The influence of particle size on separation and dustiness in powder mixtures during nonelectrostatic and electrostatic coating

• Over half of the mixtures showed separation due to a difference in particle size.
• Separation was caused by the difference in individual transfer efficiency of the powders and interactions during coating.
• Both composition and differences in size were found to be important.
• Being in a mixture did not change the amount of dust formed.

Common food powders and their mixtures, consisting of two powders with the same composition but different in particle size: fine (51–95 μm) and coarse (244–401 μm) NaCl, KCl, sucrose, rice starch, maltodextrin, whey protein, casein and soy protein, were coated on a target at 0 and −25 kV. Over half of the mixtures showed separation due to a difference in particle size. Separation was caused by the difference in individual transfer efficiency of the powders and interactions during coating. Both composition and differences in size were found to be important. Being in a mixture did not change the amount of dust formed.