Afcon Answers

What is the difference between Ethylene Glycol and Propylene Glycol? 

What You Need To Know

Both ethylene glycol and propylene glycol solutions will effectively lower the freezing point of water allowing it to be freely pumped through a variety of heat exchangers, and can be used interchangeably for most applications. While there are many minor variations in the properties between ethylene glycol and propylene glycol solutions, however there are two key differences that dictate which of the glycols is chosen for a particular application, namely toxicity and viscosity.

Toxicity

Ethylene glycol is more toxic than propylene glycol. About 2 - 4 ounces of ethylene glycol can be fatal if ingested by an adult human. Whereas, propylene glycol is a food additive and is not harmful to humans if ingested in moderate amounts. Therefore, propylene glycol solutions are preferred for many applications, particularly when human exposure can occur.

Viscosity

While differences in viscosity between ethylene glycol solutions and propylene glycol solutions at elevated temperatures are minimal, at temperatures below -18C the viscosity differences become significant. If heat transfer at these low temperatures is required, ethylene glycol solutions should be used. In addition, ethylene glycol solutions will require less pumping horsepower under cold conditions. If these liquid characteristics are important, ethylene glycol is usually chosen for the application.