When defining the performance of a product, particle size and size distribution often serve as important parameters.
Particle size measurement can be leveraged to gain a better understanding about the processability of a new material and can also be used to envisage and control properties of products, such as uniformity, stability, appearance and flow ability. Therefore, measuring the size of particle at an early stage of product development can provide immense benefits to Researchers seeking to design particular product attributes.
However, measurement of particle size distribution during early stage of development involves a number of challenges. For instance, the quantity of material available may be insufficient and as such the ability to determine small amounts of samples becomes very important. It is also vital to ensure that the preferred measurement technique has the ability to handle large amounts of samples during the later phase of development and manufacturing processes. This way, any specifications established at the early stage of product development can be carried out.
Laser Diffraction System
This article shows how the Mastersizer 3000 laser diffraction system can be used as a particle characterization tool during the development process of a product.
The Hydro SV small volume dispersion unit in the Mastersizer 3000 system has been specifically designed to facilitate measurements during the early stage of product development, and the larger volume Hydro LV, Hydro MV and Hydro EV dispersion units are designed to determine large volume samples as part of the scale-up and production process. In this study, two different materials are taken into account: a product with a finer particle size and a product with a coarse particle size.
These products present different measurement challenges with respect to sampling and dispersion. The following case studies show how the specifications, based on Hydro SV measurements, can be effectively transferred to the larger volume Hydro LV, Hydro MV and Hydro EV dispersion units.
Case Study 1: Coarse Material Measurements
Transfer of particle size specifications from small volume sample to large volume sample measurements depends on the control of the process utilized to select a sample for examination.
This factor presents a major source of inconsistency when determining rough materials having greater than 70-100 µm particle size. After a sampling process has been chosen, the material should be placed on the laser diffraction measurement system in such a way that complete size distribution is quantified in a representative way. To achieve this set up, it is important to control the suspension of the sample throughout the measurement process.
The particle size distributions achieved for a coarse material utilizing the Hydro MV (120 ml dispersant volume) and the Hydro SV (6 ml dispersant volume) is shown in Figure 1. It can be seen that there is a wide particle size distribution of this material, which includes large-sized particles. Therefore, it is important to control sampling if analogous results have to be achieved at both large and small volumes.
Figure 1. Overlay of the average particle size distributions reported for a coarse sample using the Hydro SV small volume and Hydro MV larger volume dispersion units.
In Figure 1, the results obtained through each dispersion unit are analogous and hence can be compared directly. This is established in Table 1, which displays the distribution width (Span), 90th percentile (Dv90) and median particle size (Dv50) reported by means of each accessory. Close agreement in these parameters reinforces the precision of the results achieved at small volumes.
Table 1. Comparison of Dv(50), Dv(90) and Span values associated with the particle size distributions shown in Figure 1.
|Mean Dv(50) / µm
|Mean Dv(90) / µm
The data thus imply that the specifications set at an early stage for this product can be easily transferred to later stage of development or production. This would help in ensuring that the quality of the product is consistent and would also help with trouble shooting during the scale-up process.
Case Study 2: Fine Particle Measurements
Dispersion is yet another problem related to particle size measurement and is also the biggest source of measurement consistency when determining fine materials having colloidal particles i.e. particles measuring less than 20 µm in size.
For the Hydro SV dispersion unit, it is important to control the dispersion state of the sample before introducing it into the unit for measurement. This is because a sonication probe is not included in the dispersion unit. On the contrary, the Hydro MV dispersion unit helps in sonicating the sample throughout an automated measurement sequence and enables better dispersion control. Therefore, it is important to control the dispersion process to transfer the specifications between dispersion units during the scale-up process.
Figure 2 illustrates the distribution of particle size determined using the Hydro MV and Hydro SV dispersion units for a standard micronized material. In the case of this sample, the total size distribution is less than 20 µm in size. This means, dispersion has to be controlled if similar results have to be achieved.
In the Hydro SV dispersion unit, the dispersion of the sample was performed by means of an external sonication bath before introducing the sample into the unit, while internal sonication was utilized for the Hydro MV dispersion unit.
Figure 2. Overlay of the average particle size distributions reported for a fine, micronized sample using the Hydro SV small volume and Hydro MV larger volume dispersion units.
In Figure 2, it can be seen that similar results were obtained with each dispersion unit. Also, the Span, Dv90 and Dv50 are comparable as shown in Table 2. This indicates that the dispersion process is within control for both types of measurements, giving confidence that the data thus achieved through the Hydro SV dispersion unit are representative and similar as the first case study. Specifications obtained from this data can be utilized as the basis for managing the scale-up process.
Table 2. Comparison of Dv(50), Dv(90) and Span values associated with the particle size distributions shown in figure 2.
|Mean Dv (50) (µm)
|Mean Dv (90) (µm)
When characterizing the properties of materials, particle size and size distribution play an important role, and measurement of these parameters in the early stage of product development offers significant benefits.
The above results show the ability of the Mastersizer 3000 laser diffraction system to produce comparable results for samples of different sizes using the Hydro MV and Hydro SV dispersion units.
Thanks to its ability for measuring large and small quantities of samples, laser diffraction can be applied not only at the early stages of product development, but also during the scale-up and manufacturing processes of products.
This information has been sourced, reviewed and adapted from materials provided by Malvern Panalytical.
For more information on this source, please visit Malvern Panalytical.