rPET Glossary: IV, PVC ppm, Hot-Wash, COA, TDS and Other Terms Explained
Plain-English definitions of every term you’ll meet buying rPET flakes or selling PET bottles — from IV and PVC ppm to crush, tare and FOB.
Key takeaways
- Temperature is the core difference: hot wash uses heated caustic solution; cold wash uses ambient water.
- Hot washing removes glue, grease and adhesives that cold washing leaves behind.
- Hot-washed flake commands a higher price and suits demanding applications; cold-washed is cheaper for tolerant ones.
- Neither is automatically food-grade — food contact needs a separately approved decontamination process.
What is the difference between hot-washed and cold-washed PET flakes?
The difference comes down to wash temperature and chemistry. Cold-wash lines run at roughly 10–20°C and mainly rinse off surface dust and loose contamination. Hot-wash lines heat the water to around 60–80°C and add an alkaline (caustic soda) solution, which dissolves label glue, grease and oily residues — producing a noticeably cleaner, higher-purity flake. As a rule, hot-washed flake is better quality and priced higher; cold-washed flake is cheaper and uses less energy.
Hot-washed vs cold-washed: side by side
| Hot-washed | Cold-washed | |
|---|---|---|
| Wash temperature | ~60–80°C, caustic solution | ~10–20°C, ambient water |
| Removes | Glue, oils, grease + surface dirt | Surface dirt only |
| Grade & price | Higher grade, higher price | Lower grade, cheaper |
| Best for | Fibre, sheet, packaging | Strapping, lower-spec uses |
Which grade should you buy?
Match the grade to the tolerance of your process:
- Polyester staple fibre & filament, PET sheet, thermoforming, packaging — choose hot-washed flake for cleaner melt behaviour and fewer defects.
- PET strapping and less demanding moulding — cold-washed flake often delivers the strength you need at a lower cost.
- Appearance-critical clear sheet — hot-washed, colour-sorted flake with low black-speck and contamination counts.
Whatever the grade, the numbers that matter to your line — intrinsic viscosity, moisture and contamination — should come on a Technical Data Sheet and a per-lot Certificate of Analysis. See our guide on how to read an rPET COA.
Does hot washing make rPET food-grade?
No. Hot caustic washing improves cleanliness, but food-contact recycled PET additionally requires an officially assessed decontamination process — an FDA "No Objection" letter in the US or an EFSA positive opinion in the EU. We cover this in Is recycled PET food-grade?
Frequently asked questions
Is hot-washed or cold-washed PET flake better?
Hot-washed flake is cleaner and more consistent because heated caustic water removes glue, oils and residues, so it suits higher-grade fibre, sheet and packaging. Cold-washed flake is cheaper and lower-energy and works for strapping and less demanding uses.
What temperature is used for hot washing PET flakes?
Hot-wash lines typically run around 60–80°C with added caustic soda; cold-wash lines run near ambient temperature (about 10–20°C).
Does hot washing make rPET food-grade?
No. Hot washing improves cleanliness but does not, by itself, make recycled PET food-contact approved. That requires an officially assessed decontamination process (FDA no-objection letter or EFSA opinion).
Sources: Recycling Machines — Hot vs Cold Washing; Energycle — Cold vs Hot PET Washing Lines.
