Effect of fluorescence labeling on mechanical properties of silica filled silicone rubber

The Silica filler has been successfully fluorescently labeled by bifunctional silane coupling agent and europium nitrate through chemical grafting method. The thermal weight loss of the labeled silica at 200 °C was 1.75%, which was lower than 3.57% before labeling. This indicated that the labeled material had good thermal stability below 200 °C, and the water content of the labeled filler decreased due to its reduced hydrophilicity on the surface of the filler. Polysiloxane was filled with labeled or unlabeled silica which had different filler loading levels (from 10 phr to 60 phr) by diluted mixing on the purpose of investigating effect of fluorescent labeling on the mechanical property of rubber composite. According to the results of laser confocal microscope 3D imaging and software calculation, the network connection rate increased from 23% to 60% with the increase of filling amount. When the filling contents are more than 40%, the mechanical properties of unlabeled silica filled silicone rubber decrease slightly, while the mechanical properties of labeled silica filled silicone rubber almost remain unchanged, which is related to the increase interaction of filler and matrix through organic functionalization on the surface of the latter. However, the influence trend of fillers on mechanical properties of the two systems is basically the same. Fluorescent labeled silica is expected to be an effective tool for the correlation between microstructure and mechanical properties.