PSU (Polysulfone) vs PPSU (Radel)
PSU (polysulfone) and PPSU (Radel) are transparent, high-temperature sulfone polymers used where parts must survive repeated steam sterilization and hot water. They overlap closely in strength and stiffness, but PPSU pulls ahead on impact toughness and resistance to hydrolysis — the reason it dominates repeat-autoclave surgical instruments — while PSU offers similar performance at lower cost.
The verdict
Choose PSU for sterilizable medical and fluid-handling parts where its ~160°C rating and good chemical resistance suffice at lower cost. Choose PPSU (Radel) when parts face many autoclave cycles or aggressive hot-water/steam exposure and need its superior impact toughness and hydrolysis resistance, with a higher ~180°C nominal rating.
Side-by-side data
| Property | PSU (Polysulfone) | PPSU (Radel) |
|---|---|---|
| Category | Engineering Plastic | Engineering Plastic |
| Density (g/cm³) | 1.24 | 1.29 |
| Tensile strength (MPa) | 70 | 70 |
| Yield strength (MPa) | 70 | 70 |
| Elongation (%) | 60 | 60 |
| Hardness | M69 | M86 |
| Max service temp (°C) | 160 | 180 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 0.26 | 0.35 |
| Typically used for | Sterilizable medical & fluid handling | Repeat-autoclave surgical instruments |
Which should you choose?
Choose PSU (Polysulfone) when…
- Parts are sterilizable medical or fluid-handling components within ~160°C
- You need a transparent, dimensionally stable high-temp plastic at lower cost (3.5 vs 4.0)
- Hydrolysis and repeated-steam exposure are moderate, not extreme
- Good chemical resistance (corrosion 5) and machinability (4.0) are wanted
- The part doesn't see severe impact loading
- You want sulfone-class heat resistance without paying the PPSU premium
Choose PPSU (Radel) when…
- Parts undergo many repeated autoclave/steam-sterilization cycles
- Superior impact toughness is needed — PPSU resists cracking better than PSU
- Hot-water and steam hydrolysis resistance is critical for long service life
- The higher ~180°C nominal temperature rating gives needed margin
- Surgical instruments or sterilization trays must survive years of cycling
- The higher cost (4.0 vs 3.5) is justified by durability and reuse
Key differences that matter
- PSU and PPSU share nearly identical strength/stiffness here (~70 MPa tensile/yield, ~60% elongation) — the differences are in toughness and hydrolytic durability.
- PPSU is rated higher in temperature (~180°C vs 160°C nominal) and resists steam/hot-water hydrolysis better, the key reason it survives repeated autoclaving.
- PPSU has notably higher impact toughness, so instruments resist cracking through many sterilization cycles.
- Both rate top chemical resistance (corrosion 5) and machine well (4.0).
- PSU costs less (3.5 vs 4.0), making it the value sulfone where extreme cycling isn't required.
- Both are transparent/translucent high-temp amorphous polymers used in medical and fluid-handling roles.
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Why does PPSU survive more autoclave cycles than PSU?
PPSU has superior resistance to hydrolysis — degradation from repeated exposure to hot water and steam — plus higher impact toughness, so it resists the micro-cracking that accumulates with each sterilization cycle. PSU is steam-sterilizable too, but over hundreds of cycles PPSU holds up better, which is why reusable surgical instruments favor it.
Are PSU and PPSU mechanically different?
On paper they're very close — both around 70 MPa tensile and yield with ~60% elongation in this dataset. The meaningful gap is toughness and durability: PPSU absorbs impact and resists crack propagation better, and tolerates hot-water hydrolysis longer. For static strength they're comparable; for repeated harsh cycling PPSU is clearly tougher.
Which is better for a clear sight glass or fluid component?
Both are transparent, high-temperature sulfones suitable for fluid-handling and sight components. PSU is the lower-cost choice when service stays within ~160°C and impact/hydrolysis demands are moderate. Step up to PPSU if the part sees steam, repeated thermal cycling, or impact risk and you need the extra durability margin.
Is the cost difference worth it?
Only when durability matters. PPSU costs more (4.0 vs 3.5) but lasts far longer under repeated autoclaving and impact, lowering replacement cost for reusable instruments. For single-use or lightly cycled parts within PSU's range, PSU delivers the same strength and chemical resistance for less.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.