Many countries are making efforts to replace concrete with eco-friendlier options in order to achieve their sustainability targets.
Wood is a great option, but because it is vulnerable to damage from exposure to sunlight and moisture, it requires protective coating. Researchers at Aalto University, Finland have created a low cost, safe and high performance coating suitable for construction, using lignin, a natural polymer found in wood and other plants.
“Our new coating has great potential to protect wood. It’s more water repellent than a lot of commercial coatings because it retains the natural structure of wood and its micro-scaled roughness. Since it’s hydrophobic, the coating is also quite resistant to stains, while lignin’s inherent structure resists colour changes from sunlight. It also does an excellent job of retaining wood’s breathability”, explains Alexander Henn, doctoral candidate at Aalto University, The School of Chemical Engineering.
About 60 to 120 million tonnes of lignin are isolated globally each year since, most of the time it is considered a waste product of biorefinery and pulping processes. This lignin is often burned for energy recovery. Although characteristics like poor solubility and unexceptional performance of some lignin based products have held back its commercial use, lignin actually has several beneficial properties.
Monika Österberg, Head of the Department of Bioproducts and Biosystems at Aalto University says “Lignin as a coating material is actually very promising with its many benefits compared to the synthetic and bio-based coatings currently used. It has excellent anti-corrosion, anti-bacterial, anti-icing, and UV-shielding properties. Our future research will concentrate on developing characteristics like elasticity of the coating”
The protective coatings presently used on material like concrete, wood or metals are petroleum based. Coatings made from vegetable oils such coconut, castor, tall, linseed or soybean are a much more sustainable alternative, but are not as durable, and are often mixed with synthetic materials in order to improve their quality.
The coating industry could use more natural alternatives to meet rising safety regulations. The amount of volatile organic compounds (VOCs) has been regulated because of their impact on health and the ozone layer. The European Union (EU) restricted some chemicals used by the coating industry, such as bisphenol A and formaldehyde (used in epoxy and polyurethane coatings), and recently classified titanium dioxide, widely used pigments in paints, as a class II carcinogen.