Agriculture Reference
In-Depth Information
Europe produces approximately 1 Mt of
temperature-hardened composite plastics.
Germany is the main producer and the auto-
mobile and electrical markets are the main
consumers of these materials, except in the
UK, where the construction industry is the
main consumer.
Thermoplastic polymers, whose shape
could be changed simply by increasing the
temperature and thereby softening the plas-
tic, were soon reinforced with fibres (first
glass, then carbon and polymers). At the
present time, nearly 20% of the 35 Mt of
thermoplastics transformed in Europe are
reinforced with fibres. There are few rein-
forced polymers and, currently, polyamides
are the main source. The principal applica-
tions for these products are in the automobile,
electricity, sport and leisure industries.
Recently, the use of long fibres with the same
polymers has further improved the mechani-
cal properties of these products. The volume
of thermoplastics produced per year is increas-
ing faster (5% per year) than the volume of
temperature-hardened plastics (Fig. 14.2).
The situation in the USA is much the
same as in Europe. North America has, how-
ever, shown a greater tendency to develop
composite parts for the automobile industry
(130 kg/vehicle in the USA, compared to
30 kg/car in France). The growth in this
market is very significant, especially for the
car manufacturer, SMC, who has over 100
applications for composites. Ford makes the
greatest use of composites: using them for
almost all the bonnets and radiator grills in
its vehicles. The latter was, in fact, the first
to introduce composite plastic reinforced
with natural fibres, in particular for the back
of its pick-up trucks. The consumption of
reinforced polymers in the USA is of the
order of 1800 kilotonnes (kt), of which 650
kt are thermoplastics. The relative impor-
tance of each market is comparable to that in
Europe (Fig. 14.3).
14.3
Natural Fibre Reinforced
Polymers
14.3.1 Natural fibres
Natural fibres can be of animal origin (wool,
silk…) or of plant origin (cotton, flax, hemp,
jute, sisal, kenaf, cocoa, abaca and wood).
Plant-derived fibres are the most common
natural fibres used to reinforce plastics. In
Europe, wood, flax and hemp are easy to pro-
duce and are consequently the three fibres
most commonly used. In terms of the manage-
ment of resources, it should be noted that both
hemp and flax are annual plants. Their pro-
duction can therefore be increased significantly
at short notice. Wood, by comparison, requires
many years of growth before it can be
exploited.
Vegetable fibres are all made of four con-
stituent principal components. The respective
proportions of these components vary between
plants (Table 14.1).
The main constituent of plant fibres is cel-
lulose, a polymer with entire blocks in crystal-
line form. The different constituents are not
distributed homogeneously within the complex
microstructure of the fibre. The elementary
300
250
200
150
100
50
0
Year
Thermoplastics
Thermosets
Fig. 14.2.
Consumption of reinforced fibres.
