Torlon 4203L (4203) PAI: specs and alternatives
Syensqo unfilled polyamide-imide (PAI) molding resin: density 1.42, Tg 277°C, HDT 278°C at 1.8 MPa, UL 94 V-0 in the producer’s 2015 design guide. Published data, how the resin differs from Torlon rod and plate, materials to ask about, and how to request a quote from one gaylord.
Request a QuoteThe short answer
Torlon 4203L is Syensqo’s unreinforced polyamide-imide (PAI) molding resin, formerly sold under Solvay Specialty Polymers. The data sheet describes it as a lubricated, pigmented grade (additive: PTFE lubricant) with the best impact resistance and greatest elongation of all Torlon grades. The data sheet (revised December 2020) lists density 1.42 (ASTM D792), glass transition 277°C onset, HDT 278°C at 1.8 MPa unannealed (ASTM D648), tensile strength 152 MPa (ASTM D638), notched Izod 140 J/m and CLTE 3.1 × 10-5/°C; the 2015 Torlon design guide (Solvay) adds UL 94 V-0 at 1.2 to 3.0 mm. The data sheet lists a 371°C nozzle and a 199–216°C mold, and the design guide says Torlon PAI parts must be post-cured. These are typical values; confirm on the current producer data sheet. Syensqo says 4203 has equivalent properties to 4203L. We did not find another producer’s PAI molding grade to compare; PEEK 450G and ULTEM 1000 are different polymers with lower heat ratings, and neither is a drop-in replacement.
Also written as: Torlon 4203, 4203L, Torlon 4203L PAI, Torlon PAI 4203 or polyamide-imide 4203L. The design guide gives the ASTM D5204 line callout as PAI000R03A56316E11FB41. Syensqo sells related versions as separate grades, for example 4203L-HF (high flow), 4203L-LF (low flow), 4301 (PTFE and graphite bearing grade), 5030 (30 % glass fiber) and 7130 (30 % carbon fiber). Quote the full code from your drawing or bag label, and say whether you need molding resin or machined stock shapes.
Buying Torlon 4203L: one gaylord to a railcar · supplier COA on every prime lot · ships from 22+ partner warehouse locations · a polymer chemist checks the grade code before we quote · we aim to quote within one to three business days
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Torlon 4203L specs from the data sheet
Typical values from Syensqo’s technical data sheet for Torlon 4203L (revised 12/21/2020, distributor-hosted copy), with UL ratings, relative temperature index and post-cure guidance from the Torlon PAI Design Guide (Solvay, version 5.0, 2015). Typical values; confirm on the current producer data sheet. Typical values are not specifications; the lot COA shows what you actually receive. Values only compare at the same test method and condition.
| Property | Value | Test method or note |
|---|---|---|
| Producer (brand owner) | Syensqo (formerly Solvay Specialty Polymers) | The data sheet footer reads “Solvay Specialty Polymers, a member of the Syensqo group” |
| Polymer | Polyamide-imide (PAI), unreinforced, amorphous; lubricated and pigmented | Syensqo brand page calls Torlon PAI amorphous |
| Additive | PTFE lubricant | As listed on the data sheet, which does not name the pigment or give additive levels |
| Form and process | Pellets; injection molding, profile extrusion and machining listed | Data sheet. Syensqo also lists 4203L-HF (high flow) and 4203L-LF (low flow) |
| Density | 1.42 g/cm³ | ASTM D792 |
| Mold shrinkage, flow | 0.60 to 0.85 % | ASTM D955 |
| Water absorption, 24 h | 0.33 % | ASTM D570 |
| Tensile modulus | 4,480 MPa | ASTM D638 Type I (4,900 MPa by ASTM D1708) |
| Tensile strength | 152 MPa | ASTM D638 Type I (192 MPa by ASTM D1708) |
| Tensile elongation at break | 7.6 % | ASTM D638 Type I (15 % by ASTM D1708) |
