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

to the computing effort and the subjective and manual fitting of crystallite size with the
Debye method, the Rietveld method is more suited as a standard method.
The results for cellulose content and crystallinity are presented in Table 4 and compared
in Figure 14. The highest cellulose crystallinity (90-100 g/100 g cellulose) was found in
barley straw, corn stover and Felina hemp fibres (full drawn line in Figure 14).
Intensity [Counts]..
150000
100000
50000
0
110
110
102
200
0 30
2θ [ o ]
004
Measured diffraction
Fitted total diffraction
Amorphous part of fit
Figure 13. Diffractogram of water retted hemp fibres measured in reflection mode of a
side-loaded fibre sample. Determination of the crystalline cellulose content was done by
Rietveld refinement. The obtained fits for the amorphous and the crystalline diffraction
are shown (further details in Paper III). The peak positions are marked with Miller
indices.
Norway spruce had a cellulose crystallinity of 67 g/100 g cellulose, which is similar to
previous findings of 51-71 g/100 g cellulose also determined with X-ray diffraction
(Andersson et al., 2003). The cellulose crystallinity was on the same level in filter paper
(65 g/100 g cellulose) and was also comparable to the crystallinity of 68 g/100 g
cellulose that has been measured in pine kraft pulp by 13C-NMR (Liitia et al., 2003).
The cellulose crystallinity of wood based materials was thereby found to be on the same
level when determined by X-ray diffraction and by 13C-NMR, and the pulping process
had only slight effect on the cellulose crystallinity. The present data as well as literature
data are shown in Figure 14 and related by the dotted line, which represents the sample
crystallinities at a cellulose crystallinity of 65-g/100 g cellulose.
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