PSU Polysulfone (Udel/Radel): Sterilization & Medical Device Polymer
Published: 2026-06-02
Polysulfone (PSU) combines steam sterilizability (autoclave at 134°C, 1,000+ cycles), chemical resistance, and optical clarity in an amorphous, rigid thermoplastic. This unique combination makes PSU the dominant polymer for reusable medical...
Polysulfone (PSU) combines steam sterilizability (autoclave at 134°C, 1,000+ cycles), chemical resistance, and optical clarity in an amorphous, rigid thermoplastic. This unique combination makes PSU the dominant polymer for reusable medical devices and surgical instrument handles. Unlike semi-crystalline polymers that become opaque upon sterilization-induced crystallization, PSU remains transparent. FDA Master File: PSU is listed under 21 CFR 177.1655 for repeated food contact and has extensive ISO 10993 biocompatibility data supporting medical device applications.
PSU vs PPSU (Radel R): PPSU has higher impact strength and better chemical resistance but is amber-colored (not transparent). PSU is water-clear with a slight amber tint. Processing: PSU is hygroscopic — dry at 135°C for 4 hours. Melt temperature 330-380°C, mold temperature 120-160°C. High melt viscosity requires generous runners and gates. PSU is notch-sensitive — radius all internal corners to >0.5mm. Sterilization compatibility: EtO, gamma (yellowing), steam autoclave (1,000+ cycles), and hydrogen peroxide plasma (Sterrad).
Technical Properties
| Density | 1.24 g/cm³ |
|---|---|
| Tensile Strength | 70 MPa |
| Melting Point | Amorphous (Tg 185°C) |
| Shrinkage Rate | 0.7% |
| Flexural Modulus | 2.7 GPa |
| Hdt | 174 °C at 1.82 MPa |
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 |
|---|---|
| Udel P-1700 | |
| Ultrason S | |
| Radel R (PPSU) — higher impact variant |
Frequently Asked Questions
What is the difference between PSU, PPSU, and PES?
PSU (Udel, Ultrason S): transparent, rigid, Tg 185°C, lowest cost of the three. PPSU (Radel R, Ultrason P): amber-colored, highest impact strength, Tg 220°C, best chemical resistance. PES (Ultrason E, Veradel): transparent, Tg 225°C, highest thermal performance. Select PSU for transparency + autoclave; PPSU for impact + chemical; PES for highest thermal.
Can PSU be sterilized with gamma radiation?
Yes, but gamma causes yellowing — the color shift is cosmetic and does not affect mechanical properties. For medical devices where color is critical (light pipes, viewing windows), EtO or hydrogen peroxide plasma sterilization is preferred because they do not discolor PSU.
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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