Hydrogen bond effect of azido polyurethane elastomer by dynamic mechanical analysis

Hydrogen bond effects in azido polyurethane elastomers (APUE) have been studied by dynamic mechanical analysis (DMA) and the results show that the hydrogen bond effect has stronger temperature dependence. The activation energy of hydrogen bond dissociation (E_a) and the hydrogen bond density (vs/V) have been evaluated from the elastic modulus-temperature relationship. The calculated Ea in this work is much higher than the reported values of normal polyurethane elastomer (PUE). The values of E_a are 81.3, 68.1, 53.3, and 42.3 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE-1 (CPPB/HDI trimer elastomer); 94.6, 75.8, 48.4, and 36.9 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE-2 (APPB/HDI trimer elastomer); 82.1, 74.4, 59.8, and 46.5 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE-3 (APPB/HDI trimer/EG elastomer); 145, 124, 88.0, and 75.5 kJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE-4 (APPB/HDI trimer/BD elastomer); and 72.2, 64.3, 49.8, and 39.9 KJ/mol at 150, 110, 50, and 20 Hz, respectively, for PUE-5 (APPB/HDI trimer/HD elastomer). The DMA estimations are semiquantitative for it ignores other physical crosslinking effects and the results give relative order of vs/V and E_a. The values of vs/V of crosslinked APUE (PUE-3, PUE-4, and PUE-5) are much higher than PUE-2. The test frequency could affect the values of vs/V and higher frequency would minify the difference of the values of vs/V for two given temperatures.