MEG - Mono Ethylene Glycol — Frequently Asked Questions

Polyester. Roughly three quarters of world MEG production goes into polyethylene terephthalate, where it condenses with terephthalic acid to make the polymer used in drinks bottles, film and polyester fibre. The antifreeze application it is best known for accounts for a much smaller share of consumption than the packaging and textile markets.

Because of how it is metabolised. MEG is oxidised to oxalic acid, which precipitates as calcium oxalate crystals in the kidneys and causes renal failure; the lethal dose is small and the sweet taste makes accidental and deliberate ingestion a real risk. MPG is metabolised to lactic acid, which enters normal energy metabolism and is cleared harmlessly.

Because the mixture outperforms either component. Water has much better heat transfer capacity than glycol, so pure glycol would cool an engine poorly. Glycol depresses the freezing point and raises the boiling point of the mixture. A 50 percent solution protects to around minus 37 degrees Celsius while retaining most of water's heat transfer ability.

To deter ingestion. MEG tastes sweet, which is why animals and children are attracted to spilled antifreeze, and the consequences are severe. Several jurisdictions now require a bittering agent, typically denatonium benzoate, in consumer antifreeze products. It does not reduce the toxicity, only the likelihood of accidental consumption.