Recycling of PET

The recycling of post-consumer PET (POSTC-PET) as a technology is a cross-disciplinary practice with many fields of science involved. These include polymer chemistry and physics, process engineering and manufacturing engineering. This paper presents a concise background of the current state of knowledge with respect to POSTC-PET recycling covering the disciplines mentioned above. In the first section of this paper, a brief background is presented about virgin PET synthesis, thermal transitions, processing and applications. The second section covers the PET recycling process with a focus on contamination and ways to increase the molecular weight of recycled PET (R-PET). It serves as an introduction to Section 3 where the chain extension process is described in detail. In Section 3, the current understanding of chain extenders, chain extension experimentation variables and equipment is reviewed. Reactive extrusion process is described in Section 4 with a special focus on system stability under chain extension conditions. Section 5 covers the effect of chain extension on R-PET thermal transitions and crystallinity. Section 6 presents the injection stretch blow moulding (ISBM) process as a possible application for R-PET with a focus on preform and bottle moulding. The last section gives a description of FT-IR technology to detect bottles’ orientation and conformation changes.