BAST PLANTS AS A FIBER RESOURCE:
Bast fiber plants provide a means for traditional forest products companies to maintain market share and even capture new markets through the use of alternative raw materials which possess unique and beneficial properties which are particularly fitting for certain applications. They also provide the perception of improved environmental stewardship of our resouces.
Bast fibers have been grown for centuries throughout the world. Bast plants are characterized by long, strong fiber bundles which comprise the outer portion of the stalk. Bast plants include flax, hemp, kenaf, sunn-hemp, ramie, and jute. The focus of our research has been on the species which can grow in temperate regions of the world, namely flax, hemp, and kenaf. These fiberous plants have long been noted for their exceptional strength in cordage and paper. The primary focus of our research will be from a North American perspective, although occasional references will be made to applicable international developments.
The word "bast" refers to the outer portion of the stem of these plants. This stringy, vascular portion comprises 10 - 40% of the mass of the stem depending upon the species of bast plant, as well as the particular variety, or cultivar, within a bast plant.
The remainder of the stem, inside this bast layer is a different type of fibrous material, which has different names depending upon the species selected. This inner material is known as shives when referring to flax and sometimes hemp, as hurd in the context of hemp, and as core when from kenaf. For the purpose of simplicity and consistency, we will use the word "core" when discussing this portion of the bast plant.
Overall Advantages of Bast Plants:
In general, bast plants possess the following benefits:
- High tensile strength in bast portions, especially in fiber varieties.
- Bast plants have a relatively low specific gravity of 0.28 - 0.62, yielding an especially high specific strength, i.e. strength to weight ratio, (Kozlowski, Mieleniak, Przepiera, 1994).
- Generally high fiber productivity rates, rivaling and even surpassing that of the most commercial tree species.
- Potential for even greater productivity, bast portions, and mechanical properties through focused genetic breeding.
Overall Limitations of Bast Plants:
In general, bast plants also have the following limitations:
- Rotations at least every other year generally required.
- Limited
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- Relatively high absorption of moisture in core portion.
- Diminished board properties when using core for particleboard.
- Difficulty in handling long fiber bundle lengths for processing.
- Difficulty in applying binder to long fiber bundle lengths.
Comparative Properties of Bast and Wood Species:
The following graphs illustrates the attractive properties of these bast plant relative to common wood species. These graphs illustrate first the relative cellulose contents and then the tensile strength. The final graph illustrates the specific strength which is the tensile strength relative to the specific gravity. Both tensile strength graphs compare fiber bundle characteristics, as well as those of the individual fiber. Both of these types of particles may be used depending upon the specific processes and end products produced.
