Photostabilization of PVC/PS/PMMA Blend Films by Metal Oxide Nanoparticles under Accelerated UV Aging

Degradation by ultraviolet (UV) radiation is still one of the most important issues affecting the long-term effectiveness and sustainability of polymers used outdoors. In this context, a ternary polymer blend of poly(vinyl chloride) (PVC), polystyrene (PS), and poly(methyl methacrylate) (PMMA) was synthesized by solution casting and loaded with metal oxide nanoparticles (NPs) (e.g., MgO, ZnO, TiO2, and NiO) at low concentration levels as UV photostabilizers. The incorporation of metal oxide NPs in the polymer system was done under accelerated UV irradiation (up to 300 hours) and the efficiency of the nanoparticles to prevent UV-induced degradation was investigated. The degree of UV photostabilization was evaluated by FTIR spectroscopy, weight loss, and atomic force microscopy (AFM) studies. The FTIR investigations showed a significant concentration of carbonyl groups in the untreated film; this is indicating that the polymer experienced some photo-oxidation during the UV exposure. The films with metal oxide nanoparticles showed comparatively lower carbonyl index than those of the unmodified polymer blend. Besides, the treated samples showed less weight loss compared to the blank samples. In addition, AFM examination revealed that the modified films had a lower surface roughness and cracking, in addition to less morphology degradation following UV irradiation. The higher photostabilization observed is associated with the ability of metal oxides to absorb harmful UV radiation, thus inhibiting radical reactions responsible for the degradation process in the polymer matrix. Metal oxide nanoparticles can, therefore, be considered an effective method of enhancing UV resistance of polymeric films for use in various applications. The selection of these four nanoparticles was therefore intended to enable a meaningful comparison of their photostabilizing efficiencies rather than to assume equivalent performance. Their incorporation at low concentrations also allows their UV-screening effect to be investigated while minimizing potential adverse effects associated with high nanoparticle loading, such as aggregation and changes in the physical properties of the polymer matrix. The comparison is particularly relevant to the present PVC/PS/PMMA blend, for which the effectiveness of these oxide nanoparticles as UV stabilizers has not been sufficiently established.