When the petroleum runs out, renewable sources of raw materials will have to be found to replace petrochemical feedstocks. In the case of furniture varnishes, Fraunhofer researchers at the Institute for Wood Research, Wilhelm-Klauditz-Institut WKI in Braunschweig have already developed an alternative product in which the majority of petrochemical components have been substituted. Their water-soluble furniture varnish is based on vegetable oils and sugars and has identical properties to the conventional varnishes on sale today. It is hard-wearing, scratch-proof and resistant to chemical attack. “This varnish offers the coatings industry an attractive alternative to petrochemical products that is economical to produce and performs well in all tests,” reports Dr. Claudia Philipp of the Fraunhofer WKI. The new varnish is based on the chemical compound 1,3-propandiol, which is derived from glycerin. Glycerin in turn is the basic substance found in all vegetable oils, and is readily available as a byproduct of manufacturing processes for fatty acids and biodiesel, for example. In the laboratory synthesis, the researchers transform 1,3-propandiol into polyurethane, which serves as a binder in hard, transparent, scratch-resistant varnishes. “The aim is to use the relatively cheap 1,3-propandiol as a substitute for one of the more expensive petrochemical synthesis components, without altering the coating properties of the varnish,” explains Dr. Guido Hora, department head at the Fraunhofer WKI. 1,3-propandiol has not been considered a valuable raw material in the past, and rarely enters into the composition of varnishes. “Our first step was to conduct a detailed analysis of the relationship between the starting material and the properties of the final product,” Dr. Claudia Philipp relates. The outcome was that: “As the chemical structure of 1,3-propandiol led us to surmise, the new varnish is not only hard but also resilient.” In other words, it doesn’t chip when a cup or other object is dropped onto a varnished table. A good varnish needs to be hard, but also capable of amortizing shocks to a certain extent, so as to prevent damage to the item of furniture beneath the coating. Another advantage of the new varnish is that it contains no N-methyl-2-pyrrolidon (NMP), a solvent once widely used in polyurethane coatings. This substance is meanwhile known to have a toxic effect on the growing embryo and is classed throughout the EU as a hazardous chemical requiring a warning symbol on all products containing a concentration higher than five percent.
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