Strong desire to find fully transparent coatings for exterior wood


Sustainability is one important requirements while working with natural materials like wood. What this implies for wood coatings and what other trends are currently important, explains Dr Gerhard Grüll from Holzforschung Austria, an Austrian Forest Products Research Society.

What is your general view on sustainability?

Dr Gerhard Grüll: It is a very old principle in responsible forestry to harvest the resource wood not exceeding the volume that is regrowing every year. I learned this basic definition of sustainability early in my studies of wood technology. Today the meaning of sustainability is much broader, and it is respected more and more in all aspects of life and business. It is definitely important for wood coatings. However, to me this appears not to be very special because every product must be assessed and improved in this view.

And what do you think can be done to improve sustainability of wood coatings?

Grüll: Considering sustainability we must think cradle to cradle and there are many options for steady improvement. I am observing the development of binder polymers based on renewable resources with interest. This is very similar to the sustainability of timber harvesting but here conflicts with food production must be avoided. The near future will show if the quality level of these new binders is already high enough to meet the customer´s needs. Then prices and availability will be relevant for the break through on the market. The coatings industry has done a lot to improve their products to contribute to a sustainable environment. This was and is still driven by legislation in the fields of solvents, VOCs, biocides, and heavy metals which are influencing product safety and environmental impact.

During the use phase of coated wood products a durability as high as possible, with low maintenance must be desired because this avoids the loss of primary energy stored in the products. Wood is a plant grown material and stores CO2 as long as it is not rotten or combusted. High durability is the best means to improve sustainability, and this is were coatings can help. Finally, concepts for recycling and reuse will need improvement, which starts at the question how the coating and the wood can be separated.

What other trends are currently influencing the wood coatings sector?

Grüll: As mentioned before, there is a high pressure from legislation to replace toxic and environmentally harmful substances in coating formulations. This is a significant driving force for new developments, because very often legislation seems to be beyond the technical state of the art. This means alternatives are rare and must be developed. There is still a strong desire to find fully transparent coatings for exterior wood, because it is the most beautiful substrate of all. Here, sound concepts for light protection of the substrate and the polymer must be developed further on the levels of additives, formulations and coating systems. The trend to very matt surfaces is sometimes challenging for wood coatings because there might be drawbacks for instance in scratch-resistance and polishing.

During my career I observed the development of water-borne coating materials for exterior wood. They had severe problems when the first products came to the market. In my opinion these problems have been solved and they are now even better than the “good old” solvent-borne coatings materials. Because of this I am confident that we will see a good progress to meet the challenges of the future.

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