Applicability of Fourier Transform near Infrared Spectroscopy and Principal Components Analysis for Studying Elastomers after Radiochemical Ageing

Abstract

The feasibility of using near infrared spectroscopy as a sensitive technique to follow the influence of γ-irradiation upon ageing of different EPDM (Ethylene Propylene Diene Monomer) elastomers has been evaluated. Minor differences can be observed between the spectra of non-irradiated and irradiated materials (for total integrated doses from 50 to 450 kGy using a dose rate of 1 kGy h−1 under oxygen flow). Applying a principal component analysis (PCA) in the spectral range 5500–4500 cm−1, the discrimination of polymers irradiated at different dose levels can be quickly performed and a spatial “random” separation by irradiation doses can be obtained up to 400 kGy using score plots PC1/PC2. Moreover, when spectral ranges such as 5000–4500 cm−1 or 7090–6980 cm−1 are used, scores of PC1 contain enough information for discrimination and classification by increasing irradiation doses. According to PCA analysis, the improvements brought by chemical modifications of the initial EPDM (antioxidant) seem to be inefficient as soon as the lowest irradiation doses (50 kGy) are applied. This preliminary study opens up a cost-effective opportunity for the in situ and non-destructive monitoring of polymer degradations in nuclear power plants.