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Part of the guide: Buying PU sealant from China: how to specify and verify

sourcing · compliance

PU sealant HS code: 3214.10 or 3506.90?

By the Tech Department · Reviewed by Wang · Updated 2026-11-12 · How these notes are made

Two headings decide what a polyurethane sealant costs at the border: 3214.10 (mastics) and 3506 (prepared glues and adhesives). The difference is not academic. In the EU the third-country rate for 3214 10 10 is 5% and for 3506 91 10 it is 6.5%; in the US, a PU windscreen adhesive was classified in 3214.10.0020 at 3.7%. On a €30,000 shipment that is a few hundred euros — and a misclassification that surfaces in an audit costs more than the duty.

The two headings that matter

Heading What it covers Typical rate
3214.10 Glaziers’ putty, resin cements, caulking compounds and other mastics EU 5% (3214 10 10); US 3.7% (3214.10.0020)
3506.91 / 3506.90 Prepared glues and adhesives, including adhesive sealants put up for retail sale EU 6.5% (3506 91 10)

The words in the tariff are old, but the distinction is functional: 3214 covers products used to fill and seal joints; 3506 covers products used to bond surfaces. A one-component PU sealant that is gunned into a joint and cures in place is a mastic, even if its data sheet calls it an adhesive.

Why a sealant is not a glue, for customs purposes

The Explanatory Notes to 3506 exclude products having the character of mastics of 32.14. That is why a PU windscreen adhesive — a product whose primary job is to hold glass and seal water out — was classified in 3214 by US Customs rather than in 3506, despite the broker’s original suggestion.

The practical test is a sentence: if the product is applied as a bead into a gap and its job is to keep something out or fill the gap, it is a mastic; if it is applied as a film between two surfaces and its job is to carry load, it is an adhesive. Many products do both, which is exactly why the declaration needs the application, not just the chemistry.

What customs asks for, in order

Document What it must show
Commercial invoice Product name, model, quantity, unit value, Incoterm, origin
Packing list Cartons, pallets, net and gross weight, pack format
Technical data sheet Chemistry (one- or two-component PU), use, application method
Safety data sheet Hazard classification, flash point, transport UN number if dangerous
Composition statement Polymer type, filler load, solvent content, in percentages

A classification that cannot be tied to those five documents is a guess. The SDS matters twice: it drives the HS question (solvent-borne products can classify elsewhere) and the transport question (some PU grades are not dangerous goods, some are).

Worked example: one pallet of cartridges

A 20 ft container of 310 ml cartridges, 12,800 pieces at 400 g each, is about 5.1 t of product. At a CIF value of €18,000:

  • classified in 3214 10 10 at 5% → €900 duty
  • classified in 3506 91 10 at 6.5% → €1,170 duty

The difference is €270 on one container. Where the code is wrong, the cost is not only the duty: an audit can reopen past entries, and the importer carries the penalty, not the factory.

Where classification goes wrong

  • Declaring 3506 because the product is called an adhesive. The name on the label does not decide; the function does.
  • Declaring 3214 for a structural adhesive. A crash-rated panel bond is not a mastic, and describing it as one misstates the product to customs and to the customer.
  • Ignoring the solvent. Solvent-borne products may fall outside both headings; the SDS is the document that tells you.
  • Assuming the factory’s code travels. The exporter’s declaration is a starting point. The importer’s broker is the party that signs.

What this means for buyers

Ask the supplier for the composition statement and the SDS before the first shipment, and give your broker the application in one sentence — “gunned into a concrete joint to seal water out” or “bonded between panel and frame to carry load”. The code follows from that sentence. If a supplier cannot say which heading their product falls under, that is a signal about the paperwork you will receive for the next five years.

Sources

Questions buyers ask

What is the HS code for PU sealant?
Most one-component polyurethane sealants are classified under 3214.10 as mastics, not under 3506 as prepared adhesives. The US Customs ruling NY N324403 classified a PU windscreen adhesive in 3214.10.0020 at 3.7%; the EU third-country rate for 3214 10 10 is 5%.
Why not 3506, when the product is called an adhesive?
Because 3506 excludes products that have the character of mastics of heading 3214. The test is what the product does and how it is presented, not the word on the label: a bead that seals a joint is a mastic even when it also bonds.
Does the code change between a cartridge and a 200 L barrel?
Usually not for the same product, but the declared description must match the pack. Some markets have additional lines by net weight or retail packaging, which is why the broker needs the pack format as well as the chemistry.
Who decides the code: the factory or the importer?
The importer is legally responsible for the declaration. The factory supplies the composition, use and documents; the importer, or a customs broker acting for them, makes and defends the classification.

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