Polyglycol or Polyalkylene Glycols (PAG) are a family of products formed from the polymerisation of one of more alkylene oxides. PAGs are made from ethylene oxides, propylene oxides, which in the presence of an alcohol initiator and a catalyst form a long chain polymer. Other names you may come across include: polyoxyalkylene glycols or simply glycols.
Polyglycols have at least one hydroxyl group to promote hydrogen bonding with the appropriate thickener when use to make a grease, typically silica. Polyglycol summary:
- Temperature range of -40 to 100°C
- Good lubricity and load carrying capability
- Some glycols are water soluble
- Cleaning burning oil (ideal for electrical arcing issues)
- Poor volatility above 100°C (not in terms of flammability)
- Polyglycols can have compatibility issues with some plastics/rubbers
- Viscosity Index usually over 150
Keep in mind that if a Polyglycol is used as the base oil for a grease, the thickener and additives also used in the formula will have an influence on the final characteristics and performance of the finished grease/lubricant.
Take a look at our typical thickener systems characteristics used to make a base oil into a grease.