Ding et al. J Wood Sci
(2020) 66:55
Page 6 of 9
Fig. 5 Mass-weighted size distribution of MDF sanding dust determined by flatbed scanning image analysis (histogram: differential size distribution, line: cumulative size distribution)
ratios bigger than 2, and the particles with AR as high as 0.86 existed, representing wood fibers observed in the SEM picture (Fig. 3a), which are likely to interlock with each other and form mechanical bridges in the handling processes. But given that they only accounted for less than 2% of the total in weight, interlocking should not be considered as the main mechanism influencing the han- dling behaviors of MDF sanding dust. The AR of MDF sanding dust showed different distri- bution characteristics in different size ranges. Larger par- ticles presented a wider AR distribution. But for smaller particles, a much less AR variation was found (Fig. 6). The AR of particles less than 10 μm were concentrated in a range between 0.2 and 0.3, which meant the size reduc- tion gradually reduces the shape variation of MDF sand- ing dust and made them more homogeneous. This seems to be a general trend for bio-based particles and has been repeatedly reported [23, 34, 35]. Figure 7 illustrates how particle shape varies with size reduction. The big parti- cles shown in Fig. 7a are fragments of fiber bundles with various aspect ratios while the fine particle shown in Fig. 7b presents an appearance similar to a sphere. It can also be found that big particles inherit the anisotropic nature of wood. The length of the particles is parallel to the longitudinal direction of wood fibers, which makes the particle orientation an important factor influencing
Fig. 6 Shape distribution of MDF sanding dust and its correlation with particle size
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