Buying PU sealant from China: the eight checks

Most first orders from a Chinese sealant factory fail on paperwork, not on chemistry. The product is usually fine; the specification, the labels or the documents are not.

This guide is the buying sequence we would use ourselves, in the order the mistakes happen.

1. Specify the joint before the product

Write down four things before contacting anyone: substrate, joint width, expected movement, and cure conditions (temperature and humidity in the bay or on site). A supplier who quotes a model without asking those four is quoting a price, not a solution.

The specification also protects you later: if the bead fails, the question “did we ask for the right movement class” is answered in writing.

2. Ask for the test table, not the brochure

A page of marketing claims is not a data sheet. What you want is the four-column table: property, standard, typical value, method. If a supplier quotes tensile strength without GB/T 528, or skin time without GB/T 13477.5, the number cannot be compared with anyone else’s.

Then ask one more question: “what was the measured result for the last three batches?” A supplier who cannot answer that is selling catalogue values as if they were process control.

3. Sample against your substrate, not against a steel plate

A cartridge tested on the actual substrate, at the actual temperature, with the actual preparation method. Keep the batch number of the sample so the production batch can be traced back to it.

The test that matters is a peel or a destructive bond test after full cure, not a thumb press after an hour.

4. Agree the pack format and the carton count

310 ml cartridges ship 12, 20 or 24 per carton depending on model and artwork; sausages ship 20 per carton; barrels are 200 L / 250 kg. A mixed pallet across models is normal for distributors but has to be agreed at order stage, not at loading.

Pack format also drives cost per metre more than the cartridge price does. Compare at your bead geometry, not per tube.

5. Classify the goods before booking freight

One-component PU sealants without solvent are generally not dangerous goods; solvent-borne primers and activators often are. Get the SDS and the transport classification in writing before you book, because a flammable primer changes the freight rate, the route and sometimes the carrier.

6. Approve artwork before production, not after

Your market may require a specific language, hazard statement or responsible-person address on the label. A late artwork approval means either a reprint or a non-compliant carton, and neither is the factory’s cost.

7. Know which documents travel with the shipment

Commercial invoice, packing list, bill of lading, certificate of origin, SDS, and the batch test record where your market requires it. Ask your customs broker which of these they need before the goods leave, not after they arrive.

8. Agree what happens if the batch is out of specification

The useful clause is not the warranty text; it is the evidence trail: batch number on the drum, retained sample at the factory, and a test method both sides accept. Without those three, a dispute becomes an opinion contest.

Red flags that repeat

• A capacity figure that changes between the website, the brochure and the quotation.
• A certificate number that cannot be checked with the issuing body.
• A price far below the market with no explanation of which raw material changed.
• Reluctance to name the test method behind a headline number.

When this is not the right choice

• You need retail quantities. This is a container-and-pallet supply chain; sample cartridges are the smallest unit worth shipping.
• Your market requires a certification the factory does not hold. Buy from someone who holds it rather than assuming it can be added later.
• You need a formulation nobody makes. Custom development is possible, but it is a project, not a purchase order.

What a first order actually costs

The cartridge price is the smallest line in a first order. A realistic cost stack looks like this:

Cost line	Share of landed cost	Notes
Product	45–60%	Falls as volume rises
Packaging and labelling	5–10%	Plates are one-off; cartons scale
Inland freight and port	3–6%	Depends on distance and booking
Ocean freight	10–20%	Highest variance; LCL costs more per unit
Duty and clearance	5–15%	Depends on destination and HS code
Stock carrying	5–15%	The line most often forgotten

Two consequences follow. First, a 10% discount on the cartridge price is a 5% saving on landed cost, not 10%. Second, the cheapest way to reduce landed cost is usually to reduce the number of SKUs in the container, not to negotiate the unit price.

Why the second order costs less

The second order reuses the artwork, the customs paperwork and the packaging specification, and the buyer knows which models sell. Most of the first-order cost is learning, not product — which is why changing suppliers for a 5% price difference on the second order usually destroys value.

Incoterms: what actually changes in the price

The same FOB price can arrive at three very different landed costs depending on the term. The differences are not bureaucratic; they decide who owns the risk at each point.

Term	Seller pays	Risk passes	What it hides
EXW	Nothing beyond the factory gate	At the factory	Export clearance, inland haulage, loading
FCA	Delivery to the carrier, export cleared	At handover to carrier	Ocean freight and destination costs
FOB	Loaded on the vessel	When goods are on board	Ocean freight, insurance, duty
CIF	Freight and minimum insurance to destination port	Still on board, not at destination	Insurance cover is minimum, not replacement value
DAP	Delivered to the named place, duty unpaid	At destination	Import duty, clearance, local delivery

Two practical rules for a first order:

• CIF insurance is minimum cover, not full value. If the container is damaged, the claim may not replace the goods. Buy your own cargo insurance if the value justifies it.
• FOB is the term most Chinese factories quote by default. It is also the term that leaves you responsible for a freight market you may not know. Get an all-in quote from a forwarder before comparing FOB prices between suppliers — the freight difference between two ports can exceed the product difference between two factories.

Container arithmetic: sealant cubes out before it weighs out

A 310 ml cartridge is mostly air and packaging by volume. That changes what “a container” means.

