Modern civilization is increasingly dependent on 3D printing technologies, with polyethylene terephthalate (PET) emerging as a key material due to its excellent mechanical properties and robust degradability, which simplify the recycling process. However, the application of recycled PET (r-PET) frequently encounters limitations due to its reduced viscosity and molecular weight. This paper examines four principal PET recycling techniques, elucidating the essential chemical processes involved and highlighting the importance of maintaining a high molecular weight for 3D printing applications. We propose two innovative approaches to address the challenge of diminished molecular weight: the introduction of chain extenders or other performance-enhancing additives, and the investigation of alternative printing materials. Through a detailed analysis of the development and integration of these strategies, this study not only seeks to broaden the functional applications of PET in 3D printing but also aims to bolster the sustainability of this crucial industry.