Creep enhanced adsorbtion of water or aqueous zinc chloride solution increases the creep rate of nylon 6,6

The creep behavior of nylon 6,6 at 21 degreesC was significantly altered wh en the local "dry" environment was changed to water mist or an aqueous zinc chloride mist. Nylon 6,6 was found to exhibit logarithmic creep because th e relation between the log of the strain rate and the creep strain was line ar with a negative slope. The effect of changing the creep environment from dry to wet, with the addition of moisture from an ultrasonic humidifier wa s to decrease the negative slope by 50-70% within 5-10 min. This effect cou ld be interpreted as a decrease in modulus, which allowed for easier creep deformation. Based on the stress-free diffusivity of water in nylon and the dimensions of the test sample the time to saturate the sample was estimate d to be about 100 h. Therefore, there appeared to be synergism between the creep deformation and the environment that dramatically enhanced the rate o f saturation and slowed the decrease in the creep rate, The tentative expla nation provided is that the aqueous solutions, by binding to the hydrogen b onds in nylon, are dragged into the sample during creep deformation, and th e dragged-in aqueous solution then plasticizes nylon. This is analogous to the conclusion in another recent study that showed that deformation, during a hardness test, in the presence of aqueous zinc chloride, transported the solution species deeper into the sample than could be reasonably explained by ordinary diffusion processes. (C) 2001 John Wiley & Sons, Inc.