PET Bottle to RPET Granule: How Plastic Recycling Actually Works

Every RPET granule started as a used bottle - here's exactly what happens between collection and a manufacturing-ready pellet.

By Siya Polymer & Speciality Chemicals Technical Team · Manufacturer & Supplier, Maharashtra, India

Why Understanding the Process Matters

Buyers of RPET granules often ask about quality without knowing what actually determines it - the recycling process itself is where most quality variables get decided, long before the granule reaches a moulding machine. Here is what happens at each stage.

Step 1: Collection and Sorting

Used PET bottles are collected and sorted by resin type and colour, since even small amounts of contamination from other plastics (PVC in particular) can significantly degrade the quality of the resulting RPET batch. Colour sorting also matters - clear bottles are generally kept separate from coloured ones to preserve clarity in the final granule where required.

Step 2: Baling and Pre-Washing

Sorted bottles are baled for transport and then pre-washed to remove surface dirt, labels and residual contents before mechanical processing begins.

Step 3: Shredding/Flaking

Bottles are shredded into small flakes, which increases surface area and makes subsequent washing and separation far more effective than washing whole bottles.

Step 4: Washing and Contaminant Separation

Flakes go through hot washing with detergents to remove adhesive residue, followed by float-sink separation tanks that exploit density differences to separate PET flake from caps, labels and other lighter contaminants (like polyolefin cap material, which floats while PET sinks).

Step 5: Drying

Clean, sorted flakes are dried to remove residual moisture, since moisture left in the flake can cause hydrolytic degradation during the melt-processing stage that follows.

Step 6: Extrusion and Pelletizing

Dried flake is melted, filtered (to catch any remaining fine contamination) and extruded into strands, which are then cut into uniform RPET granules/pellets ready for shipment.

Step 7: Quality Testing

Before RPET granules reach a customer, quality-focused recyclers test intrinsic viscosity (IV), moisture content, colour consistency and contamination levels to ensure the batch meets the target application's requirements - packaging-grade RPET has different quality thresholds than fibre-grade or strapping-grade RPET.

What This Means for Buyers

Because contamination and moisture control happen at multiple stages, RPET quality varies significantly between suppliers - sourcing from a supplier that shares batch testing data (IV, moisture, colour) gives far more confidence than sourcing on price alone.