ESR study of the initial reaction of the photodegradation of nylon 6

The free radicals formed on irradiation of nylon 6 have been studied by means of electron spin resonance (ESR). The irradiation was performed at liquid nitrogen temperature with wavelengths in the region of solar radiation. The spectrum so obtained could best be fitted by assuming CH2ĊHCH2 and CH2ĊO to be the trapped radicals. The assignment of the spectrum supports the idea that the first step in photodegradation is the breaking of the amide bond. The splitting constant of the α proton of the alkyl radical has been found to be nearly the same for drawn and undrawn yarn. This strongly suggests that the low‐energy radiation is capable of breaking bonds only in the unoriented amorphous regions.