Uni Stuttgart: Green composite material from ...
Uni Stuttgart

Green composite material from flax and chitosan

BioMat at the ITKE/ University of Stuttgart (Source: Uni Stuttgart/Masih Imani)
BioMat at the ITKE/ University of Stuttgart (Source: Uni Stuttgart/Masih Imani)

From furniture to auto parts to skateboards: An environmentally friendly chitosan–flax composite developed by researchers at the University of Stuttgart could replace fossil-based structural materials in many areas.
Composite materials provide stability in aircraft parts, sports equipment, and everyday household items. However, most of these materials have a poor carbon footprint and are not naturally degradable. A more sustainable alternative has been developed by a team from the University of Stuttgart. This completely bio-based composite material is made of flax fibers and the biopolymer chitosan.
Composites consist of at least 2 starting materials combined in such a way that the end product has certain properties (e.g. it is both light and strong). Many conventional composite materials contain fossil-based polymers. Recycling such composites (if even possible) is complicated and energy intensive, and degrades the properties of the material. For this reason, most composites end up in landfills or incineration plants after use, thereby causing additional CO2 emissions.
In order to be able to offer more environmentally friendly products, the composites industry needs alternatives to fossil materials. The challenge is to find the right balance between economical production, good material properties, and sustainability. Bio-composites made from natural components that are biodegradable, non-toxic, renewable and thus have a low carbon footprint, offer one possible solution.
Such a material has now been developed by researchers from the Institute of Interfacial Process Engineering and Plasma Technology (IGVP), the Institute of Aircraft Engineering (IFB), and the Institute of Computer Architecture and Computer Engineering (ITI) of the University of Stuttgart/Germany. The team has successfully produced chitosan–flax bio-composites. These materials consist of flax fibers, which act as a reinforcing element, and the biopolymer chitosan, which is derived from chitin and holds the flax fibers together.
Extensive studies have been conducted to test and optimize the manufacturing process in order to achieve mechanical properties in line with those of fossil-based composites. Among other things, the researchers found that chitosan with a shorter polymer chain length is best suited for impregnating the flax fibers. This minimizes the porosity of the composites. The chitosan–flax composite is not only naturally degradable and made exclusively from carbon-neutral raw materials, but also has greater stiffness in terms of density and thus greater lightweight construction potential than composites containing epoxy resin.
This gives the bio-based material a competitive advantage, e.g. when it comes to reducing fuel consumption in automotive construction. According to the study, the chitosan-flax composite could also replace conventional materials in construction, sports equipment, and cargo crates.

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