The Freeze Point of liquids is defined as the temperature at which ice crystals first form. In the case of pure water, that point is 32° Fahrenheit. Water is unique in its property of increasing its volume by 9-10% as the freeze point is approached and achieved. Freezing water breaks pipes, pumps and containers unless there is adequate expansion room.
As glycol, glycerin, salt and other substances are dissolved in water, the volume expansion is generally reduced by the physical interaction among the various molecules in the solution. As the concentration of other substances is increased, the freezing properties of the solution changes in two ways: First, the solution may go through a longer phase change, turning into a slush before freezing hard. Second, the expansion of the fluid is reduced.
The freezing properties of Propylene Glycol are most interesting to our customers, as it offers protection in both freezing temperature and burst suppression. At a concentration of 35% PG, there is no expansion as the solution begins freezing at a temperature of 1° Fahrenheit. The solution will freeze hard and cannot be pumped or poured much below that temperature. Concentrations of PG about 60% will remain liquid at any temperature a normal facility would experience. Our ice melt and snow melt customers generally use PG concentrations of 45%-55% to insure the liquid can be circulated.