Agriculture Reference
In-Depth Information
company NAFGO GmbH (Neerstedt,
Germany) using a D
EMTEC
®
line with four
drums (Demaitre B.V., Belgium). A detailed
description of the industrial equipment has
been published by Müssig (2001b). The
resulting raw fibres were labelled as GDE-
02.
Ramie: the fibres for the experiments
the studies presented here because of its
high cellulose proportion. Lyocell fibres
with a fineness of 6.7 dtex were made
available by Lenzing AG, Austria.
These fibres and fibre bundles were tested with
the above-described testing methods. The results
are described in detail in this chapter. Because
of the extreme values reached by flax fibres, two
very different flax varieties were tested.
•
were made available by the company
Buckmann, Bremen, Germany. In this
case, chemically separated ramie fibres
(
Boehmeria nivea
H. and A.) from China
that had been processed into card slivers
were used (delivered 2000).
Cotton: in the experiments, the following
10.3.2 Density
•
Natural fibres have attracted attention in the
last decade as a possible substitute for glass
fibres in composite components. Especially for
lightweight applications, natural fibres offer a
significant lower density (> 40%) compared to
the weight of glass fibres (2.7 g/cm
3
). This can
be confirmed in the results of the true density
measurements in Fig. 10.10. The observed
density ranges from 1.30 g/cm
3
for sisal fibres
to densities of over 1.5 g/cm for cotton, ramie
and lyocell. The true densities depend more on
the structure than on the chemical composi-
tion of the fibre. Bobeth (1993) has pointed
out that various factors, like the presence
of impurities on the surface following a chemi-
cal treatment, the conditioning state of the
samples and the presence of closed cavities,
may influence the results and thus affect the
measurement. Batra (1998) also noticed a
wide scattering when comparing values from
several authors.
Due to the porous structure of natural
fibres, differences can appear between the
apparent density and the true density. Com-
parative studies (in 1971 and 1974) reported by
Batra (1998) have measured differences up to
53% for banana fibres. The lowest difference
cotton fibre was used: cotton (
Gossypium
barbadense
L.) species: US Pima; mean
length by number (Almeter) Ø 25.13 mm;
fineness (gravimetric) Ø 1.452 dtex (FIBRE,
1994).
Lyocell: lyocell (Lyo… from Greek: lyein =
•
dissolve, cell from cellulose), on the basis
that cellulose belongs to the group of indus-
trially created fibres as do viscose or cupro
(Schnegelsberg, 1999). Lyocell fibres are
gained from a solution of cellulose in an
organic solvent (N-methyl-morpholine-N-
oxide) by regenerating the cellulose to fibre
form with the aid of the NMMO procedure
and thus consist of almost 100% pure cel-
lulose. The special characteristics of lyocell
fibres such as high strength and compara-
tively low elongation are due mainly to a
highly crystalline structure and the orienta-
tion of the molecules. Application areas of
lyocell fibres are, according to Koch (1997),
particularly in the clothing sector, but also
in the field of technical textiles such as fil-
ters and special types of paper. Even
though the lyocell fibre does not belong to
the group of natural fibres, it is included in
1.70
1.54
1.54
1.60
1.50
1.40
1.30
1.20
1.10
1.00
1.48
1.50
1.51
1.46
1.42
1.30
Sisal
Jute
Flax B
Flax A
Hemp
Cotton
Ramie
Lyocell
Fig. 10.10.
Density of different natural fibres and lyocell using the suspension method.
