Coolant Base Fluids
Ethylene glycol & Propylene glycol
Ethylene glycol is a colorless, practically odorless, low-volatility and low-viscosity liquid. It is completely miscible with water and many organic liquids. The widespread use of ethylene glycol as an antifreeze is based on its ability to lower the freezing point and raise the boiling point when mixed with water.
Although Propylene glycol shares many of these characteristics, ethylene glycol is a more effective freeze point depressant, and possesses lower viscosity, higher density and better thermal conductivity. It therefore finds more widespread use as a coolant because of these superior characteristics.
Propylene glycol in of itself has lower toxicity compared to ethylene glycol, however the additives present in a finished coolant or those picked up during product use may be toxic. Like many household and commercial products, Ethylene glycol based coolants can be harmful or fatal if ingested, however installation and handling of the material as directed mitigates much of the risk. Consumer packaged coolant is supplied with re-sealable child resistance closures and labeled in accordance with federal labeling laws to ensure the health and safety of the end user. Depending on geographic locations, some coolants contain bittering agents in accordance with local legislation as an ingestion aversive measure.