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

Abstract

AbstractThe dynamic tensile modulus and energy loss have been measured for nylon 6‐6 at 35°C. over a wide range of humidity in forced longitudinal vibration experiments. The frequency range covered was about 3 to 30 cps. (radian frequency 20 to 200 sec.−1). Dispersion of mechanical properties was observed with changing humidity, the maximum in the loss factor, tan δ, occurring at about 70% RH. Small variation of energy dissipation with change in frequency is such as to suggest that the dispersion region extends over a wide frequency range and that at low humidity an energy loss maximum should be expected at a frequency below one cycle per second. Increase in the amount of water adsorbed by the nylon with increasing relative humidity leads to plasticization of the fiber and consequent increase in freedom of motion of chain segments in the amorphous region of the fiber. Examination of individual runs shows that the dynamic modulus tends to increase with increasing frequency and that the increase is of a reasonable order of magnitude for the relaxation phenomena involved.