Scientists at the University of Konstanz have presented a new generation of mineral plastics that can be completely biodegraded. Unlike previous mineral plastics, which are based on fossil raw materials such as polyacrylic acid, the researchers use the biopolymer polyglutamic acid as a starting material.
As Prof. Helmut Cölfen’s group reports, the new materials are easy to shape, stretchable and self-healing. At the same time, they exhibit high hardness and toughness. The properties are thus similar to those of conventional mineral plastics, which are, however, hardly degradable.
The key is ionic interactions between the polyglutamic acid and divalent calcium and trivalent iron ions. By varying the molar mass, the ions and the water-alcohol mixture during the manufacturing process, the mechanical properties can be specifically adjusted.
Experiments with soil samples and microorganisms confirmed the good biodegradability of the materials. According to the scientists, the nutrients they contain, such as nitrogen, calcium and iron, further promote microbial degradation.
The researchers see great potential for the use of the new mineral plastics, as they offer the interesting properties of previous materials on the one hand, but are environmentally friendly on the other. Polyglutamic acid is itself a natural substance produced by microorganisms.
By developing a sustainable alternative to existing petroleum-based mineral plastics, the Constance scientists are making an important contribution towards more environmentally friendly material cycles. The full paper, titled “Biodegradable Mineral Plastics,” can be viewed here. Ilesha Avasthi, Harry Lerner, Jonas Grings, Carla Gräber, David Schleheck and Helmut Cölfen are listed as authors.