Polysulfone Grades — Udel PSU vs. Radel PPSU

Two commercial grades of polysulfone are stocked in sheet and rod form: Udel PSU (polysulfone) and Radel PPSU (polyphenylsulfone). Both share the sulfone backbone and amber transparency, but PPSU's enhanced polymer structure delivers meaningfully higher impact resistance, a higher glass transition temperature, and dramatically better durability through steam sterilization cycles. Selecting the right grade requires matching your sterilization frequency, temperature ceiling, and budget against each material's documented capabilities.

At a glance:

• Udel PSU: lower cost, continuous 300°F, moderate sterilization tolerance, tensile 10,200 psi
• Radel PPSU: higher cost, continuous 350°F, 1,000+ autoclave cycles documented, tensile 10,500 psi
• BASF Ultrason S (PSU) and Ultrason P (PPSU) are equivalent alternative resins to Solvay Udel/Radel
• PPSU impact resistance is ~2× PSU at room temperature — relevant for clinical drop/impact events
• Both grades FDA 21 CFR 177.1655, USP Class VI, NSF 51 compliant
• Grade selection often determined by cycle count alone: <200 cycles → PSU; 200+ cycles → PPSU

Grade Overview

Udel PSU — Polysulfone (Solvay)

Udel PSU is the original commercial polysulfone, introduced by Union Carbide in 1965. Solvay now holds the Udel brand. It is manufactured as an amorphous aromatic thermoplastic with ether-sulfone linkages throughout the backbone. In sheet and rod form, Udel PSU provides consistent lot-to-lot properties and availability from multiple distributors.

Key use cases for Udel PSU:

• Moderate-cycle medical device components (under 200 autoclave cycles)
• Food and dairy processing equipment requiring NSF 51 and steam-cleanable surfaces
• Hot water plumbing fittings qualifying under NSF 61
• Filtration membrane substrates in pharmaceutical and water treatment
• Electrical components requiring dimensional stability above polycarbonate's service limit

Radel PPSU — Polyphenylsulfone (Solvay)

Radel PPSU adds biphenyl groups to the polysulfone backbone, increasing chain stiffness at elevated temperatures and greatly improving toughness and hydrolytic stability. The Tg of 428°F (220°C) is 54°F higher than PSU, and the impact energy absorbed before fracture is roughly double. Solvay's published data shows Radel PPSU retaining over 95% of original tensile strength through 1,000 steam autoclave cycles at 270°F (132°C).

Key use cases for Radel PPSU:

• High-cycle surgical instrument trays (daily hospital sterilization)
• Dental cassettes and instrument holders (multiple cycles per day)
• Animal research cage components (daily to twice-daily sterilization)
• Medical fluid management parts with USP Class VI compliance required
• Any application where impact resistance is critical alongside sterilization

BASF Ultrason — Equivalent Resin Family

BASF markets polysulfone resins under the Ultrason brand: Ultrason S (equivalent to Udel PSU) and Ultrason P (polyphenylsulfone, equivalent to Radel PPSU). Property data for Ultrason S and Ultrason P aligns closely with Solvay's Udel and Radel grades. Stock shapes are primarily sourced from Solvay resin in North American markets, but specification documents that reference the chemistry (ASTM D6107 for PSU or polyphenylsulfone) apply to both brands.

Grade Comparison Table

Sterilization Cycle Picker

Use the criteria below to identify the appropriate grade before requesting material.

Step 1 — Determine Annual Sterilization Frequency

Step 2 — Confirm Maximum Temperature

Step 3 — Evaluate Impact Requirements

If the component sustains drops, instrument placement impact, or stacking loads in clinical handling:

• Low impact risk (stationary, handled carefully): PSU acceptable
• Moderate impact risk (handled routinely, occasional drops): PPSU preferred
• High impact risk (daily clinical handling, stacking, drops expected): PPSU required

Step 4 — Regulatory Requirements

Both grades cover FDA 21 CFR 177.1655 and USP Class VI. If NSF 61 (potable water) certification is required, confirm with Udel PSU grade data sheets — this certification is grade-specific and applies to PSU rather than PPSU in most documented cases.

Filled and Modified Grades

Standard unfilled PSU and PPSU sheet and rod cover the majority of applications. Modified compounded grades exist in injection-molded form for special requirements:

• Glass-filled PSU (GF10, GF20, GF30): Higher stiffness and lower thermal expansion; used in precision electronic housings. Not commonly stocked as shapes.
• Mineral-filled grades: Improved dimensional stability for tight-tolerance components. Specialty items.
• Pigmented grades: Custom colors available in injection molding quantities; stock shapes are natural amber only.

Grade Selection by Industry

For full property data behind these grades, see the polysulfone properties datasheet. For application-specific examples in each industry, see the applications overview.

When comparing against alternative high-performance materials, Ultem PEI offers higher autoclave cycle counts but lacks the food-contact compliance of Udel PSU, and PEEK reaches 480°F continuous service at significantly higher cost. For the specific PSU vs. polycarbonate question, see the polycarbonate vs. polysulfone comparison.

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