The beauty of wood, from an environmental point of view, is twofold. It is a renewable resource which results in reduced carbon dioxide (CO2) emissions when it is used as a substitute for other materials. It also acts as a ‘carbon sink’, since it stores carbon within itself. As a result of this dual benefit, one cubic metre of wood is estimated to save a remarkable two tonnes of CO2 emissions. A 10% increase in wooden houses in Europe would, on its own, generate 25% of the total CO2 reduction called for by the Kyoto protocol.
The key problem with wood, however, is that sunlight causes it to degrade very quickly by breaking down the complex molecules within it. Existing wood coatings contain ultraviolet (UV) absorbers to protect against this, but these absorbers themselves break down within a year or two. Pigmented paint provides longer protection but this conceals the natural appearance of the wood. The absence of clear coatings that are effective for more than one or two years is a major reason why wood is often rejected as a building material.
The first focus of the WOODLIFE project, therefore, was to use nanotechnology to develop new water-based clear coating systems for wood, based on the molecular manufacture of nanoparticles that could be mixed in to the coatings to ensure improved UV protection. Such novel coatings could greatly extend the life of wood products and reduce maintenance costs.
The second area WOODLIFE turned its attention to was wood adhesives. Here, again using nanotechnology, the aim was to improve the properties of water-based adhesives, such as polyvinyl acetate (PVAc), which are prone when subjected to excessive humidity or temperature changes to what is known as ‘creep’ – an adhesion failure between the glue and the wood which results in a reduced load-bearing performance and potentially the collapse of the structure. Such improvements would not only extend the life of wood products using these adhesives, but also permit the use of the same adhesives in some load-bearing applications where more expensive, formaldehyde-based adhesives are currently required.
In both areas, says WOODLIFE’s Scientific Project Coordinator, Dr Anders Larsson of SP Chemistry, Materials and Surfaces, in Sweden, the project’s results were extremely positive. Clear coatings were developed which are currently being tested - although by definition full testing requires several years. In the words of Dr Larsson: ‘After two years of natural weathering the clear coating systems still look very attractive, which is unusual for this type of system.’
Meanwhile, on the adhesives side, prototype adhesives were developed which successfully passed stringent tests with load-bearing beams known as glulam (glued, laminated) beams.
Further testing, optimisation and validation of the products still need to be carried out, and it is too early to give precise commercial projections for them, says, Dr Larsson. But it is clear that, as well as the environmental benefits that should result from the increased use of wood made possible by WOODLIFE’s breakthroughs, the economic and competitive benefits for Europe will be considerable. Maintenance costs for joinery and wooden claddings will be reduced helping make wood a more attractive material and boosting jobs in the woodworking sector. At the same time, the development of new knowledge-based technologies such as those pioneered by WOODLIFE will help to keep Europe ahead of ever-stronger overseas competition in both the coatings and adhesives markets.
Dr Larsson is in no doubt about the significance of WOODLIFE’s achievements. ‘I think we have made a major leap forward in the material technology development of environmentally sound materials,’ he says.