| Flexural modulus, 23°C / 232°C | 5,030 MPa / 3,590 MPa | ASTM D790 |
| Flexural strength, 23°C / 232°C | 241 MPa / 118 MPa | ASTM D790 (the design guide lists 244 / 120 MPa) |
| Compressive strength / modulus | 221 MPa / 4,000 MPa | ASTM D695 |
| Poisson’s ratio | 0.45 | ASTM E132 |
| Notched Izod impact | 140 J/m | ASTM D256 (the design guide lists 142 J/m at 3.2 mm) |
| Unnotched Izod impact | 1,100 J/m | ASTM D4812 (the design guide lists 1,062 J/m) |
| Glass transition temperature | 277°C onset | DSC, Solvay method, 2nd heat; the sheet says it is equivalent to ISO 11357-2 |
| HDT 1.8 MPa, unannealed | 278°C / 532°F | ASTM D648 (°F from the design guide) |
| Coefficient of linear thermal expansion, flow | 3.1 × 10-5 /°C (31 ppm/°C) | ASTM E831 (the design guide lists 30.6 ppm/°C by ASTM D696) |
| Thermal conductivity | 0.26 W/m·K | ASTM C177 |
| Service temperature | Syensqo says Torlon PAI performs well in severe service up to 260°C (500°F) | Syensqo brand page, for the Torlon family |
| Relative temperature index | 220°C electrical (0.81 to 3.0 mm); 210°C mechanical without impact at 0.81 to 2.4 mm and 220°C at 3.0 mm; 200°C mechanical with impact at 3.0 mm | UL 746B, as listed in the 2015 design guide; check UL for the current file |
| Flammability | UL 94 V-0 at 1.2, 2.4 and 3.0 mm. The data sheet lists “flame retardant” as a feature but gives no UL 94 rating; ask for the current UL file if your drawing needs one. | UL 94, design guide table 20 (2015) |
| Dielectric strength | 23 kV/mm | ASTM D149 |
| Dielectric constant / dissipation factor, 60 Hz and 1 MHz | 4.20 and 3.90 / 0.026 and 0.031 | ASTM D150 |
| Volume / surface resistivity | 2.0 × 1017 ohm·cm / 5.0 × 1018 ohm | ASTM D257 |
| Drying | 177°C for 3 h; suggested max moisture 0.050 % | Producer processing data |
| Barrel / nozzle temperature | Rear 304°C; nozzle 371°C | Producer processing data |
| Mold temperature | 199–216°C | Producer processing data |
| Back pressure / screw | Back pressure 6.89 MPa; screw speed 50–100 rpm; screw L/D 18:1 to 24:1 | Producer processing data |
| Post-cure | Required. The design guide says Torlon PAI parts must be post-cured through a cycle of increasing temperature; cycle parameters depend on part size and geometry. | Design guide; published properties are for injection-molded, post-cured specimens |
| Specifications listed | ASTM D4000 PAI000 R03 A56316 GA140 Z1Z2Z3Z4Z5Z6, Dwg YC3P-7E195-AA; Stellantis MS-DB-405 CPN3373 (natural). The design guide gives the ASTM D5204 line callout as PAI000R03A56316E11FB41. | As listed by the producer; confirm the current revision |
| RoHS | The data sheet lists 4203L as RoHS compliant | As stated on the sheet |
| Food contact | The 4203L data sheet does not include a food-contact statement, and its disclaimer notes that food applications may be regulated. Ask Syensqo for a regulatory statement for the exact grade before any food-contact use. |
Source data sheets are listed at the bottom of this page. Where the data sheet and the older design guide differ (flexural strength, Izod, CLTE), the table uses the data sheet and notes the design guide value. The design guide says its property tables are typical of injection-molded, post-cured test specimens.
The Torlon design guide (Solvay, 2015) says Torlon PAI is virtually unaffected by aliphatic and aromatic hydrocarbons, chlorinated and fluorinated hydrocarbons and most acids at moderate temperatures, but may be attacked by saturated steam, strong bases and some high-temperature acid systems. It adds that a proper post-cure is needed for optimal chemical resistance.
