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United States Department of Agriculture

Agricultural Research Service

Title: Chemical and Spectroscopic Analysis of Lignin in Isolated Flax Fibers

Authors
item Morrison Iii, Wiley
item Himmelsbach, David
item Akin, Danny
item Evans, Jeff

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2002
Publication Date: July 1, 2003
Citation: MORRISON III, W.H., HIMMELSBACH, D.S., AKIN, D.E., EVANS, J.D. CHEMICAL AND SPECTROSCOPIC ANALYSIS OF LIGNIN IN ISOLATED FLAX FIBERS. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY. 2003. v. 51. p. 2565-2568.

Interpretive Summary: Flax is the source of lined and is being used as a replacement for glass and carbon fibers in composites. It is a commercially important crop in Europe; interest in flax/linen is gaining in the US. Flax fiber is released from the plant by a process called retting in which the action of microorganisms degrades the glue, which hold the fiber to the stalk. Aromatic compounds that have been thought to adversely affect fiber spinning properties and favorable in the composites industry are thought to be in the fibers. This study examines pure flax fibers from seed grown for oil and flax that are grown only for fiber which have been isolated so that none of the "glue" remains on the fibers. Both chemical analysis and sensitive photometric instruments are used to examine the chemical make up of the cleaned fibers. These investigations have shown that there are no aromatic compounds associated with flax fibers. The indication is that the favorable properties associated with fiber use in composites may be relate to phenolic acids present in carbohydrates remaining on the fibers after processing and not a property of the fiber itself. This work provides a better understanding of the properties of pure fibers so that standards, which are being developed to evaluate flax quality, can be more accurately related to end product use.

Technical Abstract: The chemistry of pure flax fibers free of contaminating non-fiber components has not been determined. Fibers from the center sections of the stem of seed and fiber flax (Linum usitatissium), which had been retted after soaking in water and removal of the epidermis by hand, underwent chemical and spectroscopic analysis. Wet chemical analysis showed only trace indications of aromatics and no long chain fatty acids or alcohols i fibers. Pyrolysis mass spectroscopy (PyMS) and pyrolysis gas chromatography mass spectrometry (PyGCMS) showed only track amounts of aromatic constituents that could be attributed to the presence of lignin. Mid-infrared (Mid-IR) and RAMAN spectroscopy of these fibers showed no aromatic compounds present. This study suggest that earlier work reporting the presence of lignin ranging from 1 to 4% may be the result of residual shive material remaining after the retting process which may be responsible efor the favorable properties desired by the composites industry.

Last Modified: 11/21/2014
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