Page 339 - Handbook of Properties of Textile and Technical Fibres

312 Handbook of Properties of Textile and Technical Fibres

9.5.4 Kenaf fiber

Kenaf (Hisbiscus cannabinus) is cultivated in tropical regions mainly for its fiber and
seed oil. It is primarily considered as a central Africa and southern Asia crop, and today
it is grown primarily in India and Bangladesh. It is a new crop in the United States and
has shown good potential in biocomposite applications. It is believed that kenaf has
been cultivated since around 4000 BC. In ambient conditions the plant may grow
up to 10 cm/day and matures in 3 months (Nishino, 2004; Aziz et al., 2005). As it
is a fast-growing crop, it can annually yield up to 10,000 kg/ha, and the latest varieties
may yield 30,000 kg/ha annually. The average plant grows 3 m tall with a woody base
diameter 3e5 cm. The bark consists of about 40% of the plant and the fibers are
extracted from it, with the remaining part being core wood (Lee and Eiteman,
2001). The bark has a high crystalline fiber orientation, whereas the core wood has
an amorphous pattern. The stem diameter is often 1e2 cm. It has environmental and
economic advantages; energy consumption to produce 1 kg of kenaf is 15 MJ, whereas
it takes 54 MJ for glass fibers, and the cost of the fibers is considerably lower (Nishino,
2004). The properties of the kenaf fiber are similar to that of jute fibers, and the struc-
ture of kenaf fiber is similar to that of other plant fibers. Several authors suggest using
kenaf fiber as a reinforcement in composites due to its superior toughness (Karnani
et al., 1997; Nishino et al., 2003; Shibata et al., 2006; Akil et al., 2011).

9.5.5 Ramie fiber
Ramie (Boehmeria nivea) is the bast fiber that is native to Asia, and today it is mainly
produced in China and Brazil. It has been grown in China for many centuries and is
commonly referred to as China Grass (Perry et al., 1985). It is an herbaceous perennial
plant belonging to the Nettle family and can be harvested 3e6 times a year. The plant
lasts for around 7e20 years and grows 1e2.5 m tall (Batra, 2007). The presence of
gum, pectin, and other substances in the bark makes chemical treatment mandatory
before the usage of the fibers. The fibers are coarse and have thick walls (Kirby,
3
1964). The global production of these fibers is around 100 10 tons, which is the
least among bast fibers. The low production and impure nature of the plant make it
difficult to consider it as reinforcement for composites on a large scale. Nevertheless,
the Ramie fiber is the stiffest among bast fibers. The fiber yield of the perennial plant
each year was studied by Hearle and Peters (1968).

9.5.6 Sisal fiber
Sisal (Agave sisalana) is a commercial crop produced mainly in Tanzania and Brazil. It
is also widely cultivated in China and Kenya. It is believed that sisal is native to Cen-
tral America, and its fiber was already used in pre-Columbian times (Sisal, 2012). The
sisal plant has been studied in terms of botany, cultivation, and utilization (Ramesh
et al., 2016b). The plant grows to about 1 m tall and 28 mm wide with 200e250
leaves. The leaves are dark green in color, rigid, fleshy, and lance-shaped and grown
in a rosette from the stalk (Sisal, 2012). The lifetime of the plant is about 7e10 years