Biological transformation focuses on the sustainable use of biological resources such as plants or microorganisms. In the future, it is expected to reduce reliance on fossil fuels such as oil, coal, or gas, and help tackle major challenges such as climate change and global population growth. It offers options and opportunities for almost all industries. One field of application for biological resources is materials such as natural fiber reinforced plastics (NFRP).

Their advantages make them interesting as an alternative to glass and carbon fiber reinforced plastics (GRP or CFRP) — they are renewable, biodegradable, robust, use less energy in being produced, are lighter, and have better acoustic properties. The disadvantages are that they absorb water very easily, are damaged as a result, and lose their otherwise positive mechanical properties.

A fiber treatment and yarn processing technology were developed so natural fibers can fully exploit their advantages and be used more widely.

With a surface treatment of natural fibers with water-repellent layers alone, the water continues to penetrate the natural fiber via cut edges or other damage. For this reason, the fibers were treated so that they are moisture-repellent on the inside. This was done by producing polymers inside the natural fibers.

First, the monomers of the plastic penetrated into the cavities of the natural fibers. The polymerization then took place directly inside the fibers. The use of the method is particularly interesting for thermoplastic fiber composites, since in their production, the molten polymer is very viscous, does not penetrate into the interior, and only wets the fibers superficially. The advantage of thermoplastics is that they can be deformed as desired, even after production.

Researchers used flax fibers in the form of a roving; i.e., the state before spinning into yarns and their further processing into textile surfaces. In this way, the fibers can be completely soaked with the monomer, since they are still present individually. Complete impregnation might not be guaranteed on fabric or twisted yarn. This is where the yarn process comes into play. In the wrap spinning process, the natural fibers were arranged in parallel, and the parallel core of the flax fibers was wrapped with a filament. The advantage was that the fibers are not twisted, which gives them increased strength.

By combining both processes, the physical properties of natural fibers can be fully exploited. In this way, NFRP can also be used outdoors and in highly stressed components.

For more information, contact Anke Zeidler-Finsel at +49 6151 705-268.