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An infrared thermal analysis technique was used to measure the enthalpy of dissociation of hydrogen bonds in various polyamides and to test the influence of the type of nylon, annealing time, and moisture content on the strength of hydrogen bonding. Nearly all of the NH groups were found to be hydrogen bonded at room temperature for every nylon tested. Enthalpies of dissociation ranged from about 8–12 kcal/mole. Tensile tests were also performed to determine the effects of the same variables on Young’s modulus of the polyamides. The results show that while the enthalpy of dissociation of the hydrogen bonds was not significantly changed by the type of nylon or any of the tested variables, the modulus was strongly affected by several of the treatments. Since factors which do not affect the strength of hydrogen bonding do have a large effect on the modulus and failure mode, it may be inferred that hydrogen bonding does not play a primary role in determining the mechanical properties of polyamides.
Schroeder et al. (Fri,) studied this question.