Processability of flax plant stalks into functional bast fibers

• Published in: Composite interfaces 2008-01, Vol.15 (2-3), p.147-168
• Main Authors: Foulk, Jonn A., Akin, Danny E., Dodd, Roy B.
• Format: Article
• Language: English
• Subjects: COMPOSITE; FIBER QUALITY; FLAX; FLAX FIBER
• ISSN: 0927-6440; 1568-5543
• DOI: 10.1163/156855408783810902

Flax (Linum usitatissimum L.) is an agricultural crop that is being considered as cost effective alternative to glass in composites. Flax is nature's composite with strong bast fibers held together in bundles and located in the outer regions of the plant stem between the outermost cuticle-epidermis layer and the innermost, woody tissues. Agricultural production of this crop is environmentally beneficial because it is produced through photosynthesis and considered a naturally renewable and sustainable material. Its use in bio-based composites could help lessen our dependence on fossil fuels today and into the future. Despite the longevity of flax in world markets, particular problems exist to provide flax fiber economically for markets in the US and North America. Barriers to such provisions include consistent, high-quality retting methods, efficient processing of whole stems into cottonized fibers, and development of standards to judge fiber quality. Processability of plant stalks into usable fiber requires retting which selectively removes pectinaceous and matrix substances thus separating cellulose fibers from non-fibrous substances and easing mechanical cleaning. Enzymes have been tested for efficiency of retting, and recommendations are in place for particular fiber properties. Before this work began, no processing facilities existed in North America for producing high value fibers. To facilitate research on bast fiber retting and subsequent processing, the Flax Fiber Pilot Plant (Flax-PP), was designed and modified after the 'Unified Line'; it is the only research facility of this type in the US and effectively processes and extracts bast fibers from plant stalks. A separate cottonizing unit has been installed to complete processing of fibers for various applications. Each processing step creates a fiber product and byproduct both with potential uses in composites. The development of standards through ASTM International is a continuing project. Currently, emphasis is on new equipment to quantify properties of particular usefulness such as cleanliness, fineness, and color. The Flax-PP becomes a valuable tool for improving fiber processing and quality, and thus integrates all activities for a flax fiber industry in North America.