Electron spin resonance imaging of polymer degradation and stabilization

We present the application of one-dimensional (1D) and two-dimensional (2D) electron spin resonance imaging (ESRI) for the study of photo- and thermal degradation of polymers containing hindered amine stabilizers (HAS). The method is based on the formation of stable nitroxide radicals derived from HAS during polymer treatment, and on encoding spatial information in the ESR spectra via magnetic field gradients. The imaging technique allowed nondestructive profiling of the HAS-derived nitroxide radicals. The intensity profile in the sample depth was deduced by 1D ESRI, and the spatial variation of the ESR line shapes (‘spectral profiling’) was determined by 2D spectral-spatial ESRI. Application of this approach to the photodegradation of polypropylene and to the photo- and thermal degradation of poly(acrylonitrile–butadiene–styrene) will be described. The method can be used to detect spatial heterogeneities in the degradation process and to identify morphological domains that are selectively degraded. [Copyright &y& Elsevier]