PAI · grade
PAI Bearing Grade
Properties of the Bearing Grade condition, compared with the other PAI grades.
Choose for unlubricated or marginally lubricated wear parts — seal rings, thrust washers, bushings, valve seats — where low friction and high PV matter more than elongation.
What is PAI Bearing Grade?
PAI Bearing Grade is PAI in the Bearing Grade grade — choose for unlubricated or marginally lubricated wear parts — seal rings, thrust washers, bushings, valve seats — where low friction and high PV matter more than elongation. PAI Bearing Grade has a tensile strength of 117 MPa (17 ksi), stronger than 92% of polymer grades. Elongation at break is 7% and the elastic modulus is 6.8 GPa (0.986 Msi). PAI Bearing Grade has a density of 1.46 g/cm³ (0.0527 lb/in³), heavier than 85% of polymer grades. Its glass-transition temperature is 275°C (527 °F). Unfilled (Electrical) is the default condition FabDigit quotes; Bearing Grade is available on request or by drawing note.
Advantages
- Conducts heat well — 0.54 W/m·K (0.312 BTU/hr·ft·°F), better than 99% of polymer grades
- High service temperature — 250°C (482 °F), better than 94% of polymer grades
- Stiff — 6.8 GPa (0.986 Msi), better than 89% of polymer grades
- Polishes to a fine finish — 70/100, better than 78% of polymer grades
Limitations
- High embodied carbon — 14 kg CO₂/kg, worse than 95% of polymer grades
- Heavy — 1.46 g/cm³ (0.0527 lb/in³), worse than 85% of polymer grades
- Difficult to weld — 10/100, worse than 84% of polymer grades
- Limited formability — 15/100, worse than 80% of polymer grades
PAI Bearing Grade properties
Typical room-temperature values for PAI Bearing Grade — 18 properties are specific to this condition; the rest are grade-level values shared by every PAI grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical4
PAI Bearing Grade has a density of 1.46 g/cm³ (0.0527 lb/in³), heavier than 85% of polymer grades. Its glass-transition temperature is 275°C (527 °F).
Mechanical13
PAI Bearing Grade has a tensile strength of 117 MPa (17 ksi), stronger than 92% of polymer grades. Elongation at break is 7% and the elastic modulus is 6.8 GPa (0.986 Msi).
Thermal10
PAI Bearing Grade is rated for continuous service to 250°C (482 °F). It conducts heat at 0.54 W/m·K (0.312 BTU/hr·ft·°F), better than 99% of polymer grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
PAI Bearing Grade is an electrical insulator with a dielectric strength of 23 kV/mm (584.2 V/mil) and a resistivity of 1×10¹⁵ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), worse than 55% of polymer grades. UV resistance is fair.
Sustainability3
Producing a kilogram of PAI Bearing Grade takes about 300 MJ of energy and emits 14 kg of CO₂ — more than 97% of polymer grades. Typical recycled content is 0%.
Manufacturability7
PAI Bearing Grade's machinability is good (55/100, worse than 63% of polymer grades); weldability not recommended (10/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other PAI grades and fills
PAI is also supplied in 4 other conditions. The full side-by-side table is on the PAI overview.
- Unfilled (Electrical)DefaultChoose for insulators, connectors and thin-wall parts needing maximum toughness/elongation and the best dielectric properties.152 MPa tensile
- GF30Choose for stiff, dimensionally stable structural parts that must stay electrically insulating at high temperature.205 MPa tensile
- CF30Choose for the highest stiffness/strength-to-weight and lowest thermal expansion — aerospace brackets, high-speed rotating parts, ESD-tolerant applications.205 MPa tensile
- Bearing GradeChoose for unlubricated or marginally lubricated wear parts — seal rings, thrust washers, bushings, valve seats — where low friction and high PV matter more than elongation.117 MPa tensile
- LFPAI compounded with graphite plus PTFE lubricant for the lowest dry-running friction coefficient and low wear at high PV, at the cost of strength and ductility versus unfilled resin.110 MPa tensile
Working with PAI Bearing Grade
Is PAI easy to machine?
Machines like a hard, abrasive engineering plastic — use sharp carbide or PCD tooling, moderate speeds, light finishing cuts, and machine after post-cure to avoid dimensional drift.
Can PAI be welded?
Not fusion weldable in practice; join by epoxy adhesive bonding, PAI adhesive film, or mechanical fasteners with generous bearing area.
Can PAI be formed, bent or molded?
Injection mold with dried resin at 335–365 °C melt and 200–230 °C mold, then post-cure parts in stages to ~260 °C for several days to develop full strength and chemical resistance.
What surface finishes work on PAI?
Natural amber-to-black surfaces polish well and accept plasma or chemical etch before plating/bonding; paint and metallization require thorough drying because of moisture pickup.
PAI chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| titanium dioxidepigment/processing aid in unfilled 4203-type grades | ≈ 3 | 3 |
| PTFEinternal lubricant; ~3% in bearing grades | 0.5 – 3 | 0.5 |
| graphitebearing/wear grades only (4301 ≈ 12%, 4275 ≈ 20%) | 0 – 20 | 12 |
| glass fiberGF30 (5030) variant only | ≈ 30 | 30 |
| carbon fiberCF30 (7130) variant only | ≈ 30 | 30 |
| polyamide-imide (trimellitic anhydride +amide-imide backbone; base resin of all grades | balance | — |
PAI Bearing Grade — frequently asked
What is PAI Bearing Grade used for?
PAI Bearing Grade is typically used for thrust washers, bearings and bearing cages, seal rings for aero-engine and hydraulic systems, insulating washers and spacers, high-temperature electrical connectors and precision gears. In short: highest strength carbon-plastic.
What is the tensile strength of PAI Bearing Grade?
PAI Bearing Grade has a typical tensile strength of 117 MPa (17 ksi) — stronger than 92% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is PAI Bearing Grade easy to machine?
Reasonably — machinability is rated good (55/100, worse than 63% of polymer grades). Machines like a hard, abrasive engineering plastic — use sharp carbide or PCD tooling, moderate speeds, light finishing cuts, and machine after post-cure to avoid dimensional drift.
Can PAI Bearing Grade be welded?
Not readily — weldability is rated not recommended (10/100). Not fusion weldable in practice; join by epoxy adhesive bonding, PAI adhesive film, or mechanical fasteners with generous bearing area.
What surface finishes work on PAI Bearing Grade?
Natural amber-to-black surfaces polish well and accept plasma or chemical etch before plating/bonding; paint and metallization require thorough drying because of moisture pickup.
Can PAI Bearing Grade be formed, bent or molded?
Injection mold with dried resin at 335–365 °C melt and 200–230 °C mold, then post-cure parts in stages to ~260 °C for several days to develop full strength and chemical resistance.
What is the maximum service temperature of PAI Bearing Grade?
PAI Bearing Grade is rated for continuous use to about 250°C (482 °F), and briefly to 280°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in PAI Bearing Grade?
Yes — PAI Bearing Grade is available for CNC machining, sheet metal and injection molding with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- Torlon PAI Design Guide and grade datasheets (4203L, 4301, 4275, 5030, 7130) — Solvay Specialty Polymers (2021)
- Duratron T4203 / T4301 / T4501 PAI stock shape datasheets — Mitsubishi Chemical Advanced Materials (Quadrant) (2022)
- TECATOR / PAI machinable stock shapes datasheet — Ensinger (2022)
- CAMPUS / UL Prospector polyamide-imide typical property records — CAMPUS Plastics (2023)
- ASM Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.