Chapter 14 - A comparative investigation of polymers exposed to γ-rays, neutrons, and protons using optical and photoacoustic techniques

Abstract

Polymers are a special class of materials having important applications in various fields of science and technology, particularly in optics, electronics, biotechnology, photonics, and space research. The study of changes in the optical properties of two types of polymers, polymethyl methacrylate (PMMA) and Kapton, after irradiation with various types of high energy particles (neutron, proton, and γ-ray), are presented. The optical transmission spectra of Kapton foils irradiated with ≥0.1MeV neutrons and ∼0.25MeV protons (H+) have been studied in the visible spectral region using photoacoustic spectroscopy. An increase in the absorption (decrease in transmission) as well as shift in the absorption edge to the longer wavelengths is observed in Kapton foil after irradiation, and it was dominant for proton (H+)-implanted Kapton foils. These results have been compared with the optical properties (UV, Vis, and FTIR) of the gamma (γ)-irradiated PMMA and Kapton foils. Both the foils show chain scission and cross-linking process taking place at different stages of irradiation. Dimerization of the carbonyl group and absorption of moisture are observed in both the PMMA and Kapton foils after gamma irradiation. Presence of moisture enhances the cross-linking process in the polymers. Some of the processes exhibit opposite behavior in PMMA and Kapton. Degradation behavior of these polymers after irradiation is also discussed.