InsightsPET purification
Why must PVC be removed from PET?
Direct answer
PVC and PET can be visually indistinguishable, so a color sorter cannot catch it — yet a small fraction of PVC degrades and discolors reprocessed PET. Removing it needs NIR material recognition, which reads the polymer signature instead of the appearance. On washed flakes that is PET flake purification; on whole bottles it happens before shredding.
Why the eye and the camera both miss it
Clear PVC and clear PET can be visually indistinguishable. Same transparency, same color, same shape after shredding. A color sorter classifies exactly those properties, so a PVC flake travelling in a PET stream is not a difficult detection for it — it is an invisible one.
That is what makes PVC different from an ordinary contaminant. An off-color flake, a wood chip or a metal fragment announces itself visually and gets removed. PVC does not announce itself at all, which is why it survives every visual check in the line and turns up only in the reprocessed material.
What it does downstream
A small fraction of PVC degrades and discolors reprocessed PET. The damage is disproportionate to the quantity, which is the reason PVC is treated as the priority target in PET purification rather than as one contaminant among several.
Downstream, that shows up as a quality problem nobody can trace back to a sorting decision — the flakes looked right. This is the practical argument for reading material rather than appearance: the properties that decide whether recyclate is usable are not always the properties that are visible.
What the sorter is actually deciding
When the accepted product is PET, the decision is PET vs non-PET. The machine identifies PET and ejects everything else — PVC, PE, PP, PS, PMMA, PC and other non-PET materials — using NIR material recognition. PVC is the priority target within that reject group, not a separate mode.
Framing it that way matters, because it also states what the machine is not doing: it is not sorting the ejected non-PET fraction into individual polymer categories. If PP has to be separated from PE inside that reject stream, that is a different job and a different platform.
Where in the line the removal belongs
The first question is always the material form: whole bottles before shredding, or rigid flakes after shredding and washing. It decides the platform before anything else does, and once material is shredded the whole-bottle route is no longer available.
| Where the PVC is removed | What the stream looks like | Platform |
|---|---|---|
| Before shredding | Whole bottles, roughly 0.5–2 L | MAS-B Pro, with NIR whole-bottle material recognition |
| After shredding and washing | Prepared PET flakes | MAS-P — PET flake purification |
| After shredding, when visible color also matters | Prepared PET flakes carrying an off-color load | MAS-PC, or MAS-P paired with MAS-C |
A full recycling line often stages several of these together rather than choosing one. Removing what can be removed while the material is still whole leaves a smaller, cleaner problem for the flake stage.
Where this stops applying
- MAS-P separates PET from non-PET. It is not intended to separate the rejected non-PET fraction into individual polymers such as PP vs PE or PS vs PMMA.
- Black flakes cannot be identified by polymer type, because black material absorbs the NIR signal. Remove black items first through optical color sorting.
- A color sorter cannot be configured to catch PVC in clear PET. This is not a tuning question — the difference is not a visible one.
- Removing PVC does not by itself make PET food-grade. Food-grade or medical-grade compliance depends on the complete washing, decontamination, extrusion, testing and certification process.
- Reject classes and the achievable separation are confirmed on a representative sample of the real stream, not assumed from a material list.
Common follow-ups
Why does even a little PVC matter in PET?
PVC and PET can be visually indistinguishable, so a color sorter cannot catch it, yet a small fraction of PVC degrades and discolors reprocessed PET. NIR reads the polymer signature to remove the PVC that the eye and a color camera miss.
Can a color sorter remove PVC from PET?
No. A color sorter separates by color, and PET and PVC can look identical. Removing PVC hidden in clear PET needs NIR-based material sorting, such as MAS-P for prepared flakes.
What else does MAS-P remove from PET flakes?
MAS-P identifies PET and ejects non-PET flakes — PVC, PE, PP, PS, PMMA, PC and similar — using NIR material recognition. PVC is the priority target because it looks almost identical to PET but ruins PET recyclate even in tiny amounts.
Should PVC be removed before or after shredding?
Both routes exist and the material form decides. Whole bottles can be separated by material before shredding with MAS-B Pro; washed flakes are purified with MAS-P. Once the material is shredded, the whole-bottle route is no longer available.
Does removing PVC make the PET food-grade?
No single sorting machine guarantees food-grade output. Sorting equipment supports high-purity and food-grade recycling targets as part of a complete process; final compliance depends on the complete washing, decontamination, extrusion, testing and certification chain.