Eco-friendly Sliding Components - Friction and Wear of Selected Biodegradable Plastics

A B S T R A C T Plastic waste, along with ubiquitous microplastics, is one of the most pressing environmental challenges today. In light of these concerns, biodegradable plastics have been considered a promising alternative (to conventional plastics). This article aims to provide information to answer the question of whether biodegradable plastics have the potential to be used in sliding components such as sleeve bearings or dynamic seals. The study involved testing nine biodegradable plastics. Their friction and wear were assessed under various pressures and velocities using a pin-on-disc test rig. The following materials were identified as the most promising for use in sliding components, ranked from most to least promising: PBAT, PBS, PBSA, CA and allPHA. The materials tested exhibited differences in stiffness, ranging from flexible PBAT through the slightly stiffer PBS and PBSA till the more rigid CA and allPHA. A wide range of flexibility is highly desirable, as different types of sliding components (e. g. dynamic seals, sleeve bearings or slide guides) require varying flexibility. At higher contact pressure and sliding velocity, PVA and PCL exhibited such severe wear that reliable measurements could not be obtained, whereas PLA underwent thermal deformation due to the heat generated during friction. PPC wore extremely rapidly even under the lowest of the applied operating conditions. A comparison of the friction and wear properties of the investigated biodegradable polymers with those of non-biodegradable polymers widely used in sliding components showed that the biodegradable polymers do not differ significantly from the non-biodegradable ones. There is a potential for the use of the biodegradable polymers in sliding components. However, sliding components typically utilise polymer-based composites rather than the unmodified polymers. Therefore, future research should focus on developing composites based on biodegradable polymers with additives intended to reduce friction and wear, followed by further experimental investigations in order to provide a more comprehensive answer to the question of whether biodegradable plastics can be used in sliding components.