Effect of Mechanical and Chemical Recycling Routes on the Performance of PET Monopolymer Blends

Starting from 2030, in accordance with the new European Union directive, manufacturers of plastic beverage bottles will be required to incorporate at least 30% recycled plastic, calculated as an average across all bottles placed on the market within each Member State. Within this context, the present study investigates a monopolymer blend composed of virgin poly(ethylene terephthalate) and 30% mechanically recycled PET, which is compared with a commercial blend containing 30% chemically recycled PET. The rheological – processability – and mechanical properties of the resulting materials were evaluated.

The materials used were virgin PET – PPKFR (Plastipak Group), Intrinsic Viscosity: 0.82 dL/g, Tm 249°C – and a commercial blend containing 30% chemically recycled PET (Unique G30). Mechanically recycled PET was obtained through multiple extrusion cycles and blended at 30% with virgin PET. Both the mechanical and commercial blends were further reprocessed up to two cycles to simulate industrial recycling. Rheological (shear and elongational flow) and mechanical properties were evaluated on compression-molded specimens.

The results show that the monopolymer blend with 30% mechanically recycled PET has mechanical properties similar to the commercial blend. The differences are about +10.9% for elastic modulus, +5.8% for tensile strength, and −13.6% for elongation at break. In addition, the properties are mostly maintained after reprocessing. An additive model can predict the blend behavior well, with differences between experimental and theoretical values generally below 10%

In conclusion, the monopolymer blend with 30% mechanically recycled PET shows good rheological and mechanical properties, similar to the commercial blend with chemically recycled PET, with only small decreases. These results show that mechanically recycled PET can be a good and sustainable alternative, and the additive model can correctly predict the material behavior after reprocessing.