(563h) Investigation of Particle Electrification in Mixers - Effect of Particle Size, Mixer Type, and Rotation Speed

In the manufacturing of pharmaceutical product, mixing is one of the very important processes for preparing active pharmaceutical ingredient (API) with exicipients to form a homogeneous mixture. Electrostatic charges generated and accumulated during the mixing process not only affect the product homogeneity, but also influence the processes handling these mixtures and eventually the drug delivery efficiency. Understanding particle electrification in the mixer is then very important for optimizing the formulation for dry powder inhalation drug delivery. In this work, particle electrification in the Turbula and horizontally oscillating mixers were investigated for adipic acid, microcrystalline cellulose (MCC), and glycine particles. MCC and glycine particles acquired positive electrostatic charges, while adipic acid particles attained negative charges in both mixers. Adipic acid (of sieved size larger than 500 micron), MCC, and glycine particles were monotonically charged to saturated values, and had a negligible wall adhesion. On the contrary, the adipic acid particles containing fine particles firstly acquired charges up to a maximum value, and then the charges slowly reduced to a lower saturated value with increasing mixing time. For these adipic acid particles, particle wall adhesion was found to be significant and increased with increasing mixing time. Horizontally oscillating mixer was found to charge more efficient than the Turbula mixer, and the rotation speed was shown to have negligible influence on the saturated charge value taking the measurement uncertainty into account. The results obtained from the current work suggested that electrostatic force enhanced particle–wall adhesion, and the adhered particles can have a significant impact on particle electrification.