Ethylene glycol or propylene glycol? What to choose?

• Posted on 7 July 2023
• By Glycol.eu
• 0

What is glycol?

Coolant is used to cool industrial processes. This liquid often consists of osmosis water to which various products have been added. The most important of these is an antifreeze that lowers the freezing point. Ethylene glycol or propylene glycol is mainly used for this. In addition, substances are added to prevent algae growth or corrosion. What are the differences between these two glycols and what should you look for when choosing the right refrigerant?

Differences between ethylene glycol and propylene glycol

Ethylene and propylene glycol are both glycols. A glycol contains two hydroxyl groups (OH). However, propylene glycol (C3H8O2) has one more carbon atom than ethylene glycol (C2H6O2). Both are colourless and odourless liquids that can be used as refrigerants. However, there are two major differences between the two substances. These are toxicity (toxicity) and viscosity of the glycols. The type of glycol to be used can be determined depending on the application and the requirements of the refrigeration system.

Ethylene glycol (1,2-ethanediol) is considered the best refrigerant. When 30% ethylene glycol is added to water, the freezing point drops to -15˚C. However, it is toxic to humans and should therefore not be used in the food industry. However, it is cheaper than propylene glycol. Ethylene glycol is therefore particularly advantageous for companies that purchase large quantities of refrigerants.

Propylene glycol (propane-1,2-diol) becomes viscous (syrupy) at temperatures below -18˚C. This affects the heat exchange. Propylene glycol also requires more pumping power than ethylene glycol under cold conditions. For processes operating at low temperatures or where viscosity is an issue, it is necessary to use ethylene glycol.

However, some refrigeration systems are designed so that any type of glycol can be used at low temperatures. The World Health Organisation (WHO) considers propylene glycol to be non-toxic at low levels. It can therefore be used in the food, cosmetics and pharmaceutical industries. As propylene glycol is less toxic, safety regulations are much easier to follow than those for ethylene glycol.

Use ethylene glycol for most standard industrial applications.

Ethylene has the best heat transfer properties and is therefore the right choice for most industrial applications. However, it is very toxic: the ingestion of 30 ml of ethylene glycol can already be fatal for an adult. Therefore, it should not be used in processes where the liquid comes into contact with food, beverages or drinking water. This applies to both humans and animals.

Ethylene glycol can therefore only be used if there are no low toxicity requirements.

Use propylene glycol if the refrigerant can come into contact with people or animals.

Propylene glycol has the same properties as ethylene glycol in terms of frost protection and protection against corrosion and algae. However, it has a lower toxicity. It is also faster to degrade and safer to process than ethylene glycol. Propylene glycol is therefore widely used in the pharmaceutical industry, animal husbandry, food industry, hospitality and other applications where one may come into contact with the refrigerant.

Check the refrigerant legislation of the local government.

Before deciding on the type of glycol, carefully check the laws and regulations. The type and quantity of glycol will affect the regulations for your installation. For example, safety requirements, reporting requirements and mandatory leak testing may vary. Some areas have particularly strict requirements for the use and disposal of glycols and other additives in the coolant. European regulations for the protection of the environment must also be taken into account.

Where can I buy glycol?

We supply ethylene glycol and propylene glycol both pure and mixed with osmosis water. The standard packaging contains 25 litre canisters or 1000L IBC containers, but we can supply any quantity on request.