MATERIALS | NATURAL FIBRES AND FILLERS
Above: Fraunhofer Institute researchers have produced a range of flame-retardant bio-filaments for 3D printing
Below: Testing the tracking resistance of a PLA biopoly- mer compound formulated for electrical applications at Fraunhofer WKI
improved compared to the plain PLA,” says Kugler. Inno-Comp is working with start-up end-product manufacturer Vilhemp and an undisclosed global wholesale company. Vilhemp is using the PLA-based compound for the production of cutlery that can be composted after use. Under industrial conditions, visible decomposition begins after 28 days. The materials are being produced on a produc- tion line based on a Theysohn TSK032HV/46D type two-screw extruder equipped with an Econ underwater pelletising system. It was installed and commissioned in July last year. “This tailor-made machine was configured in a way to be suitable for producing high quality specialities such as natural- filler filled biocomposites and flame retarded compounds,” Kugler says.
Electrical compounds At the Fraunhofer Institute for Wood Research (WKI), a team headed by Dr Arne Schirp working together with various partners has embarked on a new project called BioFla, which is looking into how bioplastics and biocomposites can be
produced for electronics and logistics applications. The aim is to develop flame retardant products using halogen-free systems while also providing the necessary resistance to heat and impacts. “The biomaterials currently available on the
market do not fully satisfy these requirements,” says Schirp. “We are developing materials which have the necessary properties, and which can be processed by means of injection moulding and FDM additive manufacturing. Products such as light switches, sockets, motion detectors, cable ducts or charging stations for electric vehicles could soon be produced from biomaterials.” As a first step, Fraunhofer WKI is working in
collaboration with the Fraunhofer Institute for Applied Polymer Research IAP on the development of a halogen-free bio-flame retardant based on organophosphoric acid ester. In a second step, this will be reactively bound to polylactide (PLA). The binding of the reactive flame retardants and the partial crosslinking of the PLA is achieved through electron irradiation. Compounds will contain wood fibres and impact modifiers. Schirp says that research indicates that, possibly contrary to expectation, the wood fibres have a positive effect on heat resistance and flame retardancy. “Thermoplastics have a relatively high heat of combustion and burn without charring. By adding wood, charring is induced. Replacing a certain percentage of the thermoplastic with wood particles changes the fire behaviour by decreasing the heat of combustion of the volatiles. In addition, residue formation is increased due to the wood particles,” he explains. Parallel to the developments with self-synthe- sised flame retardants, the team is also using commercially available flame retardants. Other thermoplastics, both bio and non-biobased, are also being examined. All the compounds are processed by means of
42 COMPOUNDING WORLD | May 2021
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IMAGE: FRAUNHOFER WKI IMAGE: FRAUNHOFER WKI/HAGER ELECTRO
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