Torlon 4203L vs 4203, 4301, 5030 and 7130
Syensqo splits Torlon molding grades into high-strength grades (4203L, 5030, 7130) and wear-resistant grades (4301 and others with PTFE and graphite or carbon fiber). Values from the design guide’s typical properties table; typical values; confirm on the current producer data sheet.
| Grade | Fill | Density | Tensile strength / elongation | How it differs from 4203L |
|---|---|---|---|---|
| 4203L | Unfilled; PTFE lubricant, pigmented | 1.42 g/cm³ | 152 MPa / 7.6 % | This grade. Syensqo’s general-purpose unfilled grade: best impact resistance, most elongation, good mold release and good electrical properties. Notched Izod 142 J/m; HDT 278°C. |
| 4203 | Unfilled | Not listed separately | Not listed separately | Syensqo says 4203 has equivalent properties to 4203L. One shape maker notes that other shape producers still make stock shapes from 4203 resin. Confirm which code your drawing accepts. |
| 4203L-HF / 4203L-LF | Unfilled | See producer sheet | See producer sheet | Listed on the 4203L data sheet as high-flow and low-flow versions. Ask for their own data sheets; we have not compared their values here. |
| 4301 | PTFE and graphite | 1.46 g/cm³ | 113 MPa / 3.3 % | Syensqo’s general-purpose wear-resistant (bearing) grade. The graphite makes it black. Lower tensile strength and impact (notched Izod 63 J/m) than 4203L; HDT 279°C. |
| 5030 | 30 % glass fiber | 1.61 g/cm³ | 221 MPa / 2.3 % | High stiffness and strength, good stiffness retention at temperature, very low creep. Flexural modulus 11.7 GPa; CLTE 16.2 ppm/°C; HDT 282°C. |
| 7130 | 30 % carbon fiber | 1.48 g/cm³ | 221 MPa / 1.5 % | Syensqo’s stiffest grade, with the best fatigue resistance, and electrically conductive. Flexural modulus 19.9 GPa; CLTE 9.0 ppm/°C; HDT 282°C. |
Tensile by ASTM D638, density by ASTM D792 and HDT at 1.82 MPa by ASTM D648 in every row. A filled or bearing grade is not a substitute for unfilled 4203L (or the reverse) without a drawing change; stiffness, elongation, impact, expansion and electrical behavior all move.
Molding resin vs stock shapes: Torlon is sold in two forms. Molding resin is the pellet form that injection molders run; this page covers that. Rod, plate and tube are stock shapes. Syensqo says extrusion and compression molding are used to make them for machining and low-volume production, and its design guide says parts over 15.9 mm (0.625 in) thick must be compression molded. Shape data can differ from resin data: Drake Plastics lists 138 MPa tensile strength and 105 J/m notched Izod for its extruded 4203L shapes, against 152 MPa and 140 J/m on Syensqo’s resin sheet. If you machine parts, the shape maker’s data sheet is the one that applies.
Materials to ask about instead of Torlon 4203L
We did not find another producer’s PAI molding grade with a published data sheet we could compare, so both rows below are different polymers that buyers sometimes look at for high-heat parts. None is a drop-in replacement. Both have a much lower Tg and HDT than 4203L, need their own processing and part design review, and neither producer’s sheet describes a post-cure like Torlon’s. If your part, drawing or customer approval names Torlon 4203L, any change needs engineering review, your approval and a trial.
