Polysulfone vs Polycarbonate: Autoclave Resistance vs Cost

Polysulfone (PSU) and polycarbonate (PC) are both amorphous, transparent-to-translucent engineering thermoplastics used in medical devices, laboratory equipment, food-service components, and industrial housings. At room temperature and in dry applications, they are comparable in many respects. The critical divergence is hydrolytic stability: PSU (300°F continuous) and especially PPSU (360°F continuous) survive repeated steam sterilization cycles with no degradation; standard polycarbonate begins to hydrolyze, craze, and degrade in steam above about 240°F. PC is significantly cheaper and offers full optical clarity; PSU and PPSU cost 3–5× more but are the only choice for hot-water and autoclave-intensive service.

TL;DR

• Polycarbonate (PC) is optically clear, impact-resistant (12–18 ft·lb/in notched Izod), and relatively inexpensive. Rated to ~240°F (115°C) continuous; degrades in steam and repeated autoclave cycles.
• PSU (Udel) is transparent amber, rated to 300°F (150°C) continuous, and survives repeated autoclaving at 134°C (273°F). Cost roughly 3–4× polycarbonate.
• PPSU (Radel) is rated to 360°F (180°C) continuous and handles the most aggressive repeated autoclave protocols. Impact strength (~10–12 ft·lb/in) is exceptional for a high-temperature material. Cost roughly 4–6× polycarbonate.
• PC is attacked by ketones, esters, aromatic solvents, and — critically — steam and hot water above 240°F.
• PSU and PPSU resist the same solvents better, handle hot water/steam, and maintain mechanical properties through thousands of autoclave cycles.
• For optical clarity in single-use or low-moisture environments, PC is unmatched at its price point. For reusable, steam-sterilized components, PSU or PPSU is mandatory.

When to Choose Polycarbonate

Optical Clarity Applications

PC's light transmittance of 85–90% and water-clear appearance make it the standard for lenses, machine safety guards, LED diffusers, architectural glazing panels, and instrument windows where visibility is the primary design requirement. PSU and PPSU have an amber tint and ~60–70% transmittance that renders them unsuitable for true optical applications.

High-Impact, Single-Use or Dry Environments

PC's notched Izod impact strength of 12–18 ft·lb/in is exceptional — significantly higher than PSU's 1.3 ft·lb/in (though PPSU recovers to ~10–12 ft·lb/in). For machine guards, protective shields, and impact-absorbing housings in dry environments where steam sterilization is not required, PC provides an unmatched combination of clarity, toughness, and low cost.

Cost-Sensitive Engineering Parts

PC sheet and rod costs approximately $3–7/lb for standard grades — roughly one-third to one-fifth the cost of PSU or PPSU. For high-volume non-medical applications (automotive components, consumer electronics housings, industrial enclosures, protective panels), PC's cost advantage drives the specification decision when temperature and steam resistance are not constraints.

Single-Use Medical Components

FDA-compliant PC grades (and PC blends) are widely used in single-use medical device components — IV connectors, blood oxygenators, filter housings, centrifuge bowls — where the part is used once and discarded rather than repeatedly sterilized. In this use case, PC's lack of autoclave resistance is irrelevant, and its lower cost and optical clarity are assets.

When to Choose PSU or PPSU

Repeated Autoclave Sterilization

The defining reason to specify PSU or PPSU over PC is the need for repeated steam sterilization. Standard autoclave cycles run at 121°C (250°F) to 134°C (273°F) under saturated steam at 15–30 psi. PC hydrolysis begins rapidly under these conditions — crazing and property loss appear after 20–50 cycles or sooner in more aggressive protocols. PSU handles typical 121°C protocols well; PPSU is specified for the most demanding 134°C Prevacuum and steam-flush cycles used in hospitals for rigid surgical instrument trays and container systems.

Medical Instrument Trays and Reusable Surgical Instruments

Hospital CSSD (Central Sterile Services) standards require instrument trays and surgical handles to survive 1,000+ autoclave cycles without mechanical degradation. PPSU (Radel) is the standard material for this application — specifically Solvay Radel R-5000 and R-5500 grades, which carry FDA compliance and USP Class VI designation. PC is not appropriate for reusable instruments.

Hot Water Plumbing and HVAC Components

Water heaters, mixing valves, water filter housings, and hot-water distribution fittings routinely see 140–200°F water. PSU's hydrolytic stability makes it the standard for these applications in place of PC. Plumbing component standards (NSF 61 for drinking water contact) are achievable in PSU grades; PC grades certified for continuous hot water service are much rarer.

Chemical Resistance in Cleaning Environments

Medical and laboratory equipment is regularly cleaned with aggressive disinfectants: bleach, glutaraldehyde (Cidex), peracetic acid, and alcohol-based cleaners. PSU and PPSU resist these disinfectants through many exposure cycles; PC has known sensitivity to isopropyl alcohol at elevated concentrations and to bleach in repeated exposure — crazing and stress cracking are documented failure modes.

Specs Head-to-Head

Autoclave Life — Quantified

In independent testing, PSU (Udel P-1700) maintains >90% of its tensile strength through 1,000 autoclave cycles at 121°C. PPSU (Radel R-5000) maintains >95% through the same protocol and shows minimal change through 1,000 cycles at 134°C. PC (Lexan 101) begins to show measurable property reduction after as few as 50 cycles at 121°C and exhibits crazing and yellowing above 100 cycles in steam.

Impact Resistance Within the Polysulfone Family

The PSU vs PPSU impact difference is important: PSU (Udel) at 1.3 ft·lb/in notched Izod versus PPSU (Radel) at 10–12 ft·lb/in. This makes PSU fragile in drop or shock scenarios while PPSU behaves similarly to PC in impact resistance. For applications requiring both toughness and autoclave resistance, PPSU is the only member of the polysulfone family that achieves both.

Electrical Properties

All three materials are excellent electrical insulators, but PSU has the highest dielectric strength (~425 V/mil) and volume resistivity. PSU and PPSU are used for circuit board terminal blocks, electrical insulators in medical equipment, and relay housings where dimensional stability at elevated temperature and moisture is required alongside good dielectric performance.

Dimensional Stability

As amorphous polymers, all three materials are dimensionally stable with low and consistent shrinkage — critical for precision machined components. PSU and PPSU absorb slightly more moisture than PC (PSU: ~0.3%; PC: ~0.15%), which can affect tight-tolerance dimensions in humid environments, but the difference is small and typically manageable with pre-drying before machining.

Cost & Availability

Both PSU and PPSU are available from specialty plastic distributors. PPSU in large diameters (4 in+ rod) may require lead time of 1–3 weeks.

Common Alternatives

• ABS vs Acrylic — If neither heat nor autoclave resistance is needed, this lower-cost comparison covers opaque and clear alternatives.
• PPS vs Ultem — For applications pushing above 340°F where PSU/PPSU no longer suffice.
• Ultem (PEI) Material Hub — Ultem sits between PPSU and PPS on the temperature scale (340°F), with FDA compliance and aerospace flammability ratings.

More related guides

Explore related material decisions and where these plastics show up in real production:

Applications

• Medical Sterilization
• Machine Guards
• Marine Outdoor

Industries

• Medical
• Marine

Other comparisons

• Ultem Vs. Polycarbonate
• Ultem Vs. Polysulfone
• Polycarbonate Vs. Acrylic

Spec sheets

• PSU/PPSU hub
• Polycarbonate/Lexan hub