New Low Cost Flax Fibers for Composites 2000-01-1133
Flax (Linum usitatissimum L.) has supplied fiber for textiles for thousands of years. Recently, flax has been considered as a cost-effective alternative to glass in composites. New technology and separation techniques have lowered the costs to produce fibers that are more uniform in color, strength, length, and fineness and thus better suited for composites.
Using redesigned techniques over those traditionally used in flax production, fiber separation begins at the farm using readily available agricultural equipment that has been tailored for flax harvesting. Rather than the expensive European harvest method of pulling stalks, rapid methods developed in the U.S. harvest flax stalks with a drum mower. Costly, specialized imported harvesters are no longer required to produce uniform fibers. Equipment is low cost, readily available and well understood by U.S. farmers.
To further improve fiber quality, flax is not dew-retted, which depends on indigenous fungi to separate fibers. Rather, the cut stalks are field-dried and baled for retting with commercial enzymes in designed formulations. To improve the separation of fibers from the flax, various crimping methods and enzymes are used. Fiber yields following Crimped Enzymatic Retting (CER) indicate that certain crimping forces affect fiber yield. Commercially available cleaning and cottonizing equipment further separates the shive material from the fibers producing fibers of a similar quality and lighter in color compared to dew-retted flax.
A preliminary economic study suggests that fiber flax can be grown with a profit margin. Further, initial results on straw residues from the flaxseed industry show that fibers of good yield and quality can be produced by the CER method.
Dew-retted flax fibers have a lower density but similar tensile strength values at a lower cost compared to glass fibers and, therefore, could provide an environmentally friendly alternative in composites. While, dew-retted flax fibers are capable of producing composite materials, research is required on optimal use of enzyme-retted fibers. Heretofore, characteristics important in composites have been defined from dew-retted fibers.
Replacing glass fibers with flax fibers may allow better material separation, recycling, remanufacturing, and reuse of production waste. End-of-life composite materials could be easily incinerated and used as an alternative fuel source with no glass residue. Emission and source reductions may occur because the fibers are derived from naturally renewable materials created through photosynthesis.