Dynamic mechanical studies of nylon 6.6 fibers in water/glycerol baths

A method was developed for measuring the dynamic mechanical properties of nylon (or other) fibers in mixtures of water and glycerol, so that the effect of the chemical activity of water on the a transition could be estimated. As might be expected, the alpha transition appeared to move to lower temperatures with increasing water in equilibrium with the fiber. The bath was an open system, ie. some water evaporated while the rest was being run. To obtain dynamic mechanical responses for constant water/glycerol mixtures, the glycerol content of the bath was monitored at different temperatures in a time-scheduled test, and a polynomial interpolation scheme was implemented. The results were interpreted with a method which derives a mobile, non-crystalline fraction, X, and an internal viscosity, eta, from tan delta and G. For a wide range of water fraction and temperature, eta behaved Like the viscosity of an Eyring liquid. Furthermore, over a wide range of temperature and water fraction, X was linear with mol fraction water in the bath, a parameter which to a first approximation would represent the chemical activity of the water. These results are discussed in the light of the dynamic-crystalline-gel concept of Hearle and Hearle and Greer and more recent work on thermovereversible gels.