Solid-phase photodegradation of polystyrene by nano TiO2 under ultraviolet radiation

Abstract

Solid phase photodegradation of polystyrene (PS) and Polystyrene – titanium dioxide nano composite (PS-TiO2) was studied under ultraviolet radiation of wavelength of 253 nm. Titanium dioxide (TiO2) photocatalyst was synthesized via sol-gel method and characterized using SEM, EDX and XRD. Photodegradation of PS and PS-TiO2 was monitered using GPC, FTIR spectroscopy, UV-DRS, SEM and weight loss measurements. An appreciable decrease in the values of average molecular weights were observed from the GPC data with the increase in the UV exposure time for PS as well as PS-TiO2 composites. FTIR and UV–vis spectra revealed that the photodegradation of PS and PS-TiO2 composite was accelerated by the increase in UV irradiation time and also with the increase in the percentage of TiO2. It was also evident from the FTIR spectra that photooxidative degradation was the possible mechanism of degradation. Band gap energies of PS and PS-TiO2 determined using Tauc plot decreased upon increase in UV irradiation. The change in surface morphology of the irradiated samples compared to the pristine ones were clearly observed in their SEM images. Weight loss of the polymer samples increased upon increase in UV irradiation time. Mechanical properties (tensile and flexural) of raw as well as irradiated samples of PS and PS-TiO2 composites showed an appreciable decrease in their values with increase in irradiation time. The values of dielectric constant of the UV irradiated polymer specimens showed higher values compared to that of non irradiated specimens at varying frequencies. Dielectric strength of the polymer specimens decreased with the increase in UV irradiation time.