Plastics giant thinks small

For somebody tasked with developing new plastics, Franz Brandstetter spends a lot of time looking at other materials. Prof Brandstetter, head of BASF’s polymer research competence centre in Ludwigshafen, Germany, says that more and more effort is being expended on additives – especially nano-sized additives. An example of this is a ‘high flow’ version of its Ultradur PBT material. A nano-sized additive, when mixed with the polymer, decreases its viscosity when it is molten. When it is moulded, it will make thinner parts in a shorter cycle time, at a lower temperature. Ordinarily, higher flow will lead to lower mechanical properties – but not in this case. “You can decrease cycle time by around 30% using this material,” he says. BASF did not initially understand why this effect happened. It was, in Brandstetter’s words “a real R&D invention”. And BASF could not repeat the effect with other plastics – until it understood the mechanism. “Now we know the relationship between the particles and polymers we can transfer this effect to other plastics,” he says. “It’s one of my most interesting experiences in the last 20-30 years of polymer research.” He would give no details of which polymers are next to benefit from this effect – but BASF offers everything from polystyrene to polyamide. Fine structure Nanotechnology forms an important part of BASF’s plastics-based research. But it is not just in the additives side. It is also doing a lot of work on nanostructuring – in which ‘traditional’ materials are produced in different ways. “Most properties of polymers are based on nanostructures,” he says. “We are creating new polymerisation methods to create micro- and nano-structures.” He says that these methods allow chemical molecules to ‘self-align’, in a similar way to biological molecules like DNA. This means that molecules can be designed with more specific properties. “Now, instead of asking ‘What will this material do?’ we can ask ‘What properties do we want?’” he says. This attention to detail is evident from a product that BASF is planning. The foam material is made from ordinary polystyrene. But the molecular structure of the foam is critical to its performance. “If you can make the individual foam cells smaller than the free pathway of a single gas molecule, then it cannot transport energy,” he says. “This increases the insulation.” The size of the open cells is less than 500nm. The research began in Strasbourg, then transferred to other parts of the BASF research machine. Brandstetter says it could be used with materials other than styrene – such as melamine. “In this case we knew the physical effects and then we looked for the chemical realisation,” he adds. He says that sheets made using this method would probably have half the thermal conductivity of its commercially available Basotect foam. On the downside – certainly for BASF – it may take some time to appear. “We expect this to be available in five years,” says Brandstetter. Electronic research BASF’s work on tiny structures extends beyond traditional plastics markets. It is also involved in a project to develop tiny electronic circuits using plastics rather than silicon. It has helped to develop a printed ring oscillator – which could be used to power low-cost radio frequency identification devices (RFIDs). It uses special inks and a combination of plastics. The work was carried out in conjunction with Chemnitz University, a leading centre for research into polymer electronics. “Different polymers were needed for different functions,” says Brandstetter. “We have proof of concept. Now we want to roll it out.”