Recycled Polyethylene Terephthalate (rbPET) from Post-Consumer Water Bottles: Chemical and Thermal Properties

The extensive production of Polyethylene terephthalate (PET) water bottles has led to significant environmental concern, as traditional reuse and recycling methods are often insufficient to address the improper disposal of the post-consumer PET water bottles. In this paper, post-consumer Polyethylene terephthalate (PET) water bottles were converted into recycled PET filament using a rbPET maker that was developed through 3D modelling and printing. The chemical and thermal properties of the extruded recycled PET from post-consumer water bottles (rbPET) were analysed and compared with commercially purchased virgin and recycled PET resins (vPET, rPET), and PET strip obtained from the post-consumer water bottles (bPET). Fourier transform infrared spectroscopy (FTIR) spectra reveal that rbPET retains PET functional groups with respect to vPET, rPET and bPET as no significant chemical changes is detected. The extruded rbPET lies in desired thermal stability range of 409.7- 445.4 °C with one degradation step, exhibits decomposition peak of 428.8°C, mass loss of 83.28% and the amount of residue is 10.59%, thus highlighting its robustness. The glass transition temperature (Tg) of rbPET at 74.3°C aligns well with that of the commercial PET, indicating that there is no major loss in performance. The slightly higher crystallisation temperature (Tc) and melting temperature (Tm) of rbPET at 128.3°C and 252.9°C respectively, fall within similar range to the commercial PET, suggesting comparable processing and mechanical properties. The mechanical recycling process using the developed rbPET maker did not significantly deteriorate or alter the polymer chain. The recycled PET filament is beneficial for 3D additive manufacturing in producing wide array for products. This approach is environmentally significant as it promotes resource conservation and reduces the amount of plastic waste in landfills.