Experimental Evaluation of Temperature and Screw Speed Effects on the Extrusion of Recycled PP, HDPE, and PET for Sustainable Construction Applications

This study evaluated the feasibility of using recycled plastics (PP, HDPE, and PET) for sustainable construction applications. Materials were collected, processed, and extruded following a structured methodology, and their physico-mechanical and environmental properties were assessed through standardized tests, including compression, flexural strength, water absorption, porosity, and apparent density. Compression tests showed that increasing the processing temperature led to a reduction in the compressive strength of polypropylene (PP), while high-density polyethylene (HDPE) achieved its highest strength at the lowest temperature. Polyethylene terephthalate (PET) exhibited a similar decreasing trend with temperature. The processing speed, expressed as revolutions per minute (rpm), had little influence on PP and HDPE performance but positively affected PET, where higher rpm consistently improved compressive strength. Flexural tests revealed that higher rpm values enhanced the mechanical performance of PP and HDPE. However, for PP, an increase in processing temperature resulted in a pronounced decline in flexural strength. Overall, PP and HDPE outperformed PET, reaching compressive strengths near 10 MPa compared to values below 4 MPa for PET. In flexural tests, PP achieved 44 MPa, followed by HDPE with 25 MPa. Water absorption remained below 1% for all materials. The study is limited to physico-mechanical characterization and does not include microstructural or thermal analyses to assess crystallinity, degradation, or molecular orientation. Future research will focus on advanced thermal–chemical characterization and process optimization—particularly for PET—to improve ductility and expand the applicability of recycled plastics in construction.