IEC 60641 is a series: asking for the grade beats asking for compliance

Short answer: “complies with IEC 60641” is not a specification. IEC 60641 is a series. You need the part number and the grade designation, because two materials that both “comply with IEC 60641” can differ in thickness range, density, tensile strength and electrical strength. In transformer and motor design practice, materials are specified by grade — commonly written as P.2.1 or P.4.1 — and these are not interchangeable.

How the standard is layered

A related Chinese designation, GB/T 19264, sits in the same family and is the more useful citation for goods shipped into China. Two other paths are commonly confused with presspaper and should not be mixed into one clause:

The four things to put in one enquiry

1. Part number and grade — for example IEC 60641-3-2, grade P.2.1. If the drawing names a grade, quote the grade.
2. Thickness and tolerance — for example 0.25 mm ± 0.01 mm.
3. Documents required with the goods — datasheet, test report, batch traceability. Name them now, not after delivery.
4. Application — cell insulation, motor slot, transformer layer. The same grade behaves differently in an oil-immersed winding than in a dry battery pack.

Product standard and test method must appear as a pair

A product standard says what to require; a method standard says how it was measured. The same roll of paper can produce very different breakdown-voltage numbers depending on electrode shape, whether the test is in air or in oil, and the ramp rate. Write both in the acceptance clause: “accepted to GB/T 19264, electrical strength tested to GB/T 1408.1”.

What Chengfa declares — and what we deliberately do not

Our position Our registered statement for this paper is IEC 60641, JB/T 8150 and ISO 1924-2. No mapping to a specific IEC 60641 grade such as P.2.1 or P.4.1 is registered in our documentation. We therefore do not quote by grade number and do not claim grade equivalence. Give us the grade and the drawing: we confirm against physical samples and a datasheet, and we arrange third-party testing where your design requires evidence. This makes our quotation slower to read than a competitor's one-line “P.4.1 equivalent”. It also means you will not be contracted on one grade and delivered another.

On thermal class: our published range of −40 °C to +105 °C for the non-adhesive version aligns numerically with thermal class A under GB/T 11021-2014. That is an alignment we can point at, not a class certification we hold. If your design depends on a class designation, treat it as a question to test rather than a box to tick.

If you see QB/T 3503-1999, ask a follow-up question

QB/T 3503-1999 for electrical insulating pressboard has been withdrawn. A datasheet still citing it tells you the document was not maintained — which does not prove the material is wrong, but does justify checking every other number on that page. Ask for: the product standard number and year, the standard the test report was run against, and the report number and issuing body. Those three have to agree.

Make the contract clause binding

• Cite the full number and year — “GB/T 19264”, not “to national standard”.
• Pair product and method standards in the same clause.
• Name the documents that must arrive with the goods, and make missing documents a ground for rejection.
• State the tolerance as a number with a unit and the measurement condition, not as an adjective.