Propylene glycol (PG) is an extremely hygroscopic compound with a colourless and odourless appearance. Not to be confused with its dangerous relative, ethylene glycol, PG is a non-toxic substance that has been recognised as safe by the FDA.
Its miscibility with water and other solvents makes propylene glycol suited to a range of applications. To learn more about this compound, we’ve talked about it here. Otherwise, let’s jump in to the five uses of propylene glycol.
Only within the past few years has propylene glycol been used in a new version of antifreeze that replaces ethylene glycol based formulations.
This change didn’t happen because propylene glycol was better performing than ethylene glycol, but because it was less toxic.
Ethylene glycol is an extremely toxic chemical that is converted into calcium oxalate crystals when ingested. These crystals then build up in the heart, lungs and kidneys which could cause permanent damage.
The characteristic sweet smell and taste of ethylene glycol has led to many children and pets accidentally consuming it. Pets, in particular, have been known to lap up any ethylene glycol based antifreeze that has dripped or spilled in the driveway, and this has often been fatal.
Propylene glycol antifreeze, on the other hand, is a non-toxic alternative. This is because if it is consumed, it is converted into two harmless chemicals: acetic acid (also known as vinegar) and pyruvic acid (a normal production of the glucose-metabolism process).
Propylene glycol is used in antifreeze because, like ethylene glycol, it lowers the freezing point of water by disrupting the formation of ice crystals.
Another testament to the non-toxic nature of PG is its use in the food industry where it serves as a humectant, solvent and preservative among other things. Propylene glycol has the E-Number E1520.
One reason propylene glycol is used in various food products is because it doesn’t react on its own, allowing it to do its job without affecting other ingredients.
Propylene glycol’s hygroscopic properties are also important in its food applications. By attracting and holding water-based and oil-based substances, PG is able to provide homogenous distribution in a mixture. This means that it is able to distribute food colouring, for example, evenly.
Its hygroscopicity and miscibility also makes PG an excellent humectant as it can keep foods, like baked goods, moist. This also helps to preserve them.
Propylene glycol is used in a range of oral, topical and intravenous medicines. It is also used as a drug stabiliser and as a solvent.
Its miscibility with water enables PG to be used as a solvent for insoluble pharmaceutical formulations. Diazepam, for example, benefits for the miscible properties of propylene glycol.
PG is used in a similar way during intravenous medications, where it helps the body absorb chemicals more efficiently.
While there have been concerns over the toxicity of propylene glycol, it is important to remember that it breaks down in the body within 48 hours and forms no harmful crystals. This is why it is known as being non-bio-accumulative, as it doesn’t build up in our bodies.
Propylene glycol is not only used as a humectant in the food industry, but also in cosmetics. By attracting water from the air it works well in moisturisers and hair-care products by locking in moisture. In fact, the company Lush even use it in over 67 of their bath-time products.
Not only does PG soften the skin and hair by attracting moisture, it also limits the growth of bacteria and gives cosmetic products a longer shelf-life.
In cosmetics, including at Lush, plant-based PG is gaining more popularity because of its natural production.
Rather than using PG that has been converted from propene, a by-product of fossil fuels, many cosmetic-grade PG has been derived from plants to ensure maximum safety and efficiency.
E-cigarettes are the less harmful alternative to smoking. They work by heating a nicotine cartridge that contains liquid. This happens when the user begins inhaling.
The e-liquid is transported from the cartridge to the atomiser, where cotton is usually used to soak it up. Heat caused by inhalation then converts the liquid to vapour that the individual exhales.
E-cigarettes contain several chemicals, the safety of which has come under dispute time and time again. Propylene glycol is one of these chemicals.
The liquid that is used in an e-cigarette cartridge often contains vegetable glycerin and propylene glycol. These are also mixed with flavourings and nicotine.
Glycerin is a viscous substance, and its presence in e-liquid helps to make the vapour clouds thicker. However, its viscosity as a liquid could lead to the poor transportation of the e-liquid to the atomiser. Therefore, propylene glycol is added as a thinner.
Propylene glycol makes the e-liquid more easily absorbed by the cotton in the atomiser, and its low density prevents any residue from building up inside.
PG is used in a similar way in smoke or fog machines. If you’ve ever been to a theatrical performance or music concert where artificial smoke is used, the clouds more often than not contain propylene glycol.
It’s true that propylene glycol has a wide range of applications across many industries. At ReAgent, we sell propylene glycol and non-toxic antifreeze with a promise of 100% quality guarantee. Shop online today, or contact us to speak to an expert member of our team.
The blog on chemicals.ie and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).