310 ml cartridge, 20 per carton
carton ≈ 0.5 × 0.35 × 0.25 m   = 0.044 m³
carton weight ≈ 10 kg

20 ft container   ≈ 33 m³ usable  → ~750 cartons, ~640 after palletising
                                    ≈ 12,800 cartridges, ≈ 6.4 t
40 ft high cube   ≈ 76 m³ usable  → ~1,700 cartons
                                    ≈ 34,000 cartridges, ≈ 17 t

Both containers hit their volume limit long before their weight limit. The consequences:

• Freight per cartridge falls sharply from LCL to 20 ft, and only modestly from 20 ft to 40 ft. If you are close to a full 20 ft, the 40 ft is usually worth it; if you are at half a 20 ft, LCL is usually not.
• Mixed SKUs cost cube. A pallet of four models is less efficient than a pallet of one, and the difference is paid in freight, not in product.
• Sausages and barrels change the arithmetic. 600 ml sausages pack more product per cubic metre than cartridges; 200 L barrels are the most cube-efficient format and the least convenient for a distributor.

Ask the supplier for the packed carton dimensions and gross weight before you ask for a price. A quotation without them cannot be converted into a landed cost.

Payment: what each structure costs

Structure	Typical split	Cost to you	Risk to you
T/T in advance	100% before shipment	None directly	Everything — no leverage after payment
T/T deposit / balance	30% deposit, 70% before shipment	Bank fees	Goods exist but you have not seen them
Letter of credit	At sight, against documents	0.5–1.5% of value in bank charges	Discrepancies in documents delay payment
Open account	30–60 days after shipment	Credit insurance premium	Credit risk on the supplier

For a first order, the 30/70 structure is the normal compromise: enough deposit for the factory to buy raw material, enough balance to matter if the goods are wrong. The leverage in that structure depends entirely on the inspection clause — if you pay the balance against a bill of lading without an inspection, you have paid in full before seeing the goods.

The compliance file, by market

The document set that matters depends on where the goods are sold, not where they are made.

• EU/UK — construction sealants. Non-structural sealants fall under the harmonised standard EN 15651 (parts 1–5, by application). CE marking under the Construction Products Regulation requires testing to that standard and a factory production control system. A supplier testing only to GB/T 13477 can sell you a good product that cannot legally carry CE marking for construction use.
• EU — chemicals. REACH applies to the article and the mixture; an SDS to Annex II and CLP labelling are the minimum. Ask for the SVHC declaration for the current candidate list, dated.
• US. VOC limits are set at state level for many sealant categories; the federal SDS format is OSHA 29 CFR 1910.1200. A supplier who has never exported to the US may not know which category applies.
• Everywhere. A batch test record, a certificate of origin and a packing list that matches the invoice. Customs discrepancies are the most common cause of a delayed first shipment.

Ask for the compliance file before the proforma invoice, not after. A factory that cannot produce an EN 15651 test report is not necessarily a bad factory; it is a factory whose product is specified for a different market.

Inspection: what to check and how many

A pre-shipment inspection on a first order is cheap relative to the cost of a wrong container. The sampling plan most buyers use is ISO 2859-1 general inspection level II, AQL 2.5 for major defects and 4.0 for minor.

What counts as a major defect on a sealant shipment:

• Cartridge weight outside the declared tolerance (check 20 units from three cartons).
• Label language, batch number or hazard statement missing.
• Carton count or model mix different from the order.
• Visible separation, skinning or leakage in a cut sample.
• Cap seal or piston fit that leaks under hand pressure.

What is worth testing beyond the visual check: skin time and cure rate on a sample from the actual batch, compared with the values on the certificate. A batch that skins in half the stated time will not behave like the sample you approved.

What a bad batch actually costs

1 × 20 ft container        12,800 cartridges
failure rate               3%
affected units             384
replacement + freight      product cost × 1.6 (return, reship, handling)
labour at the customer     the line stops; the customer's cost is not yours

The product cost is the smallest number in that table. The customer’s line stoppage, the rework and the loss of the account are the real exposure, and none of them appear on the supplier’s invoice. This is why the retention sample and the batch record matter more than the warranty clause: they are what let you prove which batch failed and get a replacement without a legal argument.

Questions that separate a trading company from a factory

• Which line made this batch, and can I see the batch record? A trader cannot answer.
• What is the measured value, not the specification, for the last three batches? A trader reads the catalogue.
• Who signs the test report, and what method was used? A factory has a lab; a trader has a folder.
• What happens if the second container is out of specification? A factory can remake it; a trader negotiates with someone else’s factory.

The practical position

Buy the specification, the sample and the document trail — in that order — and treat the price as the last variable. The cheapest cartridge in a container is worth nothing if the label is wrong, the SDS is missing or the batch cannot be traced. A supplier who answers the eight checks above without hesitation is telling you something about how they will behave when a batch goes wrong.

Standards and registers referenced

• ECHA Candidate List — substances of very high concern under REACH; ask for a declaration dated against the current list: echa.europa.eu.
• Regulation (EU) No 305/2011 — the Construction Products Regulation, which is what makes EN 15651 testing and factory production control a legal requirement for CE marking: EUR-Lex.
• Regulation (EC) No 1272/2008 — CLP, the classification and labelling rules that govern the SDS and the carton: EUR-Lex.
• EN 15651-1 — the harmonised sealant standard itself: CEN listing.