Continuous measurement of dynamic tensile mechanical properties in polymer solids over a wide range of frequencies. III. Effect of absorbed water on nylon 6 at 23°c

The dynamic tensile mechanical properties (E′, E″, and tanδ) of nylon 6 have been studied over the frequency range 10−25−102 Hz and water content up to 12.6 wt % at a constant temperature of 23°C. From the dispersion maps in the coordinates of frequency and water content, the relaxation behavior can be classified into three regions of water content: (A) dry to 2 wt %, (B) 2‐5 wt % and (C) 5 wt % to wet. For region B, it is found that the logarithmic frequency shift Δ logfα/Δx of the α dispersion per 1 wt % change of water content is 1.7. Taking into consideration that the change of glass transition temperature per 1 wt % change of water content Δ Tg/Δx is 3.7°C (according to Kettle), we find Δ logfα/ΔTg = 0.5. For regions A and C, such an evaluation cannot be made. The effect of absorbed water on the dynamic mechanical properties at 23°C is discussed in terms of two kinds of processes: (a) formation of water‐amide hydrogen bonds with free amide groups and (b) scission of amide‐amide hydrogen bonds.