Investigation of Tribological and Rehological Properties of a Self-Lubricant Polymeric Composite
ايناس طالب صاحب عودة, عمار عماد الكواز
كلية هندسة المواد-جامعة بابل · العراق
In order to provide a long lubricating life span, it must be ensured that the solid polymer or polymer compound provides self-lubrication and at the same time, it must provide adequate interface contact pressure, which is the most important factor with self-lubricating compounds so that the polymeric compound is able to support the dynamic stresses of the applied load and pressures. In this study, a polymethyl methacrylate (PMMA) self-lubricating compound was synthesized with solid lubricants and multi-walled carbon nanotube and selected as the self-lubricating approach. Calcium stearate, polyethylene wax, and beeswax were selected as solid lubricants that have the ability to migrate to the surface of the polymer during its service life. Using in situ polymerization of free radicals with the following parameters: PMMA (100% MMA + 0.9 wt% BPO)/ solid lubricant (0.05, 0.1, 0.2, 0.5 wt.%), PMMA / MWCNT (0.05, 0.1, 0.2, 0.5 wt.% via sonication), hybrid compound ((50% PMMA: 50% beeswax) (0.05, 0.1, 0.2, 0.5 wt.%) + PMMA). Fourier transform infrared (FTIR) was used to verify the identity of solid lubricants after in situ polymerization of free radicals and multiwalled carbon nanoparticles. On the tribological behavior of the surface of polymers reinforced with solid lubricants and nano-fills after wear test, using optical microscopy (OM) the flow is verified using a capillary pressure gauge (SR20) and a contact angle test was conducted to verify the effectiveness of solid lubricants and nano-fills in increasing the susceptibility of the polymer hydrophobic. The PMMA sheets produced are characterized by relatively round shapes, with an average diameter of 15 cm and a thickness of about 2 mm. The results of the tests for both friction and abrasion proved a higher efficiency up to (9.4%) and a friction coefficient (0.8%) for the sample filled with beeswax much more than the rest of the solid lubricants, which confirms the transfer of particles to the surface and reduces the amount of interfacial shear stress during dry friction, and by increasing over time and loads applied at a constant speed, friction negatively affects the overall wear rates and impairs the internal structure and thus the mechanical properties. The self-lubrication system works successfully and this is confirmed by the scratch test results of the samples that showed the deformation behavior of pure polymer plastic and elastic deformation of the polymer filled with beeswax and the results were consistent with the results of friction and wearing. This was evident from the residual effect after scratching, which is characterized by a very smooth area in the contact area with little contact stress and surface scratch flexibility and plays an important role in reducing the interfacial shear stress up to (0.8%). Flow resulted in PMMA/solid lubricant by weight % capillary rheometer and PMMA/reinforcing fillers wt.% showed that shear viscosity decreases with increasing shear rate and shear stress increases with increasing shear rate. Increasing the shear stress cuts the polymeric chain and reduces the viscosity. With an increase in temperature, the migration to the surface increases, which helped to postpone the extrusion process and reduce the amount of the total melting fracture. Shear stress plays an important role in indicating surface quality; it is clear that the determination of the critical region is necessary to be able to change the surface quality and its relationship to pressure, shear stress, and shear rate.