Automated image analysis allows users to make highly precise measurements of their particles. Over the years, particle size analyzers have been used to obtain results based on the assumption that all measured particles were spherical in shape. However many applications have shown that actual particle shape affects both flowability and performance in manufacturing processes. For instance, measurement of surface smoothness can help in determining the performance of abrasives.
Scientists have realized that irregularity in particle shape affects both efficacy and manufacturability and hence have turned to microscopy for shape analysis. However manual microscopy is a tedious and time-consuming process, which makes it impractical for studying large numbers of particles. It also tends to give a poor representation of the sample. Although microscopy may be suitable for acquiring an overall idea of particle shape, it is unsuitable when detailed shape analysis is required for process control or research purposes.
Measuring Fiber Particles
Fiber particles are employed in a wide range of applications from building materials to filtration media. Where raw fibers are utilized there has been a definite need to know fiber width, length, curl and aspect ratio. Analysis results expressed simply in equivalent spherical diameter do not provide sufficiently detailed information regarding the fibers and how they will perform in their final state. Moreover the use of manual microscopy for measuring such particles is impractical in a quality control setting where rapid and representative analysis is needed. Figure 1 illustrates a standard fiber sample studied using Particulate Systems’ Particle Insight dynamic image analyzer.
Figure 1. Fiber sample used for analysis.
Fibers Abnalysis Using Particle Insight ImageAnalyzer
Analysis of this fiber sample on a conventional particle size analyzer generally assumes that all particles are spherical in shape. As a result, only minimal data is reported, in this case a size of 112.1µm. Analysis of the same fiber sample on the Particle Insight image analyzer, however, provided much greater data for a large number of particles within a short time.
The measurement of length and width of a fiber is measured along with its aspect ratio, which is its length divided by width. Fiber curl, a fractional measure that is equal to 1 for a straight fiber, is another measurement that is easily determined. When the value of the fiber curl is small, the fiber has a greater degree of curvature. This can prove useful in determining how fibers will interact with each other during a manufacturing process. These measurements are summarized as follows:
- Fiber width: 22.7µm
- Fiber length: 449.9µm
- Fiber curl: 0.984
- Fiber aspect ratio: 19.82
Figures 2 to 5 give additional data statistics as shown in the figure captions.
Figure 2. Indicates the width of these fibers were rather uniform in nature. A total of10,000 particles was analyzed in 149 seconds.
Figure 3. Shows the average length of the fibers to have a mean of 123µm with a standard deviation of 74.8µm.
Figure 4. Although the width of the fibers is well controlled, the length is not. As a result, the aspect ratio results are broad. Here the aspect ratio shows a mean of 4.450 with a standard deviation of 2.262.
Figure 5. The mean fiber curl is 0.97 with a mode fiber curl of 0.99. This clearly indicates that the population of fibers is mostly non-curled.
An advanced particle size analyzer should be used to analyze important parameters effectively. As discussed above, measuring fibers on the basis that they are spherical in shape may not be the most appropriate approach for quantification. In this case size alone was not sufficient to give a detailed description of the sample. For fiber samples it proved more useful to determine the four fiber-specific parameters in order to obtain detailed insight into the particles and their manufacturing process. Hence one or more of these fiber-specific measurements can be used as a quality control specification, since the analysis is fast, precise, and can determine a large number of particles within a matter of seconds.
This information has been sourced, reviewed and adapted from materials provided by Micromeritics Instrument Corporation.
For more information on this source, please visit Micromeritics Instrument Corporation.