Five years ago, Konstanz-based chemist Professor Helmut Cölfen and his team published the synthesis of a novel bio-inspired, heat-resistant mineral plastic that can easily be recycled. Since then, they have been collaborating with academic colleagues and industrial partners to refine the material and to scale-up the synthesis of mineral plastic foams for industrial-scale production.
Plastics have become indispensable to modern everyday life due to their inexpensive production, durability and good processability. The downside is that not all plastics are recyclable and reprocessing those that are usually involves high energy consumption. In 2016, Professor Helmut Cölfen from the Department of Chemistry at the University of Konstanz and his colleagues presented a novel material that addresses this shortcoming: A readily recyclable “mineral plastic” that – in its dry, cured state – is transparent like glass, several times harder than conventional acrylic glass, yet remains extremely flexible. It also has exceptional heat resistance.
“We used the structure of crustacean shells as an inspiration for our plastic. Crustaceans store tiny particles of calcium carbonate, or ‘lime’, in their chitinous shells, which makes the shells extremely robust even though they are quite thin,” explains Cölfen. Using water as a solvent and without any energy input, the mineral plastic from the Cölfen lab can be transformed from its solid state into a so-called hydrogel. Just like a chewing gum, the hydrogel can then be reshaped as required to recycle the material.
In collaboration with Professor Cosima Stubenrauch and her lab (University of Stuttgart), Cölfen and his colleagues have meanwhile succeeded in synthesizing the mineral plastic in a solid foam form. Because of the material’s exceptional heat resistance, this foam could be key to novel, non-combustible insulating materials. It is “patent-pending” and attracting a great deal of interest from the industry. Together with industrial partners from Baden-Württemberg, the researchers are currently upscaling the synthesis of the mineral plastic foam for transfer to industrial production of insulation panels.
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Caption: Colourized electron micrograph of the mineral plastic foam. © Helmut Cölfen