Radiation Chemistry:
By Mr.Toka Swu
CHAPTER-1
INTRODUCTION
The study of radiation induced modifications in polymers is a recent yet an expanding field of research. Owing to its technological applications, it has received an immense deal of attention and is being extensively investigated. Modifications induced by irradiation may sometimes enable in achieving the desired and improved physical and chemical properties of the polymers for specific use. Thus the study of polymer modifications which comprises a study of physico†chemical variations in polymer due to irradiation is of great importance.
Radiations are produced both naturally and artificially and are thus omnipresent. They comprise of charged particles like electrons, protons, alpha particles, fission-fragments, accelerated heavy ions and electromagnetic radiations such as x-rays and gamma-rays. All these types of radiations interact with any type of substances coming in their path, irrespective of their molecular structure generating variety of species [1] through dissipation of radiation’s energy. Thus, polymers on irradiation get electronically ionized or excited resulting in structural alternations, which in turn affects their properties [2]. These changes in the polymer depend on the radiation doses, internal structure of polymer such as types of functional group present, chain length, etc. When the energy of the radiation exceeds the bond energy, the polymer having absorbed energy may suffer bond cleavage giving rise to a non-saturated fragment called ‘free radical’. These free radicals are very reactive and may cause different chemical transformation within the polymer molecule by reacting with other parts of the same molecule. As a result, chain scissions, cross-linking, etc. takes place. Various gaseous molecular species are released during irradiation. The most prominent emission is hydrogen, followed by less...