Characterization of nozzle performance in the siliconization of pharmaceutical syringes for a new design development

Siliconization of pharmaceutical syringes and cartridges is a critical manufacturing process, as it directly affects product quality and functional performance. Currently used siliconization nozzles exhibit significant efficiency variability, which may result in a non-uniform silicone deposition that leads to cosmetic defects on syringe surfaces. At present, nozzle quality assessment is largely based on non-standardized criteria, relying on subjective indicators such as visual spray assessment or cosmetic evaluation. This lack of quantitative and repeatable evaluation methodology limits the ability to characterize nozzle performance and establish robust correlations between spray behavior and final product quality. Among the fluids employed in the process, high-viscosity silicone oils are particularly critical due to their poor atomization behavior. For this reason, the experimental activity focuses primarily on this class of fluids, where the most severe performance limitations are observed. The study includes an experimental characterization of droplet formation and atomization behavior, with droplet size distribution measurements performed under performance indicators, highlighting that non-compliant nozzles generate intermittent bursts of oversized droplets, which are directly associated with visible surface defects on siliconized syringes. Experimental results are used to validate an existing mathematical model of the nozzle and to support CFD simulations aimed at improving the predictive capability of flow behavior models. By integrating experimental data and numerical analyses, critical nozzle design features are identified, leading to the development of a new nozzle design characterized by improved stability and reproducibility, while maintaining unchanged production line operating conditions.