Agriculture Reference
In-Depth Information
Table 14.3.
Production of 1 kg of fibres.
these characteristics in the plastic to which
it is added.
Hemp compounds can be coloured using
the same traditional methods in use in the plas-
tics industry. Additionally, the fibres can be col-
oured before compounding in order to produce
materials where the fibre's colouring is more
obvious.
In view of the natural humidity content
of reinforcing hemp fibres, the surface of
compound plastics possesses a conductivity
that favours the dispersal of electrostatic
charge.
Fogging tests, using the Renault D45
1727/D method, on a 70:30 PP/hemp com-
pound yielded a translucent homogeneous fog
deposition with a fogging index of 90.2.
Hemp
Glass fibre
Energy
consumption
3.4 MJ
48.3 MJ
CO
2
emissions
0.64 kg
20.4 kg
SO
2
emissions
1.2 g
8.8 g
NO
2
emissions
0.95 g
2.9 g
Biochemical oxygen
demand
0.265 mg
1.75 mg
Chemical oxygen
demand
3.23 g
0.02 g
Table 14.4.
Substitution of 1 kg of natural fibres to
1 kg of polymer.
Hemp
Polypropylene
Energy
comsumption
3.4 MJ
101.1 MJ
Suitable polymers and fibres
CO
2
emissions
0.64 kg
3.11 kg
The principal component of natural fibres
is cellulose, which degrades at tempera-
tures in excess of 250°C. Consequently,
the only polymers that are suitable for use with
reinforcing natural fibres are those whose
transformation temperatures are below
250°C. The most commonly used polymers
are the polyolefins, the styrenes and PVC
(Fig. 14.11).
Hemp provides the best mechanical
properties among the fibres in common use
(Fig. 14.12).
SO
2
emissions
1.2 g
22.2 g
NO
2
emissions
0.95 g
2.9 g
Biochemical
oxygen demand
0.265 mg
38.37 mg
Chemical oxygen
demand
3.23 g
1.14 g
Table 14.5.
Savings over the lifespan of a vehicle
consuming 7 l/100 km of petrol, assuming the
combustion and production of the amounts shown.
Energy saved
273 MJ
Reduction in CO
2
emissions
17.76 kg
Implementation
Reduction in SO
2
emissions
5.78 g
Reduction in NO
2
emissions
163 g
The implementation parameters are virtually
the same as for virgin polymers, although the
fibres do possess a number of peculiarities that
must be taken into account.
The compounds are normally conditioned
with a residual humidity less than 0.5%. After
a few months' storage, however, or after a few
hours left uncovered, the compound will need
to be desiccated before use.
The temperature at which these com-
pound plastics are used is generally lower than
that for pure polymers (e.g. PP/hemp is
injected at approx 180°C). It is imperative that
mass temperatures in excess of 220°C are
avoided.
It is generally recommended that sudden
increase in cutting force be avoided and that
Fire resistance is reduced slightly. The
addition of 15% hemp to PVS will reduce
the composite's oxygen index from 43.8
to 36. Where necessary, the fibres can
be pretreated with an intumescent pro-
duct in order to restore the fire-resistant
properties.
Polypropylene reinforced with 15% hemp,
tested according to standards XP ENV 1186,
CEE No 85/572, CEE 97/48 and CEE
2002/97, has been approved for contact with
foodstuffs.
Hemp's properties as a sound and
thermal insulator can be used to improve
