Chemically, Polyethylene Glycol is simple. Ethylene oxide units link into a chain, H(OCH2CH2)nOH, with a hydroxyl group capping each end. It has next to no color or smell, it doesn't evaporate, and water takes it up easily.
Chain length is what you're really choosing. PEG 200 sits at 190 to 210 g/mol and stays liquid down to about minus 65 °C. PEG 400 (380 to 420) is thicker, and here's a practical catch: it starts to set up near 8 °C. Leave a drum on a cold loading dock in January and you may have to warm it before it'll pump.
Much above 1,000 and you're handling a waxy solid. Our PEG 3350 melts at 53 to 57 °C, PEG 4000 at about 58 °C, and PEG 8000 somewhere between 55 and 60 °C. Heavier grades also pull less moisture out of the air, so the granules store better than people tend to expect.
Flash points? High. 176 °C for PEG 400 and 270 °C for PEG 8000. Our SDS for PEG 200, 3350, 4000 and 8000 classifies each one as not hazardous under OSHA's Hazard Communication Standard.










