Effects of common alcohols on the particle size distribution of atomised aerosol in e-cigarette vapour
In order to investigate the effects of the constituents of e-liquids on the particle size distribution of atomised aerosol in e-cigarette vapour, the particle size distributions in e-cigarette vapour were determined by using an electrical low pressure impactor (ELPI) under the atomisation conditions known from e-cigarettes. Various alcohols were subject of our study: propanol, butanol, ethylene glycol, propylene glycol, 1,2-butanediol, glycerol, 1,2,4-butanetriol, polyethylene glycol 200 (PEG200), and polyethylene glycol 400 (PEG400).
The results showed that: 1) The type of alcohol influenced the particle size distribution of atomised aerosol. The aerosol particle size distributions (number concentration: NC) of alcohol, propanol, butanol, ethylene glycol, 1,2-propanediol, 1,2-butanediol could be characterised by a curve with single peak; the peak ranged from 0.02 µm to 0.05 µm. The aforementioned alcohols showed the following order with respect to their maximum peak value of the concentration of particles: alcohol ≤ propanol < butanol, ethylene glycol < 1,2-propanediol < 1,2-butanediol. 2) The aerosol particle size distributions (NC) of glycerol and 1,2,4-butanetriol resulted in a curve with a double peak, and the peaks appeared in 0.02-0.05 µm and 0.1-1 µm, respectively. The peak value of particle number concentration of 1,2,4-butanetriol was higher than that of glycerol and was within the range of 0.1-1 µm. 3) The aerosol particle size distributions (NC) of PEG200 and PEG400 also resulted in a curve with a double peak, with the two peaks appearing in ranges 0.05-0.1 µm and 0.1-1 µm. 4) With the increase of glycerol and the decrease of propylene glycol in the e-liquid, the number of large particles in atomised aerosol increased whilst the number of small particles and the particle number concentration in aerosol decreased. The results suggest that the molecular structure and physical properties of alcohols in e-liquids are the main factors influencing the aerosol particle size distribution of e-cigarette vapour.