Preparation and Characterization of Bis-GMA/TEGDMA/Clay Nanocomposites at Low Filler Content Regimes

Photo-curable polymer/clay nanocomposites have been prepared using Bis-GMA/TEGDMA (50/50 wt%) and modified as well as unmodified clays at different loading levels < 10 wt%. The dispersion state of the clay layers has been studied using wide-angle X-ray diffraction and transmission electron microscopy as the key factor affecting the properties of the final cured nanocomposites. Photopolymerization induced volume shrinkage and double bond conversion percent was determined using density measurement techniques and Fourier transform infrared spectroscopy in order to verify the opacity of the clay filler on polymerization characteristics. Mechanical properties (flexural strength, flexural modulus, and diametral tensile strength) of the photo-cured nanocomposites were also evaluated according to standard test methods provided for materials with dental application. The results showed that the exfoliation or intercalation of the layers play to be the key factor on polymerization features and the mechanical properties of the final nanocomposites. The dispersion state is determined, first, to be dependent to the compatibilization level of the clay and secondly to its content in the composition. Experiments carried out by thermogravimetric analysis revealed also the thermal property dependence to relative abundance of exfoliated/intercalated layers.