Polyimide Fiberglass Sleevings
Electrical sleeving that combines polyimide with fiberglass reinforcement, positioned for winding, lead and component insulation where rubber constructions reach their limits. Aircraft motors and transformer windings are the reference applications. Two qualifications govern this page: the sleeving is generic polyimide with no film-brand claim, and the extreme-temperature values carried in the earlier catalogue are being verified, with continuous and short-term figures to be issued separately from the grade's test data. Construction details, wall build and dielectric values are held in the data note below until confirmed. Send the conductor size and thermal class and we return the sleeving specification.
What is confirmed and what is being verified
This page states the product honestly rather than copying the old catalogue through. Three things are confirmed by the construction itself:
- The material family. Polyimide is the polymer of record : one of the few plastics that keeps dielectric integrity across cryogenic-to-high-temperature service and carbonises rather than melting. That is why it is the insulation family for windings and extreme-duty leads.
- The reinforcement. A fiberglass element is part of the wall, adding cut-through and abrasion resistance and holding the wall shape during coil winding and varnish processing.
- The form. Non-shrink sleeving : protection comes from the materials, not from a recovery step.
Three things are not yet published, each tied to the data note: the exact construction (polyimide film on braid, coated braid, or laminate. The behaviour differs, most visibly in flexibility and edge handling), the temperature values (the old single -200℃~+400℃ range mixed continuous and short-term behaviour; verified figures will be split and sourced), and dielectric data per wall build. Until those arrive, this page claims none of them.
Where Polyimide Fiberglass Sleevings is used
Primary applications: aircraft motor and transformer windings, lead insulation, winding-end protection and component wrapping inside extreme-temperature electrical equipment. It is an insulation component inside equipment, not a harness cover: the wall does not cushion, seal or stretch.
How to select the right sleeving
Selection is by the winding it protects:
- Finished conductor diameter. The sleeving ID must pass the conductor with its enamel or wrap insulation in place : send the finished diameter, not the bare wire.
- Thermal class. State the continuous and peak winding temperatures from your program; the issued values for this sleeving will be matched against them once verified.
- Downstream process. Varnish dipping, VPI and potting each stress the wall differently : state the process so the wall build is confirmed against it.
- Standards. Name any aerospace or motor standard the part must satisfy; thermal-class certification is part of the pending documentation.
Specification
| Material | Polyimide (generic : no film brand claimed) + fiberglass reinforcement |
|---|---|
| Construction | Pending verification: film-on-braid, coated braid or laminate |
| Operating temperature | Pending verification : continuous vs short-term values to be issued separately |
| Shrink behaviour | Non-shrink |
| Positioning | Equipment insulation component (windings, leads), not a harness cover |
Common Failure Modes & How to Prevent Them
These are the failures specific to a polyimide-fiberglass sleeving, with the root cause and the prevention for each.
A nick at the edge propagated into a split
Root cause: Polyimide construction cuts cleanly but a small nick or tear at an edge concentrates stress and propagates under handling or thermal cycling: the known weak point of film-type walls.
Fix: Cut with a sharp blade in one clean pass, inspect every cut end, dress nicks before installation, and never force the sleeving over sharp conductor features. A damaged edge does not heal.
The sleeving was installed stretched tight over a corner
Root cause: The wall is rigid-when-cured, not elastic. Pulled tight around a bend or corner feature, it sits permanently stressed and cracks there first through thermal cycling.
Fix: Size so the sleeving passes over features with clearance, not tension. Where a corner is unavoidable, use a formed length or a slightly larger ID rather than stretching the wall.
Varnish locked the wall in the wrong shape
Root cause: During dipping or VPI the sleeving was positioned overlapping or kinked; the varnish cure fixed that geometry permanently, and the kink became the failure site in service.
Fix: Position and support the sleeving square and complete before the process starts. It will hold whatever shape it is cured in. Confirm the wall build against the impregnation process at specification stage.
It was asked to behave like a rubber sleeve
Root cause: The part was speced as a harness cover, expected to cushion, seal or stretch over a bundle. Polyimide-fiberglass does none of those; it cracked at the first bend and did not seal anything.
Fix: Match the product to the duty: equipment insulation (windings, leads, wrapping) is this sleeving's job. Flexible covering and sealing go to the silicone and coated-fiberglass families.
Temperature figures were quoted from the old catalogue
Root cause: The single -200℃~+400℃ range was carried into a design file as continuous rating. The range mixed continuous and short-term behaviour; the true continuous value is lower, and the design margin was never real.
Fix: Design from the verified figures once issued, split continuous versus short-term, and hold designs against the customer's own thermal class until then. Do not copy the old range into new documentation.
Frequently asked questions
Is the polyimide layer film, coating or another construction?
That is exactly what is being confirmed for this product. Polyimide-fiberglass parts are made in more than one way (a polyimide film carried on a fiberglass braid, a polyimide-coated braid, or a laminated wall), and the installed behaviour differs between them, especially in flexibility and cut-edge handling. Until the manufacturing record for this sleeving is verified, the construction is stated as pending rather than guessed, and no wall build is published.
Is the material actually Kapton-branded film?
No brand claim is made on this page. The sleeving is specified as polyimide, the generic polymer. Kapton is a DuPont trademark and naming it requires a verified source and grade for the film actually supplied. The earlier catalogue wording is withdrawn until that evidence exists. If your program requires branded film, state it at RFQ and the grade will be confirmed with the shipment documentation or the order will be declined.
Which temperature value is continuous service versus short-term exposure?
Neither value is published yet. The catalogue carried -200℃~+400℃ as a single range, which mixes continuous and short-term behaviour without saying which is which. That split is precisely what the verification has to establish from the grade's test data. Until it is supplied, size the application from your own thermal-class requirement and treat every temperature figure for this sleeving as pending confirmation.
How does polyimide behave differently from silicone or coated-fiberglass sleeving?
Polyimide is a rigid-when-cured polymer, not a rubber: the wall keeps its shape, does not cushion, and does not seal. Its value is thermal and dielectric stability across a range where rubber constructions fail, so it serves windings, lead insulation and component wrapping rather than harness covering. Choose polyimide-fiberglass when the duty exceeds rubber limits; choose silicone or coated fiberglass when the run needs flexibility and surface sealing.
How are cut ends and edges handled during installation?
Cut with a sharp blade in one clean pass and support the wall so the cut does not tear. Edges and nicks are the known weak point of polyimide construction (a small cut can propagate under handling), so inspect each end after cutting, dress any nick before installation, and avoid forcing the sleeving over sharp conductor features.
What is needed to specify a winding application?
Four inputs: the finished conductor diameter including its enamel or wrap, the winding temperature class, the downstream process (varnish dipping, VPI or potting), and any standard the program must meet. The sleeving ID is sized from the finished conductor, the wall build is confirmed against the impregnation process, and the temperature and dielectric figures are issued from the verified test data rather than this page.
Request a quote for Polyimide Fiberglass Sleevings
Send the finished conductor diameter, the thermal class, the downstream process and quantity. We return the sleeving specification with the verified construction and temperature values for the order.
Size range & specification notes
Sleeving IDs are issued against finished conductor diameters. Construction type, wall build and verified temperature/dielectric values are held in the data note above until confirmed.