Recycling, thermophysical characterisation and assessment of low-density polythene waste as feedstock for 3D printing

Low-density polyethene (LDPE) is extensively used in single-end-use food packaging and contributes significantly to global waste plastic. This study addresses this challenge by introducing a sustainable approach to reclaim and valorise waste LDPE from milk packaging by converting them into 3D printing filaments. The process involves extruding shredded LDPE pouches into continuous filaments using a modified thermal extruder. The research comprehensively investigates the effects of two key extrusion parameters, nozzle temperature and screw speed, on the resulting filament's physical and mechanical properties. Characterisation efforts include dimensional analysis, morphological evaluation, chemical integrity assessment, thermal stability analysis, and tensile testing. The results show that filaments remain consistently close to 1.75 mm diameter, which is required by most commercial FDM 3D printers. The filaments are chemically intact, thermally stable, and have high toughness across the range of extrusion parameters. The results and a preliminary demonstration of 3D printing indicate that the LDPE waste can be effectively transformed into consistent filaments that have the potential for 3D printing. A carbon footprint assessment underscores the environmental benefits of this approach, showing substantial reductions in estimated CO₂ emissions compared to conventional filament production methods. While challenges related to the quality of printed parts remain, the research opens avenues for optimizing 3D printing parameters and exploring multiple recycling cycles. This work represents a step towards sustainable plastic waste management and offers insights into transforming single-use plastic items into valuable resources.