PVC contamination in PET recycling is difficult to correct after the bottles have been ground. PVC and PET both sink in water, so a standard float-sink tank cannot reliably separate the two polymers. A stable process removes PVC as early as possible, then uses flake-level sorting and quality checks to control what remains.
This guide explains where PVC enters a PET bottle stream, which detection method fits each process stage, and how to set up practical control points without treating one machine as a complete solution.
PVC Contamination Control at a Glance
| Etapa del proceso | Typical PVC source | Preferred control | Main limitation |
|---|---|---|---|
| Before debaling | Out-of-specification bales | Supplier specification and bale inspection | Inspection cannot find every hidden label or liner |
| Whole-bottle sorting | PVC bottles, sleeves, and safety seals | Manual quality control plus sensor-based polymer sorting | Dirty, overlapping, or black items can reduce detection accuracy |
| After granulation | PVC fragments and label pieces | Flake sorting or dry electrostatic separation | Moisture, particle size, and presentation affect separation |
| Finished PET flakes | Residual PVC missed upstream | Representative sampling and buyer-specific laboratory testing | A small sample may not represent an uneven batch |
Why PVC Is a Serious PET Contaminant
El PET se procesa a temperaturas que pueden provocar la deshidrocloración del PVC. El cloruro de hidrógeno resultante acelera la degradación del PET y puede contribuir al amarilleamiento, los puntos negros, la reducción del peso molecular y la fragilidad. Un estudio de procesamiento revisado por pares detectó degradación y decoloración medibles del PET con 100 ppm de PVC, lo que demuestra que una corriente de escamas visualmente limpia aún puede incumplir la especificación del cliente.
El límite aceptable no es universal. Los clientes de fibra, lámina, fleje y botella a botella pueden fijar límites distintos, y las aplicaciones en contacto con alimentos requieren controles adicionales al PVC. Por tanto, el objetivo operativo debe proceder de la especificación escrita del comprador de las escamas terminadas y de un método de laboratorio definido, no de una cifra genérica en ppm.
Where PVC Enters a PET Bottle Stream
- PVC bottles can resemble PET bottles when shape and color are the only sorting criteria.
- Shrink sleeves, tamper-evident seals, and pressure-sensitive label components can remain attached until granulation.
- Closure liners and small PVC components can pass through coarse manual inspection.
- Cross-contamination can occur when conveyors, bunkers, or flake handling equipment process more than one polymer without adequate cleaning.
How to Separate PVC from PET
Whole-Bottle Sorting Before Granulation
Remove PVC while the item is still large enough to identify and eject. Manual quality control can catch obvious PVC bottles and sleeves, while near-infrared or other sensor-based systems classify polymers and trigger air-jet rejection. The sorter must receive a stable, single-layer material presentation; unopened bales, overlapping bottles, dirt, and excessive conveyor loading reduce the value of even a capable sensor.
Why Plain-Water Float-Sink Separation Is Not Enough
Float-sink separation is effective for removing floating PP and PE caps from sinking PET. It does not provide a dependable PET/PVC split because PVC also has a density above water and sinks with PET. The Association of Plastic Recyclers specifically identifies PVC as difficult to remove from PET, particularly after it has become small fragments.
Flake-Level Optical and Electrostatic Sorting
Si queda PVC después de triturar y lavar, utilice un sistema diseñado para presentar las escamas. Los clasificadores ópticos pueden reconocer diferencias de polímero o color y expulsar partículas individuales. Los sistemas electrostáticos o triboeléctricos en seco también pueden separar escamas acondicionadas de PET y PVC, pero requieren humedad, distribución granulométrica, limpieza superficial y caudal controlados. Una prueba piloto con el material real de la planta es más fiable que elegir a partir de una lista genérica de equipos.
Why Thermal Treatment Should Not Be the Primary Control
Heating a mixed PET/PVC stream can expose PVC to the same degradation pathway the recycler is trying to prevent. Any thermal method needs engineered temperature control, corrosion-resistant components, gas capture, and an emissions review. For a PET washing plant, upstream polymer sorting and flake-level rejection are normally safer control points than intentionally heating contamination.
Recommended Control Points in a PET Recycling Line
- Define the incoming bale specification and record contamination by supplier and load.
- Open bales and spread bottles into a consistent single layer before automated sorting.
- Place manual quality control after the primary sorter to monitor misses and changing feedstock.
- Remove labels before granulation whenever the container and label format allow it.
- Use washing and float-sink separation for dirt, adhesive, caps, and polyolefins, but not as the sole PVC control.
- Verify finished flakes with a documented sampling plan and retain samples when investigating a rejected batch.
Quality-Control Questions Before Selecting Equipment
- Is the PVC present as whole containers, labels, or small flakes?
- What PVC limit and test method does the finished-flake buyer require?
- Does the sorter receive dry, clean, separated material within its specified particle-size range?
- Where will rejected material go, and how will the plant measure false rejects and recovery loss?
Estas preguntas determinan si el proyecto necesita un clasificador de envases enteros, un clasificador de escamas, un separador electrostático o una combinación por etapas. También evitan un error de diseño frecuente: comprar una máquina de separación antes de definir la forma del contaminante y la prueba de aceptación del cliente.
Preguntas frecuentes
¿Por qué el PVC es un problema en el reciclaje de PET?
PVC can degrade under PET processing conditions and release hydrogen chloride. This accelerates PET degradation and can cause yellowing, black specks, reduced molecular weight, corrosion risk, and brittle recycled products.
¿Cómo se separa el PVC del PET?
Sort PVC from whole bottles before granulation with manual quality control and sensor-based polymer sorting. For washed flakes, use a validated optical flake sorter or a properly conditioned electrostatic process. Plain-water float-sink separation alone cannot reliably separate PET from PVC because both polymers sink.
¿Qué ocurre si no se elimina el PVC del PET?
El PVC residual puede decolorar el PET reciclado, crear puntos negros, reducir las propiedades del material, corroer los equipos de procesamiento y hacer que un lote terminado incumpla la especificación de contaminación del comprador.
Related PET Recycling Equipment and Guides
- PET sistema de lavado de botellas y reciclaje
- Guía de compra de máquinas de reciclaje de PET
- PET bottle recycling process guide
- PET flake grades and quality requirements
- Sink-float separation tank for PET, PP, and PE
Technical Sources
- Association of Plastic Recyclers: PET Rigid Design Guide
- Peer-reviewed study on small amounts of PVC in recycled PET
- Sensor-based flake sorting equipment reference
Build PVC Control Around the Feedstock
Ningún separador puede corregir todas las fuentes de PVC. Empiece por el material entrante, retire la contaminación en piezas enteras antes de triturar, añada clasificación de escamas solo cuando el riesgo medido lo justifique y ensaye el producto terminado según la especificación del comprador. Para configurar una línea según la mezcla de botellas, el rendimiento y la calidad de escama objetivo, contact Energycle about a PET recycling project.
