PSU Udel: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-05-28
Polysulfone (PSU), commercially known as Solvay Udel, is the foundational member of the sulfone polymer family—the original high-temperature amorphous thermoplastic that established the market for transparent, sterilizable engineering polymers....
Polysulfone (PSU), commercially known as Solvay Udel, is the foundational member of the sulfone polymer family—the original high-temperature amorphous thermoplastic that established the market for transparent, sterilizable engineering polymers. With a glass transition of 185°C and continuous service rating of 160°C, PSU offers the best price-to-performance ratio in the sulfone family, costing significantly less than PES (Tg 225°C) or PPSU (Tg 220°C) while still providing excellent hydrolytic stability, clarity, and biocompatibility.
PSU is the workhorse material for medical device manifolds (dialyzer housings, surgical instrument handles), hot-water plumbing fittings, reverse osmosis membrane supports, and food service equipment. It is naturally transparent (slight amber tint) and maintains clarity after 1000+ autoclave cycles. PSU is FDA-compliant for repeated food contact and meets USP Class VI and ISO 10993 biocompatibility standards for medical devices. The material processes at melt temperatures of 330-380°C with mold temperatures of 80-150°C—the higher end of the mold temperature range produces lower molded-in stress and better environmental stress crack resistance (ESCR). Drying at 135°C for 3-4 hours to <0.02% moisture is required.
Recommended Applications
PSU Udel is commonly specified for:
Selection & Application Guide
Polysulfone (PSU) is a transparent, high-temperature amorphous polymer offering 150°C continuous service, excellent hydrolysis resistance, and autoclave capability at lower cost than PEEK or Ultem. Choose PSU when you need transparency with steam sterilization resistance — it fills the gap between polycarbonate (limited to 130°C, poor steam resistance) and Ultem (higher temperature but more expensive and amber-tinted). PSU is the standard for medical and food-service applications requiring repeated sterilization.
Real-World Applications
PSU withstands thousands of steam autoclave cycles at 134°C without degradation, making it standard for surgical instrument trays and dental cassette systems.
PSU's biocompatibility, transparency for visual inspection, and resistance to blood-contact sterilization make it the material for hemodialysis component housings.
PSU is FDA-compliant for repeated food contact and withstands commercial dishwashing temperatures — used for coffee machine components, hot water dispensers, and food processing sight glasses.
PSU's clarity, chemical resistance, and autoclave capability make it ideal for beakers, filter housings, and other lab ware that requires repeated sterilization.
Processing & Cost Considerations
Manufacturing Tips
- PSU processes at 360-390°C melt temperature with mold temperatures of 100-150°C. These temperatures are achievable on standard high-temperature injection molding machines — no special equipment required.
- PSU must be thoroughly dried before processing (120-130°C for 3-4 hours) as it is hygroscopic. Moisture causes splay marks and reduces mechanical properties.
- PSU has higher melt viscosity than polycarbonate — higher injection pressures and faster fill speeds are needed. Optimize gate design for adequate flow length, especially for thin-wall parts.
PSU costs $15-35/kg — less than Ultem ($30-80/kg) and significantly less than PEEK ($80-200/kg). This positions PSU as a cost-effective choice for transparent, sterilizable components. When opacity is acceptable and higher temperature is needed, Ultem may justify its higher cost. When transparency and autoclave resistance are the primary requirements, PSU is typically the most economical choice.
Technical Properties
| Density | 1.24 g/cm³ |
|---|---|
| Tensile Strength | 75 MPa |
| Melting Point | N/A (Amorphous, Tg 185°C) |
| Shrinkage Rate | 0.6-0.7% |
| Flexural Modulus | 2.7 GPa |
| Hdt | 174 °C at 1.82 MPa |
| Continuous Service Temp | 160 °C |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Solvay Udel PSU | |
| BASF Ultrason S | |
| Sumitomo SumikaExcel PSU |
Frequently Asked Questions
What is the environmental stress crack resistance (ESCR) limitation of PSU?
PSU has good chemical resistance to aqueous solutions, acids, and bases, but it is susceptible to environmental stress cracking (ESC) when exposed to polar organic solvents—particularly ketones (acetone, MEK), esters, chlorinated solvents (methylene chloride), and aromatic hydrocarbons. The cracking occurs when the chemical attacks the polymer while the part is under molded-in or applied stress. Mitigation: (1) anneal parts after molding (160°C for 2-4 hours) to relieve molded-in stresses, (2) avoid press-fit or interference-fit designs that create sustained tensile stress, (3) use radiused internal corners (minimum 0.5 mm radius) to reduce stress concentration factors. For applications involving repeated solvent exposure, upgrade to PPSU (Radel) which has significantly better ESCR.
What is the difference between PSU, PES, and PPSU?
PSU (polysulfone, Udel) has 150°C continuous service, excellent clarity, and the lowest cost of the three. PES (polyethersulfone, Veradel/Ultrason) offers 180°C service and better chemical resistance at higher cost. PPSU (polyphenylsulfone, Radel) provides the highest impact toughness (notch sensitivity 10× better than PSU) and 180°C service. Choose PSU for standard sterilization, PES for higher temperature, PPSU for impact-critical medical applications.
Is PSU truly transparent?
Yes. PSU is water-clear transparent with a slight yellow tint, providing better clarity than Ultem (which is amber-tinted). PSU's light transmission is approximately 85-90% for 3mm thickness, suitable for sight glasses and inspection windows.
How many autoclave cycles can PSU withstand?
PSU typically withstands 1,000-2,000 autoclave cycles at 134°C before showing significant property degradation. This is far superior to polycarbonate (50-100 cycles) and comparable to Ultem. For applications requiring even more cycles, PPSU offers the best autoclave resistance among transparent polymers.
Can PSU be bonded or welded?
Yes. PSU can be solvent-bonded using methylene chloride or dichloroethane for strong, clear bonds. It can also be ultrasonically welded and heat-sealed. Solvent bonding is the most common joining method for medical device assembly.
Is PSU resistant to chlorine and chlorinated water?
PSU has good resistance to chlorinated water at moderate temperatures, making it suitable for pool and spa components and water treatment equipment. However, prolonged exposure to hot chlorinated water above 60°C can cause stress cracking. For continuous hot chlorinated water service, PPSU offers better resistance.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org