PES stands for polyethersulfone, a high-performance thermoplastic known for holding up under extreme heat, harsh chemicals, and heavy mechanical stress. It belongs to the polysulfone family of polymers but outperforms standard polysulfone in chemical resistance and impact strength. If you came across “PES” on a product spec sheet, a filter membrane, or an engineering datasheet, this is the material being referenced.
Chemical Makeup and Key Properties
Polyethersulfone is an amorphous, aromatic polymer, meaning its molecular chains don’t form a crystalline structure. That amorphous quality gives PES excellent dimensional stability and transparency in its natural state. The “sulfone” in the name refers to sulfone groups in the polymer backbone, which are responsible for much of the material’s thermal and chemical toughness.
The standout number for PES is its glass transition temperature: 225 to 230°C (roughly 437 to 446°F). The glass transition temperature is the point where a rigid plastic begins to soften and lose structural integrity. At 225°C and above, PES can handle sustained heat far beyond what commodity plastics like ABS or polycarbonate can tolerate. For context, standard polycarbonate softens around 147°C.
Mechanically, PES is stiff and strong. Its Young’s modulus, a measure of rigidity, falls between 2,600 and 2,800 MPa. That translates to a material that resists bending and deformation under load, making it suitable for structural parts that need to hold their shape under pressure and temperature. PES also delivers high hardness and strong resistance to creep, the slow deformation that can happen when a plastic is under constant stress over time.
How PES Compares to Other Sulfone Plastics
PES sits in a family with two close relatives: polysulfone (PSU) and polyphenylsulfone (PPSU). All three share the sulfone backbone chemistry, but they differ in performance and price. PSU is the baseline option, offering solid heat and mechanical resistance at a lower cost. PES steps up with better chemical resistance, a higher service temperature, and improved impact strength. PPSU goes further still, with the highest impact resistance and chemical durability in the group, which makes it the go-to choice in aggressive chemical environments or applications where parts face repeated steam sterilization.
For engineers and product designers, the choice between the three usually comes down to how demanding the operating environment is. PSU works well for everyday engineering applications. PES is the middle ground for situations that need more thermal or chemical headroom. PPSU is reserved for the toughest conditions, with a price tag to match.
Where PES Is Used
PES shows up across a surprisingly wide range of industries, almost always in roles where ordinary plastics would fail.
Aerospace: PES is used in aircraft interior components, particularly in honeycomb sandwich structures that form wall panels, overhead bins, and flooring. Foams made from PES (sold under the brand name Ultrason E by BASF) are approved for use in aircraft, where flame resistance and low smoke generation are non-negotiable requirements.
Medical devices: PES membranes are widely used in dialysis machines, where they filter waste from blood. They also serve as filters in intravenous infusion sets. The material’s ability to withstand repeated sterilization without degrading makes it a natural fit for medical environments.
Food and beverage processing: PES membranes handle filtration tasks like separating milk solids, clarifying juice, and concentrating whey protein. The material’s resistance to both pH extremes and high temperatures means it can work in the acidic, hot conditions common in food processing without breaking down.
Water treatment: PES is used in filtration membranes for water purification and wastewater remediation. One specialized application involves immobilizing biosorbents on PES to remove lead and other heavy metals from industrial wastewater.
Transportation: Beyond aerospace, PES appears in automotive and rail components where parts face high temperatures, chemical exposure, or both. Its combination of thermal capability and mechanical strength gives it an edge over standard polysulfone in these demanding settings.
How PES Is Manufactured
PES is a thermoplastic, which means it can be melted and reshaped without permanently altering its chemistry. Manufacturers process it using four main methods: injection molding (for complex, high-volume parts), extrusion (for sheets, films, and profiles), thermoforming (for shaping pre-made sheets), and solution casting (for thin membranes and films). The solution casting method is particularly important for producing the filtration membranes used in medical and water treatment applications.
Processing PES requires higher temperatures than most engineering plastics because of that elevated glass transition point. Equipment needs to handle melt temperatures well above 300°C, and molds or dies may need special coatings to prevent sticking. These processing demands add to the cost of finished PES parts.
Cost Considerations
PES is a specialty polymer, and its price reflects that. As of mid-to-late 2025, polyethersulfone resin trades in the range of roughly $10,500 to $11,300 per metric ton on international markets. That works out to approximately $10.50 to $11.30 per kilogram, or around $4.75 to $5.13 per pound.
For comparison, common engineering plastics like nylon or polycarbonate typically cost a fraction of that. The premium pricing means PES is rarely chosen when a cheaper plastic would do the job. It earns its place in applications where the cost of failure (a melted component, a contaminated medical filter, a compromised aircraft panel) far outweighs the cost of the material itself. Designers typically use PES only after confirming that lower-cost polymers can’t meet the thermal, chemical, or mechanical requirements of the application.