Our team sees no limits in discovering ways to realize its huge potential. Apart from constant active research and development activities and frequent participation in all the latest vape, tobacco, HnB and cannabis-related international exhibitions held globally, we are deeply involved in scientific work. The recent research of our teammate was published in Addictology Journal, which is a professional periodical for the prevention, treatment, and research into addiction. The article provides an overview of the relevant properties of the effect of PG/VG ratio in e-liquid on aerosol formation. You may see a brief article abstract below, although, if you are interested in the full version, follow the direct link to the article.

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“Effect of Propylene Glycol and Vegetable Glycerine Ratio in E-Liquid on Aerosol Formation: Overview of Relevant Properties”

Aerosol generated by e-cigarettes is influenced by the characteristics of devices’ components, as well as e-liquid compositions. As e-liquid consists of base (vegetable glycerine (VG) and propylene glycol (PG)) with or without nicotine, water and flavors, the ratio of these constituents must be correlated in order to improve the quality of the emitted product.

Numerous studies have paid attention to this question, but there are no reviews with a combination of these findings in order to compare them and draw relevant conclusions. The aim of this review article is to provide an impact description of a PG/VG ratios of the base on the physical properties of the liquid used and the behavior of the aerosol generated and particles separately. 

Figure 1. (a) – molecular structure of propylene glycol; (b) – molecular structure of propylene glycol

Due to its chemical and physical properties, PG and VG affect mixtures obtained differently. Firstly, VG largely contributes to the formation of more viscous e-liquid as compared to high PG e-liquid, while the molecular weight of VG is greater than that of PG. Accordingly, this is more likely to cause coalescence and larger particle sizes. Also, due to the greater number of hydroxyl groups in VG, e-liquids with high VG content have a greater ability to accumulate or supply moisture from the surroundings – high hygroscopicity (see Figure 1 (a) and (b)). Also, the number of OH groups in VG causes less volatility of VG (VG has one more OH group than PG, which leads to stronger hydrogen bond intermolecular forces in the e-liquid solution). Secondly, high-VG e-liquid has a larger boiling point, which leads to deformation of the heating-vaporization process. 

Thirdly, a larger ratio of PG can cause a “throat-hit”, whereas VG leads to visible “cloud effects” due to the accretion of refractive index with an increasing VG content and because of lower vapor pressure of VG, which leads to “long-lived” aerosol clouds. Moreover, PG/VG ratio also has an impact on nicotine flux, particle size distribution and carbonyl emission. The dependencies between PG/VG ratios and these properties varies between studies and special characteristics and it is precisely described in full-text of this article. 

Overall, this review article provides an understanding of the general properties of PG and VG, features of their chemical structure, and its effect on e-cigarettes emission as well as its physical and chemical properties.