PEEK and PAI Selection: Material Data Is Not a Part Rating

Start with the complete grade designation

A purchase description such as "high-temperature PEEK seal" does not identify an engineering material or a qualified part. The grade, reinforcement, stock-shape or moulding route, drawing and service conditions all affect what evidence is needed.

The examples here use TECAPEEK natural and TECAPEEK GF30 natural from Ensinger's China-region pages, plus TECAPAI CM XP530 black-green from its international revision AB sheet. The names and source boundaries are intentional. Data from another regional sheet or a similarly named moulding grade must not silently replace the referenced values.

Modulus answers a stiffness question

Tensile modulus describes the specimen response under the specified test conditions. It does not directly supply a finished ring's allowable pressure, leakage rate or operating life. The model-reference table preserves the test standard, speed and specimen details supplied by each source.

When a bidder proposes a stiffer grade, ask which component requirement the change addresses. A stationary support, a sliding sealing surface and an electrical connector are different design problems. Ranking materials by one modulus value does not establish a preferred grade for all three.

Compression values must stay paired with strain

The cited natural PEEK and XP530 data distinguish compressive stress at specified strains. Moving a value into a spreadsheet without its strain label changes the question being answered. The largest value in that group is not automatically a conservative working limit.

For a backup ring, the material sheet and the component design answer different questions. Groove geometry, extrusion clearance, stress, fluid exposure, temperature history and cycling remain part of the design review.

Glass reinforcement has a counterface trade-off

The GF30 description specifically warns about mating-surface abrasion and limited suitability for bearing or wear applications. That warning belongs next to the stiffness discussion, not hidden in a general disclaimer.

It does not mean that every reinforced component is unsuitable. It means the proposed contact pair and motion need evidence. Ask the responsible designer and material source to address the actual duty; do not assume that increased stiffness alone makes a substitution acceptable.

Processing route and acceptance values

The XP530 source concerns compression-moulded stock shapes. Its guidance values are not presented as guaranteed minimum or maximum acceptance values. A buyer should not copy them into a mandatory pass/fail inspection specification without an agreed basis.

Separate material identification, batch traceability, dimensional acceptance and application qualification. If the project requires rapid-gas-decompression or sour-service evidence, request the exact grade and test scope. A general industry application page is not a certificate for every grade or finished geometry.

Build a useful part-level RFQ

For stock shapes, state the grade, form, dimensions, quantity and traceability requirements. For finished components, add the controlled drawing, tolerances, surface finish, mating geometry and inspection method. State the process medium and operating/transient conditions for technical review.

Require the quotation to identify substitutions and supporting documents explicitly. Retain the manufacturer sheet's edition and regional source with the bid comparison. The PEEK and PAI product reference collects the source-bound values; the material-certificate guide helps separate test data from shipment records.

Send an RFQ with the drawing and unresolved qualification questions. Neither this guide nor a material-property table establishes a finished component's approved operating envelope.