YT511 Uncalendered Aramid Paper
YT511 Uncalendered Aramid Paper
Uncalendered aramid paper with high porosity and excellent resin/varnish absorption. Ideal for composite laminations and applications requiring complete impregnation.
Priced per requirement — tell us grade, width, thickness and quantity and we quote against it.
Technical specifications
| Composition | 100% meta-aramid fibre |
|---|---|
| Thermal class | Class H (180 °C) / Class R (220 °C) |
| Thickness range | 0.05–0.76 mm (2–30 mil), typical |
| Width range | Slit 10–1,000 mm |
| Density | 0.7–1.1 g/cm³ calendered, 0.3–0.6 g/cm³ uncalendered |
| Dielectric strength | 10–35 kV/mm, varies with thickness and grade |
| Limiting oxygen index | ≥ 28% — does not melt or support combustion |
| Form | Reels, slit to width; sheets to size on request |
| Compliance | UL, CE, RoHS, REACH |
Typical values for this material class, given as a guide. The datasheet carries the property table, test methods and tolerances for the grade and is the governing document.
Overview
YT511 is 100% meta-aramid paper supplied without calendering. Where YT510 is pressed dense and smooth, YT511 is left open and porous — and that porosity is the whole point of the grade.
An uncalendered sheet takes up varnish and resin readily and holds it, so the impregnant penetrates the paper rather than sitting on its surface. In a vacuum pressure impregnated winding this produces a solid, void-free insulation system: the paper becomes part of the resin matrix instead of a barrier sitting inside it.
YT511 or YT510?
Same fibre, same thermal class, different finish — and the choice follows the process, not the quality.
- YT511 (uncalendered) — porous and absorbent. Choose it when the winding is impregnated, laminated or bonded, and the resin needs to get into the paper.
- YT510 (calendered) — dense and smooth. Choose it when dielectric strength per unit thickness and clean feeding through automated slot-insertion equipment matter more than absorption.
Tell us the impregnation system and the winding method and we will say plainly which one to specify.
Key properties
- High porosity and resin uptake — impregnates fully rather than superficially
- Continuous service at 180 °C (Class H), used in Class R systems to 220 °C
- High mechanical and tear strength for a sheet of its density
- Dimensional stability through thermal cycling
- Inherently flame resistant — does not melt or drip
- Chemically stable against transformer oils, varnishes and solvents
Applications
Impregnated windings
Slot and phase insulation in VPI and trickle-impregnated motors and generators, where the resin is expected to penetrate the paper and cure into a monolithic system.
Laminates and composites
Base ply for flexible laminates and composite build-ups, where the open surface gives the adhesive something to key into.
Transformers
Layer and barrier insulation in resin-impregnated dry-type transformers.
Coil wrapping
Wrapping and taping where the wrap is subsequently varnished.
Standards and compliance
- UL recognised component — certification held by the manufacturer
- CE marked
- RoHS compliant
- REACH compliant
- Manufactured under ISO 9001:2015
Certificates of conformity and mill test certificates are supplied with each shipment. Third-party testing can be arranged on request where a specification demands independent verification.
Sizes, packing and supply
- Thickness: 0.05–0.76 mm (2–30 mil), typical range
- Width: slit to any width from 10 mm to 1,000 mm
- Form: reels as standard; sheets and die-cut parts to drawing
- Packing: reels on cores, moisture-barrier wrapped, palletised for export
Slit to your dimensions rather than sold from fixed stock widths, so there is no need to buy wide and trim.
Quality and inspection
Every consignment is inspected before shipment and supplied with its mill certificate. For repeat programmes we hold the approved specification on file so a reorder repeats a known outcome rather than reopening the conversation.
Frequently asked questions
Is YT511 the same as Nomex® 411?
Functionally comparable — both are uncalendered 100% meta-aramid papers used where impregnation matters. They are separate products from separate manufacturers. Where a specification names a brand by trade name rather than by performance, we supply that brand instead.
Why would I choose a porous paper over a dense one?
Because of what happens after the paper is fitted. If the winding is impregnated, a porous sheet absorbs the resin and becomes part of a solid insulation system. A dense sheet resists the resin and can leave voids at the interface, which is where partial discharge starts.
Does the lower density mean lower dielectric strength?
Per unit thickness, yes — an uncalendered sheet has lower breakdown voltage than a calendered one of the same thickness. Once impregnated and cured, the system as a whole performs differently again, which is why the grade is specified by process rather than by the bare sheet.
Can it be used unimpregnated?
It can, but it is rarely the right choice. If the winding is not being impregnated, YT510 will give more dielectric strength in the same space.
What documentation comes with a shipment?
Mill test certificate, certificate of conformity, packing list and the commercial export set. RoHS and REACH declarations on request.
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Next step
Tell us the size and quantity
Send the thickness, slit width and annual volume for https://aramidpapers.com/wp-content/themes/aramidpapers and we come back with a costed offer, a firm lead time and the mill certificate you will receive with it.