A new fixture for the mechanical characterization of thin polymer films under controlled temperature and relative humidity conditions is reported. Novel conducting polymers are often synthesized in small quantities and processed into films on the order of 10-100 microns thick. Standard tensile tests do not allow for adequate testing of these small sample sizes. Hence, a modification of the Sentmanat Extensional Rheometer (SER) to perform tensile testing on thin membranes is presented. Since the standard L-shaped pins do not secure thin polymer films at lower temperatures (i.e., below the melting point), screw down clamps were created to allow for mechanical characterization of solid polymer films. The new testing apparatus allows for mechanical characterization with as little as 2 % of the material needed for testing on a traditional tensile tester. In a parallel effort, a humidity delivery system developed for the TA Instruments ARES-G2 rheometer allows for testing at a range of temperatures (30-100 A degrees C) and relative humidity conditions (0-95 % RH). The novel oven was benchmarked with low density polyethylene and Nafion 115(a"double dagger). While the new experiment was built for characterization of ion exchange membranes for fuel cells, the oven is capable of characterizing any environmentally sensitive material using all standard rheometer geometries.