Investigation of rheological and thermal properties of recycled PET from bottles and preforms for 3D printing applications

The growing adoption of 3D printing across industries has spurred interest in eco-friendly materials, with recycled polyethylene terephthalate (PET) emerging as a promising candidate. This study investigates the rheological and thermal properties of recycled PET derived from post-consumer bottles and preforms to assess its suitability for 3D printing. Key rheological parameters, including melt viscosity, melt flow rate, and shear-thinning behavior, were characterized using a rheometer, while thermal properties such as glass transition temperature (Tg), melting temperature (Tm), and crystallization temperature (Tc) were analyzed via differential scanning calorimetry (DSC). Results revealed significant shear-thinning behavior, with viscosity decreasing from 40,000 Pa·s (bottles) and 4,000 Pa·s (preforms) to below 500 Pa·s as the shear rate increased from 20 to 1,000 s⁻¹. Thermal analysis indicated a melting point of 255 C for both materials, with optimal printing temperatures identified at 250 C for bottles and 253 C for preforms. These findings highlight the importance of temperature regulation, particularly for PET preforms, which exhibit lower viscosity and are prone to degradation. Based on comprehensive rheological and thermal analyses, optimal processing conditions were established at 250 C – 260 C for bottle-derived PET (with 260 C showing superior flow characteristics) and 253 C – 256 C for preform-derived PET (with 253 C demonstrating optimal filament formation). These findings advance the sustainable implementation of recycled PET in additive manufacturing by providing empirically validated processing parameters that balance material flow properties with thermal stability, enabling reliable printability while minimizing degradation risks.