Pet Flake Sorting Machine | AISORT
Application Overview
PET Flake Sorting for Bottle-to-Bottle and Food-Grade Recycling
PET flake sorting is the critical quality gate in bottle-to-bottle recycling. Achieving food-contact approval (EFSA, FDA) requires removing PVC, other polymers, colored PET, metals, and organic residues from the flake stream — typically to contamination levels below 50 ppm. Optical sorting with multi-spectral sensors is the standard technology for meeting these specifications at commercial throughputs of 2-10 tonnes per hour.
Modern PET flake sorters combine visible-spectrum color cameras, NIR spectroscopy, and in some cases UV fluorescence to detect and eject contaminants that are invisible to the human eye but disqualify material from food-grade reuse.
Purity Target
50-100 ppm PVC
EFSA requires <50 ppm PVC in food-grade rPET. A single PVC flake per 10,000 PET flakes can fail certification. This demands detection accuracy at the individual-flake level.
Throughput Range
2-10 tonnes/hour
Flake size typically 2-15mm. Higher throughput requires wider chutes, more sensor channels, and faster ejection valves to maintain ppm-level rejection accuracy.
Key Contaminants
PVC, PO, metal, colored PET
PVC is the #1 purity killer (chars at PET processing temperatures). Polyolefin caps and labels, aluminum seals, and opaque/colored PET bottles are the most common reject materials.
Regulatory Gate
EFSA / FDA / local
Food-contact rPET requires regulatory approval of the entire recycling process, including sorting technology validation. Optical sorter performance data is part of the submission package.
PET Recycling Market Context
Global rPET demand is projected to reach 18 million tonnes by 2030, driven by:
- EU Single-Use Plastics Directive: mandates 30% recycled content in PET beverage bottles by 2030, rising to 35% by 2040
- Brand commitments: Coca-Cola, PepsiCo, Nestlé, and Danone have all committed to 50-100% rPET in bottles across major markets
- US state-level EPR laws: California, Maine, Oregon, and Colorado now require minimum recycled content, creating demand pull for high-purity rPET flake
- Voluntary packaging pledges: The UK Plastics Pact, ANZPAC, and similar initiatives across 20+ countries are driving demand for food-grade recycled content
Sensor Technologies for PET Flake Purity
| Sensor | Detects | Detection Limit | Notes |
|---|---|---|---|
| RGB Visible Camera | Color differences — separates clear/light-blue PET from colored PET, opaque bottles, green/brown flakes | Color ΔE > 2 | Standard on all PET flake sorters. Resolution typically 0.1-0.3mm per pixel at flake size. |
| NIR Spectroscopy | Polymer type by spectral signature — separates PET from PVC, PE, PP, PS, PLA, and other polymers | Single flake (2mm+) | The workhorse for polymer identification. Cannot distinguish clear PET from clear PVC without sufficient spectral resolution. |
| UV Fluorescence | PVC and some additives that fluoresce under UV excitation | Supplements NIR for PVC detection | Useful as a secondary check when NIR alone cannot reliably separate thin PVC labels from PET. |
| Electromagnetic / Induction | Metal fragments — aluminum seals, steel from wear, copper from wiring | 0.5mm+ metal particles | Essential for food-grade lines; metal contamination can damage extrusion and injection molding equipment downstream. |
| AI Vision (Deep Learning) | Shape and pattern anomalies — whole labels, multi-layer fragments, silicone residues | Training-data dependent | Emerging technology; particularly effective for detecting multi-material fragments that RGB+NIR alone struggle with. |
Typical Bottle-to-Bottle Flake Sorting Line
- Whole-bottle pre-sort: Remove non-PET bottles (PVC, HDPE, PP), colored bottles, and oversized contaminants before grinding.
- Wet grinding and washing: Bottles ground to 2-15mm flake; hot caustic wash removes labels, adhesives, and organic residues.
- Density separation (sink/float): Separates PET (sinks, SG 1.38) from polyolefin caps and labels (float, SG <1.0).
- NIR flake sorting — Stage 1: Primary polymer sort removes PVC, PE/PP, PS, and other polymer contaminants. Target: <200 ppm PVC.
- NIR flake sorting — Stage 2: Secondary purity sort targets <50 ppm PVC. Often combined with metal detection.
- Color sorting: Final pass removes remaining colored flakes (blue, green, amber) to achieve clear-flake purity.
Economic Drivers for PET Flake Sorting Investment
Food-grade rPET flake commands a premium of $200-400/tonne over non-food-grade flake. At 10,000 tonnes annual throughput, the incremental revenue from food-grade certification is $2-4 million per year — easily justifying the capital cost of a multi-stage NIR sorting line.
Beyond the food-grade premium, effective flake sorting reduces downstream processing costs: cleaner flake extends extruder screw and filter screen life, reduces IV loss during SSP (solid-state polycondensation), and minimizes off-spec production batches.
Regulatory Compliance Notes
Food-contact rPET processes in the EU require EFSA opinion under Regulation (EC) No 282/2008. The FDA issues Letters of No Objection (LNO) for US processes. Both regulators require the recycling process to demonstrate that decontamination reduces incidental contaminants to levels that pose no health risk. The sorting stage is evaluated as part of the overall process, and sorter performance data — including challenge test results with known contaminants — must be submitted as part of the application.