964
Cellulose (2019) 26:959–970
Fig. 1 a – c Logarithmic density plots of light scattering in the forward direction (FSC) versus the light scattering in the side direction (SSC) of CNCs made from the different kraft pulps. The size estimation ( l m) of the particles from side scattering are also plotted as normalized curves
in a particle, while the FSC offers information about the transparency of a particle, as well as the complex- ity of its external or internal texture. However, both the SSC and FSC are connected to particle size. Informa- tion about the structural density of particles in suspension can be obtained by comparing the size estimation from FSC and SSC (Strand et al. 2018). The SSC of particles, in combination with calibration curves, has previously been shown to satisfactory estimate the particle size of a wide array of particles in suspension (Va¨ha¨salo et al. 2003). The average values
of the different particle populations were calculated and documented into Table 2. The determined average SSC of the different CNCs showed that birch kraft pulp resulted in slightly larger particles than eucalyptus kraft pulp, and significantly larger particles than the softwood kraft pulp. It is known that different raw materials will result in CNCs of different dimensions, depending on the LODP of the cellulose raw material (Marchessault et al. 1961; Ha˚kansson and Ahlgren 2005). It has previously been reported that treatment of black spruce kraft pulp with
Table 2 Determined and calculated properties of the three different CNCs by FCM analyses
Particle count (particles/ l L) SSC ( l m) FSC ( l m) Hydrophobicity (red intensity) Structural density (FSC/SSC)
CNC
Eucalyptus 2963
0.21
0.34
0.75
1.62
Birch
2616
0.27
0.40
1.91
1.48
Softwood 12,113
0.17
0.31
0.39
1.82
SSC particle size calculated from light scattering in side direction, FSC particle size calculated from light scattering in forward direction, FSC/SSC measure of the structural density of particles
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