Properties of hemp fibre polymer composites -An optimisation of ...

5 The hemp plant
The experimental study of hemp fibre structure (Part 5.2) and chemical composition
including cellulose crystallinity (Part 5.3) are based on investigation of the middle
section of hemp stems from the Felina cultivar cultivated at Danish Institute of
Agricultural Sciences in 2001 as described in Part 5.1.
5.1 Hemp cultivars and growth
Hemp (Cannabis sativa L., Figure 2) belongs to the Angiosperm phylum since it has
vessel elements in the woody core (xylem) like hardwood. It belongs to the
eudicotyledons like hardwoods, numerous bushes and herbs, since it has two cotyledons
(i.e. seed leaves). The long and flexible hemp fibres are embedded in the bark (cortex) on
the surface of the stem.
In Northern Europe, hemp plants get 1.9-2.5 m tall dependent on cultivar, sunlight and
weather conditions (Cromack, 1998). In the cultivation experiments at Danish Institute
of Agricultural Sciences in 2001, the stems diameter was highest for the cultivars, Felina
and Futura (7-12 mm) and lowest for Finola and Fedora (5-7 mm) (Table 1).
Figure 2. Hemp field with mature hemp plants (left). Hemp stem, leaf and plant top
(right).
5.1.1 Cultivation including the experiments at Danish Institute of
Agricultural Sciences
Hemp originates from Central Asia (van der Werf et al., 1996) but can be cultivated from
the Equator to the polar circle (Vavilov, 1926). In Central Europe, the optimal stem yield
is obtained when the plants are sowed in March. Then the period with maximum daylight
(May-July) will be used fully.
The cultivation experiments at Danish Institute of Agricultural Sciences in 2001 were
done at the research site Flakkebjerg of The Danish Institute of Agricultural Sciences.
The location is 55°20’N, 11°10’E and 0-50 m above sea level. The hemp cultivars
Fedora, Felina, Fenola and Futura, were sown May 7 th due to the risk of frost in April (