Factors influencing the photochemical behavior of multicomponent polymeric materials

The study of photo-degradation and stabilization of polymers has an extremely importance from academic, economic and environmental point of view and a better understanding of the mechanism of degradation and correlation between weathering external factors, such as wavelength and irradiation dose, temperature and humidity, and chemical, physical and mechanical effects that they induce are the primary requisites to control the stability and ensure long life of the final product. Although the study on the chemistry of interactions between various constituents (including the polymer itself and the presence of impurities, fillers, antioxidants, photo-stabilizers, dyes, pigments, nucleating agents, flame retardants, and other additives such as catalyst residues) in polymer-based composites exposed to sunlight radiation has attracted a large scientific effort during the last few decades, the changes that occur at molecular level and the degradation kinetics have not been thoroughly elucidated. To predict the photo-damage to a certain formulation under solar UV radiation is still challenging because composite materials are typically exposed to multiple environmental variable during service. While individual degradation variables can lead to formation of chromophores and initiate the photo-degradation mechanism, their combinations may have unknown synergistic or antagonistic effects. This article review sets out to discuss the influence of the primary environmental parameters, i.e., light, heat and moisture, and the polymer structure and chemical make-up of the polymeric composites on fundamental photo-degradation processes. Each of the variables is briefly examined and examples of polymeric material degradation reported by scientific studies during the last two decades are given.