The recycling of fiber composites
The recycling of fiber composites: Research team of TH Nuremberg develops innovative recycling process with low energy consumption
The industrial use of fiber composite plastics in lightweight construction, such as in the aviation and automotive industries, is growing steadily. Therefore, the economy and politics have a great interest in recycling the discarded components made of fiber-reinforced plastics. The working group around Prof. Dr. Gerd Wehnert of the Faculty of Applied Chemistry of the Technical University of Nuremberg develops a method in the research project “CERES” to recycle crosslinked plastics based on epoxy resin simply, quickly and with low energy consumption. The STAEDTLER Foundation fortunately promotes this exciting project with 40,000 euros.
Nuremberg, March 7, 2019.
The research team headed by Prof. Dr. med. Gerd Wehnert of the Faculty of Applied Chemistry of the Technical University of Nuremberg is researching a method for the cost-efficient recycling of fiber composites in the project “CERES” (Chemical Recycling of Epoxy Resin Based Materials). A breakthrough could bring a big gain to the economy.
The Airbus A350, the BMW i3 and wind turbines all have one thing in common: they are all made from fiber-reinforced plastics. Fiber composite plastics consist of reinforcing fibers and a plastic matrix. They form a synergetic combination of the properties of their individual components: the reinforcing, force-absorbing fibers and the forming matrix, which also serves as protection against external influences. The composites have a high strength and stiffness with a comparatively low density – which makes them interesting for lightweight construction, such as in aviation or in the automotive industry, but also for the sports and leisure industry.
Due to the steadily increasing use of fiber reinforced plastics, the economy and politics have a great interest in increasing the sustainability of these substances. Prof. Dr. Gerd Wehnert develops a process to recycle fiber composites and to be able to easily and quickly recycle the contained fibers with low energy consumption.
The fiber composite plastics consist in part of a plastic matrix. This plastic matrix is often an epoxy resin – a thermosetting resin that can withstand heavy loads. The total annual sales of epoxy resins is around 9.2 billion US dollars, which holds great potential. “According to the current state of the art, it is precisely the frequently used epoxy resin-based composite plastics which can only be recycled in a very energy-intensive and time-consuming manner and thus cost-intensive”, says Prof. Dr. med. Gerd Wehnert.
Duromers, crosslinked by chemical reactions, can no longer be melted – they can not be efficiently recycled yet. A good way to reuse it would be to chemically recycle, chemically cleaving the crosslinks and breaking the duromer into smaller, soluble molecules.
In epoxy resins, such as the plastic matrix in fiber composites, it has not been possible to apply this principle technically. At this point the research project “CERES” starts. Prof. Dr. Gerd Wehnert and his team are researching a recycling reagent that enables the solvolysis of fiber composites, i.e. the breakage of the chemical bond by a special reagent. The goal is not to damage the expensive fibers, a recycling is possible. As an agent for this reaction, the research team is investigating a combination of chemicals that could easily, quickly, and almost completely decompose epoxy resin networks at low energy input. “For the recycling of epoxy resin-based fiber reinforced plastics, the key lies in chemical cleavage. Therefore, in this research project we are developing a reagent for the decomposition of the crosslinking sites of epoxy resins “, says Prof. Dr. med. Gerd Wehnert. “We make epoxy resin model networks and test reagents that can split the model networks. When a reagent is technically viable, we transfer it to epoxy resin-based fiber composites. “Once the reagent has attacked the matrix of the epoxy resin-based component, the decomposed matrix is washed by the fibers. This process secures the precious fibers, which can then be recycled for the production of new fiber composite plastics.
The Laboratory of Macromolecular Chemistry at the Faculty of Applied Chemistry of the Technical University of Nuremberg offers good conditions for research on this innovative recycling process thanks to its competent team and its functional and modern equipment. The working group around Prof. Dr. With this research project, Gerd Wehnert not only contributes to sustainability, but also to economic efficiency. Thus, one kilogram of ten millimeter long, matrix-free short carbon fibers has a market value of about 150 euros. Calculated on the total production of a year, the recycled fibers have a value of about 3.5 billion euros, for the economy that is a significant added value.
The STAEDTLER Foundation fortunately promotes this exciting project with 40,000 euros.