The durability of a novel Nafion/poly(tetrafluoroethylene) (PTFE) composite membrane was evaluated using an accelerated stress test. The composite membrane was embedded with a porous PTFE layer and was prepared by the solution-casting method using 5% Nafion solution. The porous PTFE layer was treated chemically to improve its hydrophilicity before incorporating it within the membrane. The goal of the hydrophilic treatment was to improve the interfacial bonding between the Nafion polymer and the PTFE fibers resulting in improved strength and durability. The accelerated degradation testing was performed by the wet/dry gas cycling method. The chemical and mechanical stability of the membrane was evaluated by measuring the polarization curve, hydrogen crossover, and proton resistance during wet/dry cycles. Cross-sections of the composite membrane were examined after failure by a scanning electron microscope. The results show that the degradation rate of the composite fuel cell membrane incorporating the PTFE layer with hydrophilic pretreatment was lower than the degradation rate of the membrane with untreated PTFE. Tensile testing revealed that the composite membrane with pretreated PTFE has higher mechanical strength compared to both the composite membrane with untreated PTFE, and a commercial Nafion membrane.Proton exchange membrane fuel cells (PEMFCs) have attracted significant interest in the area of renewable energy research in recent years because of their clean and efficient operation, with potential applications in automotive, stationary power generation, and portable electronics. The proton exchange membrane is critically important in terms of the performance and cost of commercial fuel cell devices. 1-3 Nafion (DuPont) has been widely used as the membrane material because of its high proton conductivity, and physical and electrochemical stability. However, Nafion suffers from a number of drawbacks such as a limited operating range of temperature and humidity, high cost, and inadequate durability over multiple start-stop cycles. 4,5 PEMFCs operate in a variety of stressful environments, especially in automobiles, which could compromise the durability and lifetime of the membrane. Novel composite membranes are needed that can address these shortcomings.Poly(tetrafluoroethylene) PTFE has high chemical and thermal stability, and excellent mechanical strength. PTFE has been used as a supporting material for composite proton exchange membranes in various operating environments with voltage, humidity, and freeze/thaw cycling to reduce the loading of high-cost Nafion. 6 In addition, the development of ultrathin PEMs which greatly reduces ohmic losses and improves fuel cell performance 7-10 becomes feasible with PTFE reinforcement because of its higher mechanical strength.The most common materials used in the preparation of thin, lowcost, and high-durability composite membranes are porous PTFE films which are filled with Nafion ionomer. PTFE/Nafion (PN) composite membranes show excellent dimensional stability and si...
