Achieving bottle-grade poly(ethylene terephthalate)-like properties from blends of bottle-grade and thermoform-grade poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET), both bottle grade (PET-B) and thermoform grade (PET-T), are widely used in the packaging sector. However, only PET-B is recycled and reused, while PET-T needs to be separated from recycled PET bales. This study aims to assess the impact of solid-state polymerization (SSP), chain extension and the combination of chain extension–SSP to transform PET-B and PET-T blends into PET-T-like material. The intrinsic viscosity (IV) values for PET-B blends with 10–20 wt% of PET-T are measured for the samples obtained in this study. The mechanical properties, such as tensile strength, modulus, elongation and impact strength, were also determined. The glass transition temperature, melting temperature, crystallinity and thermal degradation were also investigated. The findings suggest that the combination of SSP and chain extension leads to a significant improvement in IV and tensile strength, while SSP alone is less suitable to offer the desired IV values. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.