A novel method for assessing the coating uniformity of hot-melt coated particles using micro-computed tomography

The effectiveness of hot-melt coating depends on its uniformity and the extent to which the surface is completely covered. Compared with solvent-based coating, spreading is more limited in hot-melt coating; thus, the coating uniformity is more affected by the process parameters. This study presents a new method for identifying and quantifying factors influencing coating uniformity. The proposed method facilitates the determination of coating-thickness distribution and non-covered surface proportion based on micro-computed tomography measurements. The proposed method is based on particles that have undergone hot-melt coating in a fluidized bed, and it is compared to common methods for layer-thickness determination. The influencing factors are quantified in terms of the dependency of coating uniformity on the coating amount and material. Material properties have a significant impact because stearin and palm fat create different coating layers. The proposed method is confirmed to be well suited for analyzing coating qualities.