Polysulfone FAQ: PSU vs PPSU, Medical & Machining

Polysulfone (PSU) and polyphenylsulfone (PPSU) are amorphous, high-performance engineering thermoplastics used in medical devices, food processing equipment, water treatment systems, and aerospace components. Their combination of steam stability, FDA compliance, inherent flame resistance, and excellent mechanical properties at elevated temperatures makes them preferred alternatives to polycarbonate when autoclavability or higher temperature performance is required. This FAQ addresses the most common questions about polysulfone selection, processing, and applications.

What is the difference between PSU and PPSU?

PSU (polysulfone, sometimes labeled Udel) and PPSU (polyphenylsulfone, branded Radel by Solvay) are related but distinct polymers:

PSU (Udel) is the base polysulfone polymer. It is amber-translucent, rigid, and offers a continuous use temperature of approximately 300°F (149°C) with an HDT of ~345°F (174°C). PSU is the lower-cost option and meets FDA and USP Class VI requirements in standard grades.

PPSU (Radel) has a modified backbone structure that significantly improves impact resistance, hydrolytic stability, and continuous use temperature (~375°F / 190°C). PPSU withstands more autoclave cycles than PSU before showing surface degradation. It is preferred for demanding medical device applications that require hundreds of sterilization cycles and superior impact resistance.

PESU (polyethersulfone) occupies an intermediate position, offering higher heat resistance than PSU but lower than PPSU.

For most applications requiring autoclavability and FDA compliance below 300°F, PSU is the cost-effective choice. For the most demanding reusable surgical instrument applications, specify PPSU. Full property comparisons are in the polysulfone grades guide.

Is polysulfone autoclavable?

Yes. Both PSU and PPSU are steam-autoclavable, which is one of the primary reasons they are specified over polycarbonate in medical applications. PSU withstands standard autoclave conditions (134°C / 273°F, 30 minutes) for approximately 50–100 cycles before observable surface degradation (crazing, slight discoloration) begins. PPSU is significantly more hydrolytically stable and can sustain 1,000+ autoclave cycles in clinical testing before meaningful property loss. Neither material should be autoclaved at temperatures above its HDT; always confirm the autoclave cycle temperature against the grade-specific HDT. Polycarbonate, by comparison, typically degrades visibly after 10–20 autoclave cycles. The polysulfone applications guide documents sterilization compatibility in medical device contexts.

What is polysulfone's steam stability?

Steam stability—the ability to retain mechanical properties and dimensional integrity after repeated exposure to steam or hot water—is a defining advantage of polysulfone over other amorphous engineering thermoplastics. PSU's sulfone linkages in the polymer backbone are inherently hydrolytically stable, resisting chain scission that degrades polycarbonate and some polyesters in steam environments. At temperatures up to 150°C in pressurized steam, PSU retains usable structural properties. PPSU extends this capability to approximately 190°C in short-term service. Above these temperatures or in sustained high-pressure steam, PEEK or Ultem PEI should be considered. See the polysulfone properties guide for hydrolytic stability data.

Does polysulfone meet FDA and USP Class VI requirements?

Yes. Standard natural (amber-translucent) PSU and PPSU in unfilled, uncolored form are widely documented as meeting FDA 21 CFR 177.1655 (for repeated food contact applications) and USP Class VI biological reactivity testing for indirect medical contact. They also comply with EU Regulation 10/2011 for plastic food contact materials. PPSU (Radel) is additionally listed for compliance with ASTM F997, the standard specification for PSU used in surgical instruments. Note that glass-filled and colored grades require separate compliance verification, as additives may introduce regulatory issues. Always request a Certificate of Conformance and applicable compliance letter from the supplier when regulatory documentation is required. Full regulatory details are in the polysulfone FDA guide.

What color does polysulfone come in?

Natural (unfilled) polysulfone is an amber-translucent material—a warm golden-brown color that is semi-transparent at thin cross-sections and translucent at thicker sections. This color is intrinsic to the polysulfone polymer backbone and cannot be changed without adding pigments. Opaque black PSU and PPSU are available in some grades, typically produced with carbon black. Glass-filled grades are tan to light gray and opaque. Transparent (water-clear) polysulfone is not standard; if optical clarity is required, consider polycarbonate or a different material. The amber translucency of polysulfone is actually an advantage in medical applications where surgeons or technicians benefit from visual inspection of instrument internal channels without full transparency. Stocked color options are listed on the polysulfone product page.

How does polysulfone cost compare to polycarbonate?

Polysulfone (PSU) costs roughly 2–4× more than standard polycarbonate on a per-pound basis. PC typically runs $2–$6 per pound; PSU runs $10–$25 per pound; PPSU (Radel) commands an additional premium at $25–$50+ per pound. The cost difference reflects PSU's superior hydrolytic stability, autoclavability, and higher service temperature. For applications that do not require autoclaving or elevated temperature service, polycarbonate is the more economical transparent-to-amber engineering plastic. When the choice comes down to autoclavability or steam resistance, the cost premium for PSU or PPSU is typically justified by the extended service life in reusable applications. Compare in detail at the polysulfone vs polycarbonate comparison.

