Article Published - From Haze to Clarity

The transition from virgin PET to rPET in stretch-blow moulding is far from plug-and-play. Recycled PET often exhibits lower intrinsic viscosity, increased variability in crystallinity, and reduced strain hardening. These changes significantly affect preform stretchability, wall distribution, and bottle clarity.

Manufacturers must adapt their process settings to accommodate:

• Blow-moulding temperatures: rPET typically requires tighter control due to its thermal sensitivity.

• Stretch ratios: The strain-hardening behaviour of rPET lags behind virgin PET, which can cause early pearlescence if not properly managed.

• Residence time & drying: rPET is more hygroscopic and must be thoroughly dried to prevent hydrolytic degradation during processing.

Tools like BLOWSCAN and Digital Image Correlation (DIC) can quantify these differences and help optimise the process window for rPET materials — ensuring product performance is maintained despite material variability.

Read our article here.