Structural, Thermal and Optical Properties of PVA/AgNO3 thin Films Using Gamma Irradiation Method

Abstract

Polymeric materials are of great interest in scientific and technological research and play an important role in our modern daily life, they can be tailored to meet specific requirement for vast applications, and this is mainly due to their light weight, good mechanical strength, thermal stability and optical properties. Polyvinyl Alcohol (PVA) is one of the most important polymeric materials and the most utilized polymer in the last decades, due to its interesting applications in technology, biomedical and industry, it’s also of relatively low cost and easy in manufacturing. Furthermore, it is well documented that structural, thermal, mechanical, electrical and optical properties of polymers can be improved to a desired limit through suitable doping. In this concern and since Ag+ ions is a fast conducting ion in a number of crystalline and amorphous materials, its incorporation within a polymeric system may be expected to enhance its thermal, mechanical, electrical and optical properties. This present study intended to investigate the effects of γ-ray irradiation and the concentration of the inorganic dopants (AgNO3) on the structural, thermal and optical properties of the composite material. PVA/Ag composites with different contents of inorganic filler i.e. (5, 10, 15 and 20) wt% Ag were prepared by reduction of Ag+ ions in PVA solution using gamma irradiation with different doses i.e. (0, 5 and 10) Gy. Structural studies of the synthesized PVA/Ag composites were carried out using X-ray diffraction (XRD) technique; thermal studies have been carried out using simultaneous thermal analysis (STA), i.e. thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore, the dependence of the optical properties of PVA on the concentration of the filler as well as the effects of γ- irradiation has been studied through UV-Vis spectroscopy. VI The results showed that the irradiation of the PVA/Ag films with γ-ray doses induces color change and the color intensity increases with increasing γ-ray doses. Measurements of the onset temperature of thermal decomposition showed that the composite material of PVA/Ag was more thermally stable than its pristine components, i.e. pristine PVA and AgNO3 and the thermal stability improved with the increment of AgNO3 concentrations and the applied radiation doses. DSC thermograms show that melting points shift to higher temperatures with increasing radiation dose and filler concentration. UV-Vis analysis of the films showed absorption band peaking at the wavelengths around 230 and 450 nm and the intensity of peaks in proportional increment with radiation dose. In addition, the specific absorbance and the absorption coefficient of the films were found to be directly proportional to the applied γ-ray doses. Moreover, γ- irradiation of PVA/Ag samples leads to the formation of Ag nanoparticles, and chain scission and/or cross-linking in the polymer as confirmed by XRD analysis, these consequently improved the thermal, optical and mechanical properties of the prepared films.