The electron microscope images clearly show how the wood structure changes due to plasma coating (top treated, bottom untreated).
Although few of us are probably aware of it, every eyeglass lens, every ballpoint pen and many an outdoor jacket have something in common. Along with almost any object made of plastic they undergo a production process known as plasma coating. Materials are treated with partially ionized gas mixtures in a coating chamber to make them water or dirt-repellent, to give them a finish, to make them very durable, or to make them rustproof or printable. Professor Dr Volker Bucher, who lectures and conducts research at the Faculty of Mechanical and Medical Engineering at Furtwangen University, specialises in plasma coatings – in particular, surface technologies for medical applications. Professor Bucher also heads the Rottweil Study Center – a Furtwangen University laboratory where students work on their theses and projects, and where Bucher himself carries out research projects.
Spectacular change
Bucher is currently working on a process that promises to be a spectacular new development in the field of plasma coating. In the "PlasmaWood" project, instead of plastic, wood is treated – resulting in a change in its properties. Professor Bucher shows images from the electron microscope that illustrate how the plasma process penetrates the pores of the wood. "The wood is stripped of its resin, and then the cellulose – the substance of the wood – is coated," Bucher explains enthusiastically. "You get a wood that a normal lamp can shine through, for example!" This opens up entirely new possibilities for interior design and the construction industry. But, explains Bucher, "The biggest advantage of all is that plasma-coated wood does not weather." Construction timber, facades, terraces – everything is virtually everlasting, regardless of the weather. It is no surprise that the joint "PlasmaWood" project was initiated by a construction company. The special wood protection process being researched, which is also extremely environmentally friendly as it uses no varnishes, glazes or oils, is being funded by the German Federal Ministry of Education and Research until the end of 2023.
Design of a large-scale plant
During that time, Professor Bucher and his colleagues Wolfram Kintzel and Felix Blendinger will not only work on applying plasma coatings to different types of wood, but also on developing a system that can coat large panels. "This is a very green technology," Bucher reports of the process. "Plasma processes are environmentally friendly because only common gases such as oxygen, nitrogen or vapours from non-toxic liquids containing silicon are used. Reaction products from these harmless substances are used to coat the workpieces. This doesn’t harm anyone." The large-scale system being co-developed by the team of HFU scientists and their industry partner plasma technology GmbH of Herrenberg, will later be set up at the Schwörer-Haus KG construction company in Hohenstein/Oberstetten. "The goal is to coat domestic spruce wood with a UV filter to prevent water absorption," says Bucher. His project colleague Kintzel then explains how they will achieve this, the "steaming" in the plasma process. "Usually, this process is carried out in a vacuum. Pressure of 10-4 millibars is exerted on a gas mixture and the electrically accelerated electrons 'ignite' the plasma." Once they succeed in treating large areas of wood with the plasma coating, the new properties of the panels will be tested by means of a salt spray test in a climate chamber. AlthoughBucher and Kintzel already havevery clear ideas about what these tests will reveal – the scientific journey remains exciting. "In short, we'll just wait and see what happens," Kintzel laughs.