Reading a Polymer Certificate of Analysis: A Buyer's Checklist

Every shipment of polymer arrives with a Certificate of Analysis. It is the single most important document in the box — more important than the packing list, more important than the bill of lading. It is the producer’s formal statement of what was actually in that batch when it left the silo.

Most procurement teams treat the CoA as a filing requirement. They scan it and forward it. That is a missed opportunity, because every CoA dispute starts with something that was on the page from day one.

What every CoA must contain#

• —Producer name, plant, and reactor train (or grade designation that uniquely identifies the train)
• —Lot number and silo number
• —Production date — not the date the CoA was printed
• —Tested MFI (or MFR), with method and weight — see our MFI primer
• —Density (for polyolefins) or K-value (for PVC) or molecular weight indicator
• —Additive package summary — antioxidant, slip, antiblock, UV stabiliser
• —Compliance statements — REACH and RoHS for EU shipments, FDA food-contact where relevant
• —Net weight per package and total package count

Three checks to run before release#

First, match the spec window. The order said MFI 0.9–1.1; the CoA says 0.95. That passes. The order said MFI 0.9–1.1; the CoA says 1.15. That fails. Do not accept verbal reassurances on out-of-window CoAs — either get a replacement lot or a written deviation note from the producer.

Second, match the package count. Standard PE/PP packaging is 25 kg bags on a 1.0–1.05 MT pallet, with 40–42 pallets in a 40-foot container. PVC powder typically ships in 1.0 MT FIBC bags, 20 per container. If the CoA shows a package count that does not match the bill of lading, somebody has miscounted.

Third, match the lot to the silo. Real producers test every silo, not every package. That means a single shipment can carry CoAs from two or three lots — each silo discharge is its own analysis. If the CoA shows one lot covering twenty pallets that arrived from two silos, the document was generated by accounting, not by the lab.

Why this matters in dispute#

When a buyer downstream files a quality claim, the first thing every adjuster pulls is the CoA. If the CoA on file shows an out-of-window MFI that nobody flagged at intake, the claim almost always settles against the buyer. The dispute is not about whether the polymer was bad — it is about whether the buyer accepted bad polymer in writing.

A clean CoA file is cheaper than insurance. We treat it as the precondition for release of payment under documentary collection or LC, and we recommend our buyers do the same internally.