Agriculture Reference
In-Depth Information
20
Cotton
Flax B
Flax A
Hemp
15
10
5
0
0
10
20
30
40
50
60
70
80
Fineness (
μ
m)
Fig. 10.15.
Example of fibre fineness distributions for cotton and bast fibre bundles.
chemical-physical or enzymatic) separation, the
property profile of the fibre bundles can be varied
in accordance with product requirements.
To demonstrate the adaptability of the pro-
posed testing methods, hemp fibre bundles were
tested after different separation steps. For this
trial, hemp (
Cannabis sativa
L
.
) variety Felina
34, grown in Klagenfurt, Austria, was used. A
detailed description of the harvesting process of
the hemp used is given in Müssig (2001a). The
thin and well-retted hemp stems were separated
in a separation plant, as shown in Fig. 10.16.
Samples were taken at different positions
of the line. The peeled bast of the thin stems
was labelled as (RS). Coarsely separated (GA),
medium (MA) and finely separated (FA)
fibre bundles were produced. After the coarse
separator, a part of the material was removed
from the line to be separated in a steam explo-
sion process (GAD) and afterwards opened
with an opener (GADO). The objective of this
trial was to demonstrate the wide range of pos-
sible fibre properties that could be produced
based on hemp. The results of the measure-
ments are presented in the following sections.
illustrate how large the variations in fineness
are at different separation steps.
As described previously, the gravimetric
fineness measurement test is very time-
consuming, but the need for special testing
equipment is low. A disadvantage of this pro-
cess is that no fineness distribution is available
based on the measurements of one sample set
(here, 370 tested fibre or fibre bundles). This
leads to missing statistical data like the stand-
ard deviation and the coefficient of variation.
In this context, Simor (1965) mentioned the
work of Fröter and Zienkiewicz (1952), in
which a level of confidence of ±3% at 95%
security level was achieved only after 5000
gravimetric measurements on flax. With a view
to fast measurements, the gravimetric fineness
measurement method is not the best choice.
OFDA
The fineness of fibre bundles was examined
by the OFDA (optical fibre fineness analyser)
method. The optical fibre fineness analyser
was developed for measuring the diameter of
wool fibre (Baxter
et al
., 1992). This appara-
tus measures the width distribution of bast
fibre bundles efficiently and results have been
found to correlate well with those of other
methods. Because of the large number of
measurements taken, our results could be
reproduced well. This method is very rapid,
as well as being highly reproducible (Drieling
et al
., 1999).
10.4.1
Fineness (GA - GADO)
Gravimetric fineness (GA-GADO)
Refinement of hemp bundles by the separation
process is shown in Fig. 10.16, as determined
by the gravimetric fineness measurement
method. The results given in Fig. 10.17
