Agriculture Reference
In-Depth Information
need the fibres to be organized. What matters
to them is their homogeneity. By contrast,
where thread is being produced, it is essential
that the fibres be aligned in parallel. This there-
fore requires a very particular production
organization and equipment.
These qualitative characteristics will
guide the conceptualization of the industrial
tool(s).
dried, the straw is stored in stacks before being
sent to the mill.
In Serbia, we have observed the ancient
technique of immersion in which the straw is
plunged into a retting bath. At the end of this
process, the sheaves are taken out and placed
to dry in bundles, as described above.
The retting achieved by this technique is
both deep and intense, the straw is easy to
break and fibres are easy to extract.
9.3 The Different Techniques
for Fibre Preparation
Fibre extraction
The fibre extraction techniques currently used
to produce textile fibres are similar to those
used for flax fibres and rely on the same
principle:
Fibres can have different end uses correspond-
ing to particular technologies. We will discuss
in order:
•
mechanical crushing using fluted rollers;
1. Fibres for use in textile manufacturing.
2. Fibres for use in paper manufacturing.
3. Fibres for technical uses.
•
the chain is fed manually or mechanically,
ensuring that an even layer of stems is fed
into the rollers;
the crushing rollers break up the fibre and
•
the hurds.
Once the fibre has gone through two sets
of rollers, it is collected by an operator,
who creates a bundle weighing between
1 and 3 kg.
The hurds are recovered from below the
rollers using a pneumatic or chain-driven sys-
tem. Figure 9.2 illustrates the principles of
this operation and the machines involved.
These machines are still based on a tool
designed at the end of the 19th century
(Renouard, 1909).
9.3.1 Preparation of threads
for yarn, textile and rope, etc.
Quality demanded for the
manufacture of textile fibres
At the end of the processing phase, the fibres
extracted must be as long as possible, organ-
ized longitudinally and perfectly clean, without
any residue of hurds.
Retting
In order to obtain the quality of product
described above, hemp must be retted for a
long period of 2-3 weeks.
Today, this phenomenon cannot be seen
in France and it is necessary, in the 21st cen-
tury, to visit facilities in Serbia or Ukraine in
order to get a good idea of what was still
practised in Europe as recently as a few dec-
ades ago.
In Ukraine, hemp is cut by a reaping
machine (using a Russian machine, the design
of which resembles that of a reaper-binder),
then gathered into sheaves after a period of
time spent retting on the ground. The sheaves
are then placed in bundles of 5-8. In this way,
the straw continues to ret while drying. Once
Fig. 9.2.
Principle of the crushing machine.
