Characterization Of Micro Dispersion And Reinforcement Mechanism Of Nano-SiO₂ Filled Silicone Rubber

The organic-inorganic hybrid characteristics of silicone rubber molecular chain endow it with excellent high and low temperature resistance and aging resistance,but its mechanical strength is insufficient.After reinforcement by filler network composed of nanoparticles,its mechanical strength can be increased by tens of times.These excellent mechanical properties are derived from the synergistic effect of nanofiller network morphology and filler / polymer adhesion.Although many theoretical and experimental studies have studied the prominent enhancement effect of filler network and its interaction with silicone rubber molecular chain on the mechanical properties of silicone rubber,people still lack understanding of its mechanism and quantitative description of the enhancement effect.One of the main obstacles is the lack of quantitative characterization technology for the three-dimensional network morphology formed by complex nano-filler networks in silicone rubber matrix and the corresponding theoretical model for quantitatively describing the contribution of filler network structure and bonding force to the enhancement effect.In this paper,the contribution of fillers to filler-filler interaction and filler / silicone rubber interface interaction on the properties of materials under ideal monodispersity was studied based on the monodisperse silica filling system with simple distribution structure,and it was used as the basis for explaining the microscopic reinforcement mechanism of complex polydisperse silica system.Furthermore,the precipitation silica filled silicone rubber system was taken as the research object,and the real three-dimensional image of its dispersion and aggregation structure in silicone rubber was obtained by combining fluorescence labeling with laser scanning confocal and laser scanning confocal microscopy.The microstructure evolution of nano-particle aggregates caused by the increase of filler volume fraction was quantitatively described,and the enhancement mechanism of the aggregation filler network with complex distribution formed by a large number of nano-particles on rubber was studied.The Mermet-Guyennet equation was modified by introducing the quantitative parameters describing the dispersion of nanofillers into the reinforcement model.A reinforcement prediction model of nano-composites based on volume fraction,particle shape,interaction and filler dispersion was established,and then the filler / polymer interface force was adjusted by temperature change.It was further proved that the model can quantitatively describe the filler network and its interaction with the molecular chain.The main results are as follows :The reinforcing effects of hydrophilic monodisperse silica S200 and hydrophobic monodisperse HS200 on silicone rubber with high and low phenyl contents were studied.Monodisperse spherical silica can be uniformly dispersed in the silicone rubber system by strong shear,so in addition to the ' strain amplification ' effect caused by the filling volume,the main enhancement is mainly reflected in the particle size and interface strength.The results show that the Mermet-Guyennet equation can well describe the enhancement effect of monodisperse spherical silica.The calculated interfacial force parameters are only(5 ? 6)?m,and the interfacial interaction of each enhancement system is very weak.Rare earth europium was used to label the surface hydrophilic precipitated silica T36-5,and the fluorescent labelled silica reinforced silicone rubber was prepared with high and low phenyl silicone rubber as the matrix.Two phenyl silicone rubbers that were the same as those in the first part were used as the matrix.The variation law of the three-dimensional dispersion structure of the filler with the increase of the filler content was studied by fluorescence labeling-laser scanning confocal microscopy.The corresponding relationship between the characteristic parameters of the filler particle structure and the change of the filler content was quantitatively analyzed,and the evolution process of the filler from isolated distribution to self-agglomeration was revealed.Finally,the filler was connected to each other to form a network.Based on the Mermet-Guyennet equation,the dispersion of filler was introduced into the reinforcement model of T36-5 filled silicone rubber system with complex dispersion state,and a prediction model of composite reinforcement based on volume fraction,particle shape,interaction and dispersion of filler was established.The calculation results show that in the nanofiller network with high order aggregation structure,the force parameters between the nanofiller network and the molecular chain reach millimeter level,which is two orders of magnitude higher than that of the monodisperse system,which is the main internal mechanism of the nanofiller network to realize its outstanding reinforcement effect.In the dynamic amplitude scanning test,the influence of filler / polymer interaction under small strain deformation was studied by this model,and the Arrhenius equation was fitted to verify the temperature dependence of interfacial interaction and its key role in the thermodynamic effect of polymer materials.Finally,the quantitative evaluation equation of the thermodynamic behavior of filler / polymer interface interaction strength under the given system was obtained.