Mechanical properties of proton exchange membrane at different strain rates and temperatures

Proton exchange membrane (PEM) is an important part of proton exchange membrane fuel cells (PEMFCs). The evaluations of PEM are mainly focused on the conductivity and methanol diffusion resistance. There are few studies on mechanical properties and reliability of PEM. In this study, the stress-strain behavior, creep-recovery behavior and stress-relaxation behavior of PEM at different strain rates and temperatures have been obtained on Dynamic Mechanical Analyzer. Strain controlled tensile tests were conducted at different strain rates of 0.1%/s, 1%/s and 8%/s and five different temperatures of -30 degrees C, 0 degrees C, 30 degrees C, 55 degrees C and 85 degrees C. There are three phases in tensile stress-strain curves of membrane samples, i.e. linear elastic, nonlinear hardening, and linear hardening. Creep-recovery tests were conducted with the stress level of 21VIPa, 4MPa, 6MPa and 8MPa, and with the temperature of 30 degrees C, 55 degrees C and 85 degrees C. Creep strain increases rapidly as the stress increases. The phenomenon is more obvious at high temperature especially. Creep strain increases rapidly as the temperature increases at the same stress and creep time. Stress-relaxation curves at strain of 10%, 50%, 100% and the environment temperature of 30 degrees C, 55 degrees C, 85 degrees C were conducted. The larger the initial strain, the higher the initial stress. The stress decreases rapidly at beginning, and then the change becomes more and more gentle.