What are the freeze points of propylene glycol solutions?
When liquids are cooled they eventually either crystallize like ice or become increasingly viscous until they fail to flow and set up like glass. The first type of behavior represents true freezing. The second is known as super-cooling. Glycols do not have sharp freezing points. Under normal conditions, propylene glycol and its homologs set to glass-like solids, rather than freezing. The addition of water to a glycol yields a solution with a freezing point below that of water. This has led to the extensive use of glycol-water solutions as cooling media at temperatures appreciably below the freezing point of water. Instead of having sharp freezing points, glycol-water solutions become slushy during freezing. As the temperature is lowered, the slush becomes more and more viscous and finally fails to flow. Freeze points and burst points of glycol-water solutions are shown in the table below.
