| In some application environment,silicone rubber has faced the combined effects of irradiation,temperature,humidity and vibration shock for a long time,resulting in its performance degradation and even functional failure.In this paper,we focus on silica-filled silicone rubber,gamma rays were used to irradiate silicone rubber and fillers,the interaction between fillers and polymer matrix were studied.Furthermore the modification methods and mechanisms of silica were also investigated,using a variety of characterization techniques to analyze the structure and properties of the silicone rubber and silica.The main work and conclusions of this paper are as follows:(1)The changes of paramagnetic materials in silica-filled silicone rubber under gamma irradiation were studied.The results show that the EPR signal in silica-filled silicone rubber are mainly caused by silica.The concentration of the paramagnetic materials of silicone rubber is positively correlated with the amount of filler and the absorbed dose.When the absorbed dose is less than 100 kGy,the concentration of the paramagnetic ruaterials is linearly related to the absorbed dose.When it exceeds 100 kGy,the concentration of the paramagnetic materials become saturation.(2)The changes of paramagnetic materials in nano-silica after irradiation and the reaction of irradiated silica grafted with methyl silicone oil were studied.Electron paramagnetic resonance spectroscopy(EPR)results show that the paramagnetic materials in nano-silica induced by the radiation in holes and electrons,and they are more stable and have higher concentration than those irradiated in the atmosphere of air.The paramagnetic materials can react with oxygen in air inducing the decrease of the concentration,and at the same time increasing the temperature will also accelerate the quenching rate of the paramagnetic materials.After adding methyl silicone oil which chemical structure is similar to that of silicone rubber to the irradiated nano-silica,it was found that the complex viscosity of the irradiated nano-silica system was significantly higher than that of the unirradiated system,and it was more difficult to get precipitate by centrifugation,indicating that methyl silicone oil was grafted onto the silica particles.This result verifies that when silica is used as filler,its radial paramagnetic materials will react with the silicone rubber.Infrared spectra results showed that-CH3 and Si-C peaks appeared in the silica system after irradiation,indicating that methyl silicone oil was successfully grafted onto the surface of silica particles.Through transmission electron microscopy(TEM),it can be seen that there is a small amount of aggregation or even mono-dispersion among the particles in silica after irradiation,indicating that methyl silicone oil is grafted on the particle surface,which improves the dispersibility of silica.(3)The changes of irradiated silica filled silicone rubber were studied.The tensile results show that after the silica is filled into the silicone rubber,the elongation at break of the silicone rubber composite increases with the increase of the absorbed dose of the silica,which significantly improves the phase between the filler and the polymer matrix.In the early stage of irradiated silicone rubber,polysiloxane is broken to generate free radicals to undergo cross-linking reactions.When the absorbed dose is increased to a certain extent,the brittleness of silicone rubber increases.Thermogravimetric results show that the addition of irradiated silica to silicone rubber can increase the thermal stability of silicone rubber.This study is of great significance to the chemical changes of silica as a filler under irradiation and the interaction mechanism between filler and the polymer matrix,and it can also provide some technical support for the life evaluation in the radiation aging of silicone rubber. |
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