Agriculture Reference
In-Depth Information
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Aw of hemp
Absorption
Desorption
Fig. 14.9. Water absorption and desorption for hemp fibres at 25°C.
These can be attributed to the inclusion of
hemp, which itself is an important carbon sink.
If we compare a compound reinforced
with natural fibres to a compound reinforced
with glass fibre, setting aside the lack of toxic-
ity, the low cost, low density, the absence of
abrasion and the improved dimensional stabil-
ity, we can identify enormous advantages
in terms of sustainable development (see
Tables 14.3 and 14.4).
A 1 kg reduction in the weight of a vehicle
arising from the use of hemp fibres will result in
the savings shown in Table 14.5.
Furthermore, hemp is able to store 0.79 kg
of CO 2 /kg of fibre and can release 10 MJ/kg of
energy when incinerated at the end of its life.
It should also be remembered that hemp
has the ability to smother undesirable weeds,
thereby economizing on herbicide treatments
and reducing the cost of cultivation for the sub-
sequent crop.
Hemp fibres are also sufficiently supple to
allow them to withstand mixing in a viscous
environment in a vice/press for injection or
extrusion many times. Their length, and there-
fore their L/D ratio, is preserved and their
properties as reinforcing agents are not affected
by multiple recycling.
Fig. 14.10. Hemp fibres are not oriented in the
direction of the flow of material when an object is
moulded.
Increased geometric stability even when
hot. No post-moulding deformation.
Unmoulding of pieces possible at very
high temperatures. This economizes time
in the production cycle (currently a saving
of 30%).
Very little retraction.
ENVIRONMENTAL IMPACT . The act of reinforcing a
polymer such as PVC with 30% natural fibre
produces a final product with a fossil fuel con-
tent that is only 70%. The ecological impact is
therefore significant, especially in view of the
improvements in the properties listed above.
Other properties
Resistance to ultraviolet (UV) light is unaffected
by the presence of hemp, which itself is resist-
ant to UV.
 
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