DITF, Fiber Engineering highlight biodegradable natural fiber plant pot project | CompositesWorld

Materials and fabrication process R&D achieves low-cost, compostable plant pots made from invasive hyacinth fibers and a thermoplastic matrix processed via hot press.

Final biodegradable plant pots. Source | Fiber Engineering GmbH

Together with Fiber Engineering GmbH (Karlsruhe, Germany), the German Institutes of Textile and Fiber Research Denkendorf (DITF) presents a process for the production of plant pots that are fabricated from a natural fiber-reinforced thermoplastic that has proven to be fully biodegradable.

Controlling the spread of water hyacinth, an invasive species that now exists in water ecosystems across many countries, was the starting points for this research co-led by the DITF, which aims to produce a cost-effective composite material from the fibrous plant material’s biomass. The result is a prototype plant pot that is competitive and meets all the technical requirements of the project objectives.

At the beginning of the project, project partners defined the material requirements for the plant pot. These include good dimensional stability, which must also be ensured when the pot is filled with wet soil. The use of physiologically harmless materials for contact with food plants is also an important requirement. However, the main focus is on complete biodegradability and thus unrestricted compostability.

Biomaterial for the production of the plant pots comes from Louisiana and is directly marketed by In-Between International under the Cynthia product name. This raw material has been extensively tested and modified at the DITF with regard to its composition and suitability for technical processing. It consists mainly of cellulose and must first be screened and treated with a hydrophobic agent for further processing; hydrophobing is necessary to give the plant pots a certain resistance to moisture.

Next, the prepared raw material required a binder to ensure the plant pot maintains dimensional stability. Laboratory tests with various binders have identified those that guarantee good processability and dimensional stability of the fiber composite. A thermoplastic was selected that was easy to process in a hot press and that fully met the requirements for biodegradability.

Lauffer VCP500 hot press used for the tests at DITF. Source | DITF

Further laboratory tests determined the ideal ratio of binder to fiber raw material. Tests in an industrial composting plant showed that the material was fully biodegradable and that the plant pots would decompose within a reasonable period of time — a stability of 4-6 weeks was the project’s goal.

Researchers produced test samples for all preliminary tests in the form of fiber composite panels on a hot press. The next step was to produce the first pot prototypes from the pretreated fiber material with the appropriate binder. This part was carried out by Fiber Engineering GmbH, which offers extensive expertise in fiber injection molding (FIM). The company optimized its existing process for processing the water hyacinth fiber, and successfully produced a series of plant pots.

According to partners, when taking into account the materials and processes used, the plant pots could be produced very cheaply, at a production price of less than five cents per pot, making them marketable. In daily use, garden centers could appreciate the haptic advantages — strength and moisture resistance despite the fact that the material is completely biodegradable.

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