What are the primary medical applications for polysulfone?

Polysulfone is one of the most widely used engineering plastics in medical devices, specified for:

• Reusable surgical instruments: handles, guides, and structural components that require repeated steam autoclave sterilization
• Surgical trays and containers: for sterilizable instrument organization
• Fluid management components: blood oxygenator housings, dialysis membrane housings (taking advantage of biocompatibility and steam sterilizability)
• Dental instrument handles and housings: where autoclave compatibility and chemical resistance to dental disinfectants matter
• Food processing equipment: pump housings, valves, and fittings in hot-water sanitation environments

PPSU is preferred over PSU for applications requiring the highest number of sterilization cycles or the best impact resistance. See the polysulfone applications guide for device-specific case studies. For sterilizable medical parts that also require FDA food-contact compliance, review the polysulfone FDA guide.

Are glass-filled grades of polysulfone available?

Yes. Both PSU and PPSU are available in glass fiber-reinforced grades, typically at 10%, 20%, or 30% glass content. Glass-filled polysulfone offers:

• Tensile strength increased by 50–80% over unfilled grades
• Significantly higher stiffness (flexural modulus)
• Reduced thermal expansion (lower CTE)
• Higher HDT (up to ~375°F / 190°C for 30% GF PSU)

The tradeoff is loss of translucency (glass-filled grades are opaque), reduced impact resistance, and increased abrasiveness during machining. Glass-filled grades may also require additional compliance verification for medical or food-contact applications, as not all glass-fiber additives are cleared for regulated uses. For the highest-strength, highest-HDT polysulfone applications, 30% glass-filled PPSU is available. Compare grades in the polysulfone grades guide.

How do you machine polysulfone?

PSU and PPSU machine similarly to other amorphous engineering thermoplastics like Ultem PEI or polycarbonate—cleanly with proper tooling. Use sharp HSS or carbide tooling with positive rake angles; cutting speeds of 300–600 SFPM for turning. Polysulfone is sensitive to heat—elevated temperatures cause yellowing or surface hazing, and thermal stress can cause cracking in thin walls. Use compressed air or water-soluble coolant (avoid chlorinated cutting fluids, which attack polysulfone). Maintain moderate chip loads; avoid rubbing tools that generate heat without cutting. Tapping: 65% thread engagement with spiral-flute taps. Drilling: standard twist drills work; reduce feed when breaking through to avoid grabbing. Glass-filled grades require carbide tooling and generate more abrasive dust. Full machining parameters are in the polysulfone machining guide.

How does polysulfone compare to PEEK for medical applications?

PEEK and polysulfone both meet FDA and USP Class VI requirements and are used in medical devices, but they occupy different performance tiers. PEEK offers a higher continuous use temperature (~480°F vs ~300°F for PSU), better fatigue resistance, and superior chemical resistance to solvents and some disinfectants. PSU and PPSU are significantly less expensive (typically 3–8× cheaper than PEEK), more easily machined in prototype quantities, and provide amber translucency useful for visual inspection. For sterilizable surgical instruments and food-processing equipment at temperatures below 300°F, polysulfone provides equivalent regulatory compliance at much lower cost. For implantable devices, high-fatigue loading, or temperatures above 300°F, PEEK is required. See the polysulfone vs PEEK comparison and the Ultem vs polysulfone comparison.

Does polysulfone resist common chemical sterilants and disinfectants?

PSU and PPSU resist many chemical sterilants used in healthcare settings, including dilute glutaraldehyde solutions, hydrogen peroxide vapor (at appropriate concentrations), and peracetic acid at dilute concentrations. However, polysulfone is NOT compatible with high-concentration sodium hypochlorite (bleach >1% solutions), concentrated hydrochloric acid, or prolonged exposure to aromatic solvents (toluene, MEK, THF), which cause swelling or stress cracking. Isopropyl alcohol is generally acceptable at room temperature for cleaning. Always verify compatibility with the specific disinfectant formulation, concentration, and contact duration before finalizing material selection for reusable device applications. The polysulfone chemical resistance table lists compatibility with common healthcare sterilants and industrial chemicals.

What sizes and forms is polysulfone available in?

Standard PSU and PPSU are available in:

• Sheet/plate: typically 0.062″–3.0″ thick in 24″ × 48″ or 48″ × 96″ format
• Rod: 0.25″–6.0″ diameter in standard lengths
• Tube: limited selection of standard OD/ID combinations

Natural (amber) PSU rod and sheet in common sizes is typically stocked for same-day to 1-week shipment. PPSU in standard rod and sheet is widely stocked but may have slightly longer lead times than PSU. Glass-filled and black grades, large-diameter rod, and thick plate may require 3–8 weeks. Confirm availability at the polysulfone product page before committing to a design schedule.

More related guides

Cross-cluster suggestions to help shoppers and engineers explore adjacent topics:

Applications

• Medical Sterilization

Industries

• Medical

Compare to other materials

• Ultem Vs. Polysulfone
• Polysulfone Vs. Polycarbonate

Frequently asked questions — Polysulfone FAQ