Dynamic mechanical properties of nylon 66 and the plasticizing effect of water vapor on nylon. II

The dynamic tensile modulus and energy loss have been measured for nylon 66 monofilaments at 9 and 60°C. over a wide humidity range in forced longitudinal vibration experiments. The frequency range covered was about 3 to 30 cycles/sec. (radian frequency 20 to 200 sec. −1 ). The results show dispersion of mechanical properties with change in humidity at both temperatures. At 60°C. a well‐defined maximum in the energy loss was observed, similar to that obtained previously at 35°C., but occurring at a somewhat lower water content. If a maximum in the energy loss exists at 9°C. (it is not well‐defined), it occurs very near 100% R.H. A time‐humidity superposition procedure is discussed by means of which the individual curves of modulus against frequency for the various humidities can be combined into a single “master curve” of modulus against reduced frequency. The order of magnitude of the activation energy for the dissipation mechanism has been estimated at 60–80 keal./mole.