PET — Polyethylene Terephthalate

PET is a material whose processability rests on two parameters: intrinsic viscosity (IV) and moisture. IV indicates chain length; bottle-grade resins carry a higher IV to provide the melt strength stretch blow moulding demands, while fibre grades sit in a lower range.

Drying is not optional

PET is hygroscopic. Processed without adequate drying, hydrolytic degradation begins in the melt, IV falls, and preforms yellow and turn brittle. This is the most common PET problem in practice, and it almost never originates in the resin — it originates in the dryer.

Bottle production is a two-stage process: injection moulding of the preform, then stretch blow moulding into the final container. Recycled rPET is viable in food-contact applications where the material carries the appropriate process authorisation and where feedstock discipline keeps quality variation under control.