| Grade | Producer | Polymer | Density | Key property | How it compares |
|---|---|---|---|---|---|
| PEEK 450G | Victrex | Polyetheretherketone (PEEK), unfilled, semi-crystalline | 1.30 g/cm³ (ISO 1183) | Tensile stress at yield 98 MPa (ISO 527-2); Tg 143°C onset, melting point 343°C; HDT 152°C at 1.8 MPa, unannealed (ISO 75-2/Af); RTI 260°C electrical, 240°C mechanical without impact, 180°C with impact (UL 746B) | Different polymer. Much lower Tg and HDT at 1.8 MPa than 4203L. Victrex lists higher electrical and mechanical-without-impact RTI values (260°C and 240°C) than the 2015 design guide gives for 4203L, but a lower with-impact RTI (180°C against 200°C). Victrex molds it with a 375°C nozzle and a 170–200°C mold, and its sheet does not describe a post-cure. Tests are ISO, so numbers do not line up one-to-one with Torlon’s ASTM values. See PEEK 450G and the PEEK buying guide. Quote this alternative › |
| ULTEM 1000 | SABIC | Polyetherimide (PEI), unfilled, amorphous | Specific gravity 1.27 (ASTM D792) | Tensile stress at yield 110 MPa (ASTM D638, 5 mm/min); Tg 217°C; HDT 190°C at 1.82 MPa, 3.2 mm, unannealed (ASTM D648); RTI 170°C (UL 746B); UL 94 V-0 at 0.75 mm and up | Different polymer with a lower heat ceiling: Tg and HDT are roughly 60–90°C below 4203L’s, and RTI is 170°C against 220°C electrical for 4203L. Lower density (1.27 against 1.42). Processing and part design need their own review, and the SABIC sheet does not describe a post-cure step. See Ultem 1000. Quote this alternative › |
From each producer’s published data. Typical values; confirm on the current producer data sheet. For a wider view of high-heat options, see high-temperature plastics and PEEK alternatives.
Typical uses for Torlon 4203L
Syensqo’s data sheet and Torlon brand page describe 4203L and Torlon PAI for:
- Electrical parts such as connectors, switches and relays, where the data sheet points to its electrical properties
- Thrust washers, spline liners, valve seats, bushings, bearings, wear rings and cams that need strength at high temperature and wear resistance
- Aircraft hardware and fasteners, automotive transmission and powertrain parts, and oil and gas equipment (Syensqo’s examples for the Torlon family)
- Semiconductor fabrication and test parts, which Syensqo names as a common use for Torlon PAI’s insulating properties
For moving parts in heavy wear service Syensqo points to its wear-resistant grades such as 4301; for higher stiffness it lists 5030 (glass) and 7130 (carbon).
What to check before you switch
- Confirm the exact code. 4203L, 4203, 4203L-HF, 4203L-LF, 4301, 5030 and 7130 are separate Syensqo grades. Syensqo says 4203 and 4203L have equivalent properties, but confirm your drawing or customer accepts either.
- Resin or shapes? Molding resin and machined rod or plate are bought from different suppliers and carry different data sheets.
- Plan the post-cure. The design guide says Torlon PAI parts must be post-cured through a cycle of increasing temperature set by part size and geometry. Ask the producer for the cycle for your part.
- Re-cure machined parts. The design guide says parts for friction, wear or harsh chemical service should be re-cured after machining, and strongly recommends it when more than 1.6 mm (0.0625 in) has been machined off.
- Check the molding window. The data sheet lists a 304°C rear zone, 371°C nozzle and 199–216°C mold. The design guide notes a relatively high melt viscosity that limits flow length, suggests hydraulic accumulators and precise process control, and caps injection-molded thickness at 15.9 mm.
- Dry it. The data sheet lists 177°C for 3 hours to a suggested maximum of 0.050 % moisture. See our resin drying guide.
- Ask for each document by grade: the current UL file (the design guide’s V-0 and RTI listings date from 2015), any regulatory statement, and customer-required certifications. Alternatives will not carry the same listings.
- PEEK and PEI are not Torlon substitutes without redesign. See PEEK alternatives and PEEK vs. PEI.
- Run a trial lot and check shrinkage (0.60 to 0.85 % in flow on the data sheet), post-cure results, dimensions and appearance before you switch production.
Buying Torlon 4203L: price, lead time and lot size
- Lot size. From one gaylord to a railcar. See gaylord, LTL and truckload for typical weights per box.
- Where it ships from. 22+ partner warehouse locations. Material already in a partner warehouse usually moves sooner than a grade that has to come from the producer; your quote says which applies.
- Price. We do not publish prices because they move with feedstock, freight and order size. What moves your price most: lot size, ship-to region, and whether you need Torlon 4203L itself or want to review a different material. See how resin is priced and the monthly market update.
