Tribological Performance of High-Density Polyethylene (HDPE) and Recycled Polyvinyl Butyral (PVB) Blends During Pin-on-Disk Tests.

High-density polyethylene (HDPE) is a widely used thermoplastic known for its chemical resistance and ease of processing, but it has limited wear performance and moderate mechanical properties. In this study, recycled polyvinyl butyral (rPVB) was incorporated into HDPE at 5, 10, 15, and 20 wt.% to evaluate its effect on tribological performance. Pin-on-disk wear tests were conducted at 12, 15, and 18 N to assess the coefficient of friction (CoF) and wear resistance. Mean CoF values decreased by up to 40% with rPVB addition, with the best performance observed at 15 wt.% rPVB, although some variation was observed across replicates. SEM analysis revealed that rPVB promotes finer debris and transfer film formation, explaining the CoF reduction. However, wear resistance exhibited a complex trend: while rPVB improved adhesion and reduced material loss at lower loads, volume loss increased at higher loads, likely due to rPVB's lower hardness. Mechanical testing showed an increase in elastic modulus at low rPVB contents due to higher crystallinity, confirmed by DSC; however, tensile strength and impact resistance decreased with rPVB. The results suggest that incorporating 10-15 wt.% of rPVB into HDPE can enhance frictional performance without severely compromising mechanical integrity, offering a sustainable way to valorize rPVB.