PU leather Specification: What Each Number Actually Changes

Two suppliers can quote the same pu leather at the same headline figure and deliver different products. The difference is in the numbers nobody puts in the quotation, and in the tolerance behind the number that is quoted.

Why the headline number is the least useful one

Every quotation leads with thickness. It is easy to compare and it is the number the factory can hit most cheaply. But it tells you almost nothing on its own: thickness sets the frame, and the parameters below set whether the product survives its first year in service. A buyer who compares only the headline figure is buying a sample, not a supply agreement.

For PU leather, the practical rule is to fix the headline figure at the level your product needs and then spend your negotiating attention on peel strength and hydrolysis resistance. Those two are where cheap goods differ from adequate goods, and they are usually absent from the quotation sheet.

The numbers that decide performance

Read the table as a set of trade-offs rather than a checklist. Moving any single line usually costs money somewhere else, and the cheapest way to hit one figure is often to let another slip.

Thickness

Typical range: 0.5-1.5 mm. Handle and fold behaviour. Under 0.6 mm the material creases sharply and cracks.

Backing

Typical range: knitted / woven / non-woven. Knitted stretches, woven is stable, non-woven is cheapest and weakest at seams.

Peel strength

Typical range: >= 6 N/50 mm. The number that predicts whether the skin separates from the backing.

Hydrolysis resistance

Typical range: 5 years at 70 C / 95 % RH equivalent. Critical for bags and furniture shipped to humid markets.

Abrasion

Typical range: >= 20 000 Martindale cycles. Seat and bag applications; below 10 000 the surface goes shiny then breaks.

How to write a PU leather specification that protects you

A specification is only useful if a substitution becomes visible. That means writing the construction and the performance together, and naming the test that proves each one. For PU leather, the clause has to pin peel strength and hydrolysis resistance, because those two separate a compliant lot from an adequate one:

PU leather, 1.0 mm +/- 0.05, knitted backing, peel >= 8 N/50 mm, hydrolysis-resistant, 30 000 Martindale, cold flex -20 C 30 000 cycles, release-paper grain, Pantone 19-1016 TCX

Note what is missing from that line: adjectives. No ‘high quality’, no ‘premium’, no ‘export grade’. Every clause is either a number with a tolerance or a named test. If a supplier cannot quote against a line written this way, that is information about the supplier.

Where the specification usually breaks down

The first failure is hydrolysis. The surface turns tacky and peels after months in a hot, humid warehouse or in service. The cause is usually ester-based pu plus moisture plus heat. it is a chemistry problem, not a coating weight problem. The test that exposes it before you order: 70 C / 95 % RH for 7 days, then peel strength and hand assessment.

The second is peel failure at seams. The skin lifts along stitch lines and fold edges. It comes from low coating weight, poor primer, or a non-woven backing that delaminates first. Test with ISO 2411 on a sewn and flexed sample. and write the result into the purchase order, not just the enquiry.

Both failures share a pattern: they appear months after delivery, they are hard to attribute, and the cost lands on the buyer rather than the mill. That is exactly why the test belongs in the specification and the report belongs in the shipment file.

What to put in a PU leather enquiry

1. End use and the conditions, which together decide where peel strength has to sit inside >= 6 N/50 mm.
2. The one figure that must hold, with peel strength named as the proof.
3. Quantity per colour and per delivery, against a typical MOQ of 500-1000 m per colour.
4. Destination market, because compliance changes the construction, not just the paperwork.
5. A physical standard viewed under a stated light source, not a screen proof.

With those five points we can quote against a real requirement instead of a generic range. Full ranges sit on the PU leather page, and the manufacturing side of the same question is on our quality control page.

Questions buyers ask before ordering

What is the difference between hydrolysis-resistant and standard PU?

Standard ester-based PU absorbs moisture and breaks down from the inside. Hydrolysis-resistant grades use a different polyol and survive years in humid conditions. Ask for the 70 C / 95 % RH report.

Can PU leather be sewn like real leather?

Yes, with a leather needle, longer stitch and a roller foot. The risk is seam slippage on non-woven backing, so specify knitted or woven for sewn goods.

Is 1.0 mm a real thickness or a nominal one?

Always ask. +/- 0.05 mm is a real tolerance; some suppliers quote 1.0 mm for 0.85 mm goods.

Failure modes worth a clause in the purchase order

Claims rarely come from a batch that was obviously wrong. They come from a thickness figure that sat inside the quoted band and outside what the product needed.

The other two, with acceptance numbers attached, are in the full failure analysis for PU leather. A supplier who cannot name the mode he sees most often is describing a catalogue, not a process.

Seven lines that turn a quotation into a specification

Most post-delivery arguments are not about quality. They are about a document that never said which figure would be measured, on which instrument, at whose cost.

1. Backing: knitted / woven / non-woven is not an answer on its own. Ask for the last three lots’ actual readings and the spread behind them.
2. Peel strength: agree the test method with the number. Two labs, two methods, two answers, one argument.
3. Hydrolysis resistance (5 years at 70 C / 95 % RH equivalent): state where in the band this order sits. The middle of the band is not what a tolerance is for.
4. Abrasion: the figure you will accept inside the >= 20 000 Martindale cycles band, the tolerance on it, and the method used to measure it.
5. Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
6. Packing and marking: shipping mark, roll or carton count and the tolerance on quantity, since a short shipment is a claim too.
7. Who inspects: third-party, in-house or none, decided in advance, with the AQL level written down.

Related reading

• Hydrolysis resistance in PU leather
• Pu Leather vs Oxford
• Thickness in PU leather