| Silicone rubber composites are widely used in industrial,military and various complex environments due to their outstanding mechanical properties,weather resistance and thermal stability.These excellent mechanical properties depend on the interaction of the silicone rubber molecular chain and the nano-filler network.The silica?or white carbon black?as a traditional filler are widely used in the design of high performance silicone rubber composites.During the process of use,the silicone rubber filler undergoes certain structural evolutions,an d the microscopic changes such as deformation,destruction and recombination,which cause the silicone rubber composite to produce macroscopic mechanical properties such as slack,aging or fracture.This problem affecting the use of the components of the silicone rubber.However,such a network structure formed by the filler dispersion always has a non-uniform,multi-scale structure.Detecting the silicone rubber internal filler dispersion in directional method is limited by technology,so that the three-dimensional spatial dispersion structure of the filler is still unclear.Therefore,there is a need for a simple and intuitive technique for describing the fillers dispersion,which can be applied to the detection of the three-dimensional spatial silicone rubber internal filler dispersion under static or dynamic stress.This new method designed to deepen the relationship between the evolution of filler structure and macroscopic mechanical properties.The connection provides a corresponding technical means for further revealing the reinforcing effect of the filler on the silicone rubber and laid the foundation for further research on the role of reinforcing filler of silicone rubber.In this thesis,a fluorescent silane coupling agent was designed and synthesized.The surface of the SiO2 microspheres and the precipitated white carbon black were surface-fluorescent labeled by the function of chemical graft modification.The scanning electron microscopy,fluoroscopy,fluorescence spectrometry and X-ray photoelectron spectroscopy were used to analysis the modification effect.Based on the laser scanning confocal microscope and the three-dimensional reconstruction software,the non-destructive detection of the filler in the silicone rubber and the three-dimensional spatial distribution imaging of the filler were realized.The dispersion of filler,the changes of aggregate volume,the structure of the filler network,the static mechanical properties and the structural evolution under dynamic stress were analyzed.The main conclusions are as follows:?1?Through the fluorescent characteristics of rare earth ions and the properties of sensitized enhanced by organic ligands.Design a kind of di-functional ligand that can chelate rare earth ions and sensitize it to enhance fluorescence while providing coupling agent properties.The orthogonal experimental conditions were optimized for the molar ratio(MDBM:MICPTES)of 1:8,the reaction time was 6 h,the reaction temperature was 65°C,and the yield was 87%.The characteristic chemical structures of the di-functional ligand were characterized by infrared spectroscopy,nuclear magnetic resonance spectroscopy and mass spectrometry.Finally,the rare earth Eu3+was chelated to prepare a fluorescent functional silane coupling agent?Eu?DBM-Si?3?,which exhibited outstanding fluorescence performance under the optimal excitation wavelength of 395 nm,it could emit a red emission peak of 610 nm.?2?Based on the special chemical properties of SiO2 microspheres surface,the Eu?DBM-Si?3was used to react with the surface of SiO2 microspheres,which was fixed on the surface of SiO2 microspheres to present the fluorescence properties.The reaction condition of Eu?DBM-Si?3 concentration is 13%,and the reaction is 50°C for 2 h.The fluorescence intensity was optimal and a good 610 nm emission peak was still obtained in the silicone rubber.After the LSCM tomographic scanning mode and the parameters optimization of the 3D reconstruction software,the 3D reconstruction image of the filler dispersion is consistent with the traditional SEM results,which ensures the reliability of the visualization analysis.According to the visualization results of fillers three-dimensional reconstruction images,the dispersion of fluorescent SiO2 microspheres with different filling amounts of 1040 phr in the silicone rubber can be visually observed,and the size distribution of the spatial aggregates is statistically calculated.With the increase of the loading of SiO2 microspheres contents,the dispersion in the silicone rubber gradually increased.The value of aggregates volume which less than 10?m3 increased from 23.6%to 76.73%and the aggregates volume larger than 200?m3 decreased from 37.4%to 4.7.%at the same time.The increase in the content of small volume aggregates improves the interaction between the SiO2 microspheres,which increases the tensile strength of the silicone rubber from 0.14 Mpa to 0.39 Mpa.It shows that the increase of the dispersion of the filler can effectively dissipate the external mechanical energy and improve the overall mechanical properties of the silicone rubber.?3?The dispersion of precipitated white carbon black in silicone rubber and the relationship between filler network structure and macroscopic mechanical properties were studied by fluorescence labeling and three-dimensional visualization.The 3D visualization rate of the filler model that 1040 phr fluorescent white carbon black filled silicone rubber is above96.5%,which ensures the visual authenticity.Through the visual analysis,the small volume aggregates in spatial distribution is decreases with the filler loading in the silicone rubber increasing.Which the aggregate content of 1?m3 is increased from 18.10%to 45.08%.The connection rate through the filler network is increased from 39.64%to 81.33%,and the difference in storage modulus from the"Payne effect"is?E'The increase of 0.27 Mpa to2.97 Mpa.This results show that an increase in the degree of interaction between small volume fillers,which is conducive to the gradual formation of the filler network structure,so that the overall mechanical properties of the silica-filled silicone rubber are improved.At the same time,the stress state of silicone rubber is fastened through the micro-stretching device.The structure of the filler network is extended with the stress direction and broken into irregular fiber bundles.It shows that under the external mechanical force,the filler network structure effectively improve reinforcing and toughening effects of rubber.The results show that the three-dimensional visualization imaging method of filler in silicone rubber provides new technical support for studying the mechanism of filler reinforcement. |
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