Surface Chemical Transformations of UV Irradiated Silica-Epoxy Nanocomposites

摘要

Silica nanocomposites (SiNCs), which are silica nanoparticles (SiNPs) incorporated into a polymeric matrix, are used in a wide variety of commercially available products for numerous applications. Environmental factors, such as light, may modify the SiNCs during their lifetime of service, giving rise to the possibility of degradation leading to SiNP release. Ultimately, light-induced modifications are most likely to occur at the SiNC-air interface, which suggests that surface transformations will play a major role in the potential release of SiNPs throughout the lifecycle of this material. To better understand these surface transformations, we investigated the impact of high intensity simulated solar radiation (290 nm to 400 nm) on the surface and bulk properties of SiNCs created from unmodified SiNPs. Surface spectroscopic analysis (XPS) was employed to understand the chemical transformations that occur as a result of UV-aging of SiNCs. Results demonstrate that UV-induced transformations of SiNCs occurred via photo-oxidation of the epoxy matrix resulting in a subsequent loss of polymeric material and surface enhancements in the silicon and nitrogen concentrations.