Synthesis, fabrication and tribo-mechanical studies of microcapsules filled and Al2O3/glass fibre reinforced UHMWPE based self-lubricating and self-healing composites

Development of composites containing both self-lubricating and self-healing (SLSH) characteristics is a nascent area of research for applications where direct lubrication is discouraged such as marine, textile, and food processing industries. For instance, SLSH composites may enhance the longevity of propeller shafts, bearings, and other dynamic components in such applications. The present work focuses on the synthesis of microcapsules with molybdenum disulfide (MoS2) as a core and polysulfone as a shell material, using the solvent evaporation method. The composites were fabricated by blending synthesized microcapsules in ultra-high molecular weight polyethylene (UHMWPE) matrix via injection moulding technique. Aluminum oxide (Al2O3) nanoparticles (3-12 wt.%) and glass fibres (10 wt.%) were also used as reinforcements. Flexural and tensile tests of the fabricated composites were conducted to evaluate their mechanical properties. Tribological behaviour was also investigated using a pin-on-disc tribometer. The polymer composites with a constant dose of 10 wt.% glass fibre and 5 wt.% microcapsules along with 6 wt.% Al2O3 exhibit the best performance. The maximum reductions in wear rate and coefficient of friction (COF) are 45.28% and 54.47%, respectively, as compared to the base matrix. Moreover, flexural and tensile strength increased by 43.55% and 39.77%, respectively. The worn surfaces exhibited fractured microcapsules which acted as SLSH agents, due to the high thermal stability of the polysulfone shell and release of the solid core. Various analytical tools, including optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA), are employed in this study.