Natural fibre bioplastics become largely sulphur-free

Materials World magazine
29 Jan 2009
A spherical loudspeaker made from the largely sulphur-free Arboform

A hemp or flax-based bio-plastic that uses 90% less sulphur has made the material suitable for consumer goods such as toys and electronics, say researchers at the Fraunhofer Institute for Chemical Technology in Pfinztal, Germany.

‘The [sulphur] reduction was possible by making modifications to the bioplastic recipe,’ says Emilia Inone-Kauffmann, team leader for the project. ‘We used different materials (also from renewable sources) to substitute lignin as the main binder.’ The group could not reveal which non-sulphur additives were used.

Traditionally, in ‘liquid wood’ bioplastics, the fibres from hemp or flax are mixed with the lignin from wood and a natural additive such as wax. To separate the lignin from cellulose and hemicellulose, sulphurous chemicals are required. The resulting unpleasant odour makes these plastics unsuitable for products that are in close contact with consumers.

The natural resins of the new bioplastic, Arboform, are said to be water insoluble, meaning toys made from this plastic will not dissolve in children’s mouths.

A cold-extrusion process mixes the component materials and forms them into pellets, which can be melted and injection-moulded. ‘Production is lower-cost than in common composites, and uses less energy, as it is not a [hot] extrusion process,’ notes Inone-Kauffmann. At the end-of-life, the plastic can be broken down and re-pelletised.

Arboform has been used to produce a range of nativity toys, as well as a spherical loudspeaker (see image above), developed as part of a European-funded project. The material is being produced by Fraunhofer spin-out company Tecnaro GmbH.

Further information: Tecnaro