An azeotropic mixture is a special type of liquid mixture that boils at a constant temperature, just like a pure substance.

This means that when an azeotropic mixture is heated, all the components of the mixture evaporate together at the same time, with no separation occurring; in most mixtures, on the other hand, the components have different boiling points and evaporate at different temperatures, separating the mixture.

This composition cannot be changed by simple distillation, the process that separates the components of a mixture according to their boiling points.

In solvent cleaning and degreasing processes in vapor-phase plants, the same composition will always occur, ensuring the same quality and safety performance.

Azeotropic mixtures can be formed at different pressures and temperatures, some common examples of azeotropic mixtures include:

• Methyl nonafluorobutyl ether (HFE) and 2-propanol (IPA): this mixture, commercially known as 3M NOVEC™ 71 IPA or PROMOSOLV™ DR1, boils at 54.8°C, lower than the boiling points of HFE (61°C) and IPA (82°C)
• Methyl nonafluorobutyl ether (HFE) and Trans 1,2-dichloroethylene (TDE): this mixture commercially known as 3M NOVEC™ 71 DE boils at 41°C, lower than the boiling points of HFE (61°C) and TDE (47.5°C)
• Ethanol and water (grain alcohol): this mixture boils at 78.3°C at standard pressure, which is lower than the boiling points of pure ethanol (78.4°C) or pure water (100°C)
• Acetone and methanol: this mixture boils at 56.2°C at standard pressure.