- Paperwork. Supplier COA on every prime lot (what a COA shows). Ask for the producer’s regulatory letter or UL file if your part needs them.
- Trying an alternative? Start with one gaylord as a trial lot, molded and checked before you commit a full release.
- If Torlon 4203L itself is not available. Some branded grades are sold only through the producer’s own channels or go on allocation. If we cannot source it, we tell you, then name any material worth reviewing with a side-by-side comparison.
Send the grade code, your annual volume and ship-to location. A polymer chemist checks it before we quote; we have been in the resin business for 30+ years. For several grades at once, use the resin RFQ template. See also the grade cross-reference and the PEEK buying guide.
Trade names belong to their owners. ResinBridge is not affiliated with these producers; grade names are used only to identify the material. Data reflects published sheets as of November 2026.
Sources
- Syensqo (Solvay Specialty Polymers) Torlon 4203L technical data sheet, revised 12/21/2020 (PDF, distributor-hosted)
- Syensqo Torlon PAI brand page (grade list, 4203/4203L note, service temperature)
- Solvay Torlon PAI Design Guide, version 5.0, revised July 2015 (PDF, distributor-hosted; grade table, UL 94, RTI, post-cure)
- Drake Plastics Torlon 4203L and 4203 extruded shapes data sheet, May 2025 (PDF, shape-maker data, not resin data)
- Victrex PEEK 450G data sheet, March 2026 (PDF)
- SABIC ULTEM 1000 global technical data sheet, June 2026 (PDF, distributor-hosted)
Common questions
What is Torlon 4203L?
Torlon 4203L is Syensqo’s unreinforced polyamide-imide (PAI) molding resin, formerly sold under Solvay Specialty Polymers. The data sheet calls it a lubricated, pigmented grade with PTFE lubricant listed as the additive, and says it has the best impact resistance and greatest elongation of the Torlon grades. Syensqo groups it with its high-strength grades.
Is Torlon 4203 the same as 4203L?
Syensqo’s Torlon brand page and design guide say 4203 has equivalent properties to 4203L. They are still two grade codes, so if your drawing or customer approval names one, confirm the other is accepted before you substitute. Searches for “Torlon 4203” usually mean this material.
What are the Tg, HDT and UL 94 rating of Torlon 4203L?
Glass transition 277°C onset (DSC) and HDT 278°C at 1.8 MPa, unannealed (ASTM D648), on the data sheet. The 2015 design guide lists UL 94 V-0 at 1.2, 2.4 and 3.0 mm and a UL relative thermal index of 220°C electrical. Typical values; confirm on the current producer data sheet and the current UL file.
Do Torlon 4203L parts need a post-cure?
Yes. The Torlon design guide (Solvay, 2015) says Torlon PAI parts must be post-cured, through a cycle of increasing temperature set by the part’s size and geometry, and that chemical and wear resistance are only reached with a thorough post-cure. Published properties are for injection-molded, post-cured specimens. Ask the producer for the cure cycle for your part.
What is the difference between Torlon resin and Torlon rod or plate?
Molding resin is the pellet form that injection molders run. Rod, plate and tube are stock shapes made by extrusion or compression molding and sold by shape makers for machining. Shape data sheets can differ from the resin sheet: one shape maker lists 138 MPa tensile strength for its extruded 4203L shapes, against 152 MPa on Syensqo’s resin sheet.
What is equivalent to Torlon 4203L?
We did not find another producer’s PAI molding grade with a published data sheet to compare. High-heat polymers buyers ask about include Victrex PEEK 450G and SABIC ULTEM 1000, but both have a lower Tg and HDT and are different polymers. Neither is a drop-in replacement; any change needs redesign review, a trial and approval.
Can ResinBridge supply Torlon 4203L?
We quote Torlon 4203L molding resin when our supply partners can source it. If they cannot, we say so up front and tell you which alternatives might be worth reviewing, named on the quote with their data sheets, so you can decide whether a trial makes sense.
If your grade is not listed, tell us what you run. We source commodity, engineering and specialty resins.
Need Torlon 4203L or an alternative?
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What to send for an accurate quote
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