Boiling points of the propylene glycol + glycerol system at 1 atmosphere pressure: 188.6–292 °C without and with added water or nicotine

Abstract

In electronic cigarettes (“electronic nicotine delivery systems”, ENDS), mixtures of propylene glycol (PG) and/or glycerol (GL; aka “vegetable glycerin”, VG) with nicotine are vaporized to create a nicotine-containing aerosol. For a given composition, the temperature required to boil the liquid at 1 atmosphere must be at least somewhat greater than the boiling point (BP). The use of ENDS is increasing rapidly worldwide, yet the BP characteristics of the PG + GL system have been characterized as the mixtures; here we re-do this, but significantly, also study the effects of added water and nicotine. BP values at 1 atmosphere pressure were measured over the full binary composition range. Fits based on the Gibbs–Konovalov theorem provide BP as a function of composition (by mole-percent, by weight-percent, and by volume-percent). BPs of PG + GL mixtures were then tested in the presence of additives such as water (2.5 and 5 mol% added) and nicotine (3 mol%). Water was found to decrease the BP of PG + GL mixtures significantly at all compositions tested, and nicotine was found to decrease the BP of PG + GL mixtures containing ∼75 GL: 25 PG (by moles) or more. The effect of added water (5, 10, and 15 mol% added) on electronic cigarette degradation production (some aldehydes and formaldehyde hemiacetals) was examined and found to have no significant impact on solvent (PG or GL) degradation for the particular device used.

Keywords:

• E-Cigarette liquid
• Electronic cigarette
• Electronic nicotine delivery system (ENDS)
• Glycerol
• Heat exchanger fluid
• Propylene glycol

Acknowledgments

The authors thank Dr. Shankar Rananavare for suggestions regarding the Gibbs–Konovalov parameterization; Michael Lethin and Astrid Woodall for assistance with the boiling point measurements. The authors are also grateful to Alex Chally for expert assistance with the syringe pump and vaping apparatus setup.

Additional information

Funding

This work was supported by the U.S. National Institutes of Health under Grant R01ES025257; research reported in this publication was supported by the NIEHS and FDA Center for Tobacco Products (CTP).