Particle shape information may be either desirable or critical depending on the
degree to which shape affects product performance. Particle shape influences bulk
properties of powders including flow and compaction behavior and the viscosity of
suspensions. For specific application such as glass
beads used in highway paint,
shape is a critical factor for reflectivity. When particle shape information is required,
microscopy and image analysis are the only techniques that delivery the desired
data. Manual microscopy provides basic qualitative size and shape information, but
automated image analysis generates quantitative data that is statistically significant.
For this reason, both dynamic and static image analysis
are growing techniques
replacing manual microscopy.
Surface charge or zeta potential of suspensions is important information for
formulators or chemists working on dispersion stability. For these applications a DLS
system providing both particle size and zeta potential (along with other such as pH
or conductivity) may be the best option.
Consider the application of wanting to measure the particle size distribution of 50nm
colloidal silica. Just considering the size range of the sample indicates that possible
techniques include laser diffraction or DLS. One question
worth asking would be will
I need other capabilities in the future? If I might need zeta potential in the future,
this removes laser diffraction from the list of possible techniques. If I might have
particles > 1µm in the future, this would eliminate DLS.
Be forewarned that future
requirements can be difficult to ascertain and additional capabilities always carry
incremental cost.
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