From Nautical Waste to Additive Manufacturing: Sustainable Recycling of High-Density Polyethylene for 3D Printing Applications

High-density polyethylene (HDPE) is a highly versatile plastic utilized in various applicative fields such as packaging, agriculture, construction, and consumer goods. Unfortunately, the extensive use of polyethylene has resulted in a substantial accumulation of plastic waste, creating environmental and economic challenges. Consequently, the recycling of polyethylene has become a critical concern in recent times. This work focuses on the recycling of HDPE parts recovered from end-of-life boats into materials suitable for the marine environment with additive manufacturing technology via screw-assisted extrusion 3D printing. In particular, rigid materials are obtained by adding glass fibers to HDPE to mitigate the loss of mechanical performance upon recycling. Eventually, the properties obtained with two different production methods were compared, namely compression molding and screw-assisted extrusion 3D printing. Since the developed materials will be exposed to an aggressive environment, an extended thermos-mechanical characterization (including fatigue resistance) and investigation of the stability to UV exposure were performed.