Measurement of Water Uptake and States in Nafion Membranes Using Humidity-Controlled Terahertz Time-Domain Spectroscopy

Perfluorinated sulfonic acid ionomers are well known for their unique water uptake properties and chemical/mechanical stability. Understanding their performance–stability trade-offs is key to realizing membranes with optimal properties. Terahertz time-domain spectroscopy has been demonstrated to resolve water states inside industrially relevant membranes, producing qualitatively agreeable results to conventional gravimetric analysis and prior demonstrations. Using the proposed humidity-controlled terahertz time-domain spectroscopy, here we quantify this detailed water information inside commercially available Nafion membranes at various humidities for direct comparison against literature values from dynamic vapor sorption, differential scanning calorimetry, and Fourier transform infrared spectroscopy on selected samples. Using this technique therefore opens up opportunities for rapid future parameter space investigation for membrane optimization

Heating Rate Effects on Thermal Analysis Measurement of Tg in Composite Materials

Three measurement techniques used to measure the glass transition temperature (Tg) have been subjected to a critical comparison; dynamic mechanical analysis (DMA), thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). A new procedure, whereby different specimens are tested over a range of heating rates, has been used in order to eliminate the effects of thermal lag and determine a Tg independent of heating rate (Tg(0)). It has been shown that for measurements of Tg(0) for composites, the DMA thermal lag ‘corrected’ method gave the most reliable data. The work has provided additional guidance on these techniques that could usefully be incorporated in future standards, to improve precision, comparisons and consistency of Tg measurement