Up to now polycarbonate (PC) has always been the plastics of choice for automotive glazing. The latest is the first moving side panes in the newly introduced 1-litre car from VW. But PMMA is also leading the charge. In the interview with Dr Ackermann, Head of the PMMA Business Unit at Evonik, he points out the steady progress that the material has been making. In the case of the Chinese automobile brand Roewe (Saic), the purchaser can choose, for the E50 electric car, between heavy glass or lightweight PMMA for the glazing on the rear door.
From left to right: Dr Ackermann with a non-transparent PMMA application, the front cladding on an HGV; next to this a prototype roof module made from PMMA with flexible solar cells, then the Lotus Exige featuring “load-lightening“ PMMA which is already on the road in the shape of an e-vehicle and, last but not least, the rear glazing on the Chinese Roewe E50.
Overall, there are some lightweight materials that figure on the E50. The Chinese also manufacture the fixed side windows from PMMA. In other places structural foam made from polymethacrylimide (PMI) is used.
In principle, similar advantages apply to PMMA as to PC, although PC is slightly more resistant to impact which means that it is more impervious to stone chips. PMMA, however, compensates for this with perfect flow properties, in particular when it comes to thermoforming. There is no sign of any streaking here. The material proved its UV resistance with the roof of the Olympic Stadium in Munich, where some of the panels have been in situ since 1972. The practice of covering solar panels with PMMA also testifies to its weatherproof characteristics.
But the most important reason is definitely freedom from streaks; helicopter cockpits are made from this material, and any streaks here would immediately mean that the helicopter would not be licensed. However, as far as automotive construction is concerned, thermoforming is only suitable to a limited extent. For quantities in excess of 10,000, injection moulding is more economical, although here PMMA is less impressive with freedom from streaking following the hot moulding process. However, in the injection moulding process, further functional elements can be installed directly at the same time, be it reinforcements, seals or optical covers.
As regards the future, Dr Ackermann has in mind a combined thermoforming / injection moulding process that combines the advantages of both systems, the freedom from streaks derived from thermoforming and the multi-functionality that injection moulding is able to offer.
With the aim of demonstrating the innate potential of PMMA and structural foam, Evonik opened a lightweight construction centre in Darmstadt three years ago. Dr Ackermann presented the solutions to us there.
www.evonik.com
