Development of Processing Strategies to Enable 3D Printing of LLDPE With Sisal Fiber Reinforcement

Abstract

Linear low-density polyethylene (LLDPE) is a packaging material with superior properties compared to conventional low-density polyethylene. However, due to its low thermal stability, it cannot yet be used in high-performance applications. Due to its use as single-use packaging and low natural degradation in nature, the continued use of this material may delay the achievement of the UN's sustainable development goals. Therefore, sisal fibers can be used in LLDPE, reducing the carbon footprint of this material and utilizing agro- industrial residue. However, the use of these fibers reduces the processing temperature to approximately 200 °C due to their degradation and therefore brings even more challenges to the application of this material in 3D printing. This polymer exhibits significant thermal shrinkage due to crystallization, which hinders its application in 3D printing. To this end, this work aims to develop new techniques for printing a novel LLDPE/ sisal fiber composite. Printing temperatures between 175 and 190 °C were tested, and it was observed that temperatures below 190 °C caused problems due to the low polymer fluidity in the 3D printer's small extruder nozzle. However, this temperature was enough to guarantee the completion of the printing. Three substrate materials were analyzed: polyethylene terephthalate glycol (PETG), high-impact polystyrene (HIPS), and polylactic acid (PLA), at a printing bed temperature of 80 to 123 °C. The experiments enabled the printing of good-quality test specimens using HIPS and PETG as substrates, but only at a bed temperature of 123 °C. The test specimens produced enabled the feasibility of future mechanical characterization of the material, and the methods developed will enable the development of LLDPE in the literature. As future research, the generation of a customized g-code will be studied that will allow the use of the same substrate to manufacture multiple test specimens, thus reducing process waste.