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

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Abstract
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.
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