Checking rPET Flakes at the Mill Gate: A Practical Guide for Faisalabad Fibre Mills
How Faisalabad fibre mills can check an rPET flake delivery at the gate — sampling, quick tests for PVC, PP/PE and moisture, and when to call the lab.
Key takeaways
- A TDS is the target spec; a COA is the actual measured result for the lot you're buying.
- IV drives processability — recycled PET flake IV is commonly around 0.70–0.80 dL/g.
- Moisture is usually specified below 1.0%; even trace water lowers IV in the melt.
- PVC is the villain: it degrades PET, so it's held to very low ppm.
- Always ask for a per-lot COA — not a one-time certificate.
What is the difference between a TDS and a COA?
A Technical Data Sheet (TDS) states the target specification for a grade — the range a supplier commits to. A Certificate of Analysis (COA) reports the actual measured values for one production lot. Reputable rPET suppliers issue a COA with every shipment so you can confirm the material matches what you ordered.
What do the key COA parameters mean?
Intrinsic viscosity (IV)
IV is a measure of PET's molecular weight and, in practice, how it will process. A typical recycled PET IV is around 0.67–0.80 dL/g. If IV is too low, PET becomes brittle and creates more fines when granulated; if it's too high, the melt viscosity can interfere with moulding or spinning. Match IV to your process rather than assuming "higher is better."
Moisture
Post-consumer PET flake moisture is generally specified below 1.0%, and cleaner grades target well under that. Moisture matters because PET is hygroscopic — even small amounts of water can break polymer chains at melt temperature, cutting IV and mechanical properties. Lower moisture means less pre-drying for you.
PVC and foreign-polymer contamination
PVC is the single most damaging contaminant in PET recycling: it degrades and discolours PET during melting. Specifications hold it very low — often single-digit to low-tens of ppm. PP/PE (from caps) is also limited because it doesn't melt with PET.
Total contamination, metal, glass and specks
Cleaner grades also report floatable/label content, metal, glass and black-speck counts. Indicative "good" targets seen in industry specs include floatables under ~15 ppm, metal under ~10 ppm and black-speck particles in the low tens of ppm — but always use the numbers on your supplier's TDS/COA.
What does a typical rPET flake COA look like?
Below are general industry-typical ranges for context only — not a specific product spec. Ask your supplier for their actual TDS and per-lot COA.
| Parameter | Typical range (context only) |
|---|---|
| Intrinsic viscosity (IV) | ~0.70–0.80 dL/g |
| Moisture | < 1.0% |
| PVC | Very low ppm (≈ <5–50 ppm) |
| Total contamination | Low tens of ppm |
What should buyers ask for?
- A TDS per grade and a COA per lot — not a single annual certificate.
- The test methods used (e.g., ASTM references) so results are comparable.
- A sample to run on your line before committing to volume.
Frequently asked questions
What is a good intrinsic viscosity (IV) for rPET flakes?
Recycled PET flake IV commonly sits around 0.70–0.80 dL/g. Low IV makes PET brittle and prone to fines; very high IV raises melt viscosity and can disturb moulding or spinning. Match the IV to your application.
How much moisture should rPET flakes have?
Moisture is typically specified below 1.0%, and cleaner grades target well under that. Even trace moisture can lower IV during melting, so low moisture matters.
Why is PVC contamination important in rPET?
PVC degrades PET during melt processing, causing discolouration and defects, so it is tightly limited — often single-digit to low-tens of ppm. It's one of the most important numbers on a PET flake COA.
Sources: Association of Plastic Recyclers — PET Rigid; INTCO — rPET Flakes for Fibre & Strapping; ScienceDirect — PVC in PET recycling.
