Page 340 - Handbook of Properties of Textile and Technical Fibres

Hemp, jute, banana, kenaf, ramie, sisal fibers 313

and on maturity the fibers are extracted from the leaves; each leaf has about 1000 fiber
bundles of which only 4% is fiber (Mukherjee and Satyanarayana, 1984). The fibers
are traditionally used for rope, twine, and as textile fiber. Decortication is the common
process by which the fibers are extracted. These fibers have been classified into three
types based on the place of extraction, namely mechanical, ribbon, and xylem (Bisanda
and Ansell, 1992). The mechanical fibers have the highest strength among the three,
whereas xylem fibers have the lowest strength; this is because the former fibers are
extracted from the periphery of the leaf and have a defined shape, whereas xylem fibers
are irregular in shape and have thin-walled cells (Bisanda and Ansell, 1992). Ribbon
fibers are intermediate fibers, which are extracted from conducting tissues in the me-
dian line of the leaf and have considerable mechanical strength (Bisanda and Ansell,
1992). The sisal fiber dimensions and their mechanical properties have been studied by
Bisanda and Ansell (1991). The fiber extraction was studied by several researchers
(Mukherjee and Satyanarayana, 1984; Chand et al., 1988). The chemical composition
of sisal fibers is presented in Table 9.1. These fibers are widely used as reinforcement
in composites (Mukherjee and Satyanarayana, 1984; Bisanda and Ansell, 1992;
Mishra et al., 2004).
The sisal fiber and its composites have been reviewed by many researchers (Mishra
et al., 2004; Joseph et al., 1999). Sisal fibers are extracted from the leaves of the sisal
plant. The fibers are extracted by a hand held extraction machine composed of either
serrated or nonserrated knives. The peel is clamped between a wooden plank and knife
and hand-pulled through, removing the resinous material. The extracted fibers are sun-
dried, which whitens the fibers. Once dried, the fibers are ready for knotting. Bunches
of fibers are mounted or clamped onto a stick to facilitate segregation. Each fiber is
separated according to fiber sizes and grouped accordingly. To knot the fiber, each fi-
ber is separated and knotted to the end of another fiber manually. The separation and
knotting is repeated until bunches of unknotted fibers are finished to form a long
continuous strand. These sisal threads can be used for making variety of products
(Ramesh et al., 2013).

9.6 Properties of plant fibers

Plant fiber properties are affected by maturity, geographical cultivation, harvesting
type, weather, etc. It is not possible to generalize or reproduce the properties of plant
fibers as can be achieved with regenerated cellulose fibers. The fiber properties are re-
flected in the composites. In general, every fiber mentioned above has reinforcement
potential in composites for diverse applications. Recycled fibers could also be used
as reinforcement to produce composites and their properties have been investigated
(Huda et al., 2005; Sanadi et al., 1994). Waste textile fibers have been reused as rein-
forcements in composites and their properties studied (Ramamoorthy et al., 2014; Zou
et al., 2011). Every fiber could be used as a reinforcement in several thermoset and
thermoplastic plastics, but not all their properties have yet been evaluated for mechan-
ical, thermal, electrical, chemical, viscoelastic, water absorption, morphological