Safety in the Plant


Novel technique combines plastics with carbon nanotubes to create new properties


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esearchers at the Fraunhofer Institute have found ingenious ways to combine plastics with nanoparticles to endow them with new properties. As an example of what might be possible, aircraft could in future be better protected against lightning strikes. It is by no means a rare occurrence for aircraft to have to pass through storms, but when they do there is always one major danger: lightning. Naturally, aircraft manufacturers do everything they can to protect their machines against strikes, but even aircraft made of aluminium do not always escape entirely unscathed. And when polymer components – usually carbon fibre reinforced plastics (CFRPs) – are incorporated into the design as a weight-saving measure, the situation becomes even more problematic, because they do not conduct electrical current as well as aluminium.


At the Fraunhofer Institute for Manufacturing Technology and Advanced


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Materials (IFAM) in Bremen, Germany, researchers have developed a process for manufacturing new materials that should afford aircraft better protection against lightning strikes. They have been focusing on the unique material properties of carbon nanotubes (CNTs). CNTs are among the stiffest and strongest fibres known, and have particularly high electrical conductivity. In order to transfer their properties to CFRPs, the scientists have been combining these nanoparticles with plastics. Dr Uwe Lommatzsch, project manager at the IFAM, explains: “By mixing nanoparticles with plastics, we have been able to significantly enhance the material properties of the latter.” To give just two examples, CNTs are being used to optimise the electrical conductivity of plastics, and their heat dissipation properties are likewise being improved by the addition of metal particles.To do this, the scientists employ plasma technology. They use an atmospheric plasma to alter the surface of the particles in such a way that they can be more readily


chemically bound with the polymer. A pulsed discharge in a reaction chamber creates a reactive gas. Lommatzsch’s colleague, Dr Jorg Ihde, explains: “We spray the particles – ie the nanotubes – into this atmospheric plasma.” They fall into the selected solvent, which can then be used to process the polymer. The procedure takes a few seconds – which is an advantage over the old method, in which CNTs were generally prepared in an acid bath using a wet chemical process. That took several hours or days, required more chemicals, and generated significantly more waste. In addition to improved CFRPs for use in aircraft, the IFAM researchers have several other potential applications in mind. Ihde says: “We can increase the heat dissipation properties of electrical components by giving metal particles of copper or aluminium an electrically insulating coating in the plasma and then mixing them into a polymer.” ❒


For more information, visit www.fraunhofer.de P


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