Renewable sources provide the raw materials for a growing variety of everyday products. One example is a meltable wood polymere called Arboform, which is injection-molded to produce different parts. In the near future, an extruder will form artists’ crayons and cosmetic pencils.
Every Christmas season, Mary and Joseph and baby Jesus take their place under the star of Bethlehem, surrounded by shepherds, wise men, angels and all the animals. The objects in the nativity scene are usually carved in wood, but they may be made of modeling paste, pewter, plastic or even beeswax. An innovation allows figurines to be manufactured cheaply by injection molding using a natural wood product. Arboform was developed at the Fraunhofer Institute for Chemical Technology ICT. But how can that be possible, given that wood neither melts nor dissolves in any common solvent.
Lignin is the most commonly occurring natural polymer after cellulose. In wood it holds the plant fibers together, forming a rigid but elastic composite material. In the paper industry, the two substances are separated using a chemical process. Engineers at ICT spin-off TECNARO in Eisenach, Thuringia, extract the lignin and mix it with natural fibers such as sisal, hemp or linen, along with certain additives and dyes, according to the customer’s requirements. The mixture is extruded to produce a granulate, in a plant with a monthly output capacity of between five and ten metric tons.
Arboform can be processed in an injection-molding machine like any normal thermoplastic, and used to manufacture aesthetically pleasing products such as nativity figures, loudspeaker units, car instrument panels, chessmen for board games, or the stock of hunting rifles. The company even has a golf tee in its product range. Less experienced golf players often hook the tee out of the ground together with the golf ball. The “Di Tee-CHAMPION” is so pliable that it doesn’t damage the sharp blades of the lawnmower. Because the tees are made from a biodegradable material, they decompose on the compost heap together with the grass cuttings.
With its extrusion process for liquid wood, TECNARO is venturing into unexplored territory. The method allows plastics to be processed in a continuous stream like pasta dough, and hence at a much faster rate. Obviously, the company doesn’t envisage wooden macaroni. “In a few months’ time, we hope to start production of artists’ crayons and cosmetic pencils,” states Jürgen Pfitzer, who founded the company together with colleague Helmut Nägele in 1998. “Our close ties with the Fraunhofer Institute give us every confidence that our extruder will be able to achieve the required product quality.” At present, top-quality artists’ crayons are still manufactured from imported cedar wood, while lip and eyebrow pencils are generally made using conventional petroleum-based plastics.