PSU (Polysulfone)
A transparent amorphous polymer, resistant to steam and hot water
Typical values for the temper in the title
PSU (polysulfone) is a transparent amorphous polymer with a Tg of about 185 °C. Its standout advantage is resistance to hot water and steam: it withstands repeated autoclave sterilization and keeps its properties, and resists acids and alkalis.
It is used for medical devices and trays undergoing sterilization, water-treatment membranes, hot-water components and food equipment. In some organic solvents it is prone to stress cracking.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 70 MPa | |
| Elongation A | 50% | |
| Modulus of elasticity E | 2.5 GPa | |
| Density ρ | 1.24 g/cm³ | |
| Max continuous service temperature | 150°C | |
| Heat deflection temperature (HDT) | 174°C | |
| Machinability | 55% | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Type | amorphous thermoplastic, transparent | transparency and stability |
| Tg glass transition | about 185 °C | |
| Hydrolysis resistance | high | repeated steam sterilization |
Typical values per producer data sheets.
Grades and versions
In engineering polymers, the choice is between an unfilled grade, filled grades (glass or carbon fiber) and special grades (bearing, medical, food). Filler strongly changes strength, stiffness and expansion.
| Version | Properties | When to choose it |
|---|---|---|
| Unfilled | transparent, ductile | medical, food, water |
| Glass-fiber filled | stiffer, opaque | structural parts |
Applications
- Medical trays and devices for sterilization
- Water-treatment membranes
- Hot-water components
- Food equipment
- Transparent covers for heat
Fabrication
Machining
Use very sharp tools, a feed that does not overheat the material, and good support (the material is flexible and deforms under clamping). For precision parts, stress-relief annealing before final machining is sometimes performed.
Chemical resistance
Resistant to hot water, acids and alkalis. Some organic solvents (ketones, aromatics) cause stress cracking.
Thermal expansion
The expansion coefficient of an unfilled polymer is several times that of a metal. In a precision part or an assembly with metal, design clearances accordingly.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| PEI (Ultem) | 105 MPa | Ultrasonic | PEI: stronger, for higher heat · material page |
| PC (Polycarbonate) | 65 MPa | Ultrasonic | PC: transparent, cheap, less steam resistant · material page |
| PEEK | 100 MPa | Ultrasonic / Laser | PEEK: chemically resistant, expensive · material page |
Common mistakes
Choosing PC for a steam-sterilized part
PC loses properties under repeated sterilization. PSU is more suitable.
Cleaning with an unsuitable solvent
Stress cracking.
Long-term loading at temperature
Like any polymer it creeps. Design to producer data.
Equivalents, standards and supply
| ISO | PSU |
|---|---|
| ASTM | D6394 |
| Standards | ASTM D6394 |
| Forms | plate · rod · pellets |
| Producers | Solvay Udel · BASF Ultrason |
Learn more
Values are typical for an unfilled grade (unless stated otherwise) and for comparison only. In polymers, properties depend on grade, filler, temperature, moisture and load duration. For design, rely on the producer data sheet for the specific grade. Sources: ASTM classification standards (D8033, D5205, D5204, D6394, D4067 and others), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026