Natural Cellulose Fibers from Renewable Resources

Keywords

Banana fiber • Pseudo-stem • Fiber extraction, fiber yield • Mechanical treatment

One of the most ubiquitous fruits, banana is widely grown across the world. About 120-150 million tons of bananas are grown annually in the world, and it is the fourth most important food product in the world. However, the banana fruit only represents about 12 % of the weight of the plant and the stem; leaves and other parts are not generally edible. Therefore, efforts have been made to use banana leaves and stems for various nonfood applications including fiber production. Fibers are obtained from the pseudo-stem of the plant mostly by mechanical means. Full — fledged banana fiber production has been reported to be operational in several countries. Some of the products developed from banana fibers include textiles, paper, floor mats, and composites. In terms of properties, banana fibers have the typical composition of fibers obtained from lignocellulosic by-products and contain about 50 % cellulose, 17 % lignin, and 4 % ash [09Gui]. However, the composition of the banana fibers reported varies widely, and fibers with lignin content as high as 17 % have been reported [08Hab]. In addition to the stem, fibers have also been obtained from the leaf and rachis of the banana plant. Considerable variations in the tensile properties were observed for the fiber bundles obtained from the different parts and also depending on the method of extraction as seen in Table 7.1 [08Gan]. Tensile properties of the fibers obtained from the banana stems are similar to those of common lignocellulosic fibers such as jute, but the elongation is considerably lower than that of the coconut and palm (Borassus flabellifer) fibers. Low elongation of the banana fibers should mainly be due to the lower microfibril­lar angle (11°) and relatively high % crystallinity [08Muk]. Banana fibers also appear to have a hollow center similar to that found in a few other natural cellulose fibers. Considerable variation in the tensile properties, especially elongation, was observed for fibers with various diameters (50-250 pm) as seen in Tables 7.1, 7.2, and 7.3 [10Ven]. In addition to the stems, fibers have also been obtained from the

leaves of the banana plant. Typically, banana plants produce about 30 leaves as long as 2 m and 30-60 cm wide [07Bil]. Fibers obtained from banana leaves had about 26 % cellulose, 17 % hemicellulose, and 25 % lignin, but the fiber properties are not reported [07Bil]. A Switzerland-based company (Swicofil) advertises that it had developed fabrics from ring — and rotor-spun banana fibers. Ring-spun yarns in counts ranging from Ne 8/1 to 40/1 and rotor-spun yarns with counts (Ne) ranging from 8/1 to 30/1 were reported to be available in 100 % form and also as blends with cotton, modal, Tencel, and soy protein fibers. Banana fibers are reported to be available on the market for about US$0.43-0.81/kg compared to $0.15-0.60 for hemp and $0.15-$0.21/kg for flax.

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