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EFFECTS OF PARTICLE SIZE ON MIXTURES DURING NONELECTROSTATIC AND ELECTROSTATIC POWDER COATING
Author(s) -
SOMBOONVECHAKARN CHANUN,
BARRINGER SHERYL A.
Publication year - 2011
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2009.00538.x
Subject(s) - coating , materials science , particle size , adhesion , starch , chemical engineering , composite material , particle size distribution , particle (ecology) , grain size , powder coating , powder mixture , sintering , chemistry , organic chemistry , oceanography , engineering , geology
Two mixtures, 44 and 256 µ m NaCl and 64 and 191 µ m starch, were nonelectrostatically or electrostatically coated onto an aluminum target. The coating processes cause the proportion of each powder in the mixture to be different on the target than in the initial mixture. First, some loss of powder occurs during the targeting step; thus, not all of the powder land on the target. This targeting loss is caused by the individual powder characteristics and interactions that occur between powders in the mixture. Also, an uneven distribution is produced on the target due to the way the powder is dispersed. Finally, adhesion loss occurs on the target, also due to individual and mixture characteristics. During nonelectrostatic coating, the largest cause of the change in proportion was targeting losses. During electrostatic coating, the largest cause was adhesion loss. Interactions in the mixture decreased the change in proportion, except for nonelectrostatically coated NaCl.PRACTICAL APPLICATIONS Food coatings consist of mixtures of powders of different sizes. It is desirable to maintain the same proportions of the powder components on each food sample as in the applied coating. Mixtures change proportions due to differences in particle size, so all of the powders in the mixture should have a similar size range to reduce changes during coating. During nonelectrostatic coating, the differences in targeting losses are the biggest cause of this change, so coating systems need to be designed to minimize the differences in targeting losses. Electrostatic coating reduced targeting loss by a large amount; therefore, it is one method to reduce the change in proportions caused by targeting loss. However, electrostatic coating increased the differences in mixture adhesion loss, so products need to be designed to minimize the adhesion loss, such as by adding oil on the product surface.