PET Bottle Recycling Process Explained: From Bale to Flakes

Post-consumer PET bottles are among the most widely recycled plastics in India. Discarded beverage and water bottles are collected, cleaned and turned into flakes that go into polyester fibre, strapping, sheet and other products. For buyers of PET flakes, and for recyclers planning a line, understanding each step helps explain why flake quality varies so much between suppliers.

Collection and baling

Bottles are collected by waste pickers, kabadiwalas, aggregators and municipal or institutional systems. Aggregators sort them roughly, often by colour, and compress them into bales to make transport economical.

Bale quality varies. Some bales contain only clean, sorted bottles; others include caps, labels, liquid residue, dirt and other plastics. See PET bottle scrap for the typical grades traded.

Recyclers usually inspect bales on arrival and may open a few to check what is inside. Bales stored in the open pick up dirt and water, which adds weight but not value, so many buyers prefer covered storage and agree how deductions for moisture and foreign material will be handled before the truck is loaded.

Sorting and pre-treatment

At the recycling plant, bales are broken open and bottles are sorted. Sorting may be manual, automated with optical sorters, or a combination. The aims are to:

• separate bottles by colour, typically clear, light blue, green and other colours;
• remove non-PET items, particularly PVC, which degrades PET during melt processing and causes black specks and discolouration even in small amounts;
• remove metal, glass, stones and other foreign material.

Labels are often removed at this stage with a delabeller, which strips sleeves and wrap labels before grinding. Caps, usually PP or HDPE, may be removed by hand or left on to be separated later.

Grinding and washing

Sorted bottles are ground into flakes, often in a wet grinder that starts the cleaning process. The flakes then go through a washing line, which typically includes:

• Pre-washing to remove loose dirt.
• Hot washing with water and cleaning agents to remove glue, residual labels and organic contamination.
• Friction washing to scrub the flakes mechanically.
• Rinsing to remove cleaning chemicals.

The quality of hot washing has a large effect on glue residue and odour in the final flakes. Read more about washing lines.

Float-sink separation and drying

PET has a density of about 1.38 g/cm3, so it sinks in water. Cap and label materials such as PP and PE float, which allows them to be separated in a float-sink tank. The floating fraction is collected and sold separately as polyolefin scrap.

PVC also sinks, so float-sink cannot remove it. That is why PVC must be removed during sorting.

After separation, flakes are dewatered and dried, usually with centrifugal dryers followed by hot air. Some lines add air classification to remove remaining label fines and dust, and flake colour sorting to remove off-colour particles. Metal detectors are also common before packing, because metal particles from caps or machinery can damage spinnerets and extruder screens downstream.

Flake quality and end uses

What buyers check

The output is washed PET bottle flakes, usually packed in jumbo bags. Buyers judge flakes on:

• intrinsic viscosity (IV), which indicates molecular weight and suitability for the end use;
• colour and the proportion of off-colour flakes;
• PVC content and other polymer contamination;
• glue, label and paper residue;
• moisture and flake size;
• metal content.

PET is hygroscopic, so flakes must be dried properly before any melt processing. Processing wet PET causes hydrolysis and lowers IV. Our recycled PET flakes buying guide explains how to specify these parameters.

Where the flakes go

• Polyester staple fibre and filament: used in textiles, fillings, non-wovens and carpets.
• PET strapping: for packing and bundling, where higher IV is generally needed.
• Sheet and thermoformed packaging: such as trays and blisters.
• Recycled PET granules for further processing, and in some cases bottle-to-bottle recycling using specialised processes that must meet food-contact regulations.

Buying or selling PET through PlasticSetu

Buyers can get quotes for PET bottle scrap, flakes or granules by posting a requirement with IV, colour and contamination limits. Recyclers and aggregators can list your materials; the sourcing desk contacts you when a buyer requirement matches.