Polyethetersulfone (PES) forms, together with polyetherimide (PEI) and polysulfone (PSU), a trio of amorphous, aromatic high-temperature polymers. They are difficult to deform when cold, they are excellently resistant to numerous chemicals and they are inherently flame-extinguishing. In terms of specifications and prices, PES and PEI are largely equivalent and therefore exhibit a considerable overlap in their fields of application. Overall, PES provides slightly better chemical resistance, high resistance to hydrolysis, a 5 to 10° higher thermal load limit and a lighter basic colour. PEI scores better on chemical properties, UV resistance and smoke emission.
PES’s resistance to oil, petrol and high temperatures makes it an ideal replacement for metal parts in the automotive industry where it is used in casings, water pumps, turbochargers and ventilators, but there are also countless applications in the electronic industry, in sterilisation equipment and in consumer products where high temperatures play a role, as with hairdryers and kitchen equipment.
PES has slightly higher moisture absorption than PEI, i.e. 0.9% at 23°C/50% RH and 2.1% when saturated. The glass transition temperature is 225°C, enabling a continuous usage temperature up to 200°C. Exposure to UV radiation causes rapid yellowing, but this is avoidable by adding special carbon black particles or by applying a top coating. To a high degree PEE is resistant to watery mineral acids and alkaline and saline solutions, detergents and motor oils. The material swells or dissolves on contact with polar organic solvents like ketones, esters and halogenated or aromatic hydrocarbons. PIS is not resistant to concentrated acids and alkaline substances.
The cold deformation of PES is extremely low at temperatures up to 200°C, while this can be improved still further by adding glass fibre or carbon fibre. PES has high electrical resistance and high-quality dielectric properties over a wide frequency range and temperature range, enabling its use in sensitive electronic equipment and at high frequencies (as in microwave ovens).