Light-Induced Polymer Drop Splashing

This study seeks to understand the role of photodegradation of aqueous polymers in drop splashing. Polymer drop impact commonly occurs in various industrial applications, such as inkjet printing, spray coating, and agrochemical sprays. In agrochemicals, the various constituent components (e.g., adjuvants) impart multiple changes to the fluid dynamics and the wetting behaviors of the drops, as well as interact with the environmental conditions. The environmental conditions (e.g., thermal degradation, photodegradation, and oxidation) of the chemicals affect the shelf stability of the intended physicochemical properties of the chemicals, which are added to stabilize drift from the spray nozzles and minimize drop bouncing from leaves. The aging effects of the adjuvants in tandem with the already low pesticide delivery efficiency have an unknown effect on the agrochemical delivery efficiency and the related environmental burden from the increased runoff. Herein, we systematically photodegraded poly(ethylene oxide) (PEO) to probe the drop splashing behavior as a result of the simulated aging conditions. Dye was added to accelerate the degradation of the polymers and caused drops to splash at Weber numbers, where the pure PEO case did not, confirming the need to consider environmental factors which contribute to adjuvant aging in agrochemical applications. We have also conducted experiments with various concentrations of PEO to probe the changes in the splash dynamics as well as include surfactants, which played a marginal role in altering the splash dynamics under our parameter space. The significance of the study is that the degradation of the polymers influences the splashing and increases the amount of splashed droplets, indicating the importance of controlling the environmental conditions under which polymer solutions are stored.