Thermomechanical Analysis of Polymer Samples

Dynamic mechanical analysis (DMA) of cylindrical samples (6 mm diameter, 5 mm length) was used to conduct thermomechanical analysis using a Q800 TA DMA (TA Instruments, New Castle, DE).^{30 (link)} Dry temperature sweep samples were equilibrated at 20 °C for 15 min and then ramped to 120 °C at a rate of 2 °C/min. The storage modulus (E’) and the loss modulus (E”) were used to determine the peak tan δ (E’/E”), with the maximum value recorded as the dry T_g. Wet samples were submerged for 5 min in 50 °C reverse osmosis (RO) water prior to analysis. Samples were equilibrated for 5 min at 25 °C and then ramped to 70 °C at a rate of 2 °C/min. The temperature of the tan δ maxima was recorded as the wet T_g. Differential scanning calorimetry (DSC) was also used to measure both dry and wet T_g using a Q200 DSC (TA Instruments, Inc., New Castle, DE). Samples of approximately 5.0 mg ±1.0 mg were sealed in TZero aluminum pans and placed in the heating cell. The test profile for dry samples was as follows: equilibration at −40 °C, heating to 120 °C at 10 °C/min, cooling 10 °C/min to −40 °C and holding for 5 min, and a final heating to 120 °C at 10 °C/min. The half-height transition of the final heating cycle was the reported T_g. Wet samples were weighed and sealed in the same manner and were then heated from −40 to 80 °C.^{9 (link)}