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50 / January 2020 powderbulk.com References 1. Floris Grasmeijer, Paul Hagedoorn, Hendrik W. Frijlink, H. Anne DeBoer. (July 2, 2013.) "Mixing Time Effects on the Dis- persion Performance of Adhesive Mixtures for Inhalation," (PLoS One)8(7): e69263. Doi: 10.1371/journal.pone.0069263 2. Collins English Dictionary, HarperCollins Publishers, https:// www.collinsdictionary.com/us/dictionary/english/demixing. 3. Wang, Zhong Lin Lin, Long Chen, Jun Niu, Simiao Zi, Yun- long, (2016) "Tribonet: About Tribology." Triboelectric Nanogenerators, 2016, https://www.tribonet.org/wiki/tribo electricity/ Doi: https://doi.org/10.1038/s41528-017-0007-8. 4. Encyclopedia Britannica, Froude Number. October 25, 2016. URL: https://www.britannica.com/science/Froude-number 5. R.L. Carr, "Evaluating Flow Properties of Solids," Chemical Engineering 1965, 72, pages 163-168. https://www.usppf. com/pf/pub/index.html For further reading Find more information on this topic in articles listed under "Mixing and blending" in Powder and Bulk Engi- neering's comprehensive article index in the December 2019 issue or the article archive on PBE's website, www. powderbulk.com. Eirich Machines Gurnee, IL 847-336-2444 www.eirichusa.com Ashely Bester-Barnett (abbarnett@eirichusa.com, 847-336-2444) is the test lab manager at Eirich Machines. She holds a BS in chemistry from Tennessee State Uni- versity and a master's degree in business and project management from Trevecca Nazarene University, both located in Nashville, TN. She has more than 10 years of experience in chemistry and quality assurance/quality control and 7 years of manufacturing experience. Nonvisual tests Nonvisual tests also can help determine an optimal mixing cycle. Vibratory sieve analysis is an effective way to measure material degradation over time and help establish acceptable mix tolerances. Often, this test is used to measure raw material degradation prior to mixing to establish baselines. The material is measured again after mixing to compare fines accumulation. In each case, material is sent through a number of sieves with different-sized mesh openings to evaluate particle size distribution. To drill down even further, X-ray diffraction and scanning electron microscopy (SEM) can be used to determine particle dispersion throughout a batch. These methods use X-ray and electron beams that focus on material samples and measure material com- position and particle characteristics. Both methods are performed using samples taken from different areas in the mix. These methods, unlike some of the others, are employed only after blending. Testing helps When mixing, the key is to homogenize materials — whether coffee beans or vermiculite — with minimal degradation but with enough energy to evenly dis- tribute pigment, liquid, or other material throughout a given mixture in the minimal amount of time needed to achieve a reaction, color, or phase change without satu- rating, demixing, agglomerating, or shearing particulates within said batch. Many manufacturers have test cen- ters, such as the example shown in Figure 5, where both the supplier and past customer test results can provide information to help you determine baseline mixing best practices. Taking the process from benchtop to pilot-scale to production-unit testing allows validation and fine-tun- ing of calculations along the way as you scale up to meet production goals. This can help optimize both batch quantity and, more importantly, batch quality. PBE FIGURE 4 Visual test showing a poor-quality mix with red lines versus an evenly dispersed mix. FIGURE 5 Supplier test labs can take you from benchtop to pilot- scale to production-scale testing to help optimize mixing cycle parameters.