Operating temperature limits for liquid PES: from -100 °С to +150 °С.
Differences between PES and PMS
- Polydiethylsiloxanes are transparent liquids with a viscosity of 1.5 to 1 × 106 mm²/s, depending on the degree of polymerisation. These liquids have significantly lower glass transition and solidification temperatures compared to polydimethylsiloxanes, but the effect of temperature on their viscosity is more significant. Polydiethylsiloxanes have a higher viscosity at 20 °C than polydimethylsiloxanes of comparable chain length. The main difference between polydiethylsiloxanes is the extremely low pour point, which is 1.5-2 times lower than that of polydimethylsiloxanes, and reaches minus 140 °C.
- Polydiethylsiloxanes under the PES brand dissolve easily in most organic solvents and, unlike other organosiloxanes, are fully compatible with mineral oils, which has led to their widespread use as a base for oils and greases.
- Replacement of methyl substituents in organosiloxanes with ethyl substituents restricts the freedom of rotation of atoms and groups around Si-O- and Si-C≡ bonds. This leads to an increase in the rigidity of the chains and thereby prevents the realization of helical conformations of the siloxane chains and the complete intramolecular compensation of the dipoles of the polar bonds ≡Si-O-. The branched structure of some polydiethylsiloxanes has the same effect.
- On the other hand, ethyl substituents and branching prevent close packing of chains, which leads to large distances between chains in diethylsiloxanes compared to dimethylsiloxanes and to a decrease in intermolecular interactions.