New materials that look and behave like plastics can be produced from a renewable raw material known as liquid wood. The bioplastics promise to displace petroleum as a feedstock for certain applications. The materials have now even been optimised for the fabrication of novelty goods, although the process may not be quite ready to manufacture toys for this Christmas, the researchers have produced Nativity figurines in collaboration with one manufacturer.
Modern plastics are usually produced from refined petroleum oil, although the original plastics Celluloid and Bakelite both had some naturally derived ingredients. A bioplastic derived from 100% renewable raw materials would represent a step forward in sustainable manufacturing.
Nativity figurines made of liquid wood © TECNARO GmbH/Fraunhofer-Gesellschaft
Now, researchers at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal and the Fraunhofer spin-off Tecnaro GmbH in German have developed Arboform from liquid wood. The cellulose, paper industry separates wood into its three main components – lignin, cellulose and hemicellulose, explains ICT team leader Emilia Regina Inone-Kauffmann. The lignin is not used in papermaking, so she and colleagues at Tecnaro are using this raw lignin mixed with fine natural fibres of wood, hemp or flax together with natural additives including wax to produce a plastic granulate material that can be melted and injection-moulded.
The company has already produced car parts and vessels composed of this bioplastic, but explains Inone-Kauffmann it was not previously suitable for making children’s toys. Toys have to be tough, because children play rough. They bite, suck, throw, and hammer their toys and leave them outside in all kinds of weather. Whatever happens to a toy, the researchers say, it is vital that the material from which it is made does not release any plastic softeners or heavy metals that could endanger children.
An obstacle in the path of making toys from lignin-based bioplastic is that in order to separate lignin from cell fibres in the initial pulping process, sulfur-containing additives are used to help in the break down process. Strong sulfur residues in children’s toys are obviously unacceptable, so the team had to find a way to circumvent this problem.
We were able to reduce the sulfur content in Arboform by about 90%, and produced Nativity figurines in cooperation with Schleich GmbH. Other products are now at the planning stage,” says Tecnaro’s managing director Helmut Nägele.
Sulfur-free lignins are usually soluble in water – and therefore unsuitable for toys, so an additive was required to prevent leaching of the materials when chewed or left out in the rain. The team has also incorporated recyclability into their material, although modern dyes mean you could theoretically have any colour you like; as long as it is green.
Further reading
The Fraunhofer Institute for Chemical Technology homepage
http://www.ict.fraunhofer.de/EN/index.jsp