Mechanism of Improvement in Tribological Properties of Polyamide 6 by Addition of Irradiated Polytetrafluoroethylene Powder

In recent years، for economical، ecological and technical reasons، the tendency to use self-lubricant materials in tribological applications has been increased. Among self-lubricant materials، the engineering plastics and their composites، especially polyamides due to their suitable physical and mechanical properties، have gained a special attention in tribological applications. Since engineering polymers in their pure form are not capable to satisfy the tribological requirements، the application of different fillers seems to be necessary. In this research، in order to improve the tribological behavior of polyamide 6، an irradiated polytetrafluoroethylene (IR-PTFE) powder as a solid lubricant with the percentages of 5، 10 and 15% was used. The composites were prepared by the melt mixing method and then formed by the injection process. In order to investigate the dispersion of IR-PTFE as the second phase in the polymer matrix، electron microscopy was used. The results showed a proper distribution of IR-PTFE powder particles and a low adhesion of the powder to the polymeric matrix. The mechanical properties in uniaxial tension for determination of a suitable percentage of the filler were used. Also، the samples were subjected to water absorption and tribological long-term experiments. The formation of the transfer films in the pure polymer and the composite containing 5wt% of IR-PTFE powder as the second-phase polymer was observed with an optical microscope. The results showed that the composite containing 5wt% the irradiated polytetrafluoroethylene powder had the least effect on decreasing the mechanical properties. Also، the addition of IRPTFE powder increased the transfer films and decreased the coefficient of friction، contact surface temperature and wear rate of polyamide 6. In addition، the application of proper quantity of the irradiated polytetrafluoroethylene powder decreased the water absorption of the composites.