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

kill the fungus. The fibres were thereafter washed in water and aligned into a planar
sheet followed by vacuum drying. The yield of fibres from the original hemp stems was
determined by 2-3 repetitions at the small, medium and large scale.
Table 1. Overview of the experimental conditions used for fungal defibration of hemp
and for water retting of hemp
Hemp
g DM 1
Stem length
cm
Mycelium
ml
Medium 2
Time
days
Fungal defibration
Small scale 5.4 6 10 75 ml NS 7 – 31 72
Medium scale 45 6 70 625 ml NS 14 72
Large scale 90 25 140 1000 ml NS 14 90
Other methods
Water retting 20000 25 None 750 l water 4 27
1: DM = Dry matter
2: NS = Nutrient solution as a growth medium
Analysis of the culture broth and the plant fibres
Dry matter
g/l medium
In the fungal culture broth solution, the peroxide content was measured with an analysis
stick placed for 1 sec in the solution. The stick was withdrawn from the solution; after 5
sec the content of H2O2 was measured on a colour scale [Peroxide 100; Quantofix at
Macherey-Nagel in Germany]. The pH-value of the culture broth was measured using a
pH-electrode.
Determination of cellulose crystallinity in the plant fibres was done by X-ray diffraction.
The raw fibre samples were cut into small pieces in a knife mill with a 0.5 mm sieve.
The milled samples (0.5 g) were wetted with distilled water and side loaded into a
sample holder to reduce the effect of preferred orientation and thereby get the correct
ratio between the diffraction peak areas. The samples of 2 mm thickness were air dried
overnight before the diffractograms were recorded. The cellulose crystallinity was
measured with X-ray diffraction in reflection mode. A Philips PW1820/3711
diffractometer with Bragg-Brentano scattering geometry, copper Kα-radiation and
automatic divergence slits was employed. Data were collected in the 2θ-range 5° – 60°
with a step size of 0.02° and a counting time of 20 sec per step. The reflection mode
intensities were corrected for the effects of the automatic divergence slit. The
diffractograms were divided into crystalline and amorphous contributions by Rietveld
refinement. The crystalline diffraction was fitted with the diffraction pattern of Cellulose
Iβ and polynomial fitting was used to determine the amount of amorphous diffraction
from amorphous cellulose, hemicellulose, lignin, pectin and ashes (Thygesen et al.,
2005b).
Before the comprehensive plant fibre analysis, the samples were milled into particles that
could pass a 1 mm sieve. This plant fibre analysis method is a gravimetric method for
fibres from agricultural plants and wood (Browning, 1967; Thygesen et al., 2005b).
Double repetition was used with 4 g fibers passing through the procedure. At first wax
was Sohxlet extracted in chloroform for 1 h. Water-soluble components were extracted
in 400 ml water for 30 minutes at 25°C. Pectin was extracted in 300 ml 3% EDTA
124 Risø-PhD-11