Biomedical Engineering Reference
In-Depth Information
Lignin as a natural additive has shown a potential for improving tensile charac-
teristics in cotton or man-made cellulose fiber reinforced PLA composites and lead to
composites with a higher degree of compaction. The tensile strength of lignin treated
composites could be improved by a factor of up to 2.0 and Young´s modulus values by
a factor of up to 1.4 compared to untreated PLA composites. The unnotched Charpy
impact strength was decreased but the values are still higher than those of many bast fi-
ber reinforced PLA composites. In comparison to a previous study dealing with lignin
treated cotton fiber reinforced PLA, the odor behavior could be improved by reducing
the lignin concentration and using the lignin in an ethanol solvent rather than in pow-
der form. Despite the lower lignin concentration similar improvement effects for the
tensile characteristics could be measured.
Brittle bast fiber reinforced composites were improved with regard to the impact
characteristics by using lyocell fibers as additives. The combination of 20% kenaf and
20% lyocell in a PLA composite leads to stiff and strong composites reaching im-
pact properties double as high as the pure matrix. In the general outline the presented
PLA composites with their good mechanical characteristics are well suitable for higher
stressed automotive applications if problems with regard to the temperature resistance
are solved in the future.
aCKNoWledGmeNt
We acknowledge Dipl.-Ing. André Decker (BIK, University of Bremen, Germany) for
supplying the compression moulding technique as well as Georg Goeddecke (NAFGO
GmbH, Neerstedt, Germany) for the support in the needle felt production. For supply-
ing lyocell and PLA fibers we thank Dr. Gunther Sames, Markus Gobl and Dr. Joseph
Innerlohinger (Lenzing AG, Lenzing Austria) as well as Norbert Schultz (RMB fibers
AG, Gütersloh, Germany). For supplying lignin powder Dr. Britta Lohmeyer (Faser-
institut Bremen e.V., Bremen, Germany) and cand. Ph.D. B.Sc. Tim Huber (University
of Canterbury, New Zealand) for carrying out the fragmentation tests should also be
acknowledged.
KeyWords
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Fiber bundles
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Fiber fragmentation
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lyocell fibers
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machine direction
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Poly lactic acid
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Polypropylene
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scanning electron microscope
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