|
Propylene Glycol
To minimize the problems associated with the toxicity of ethylene glycol, an environmentally friendly antifreeze base called propylene glycol is available for diesel engine cooling systems. Propylene glycol is an ingredient in many cosmetics and foods, from moisturizer to ice cream. It has slightly different physical properties than ethylene glycol; therefore, the density and concentration required for freeze protection is different. This explains why it is important to differentiate between ethylene glycol and propylene glycol antifreeze bases as well as the amount of propylene glycol mixed with water to obtain adequate freeze protection Figure 30. The color of antifreeze is probably the most reliable indication of the type of antifreeze base. TMC classifies propylene glycol–based antifreeze as a type III and has recommended that antifreeze producers color propylene glycol antifreeze blue. A higher concentration of propylene glycol is required to provide the same freeze protection achieved using ethylene glycol. Higher concentrations may reduce the cooling effectiveness of propylene glycol mixtures. The slippery, greasy texture of both ethylene glycol and propylene glycol antifreeze bases makes both an excellent lubricant for the water pump seal.
|
|
FIGURE 11-30: A refractometer screen has two different scales for measuring the freeze protection of propylene glycol and ethylene glycol coolants.
|