Accelerated photodegradation of polystyrene by TiO2-polyaniline photocatalyst under UV radiation

Photodegradation of polystyrene (PS) was studied under ultraviolet (UV) radiation, using nano TiO2, surface modified with polyaniline (PANI). X-Ray diffractogram reveals that the crystalline structure of TiO2 remained intact in TiO2-PANI composites. The existence of strong molecular interaction between TiO2 and PANI lead to a decrease in the optical bang gap energy of TiO2 in the composites. PS loaded with TiO2-PANI composites underwent better chain scission and photo-oxidation compared to PS and PS-TiO2 composites, upon UV irradiation. TiO2-PANI composites enhanced the mechanical properties (tensile and flexural) of PS appreciably. Tensile and flexural strengths however decreased with respect to UV exposure time, proving mechanical deterioration of the polymer composites as an outcome of photodegradation. Thermal stability of the composites too decreased upon UV exposure. A decrease in the values of break down voltage as well as increase in dielectric permittivity of the composites upon UV irradiation suggests the formation of charge centers and polarisable species in the polymer matrix. All the polymer composites underwent considerable weight loss due to the formation and evolution of volatile gases, during the course of photodegradation. Suitable mechanism of degradation of PS composites was proposed based on the observed results.