Prime, wide-spec and off-grade polymer
Prime material is original product sold under the producer’s brand and grade number, meeting every value in the TDS. Wide-spec is production in which one or more values – e.g. MFI or colour – fall outside the narrow range but remain usable; off-grade may be transition production, sweepings or contaminated material and is usually sold unbranded and without a COA. Off-grade is cheaper but varies from lot to lot, so samples must be tested and “as is” terms and claim rights made clear.
Related terms
Recycled content (PCR / PIR)
PCR (post-consumer recycled) material comes from packaging and products that have reached consumers and become waste; PIR (post-industrial recycled) comes from production scrap and trimmings. Rules such as the EU Packaging and Packaging Waste Regulation (PPWR) and brand pledges are setting minimum PCR shares in packaging. Recycled-content claims should be verified with certification such as GRS, RecyClass, EuCertPlast or ISCC PLUS (mass balance); food-contact rPET additionally needs an approved super-clean process.
Melt flow index (MFI / MFR)
The mass of molten polymer that flows through a die in 10 minutes at a set temperature and load – 230 °C/2.16 kg for PP, 190 °C/2.16 kg or 5 kg for PE – expressed in g/10 min (ISO 1133, ASTM D1238). A low MFI means high molecular weight and strength, a high MFI easy flow: pipe and blow-moulding grades are about 0.1–1, film 1–4, injection 10–60, and fibre and meltblown 25–1,500 g/10 min. When comparing offers, always check the test conditions.
Certificate of analysis (COA)
A document in which the producer or an independent laboratory reports the test results for a specific lot together with the specification limits. It shows the product name, lot number, production date, test method (e.g. ASTM, ISO), measured value and acceptance range. A TDS gives a product’s typical properties; a COA gives the actual values of the lot delivered. Under a letter of credit the COA must be issued by the party and with the content the credit requires.