Mechanism of the degradation of polyamides

Films of polyamides were exposed to heat, ultra-violet radiant energy, and different atmospheric conditions. The degradation products were collected in some cases and analysed by mass-spectrometric techniques. The unexposed and exposed specimens were examined by the following techniques to obtain information concerning the changes in chemical and physical structure of the polymer: infra-red absorption, ultra-violet absorption, viscosity of solutions, measurement of dielectric constant and dissipation factor, photomicrography, X-ray diffraction, electron microscopy, and effect of organic liquids. In addition, pyrolysis studies were made and some physical properties were determined. The results of the investigation show clearly that no single method gives a complete picture but that the results from several of the methods give an insight into the degradation mechanism. The general course of the degradation of polyamides may be described as follows : (I) splitting of the polymer chain at the C-N linkages; (2) changes in degree of crystallinity or local order; and (3) loss of dipole-associated plasticizers.