Polymer Filament Extrusion Using LDPE Waste Polymer: Effect of Processing Temperature

Abstract

Low-density polyethylene (LDPE) is a soft thermoplastic with extensive application as a packing material such as plastic bags, dispensing bottles, milk pouches, etc. Many LDPE bags are used and dumped in landfills every year, leading to millions of tons of persistent waste. In addition, the recycling of LDPE is of no commercial interest due to its low stiffness, poor mechanical properties, and limited commercial application. In the current work, we attempt to recycle milk pouches made of LDPE to create polymer filaments for fused deposition modeling (FDM), thereby adding value to waste plastic by converting it into high-value 3D printer filament. This research examines the feasibility of reclamation of waste LDPE milk pouches as filament for 3D printers and studies the changes in filament’s chemical and mechanical properties when produced at different temperatures. The waste milk pouches are cleaned thoroughly, shredded, and extruded using a single screw extruder at three nozzle temperatures, i.e., 150°C, 180°C, 210°C. The extruded specimens are analyzed using an optical microscope and scanning electron microscope (SEM) for surface texture. The effect of change in process temperature on flow behaviors is also studied by integrating a current sensor and an encoder. Fourier transform infrared spectroscopy (FTIR) analysis is performed on the filaments and the used LDPE milk pouches to compare the chemical bondings of the polymer. The mechanical properties of the extruded filaments are examined using dynamic mechanical analysis (DMA). The morphological analysis, chemical characterization, and mechanical characterization of prepared filaments are presented. The results show that the chemical bondings are intact after extrusion at all the temperatures examined in this work. The surface texture and the mechanical properties are better at higher temperatures owing to better fluidity and are more suitable for fused deposition modeling. Thus, it is possible to valorize waste LDPE milk pouches by transforming them into filaments for 3D printing.