Additive manufacturing of novel recycled polyethylene terephthalate hybrid composites for sustainable production and consumption

Increased plastic production to meet the rapidly growing global demand has led to waste management issues. A vast portion of global plastic waste ends up in landfills and leaks into the environment, causing severe damage to natural habitats and ecosystems. Therefore, there is an urgent need to reutilize this waste in a circular manner for sustainable consumption of resources. In this study, recycled polyethylene terephthalate (rPET), the most common plastic waste, is utilized to develop novel polymer composite blends for the fused filament fabrication (FFF) additive manufacturing (AM) process. rPET was blended with two different materials, PETG-CF (carbon fiber-reinforced polyethylene terephthalate glycol) and PCTG-CF (CF-reinforced glycol-modified poly-cyclohexylene dimethylene terephthalate), to produce composite filaments containing 62% rPET using an in-house filament fabrication setup. The produced filaments were used to successfully fabricate the test samples for microstructural, thermal, and mechanical testing. In total, five different materials (i.e., rPET, PETG-CF, PCTG-CF, rPET/PETG-CF, rPET/PCTG-CF) were investigated in this study. The XRD spectrum revealed a broad diffraction spectrum, referring to low crystallinity or amorphous-dominated structures in all the materials. From thermogravimetric analysis (TGA) analysis, no significant variation was observed for the degradation temperatures of the tested materials, while differential scanning calorimetry (DSC) analysis showed low-intensity T-c and T-m peaks due to the semi-crystalline nature of rPET, rPET/PETG-CF, and rPET/PCTG-CF, and no significant T-c and T-m peaks in PETG-CF and PCTG-CF due to their amorphous nature. The rPET/PETG-CF blend exhibited a tensile strength of similar to 47 MPa and a Young's modulus of similar to 994 MPa, comparable/higher than virgin PETG-CF and PCTG-CF. In addition, rPET-based materials achieved flexural strengths up to similar to 86 MPa and flexural moduli up to similar to 2449 MPa, significantly higher than virgin PETG-CF and PCTG-CF. Such hybrid materials, constituting a major proportion of recycled materials, can limit the reliance on virgin materials and can significantly contribute to sustainable production and consumption goals.