Preparation and evaluation of structural, optical, dielectric and thermal characteristics of unirradiated and irradiated polyurethane/magnesium silicate composites

Abstract

Polyurethane filled with various amounts (5, 10, 15, and 20 wt%) of magnesium silicate was fabricated by the solution casting method. The structural and physical properties of PU due to the influence of adding magnesium silicate together with gamma irradiation were investigated. The structural properties of the prepared composites were investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis shows magnesium silicate formation in the PU matrix, which was further confirmed by the surface morphology images obtained by the SEM. Optical properties were characterized by ultraviolet–visible (UV–Vis) spectrophotometer. Refractive index dispersion was analyzed via the Wemple–Didomenico models. For both the unirradiated and irradiated composites, the ratio of carrier density to the effective mass, and the plasma frequency were calculated. Influences of magnesium silicate and gamma irradiation on these parameters as well as the dependence on the aforementioned additions were investigated. The dielectric investigation of the prepared composites reflected the increase of the dielectric constant, dielectric loss, and electrical conductivity with the addition of magnesium silicate and gamma irradiation, while it lowered with raising the applied frequency. The thermal stability of the prepared composites was investigated via thermogravimetric analysis. The thermal stability of all composites is significantly enhanced with the adding magnesium silicate and gamma irradiation. Kissinger model was applied to measure the activation energy of thermal decomposition and revealed the increasing trend of activation energy with the addition of the magnesium silicate and raising gamma absorbed dose. We believe that the outcomes of this work would provide a helpful contribution to the engineering of the components and the processes involved in the given structure presented.