1. Volatile propellant droplet evaporation measurements in metered dose inhaler sprays.
- Author
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Duke, Daniel J., Scott, Harry N., Kusangaya, Anesu J., Kastengren, Alan, Ilavsky, Jan, Sforzo, Brandon, Myatt, Benjamin, Cocks, Phil, Stein, Stephen, Young, Paul, and Honnery, Damon
- Subjects
METERED-dose inhalers ,DROPLET measurement ,EVAPORATION (Meteorology) ,PROPELLANTS ,SMALL-angle scattering ,BINARY mixtures - Abstract
Many aerosol products rely on the rapid vaporization of volatile propellants to produce a fine spray. In the simplest case, these are binary mixtures of propellant and a delivered product which undergo a flash-evaporation process leaving only the less volatile product in the resultant droplet. In more complex applications, such as pressurized metered-dose inhalers, the non-propellant component may contain dissolved or suspended drug which precipitates or dries to form a matured particle. The size and morphology of the particles depend strongly on the time-history of the droplet as the propellant evaporates. However, measuring the dynamic evaporation processes that occur in dense sprays containing millions of droplets is challenging. In this paper, we demonstrate a novel application of Ultra Small Angle X-ray Scattering to measure the bulk composition of volatile HFC134a-ethanol sprays and compare the obtained results with simple evaporation models in a dry nitrogen environment. The data reveal that diffusion-limiting processes inside the droplet are equally important as external convection and mixing-limited factors in determining evaporative timescales. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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