busy street in Paris and the exhaust fumes coming out of the cars going past me are probably 100 times greater than what you would ever get coming out of a wood-based panel.’