Introduction
This chapter sets out to give you guide-lines on the interpretation of the results
that the Mastersizer generates. The first section explains some important concepts
that you have to understand before proceeding.
The second section runs through some of the terms and expressions that are used
in the standard views.
Fundamental concepts
To understand the meaning of the results from the Mastersizer there are a
number of fundamental concepts which may require explanation. These are:
.
The results are volume based.
.
The result is expressed in terms of equivalent spheres.
.
The derivation of distribution parameters.
Results are volume based
The first, and probably most important point to remember in interpreting results
from a laser diffraction instrument is that the fundamental size distribution
derived by this technique is volume based. This means that when the result lists,
for example 11% of the distribution is in the size category 6.97-7.75 microns this
means that the total volume of all particles with diameters in this range
represents 11% of the total volume of all particles in the distribution.
It is useful to consider a numerical example on this point. Suppose, for simplicity,
that a sample consists of only two sizes of particle. 50% by number having a
diameter of 1 micron and 50% by number 10 microns. Assuming spherical
particles, the volume of each of the larger particles is 1000 times the volume of
one of the smaller ones. Thus, as a volume distribution, the larger particles
represent 99.9% of the total volume.
The graph below illustrates this for a more realistic distribution. The example
below shows the result of transforming a skewed volume distribution À to
number Á. Of course, for a “mono-size” distribution such as a latex, 100% of
particles of a particular diameter will still be 100% whether expressed by number
or volume.
CHAPTER 7
GETTING STARTED
Page 7.1
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