E-Liquid: What is it?


E-liquid is a fluid that you put into an E-cig's fuel tank or a cartomizer that is pre-filled. Inside of the e-liquid is flavoring that the user chooses for taste and also has a nicotine level of their choosing. When smoking this liquid, it will create a vapor that the user will end up exhaling. The two agents that are used for creating the vapor are PG, which is Propylene Glycol, and VG, which is Vegetable Glycerin. Both of these agents, the PG and the VG, are recognized to be safe by the EPA and FDA. 

What is PG? (Propylene Glycol)

Propylene Glycol is a liquid that is thin like water. It is used for carrying and diluting flavors for the e-liquid and is also used in foods and medicines, as a food coloring ingredient and additives in a variety of medications. Less vapor may be produced when flavoring is added because this would thin the PG out further. The higher the PG ratio is, the thicker the clouds will be that are produced. Some people, but not many, will experience some sensitivity to the PG. These symptoms could include the skin or throat being irritated. A lot of the individuals who have the sensitivity will still be able to use PG in lower amounts and not have any of the effects. Most e-liquid will be PG based

Where Does PG Come From?

The PG part of e-liquid is an organic compound that is synthetic, having the chemical formula of C3H8O2. The production of PG comes from propylene oxide, which is used for food. Some manufacturers will use the non-catalytic, high-temperature process which has temperatures from 200 degrees Celsius to 220 degrees Celsius, or 392 degrees Fahrenheit to 428 degrees Fahrenheit. Others will use a catalytic method in which the temperatures range from 150 degrees Celsius to 180 degrees Celsius, or 302 degrees Fahrenheit to 356 degrees Fahrenheit while having ion exchange resin present, a little bit of sulfuric acid, or alkali. The final product has 20% of propylene glycol, 1.5% of dipropylene glycol, and then has other polypropylene glycols in small amounts. PG is then further purified and will produce industrial grade propylene glycol around 99.5% or higher.

What are Other Uses of PG?

Other than e-liquid that most people are starting to relate the use of PG with, it is used as a solvent, humectant, and a preservative for tobacco products and food. PG will also appear in a variety of consumable items like drinks that are coffee based, ice cream, liquid sweeteners, soda, and dairy products that are whipped. Another use is lowering water's freezing point to be used as a de-icing fluid in an aircraft. A frequent use is substituting ethylene glycol in an environmentally friendly, low toxicity automotive anti-freeze. Another use is for winterizing a plumbing system in some vacant structures.

What is VG? (Vegetable Glycerin)

VG, or Vegetable Glycerin, is the other component of e-liquid. This liquid will be sweet and also really thick. The result of the VG thickness will be more vapor when exhaling than PG. The negative about the thickness of the VG is the possibility of burning or clogging problems in some e-cig equipment if the concentration of the VG is high. Higher volumes should not be used with standard tanks. Because of the VG sweetness, the flavor will tend to dull or change a little bit and will also have throat hits reduced that someone experiences.

Where Does VG Come From?

The VG part of e-liquid is a polyol compound and is obtained from animal and plant sources when occurring as a triglyceride, which is an ester of glycerol that has carboxylic acids with long chains. The triglycerides will produce glycerol through transesterification, saponification, or hydrolysis. The usual sources that are plant-based are palm or soybeans. Tallow, which is derived from animals, is another triglyceride source. Glycerol is also able to be produced using a variety of routes from propylene. This method is not usually cost-effective. A process called epichlorohydrin is most vital. It will involve propylene chlorination that will produce allyl chloride. The allyl chloride will then be oxidized using hypochlorite to dichlorohydrins, which will then react with a sturdy base that gives epichlorohydrin that will be hydrolyzed, giving glycerol.

What are Other Uses of VG?

Like PG, VG also has other uses other than for e-liquid. In the food industry, VG is used as a sweetener, solvent, humectant, and could help preserve some foods. In low-fat foods, like cookies, it is used as a filler. In liqueurs, it is used as a thickening agent. Along with water, VG can help preserve particular plant leaves. It is also used for substituting sugar but is not as sweet as sucrose. However, VG does NOT feed bacteria that forms plaque that causes cavities in teeth. Frosting, or icing, has VG to keep it from getting too hard. In personal care products and medications, it is used to improve the smoothness that provides lubrication. Examples of this use are cough syrups, expectorants and elixirs, mouthwash, toothpaste, products for skin care and hair care, shaving cream, personal lubricants that are water-based, and soaps.

As a chemical intermediate, glycerol is used for producing nitroglycerin, an essential ingredient for a variety of explosives like gelignite, dynamite, and cordite. The reliance on making soap to supply glycerol was hard to have the production increased during wartime to meet demand. Therefore, processes for producing synthetic glycerol became a national defense priority during the time that led to WWII. There is a lot of research being done for making products that are value-added from crude glycerol that is obtained from producing biodiesel. Also being explored is using crude glycerol as a biomass additive for renewable energy. As a couple of fun facts, Vegetable Glycerol is used for powering diesel generators that supply electricity for FIA Formula E race cars and in the filming industry, it is used by filmmakers that involve water scenes to prevent the areas being filmed from drying out too fast.