In this study hybrid polytetrafluoroethylene (PTFE)/glass fibers were employed in hierarchical braided structure as a composite reinforcement. PTFE-covered glass fibers were braided to achieve the hierarchical structure, then the composites were prepared through vacuum assisted resin transfer molding (VARTM) process. Tribological experiments were performed on the composites. The results showed self-lubricating and lower dynamic friction coefficient due to the PTFE transfer film formation. SEM micrographs confirmed the transfer film formation. Friction coefficient of 0.112, 0.105 and 0.096 were obtained under loading of 20, 30 and 40 N forces, respectively. The experimental coefficient of friction results were confirmed by mixture theory. The self-lubricating feature of PTFE-glass braided epoxy composite along with its mechanical characteristics makes it a feasible alternative for traditional wet bearing parts.
Functionalized nanofibrous membranes have been produced via electrospinning with a polymer solution of 19% (w/w) of nylon 66 prepared in a formic acid/chloroform mixture (75:25 v/v). The optimum parameters of electrospinning, like voltage, flow rate, tip and collector distances, were achieved and produced nanofiber membranes with a thickness of 287 nm. Then the nanofiber membranes were functionalized by (3-mercaptopropyl)trimethoxysilane (TMPTMS) at various amounts. Three different initial concentrations of metal ions and three different levels of pH were chosen. The effect of filtration process parameters such as the initial concentration of metal solution, pH of the solution, and the amount of functionalizer trimethoxysilane (TMPTMS) on the adsorption was studied. In surveying filtration process parameters, the results showed that metal ion rejection increased by increasing the pH of the solution and decreased by increasing the initial concentration of the effluent. By increasing the amount of functionalizer, removal efficiency increased. The results showed that the maximum efficiency of absorption of cadmium and nickel were 93.0 and 97.6%, respectively, and the filtering mechanism of the membrane is the blocking pores type. The adsorption data of cadmium and nickel ions fitted particularly well with the Freundlich isotherm.
The phenomenon of wear and friction in a variety of environments, including dry, seawater, and high temperatures, has always been a source of contention.Designing and fabricating parts that can function optimally in these conditions, such as self-lubricating composites, is helpful. This work investigated the tribological and thermal properties of a three-dimensional braid composite consisting of PTFE yarns and three types of reinforcement in the hierarchical structure under different operating conditions. In this study, the effect of different speeds was considered as well as effect of load. Roughness (Rq) and wear rate of the worn surface were also taken into account while evaluating the friction coefficient. By the response surface method (RSM) and D-optimal design, the tests were planned experimentally so that the minimum test was performed. Statistical models from the analysis of experimental data by RSM revealed that the friction coefficient of all composites rises in dry conditions with increasing load and sliding speed. In contrast, in seawater conditions, the more difficult the test conditions, the friction took a positive trend. Glass fiber reinforced composites were temperature sensitive and behaved differently in different conditions. The most optimal cases were calculated and reported by the utility function. Furthermore, the coefficient of friction values obtained in all cases were desirable and reliable.
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