Arboform
Arboform (from {{langx|la|arbor}} meaning tree) is a trade name for a bioplastic composed of three natural components: lignin, cellulose fibers and some additives. As a thermoplastic, it can be molded and is therefore also called 'liquid wood'.
History
Arboform was developed in 1960 by Helmut Nägele and Jürgen Pfitzer at the Fraunhofer Institute for Chemical Technology. In 1998, they founded a spin-off company Tecnaro, and already in 2002, the company produced about 300 tonnes of Arboform and was selling it at a price of about $9.5/kg. In 2009, Nägele and Pfitzer received the European Inventor Award for their work on Arboform.
Composition and properties
Arboform consists of the two most abundant natural materials: lignin (ca. 30%) and cellulose (ca. 60%). The remaining part is natural additives that function as plasticizers, dyes, antioxidants, fillers, etc.Nägele, 107 It has a similar composition, appearance and properties to those of wood, but it can be melted upon heating and molded like a thermoplastic.Nägele, 101–102 It has been designed toNägele, 104
- contain no synthetic phases
- have mechanical porporties similar to those of polyamide
- be thermally stable up to 95 °C
- be moldable at temperatures below 160 °C.
When the amount of cellulose in Arboform is increased from 30 to 60%, its tensile strength increases from 9.5 to 14.5 N/mm2 and bending stress increases from ca. 23 to 39 N/mm2, while the indentation hardness and impact strength remain almost constant at ca. 135 N/mm2 and 3.2 mJ/mm2, respectively.Nägele, 109–110 Other typical properties of Arboform are:Nägele, 116 thermal conductivity 0.38 W/(m·K), electrical resistivity ~5 GOhm, water content 2–8%.
| class="wikitable"
|+Comparison of properties of Arboform and common plasticsNägele, 115 !Property!!Arboform!!Polyethylene !! Polypropylene !!Polystyrene | ||||
| Tension at break (N/mm2) | 14–22 | 8–30 | 30–40 | 45–65 |
| Modulus of elasticity (in tension, N/mm2) | 2000–7000 | 50–500 | 600–1700 | 1200–3300 |
| Thermal expansion (10−6/C) | 10–50 | 170–200 | 100–200 | 70 |
| Shrinkage upon molding (%) | 0.1–0.3 | 2–3 | 2–3 | 1–3 |
Synthesis
Arboform is typically sold as pea-sized granules of various colors. Their production method differs from those used for synthetic polymers in that it avoids excessive thermal stresses and overheating that can degrade the natural components of Arboform.Nägele, 106 The granules can then be molded into desired shapes, e.g. a wrist watch frame, using injection molding at temperatures of 150–170 °C. After molding, the material has a density of about 1.4 g/cm3.Nägele, 111 It can be sawed, burned and disposed of in ways similar to those for wood, i.e. it is a biodegradable material.Nägele, 114
References
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Bibliography
- {{cite book|author=Nägele, H.|chapter=Arboform® – A Thermoplastic, Processable Material From Lignin and Natural Fibers|editor=Thomas Q. Hu|title=Chemical Modification, Properties, and Usage of Lignin|url=https://books.google.com/books?id=kUTul-zi7nIC&pg=PA101|year=2002|publisher=Springer|isbn=978-0-306-46769-1|pages=101–117|display-authors=etal}}