Measurement of the Saturated Vapour Pressure of Low-GWP Propellants in Conjunction with Ethanol
J. A. Thorne1, P. Allsop1, D. P. J. Cotton1, S. B. Kirton2, M. Knowles1, K. C. Lee3, D. Murnane2, A. I. Sapsford1
1Recipharm, Bergen Way, King’s Lynn, PE30 2JJ, U. K.
2University of Hertfordshire, College Lane, Hatfield, Hertfordshire, AL10 9AB
3University of East London, Docklands Campus, University Way, London, E16 2RD
Measurements of the saturated vapour pressure (SVP) of low global warming potential (GWP) propellants, R152a and HFO1234ze(e), in conjunction with ethanol, at various concentrations, were conducted to investigate for possible deviation from Raoult’s law. This law allows the vapour pressure of a volatile mixture to be predicted based upon the individual vapour pressures of the constituents and their respective mole fractions in the mixture. Knowledge of the vapour pressures of these mixtures is vital for simulating the aerosolisation process for pressurised metered dose inhalers (pMDIs) using thermofluid mechanic modelling, as the vapour pressure is one of the key driving forces for aerosolisation. Any deviation from Raoult’s law would necessitate a full experimental study to map the vapour pressures of these mixtures as a function of ethanol fraction and temperature.
Saturated vapour pressure measurements were taken for various low-GWP propellant and ethanol blends, illustrating a deviation from Raoult’s law for both propellants.