Study On Physical Mechanism Of SiO₂ Reinforced Silicone Rubber Based On Synchrotron Radiation 3D Nano Imaging And Neutron Scattering Technology

Rubber matrix nanocomposites have become the research focus and hotspot in the field of materials science and engineering,with a high industrial application background and scientific research value,due to thier excellet propertied.The filler network structure in the rubber matrix nanocomposite system is an important factor that affects the processing performance of the compound and the dynamic and static mechanical properties of the vulcanizate.However,due to the intrinsic complexity of filler network and the restriction of analyzing technologies,up to now,the research on the filler network has been indirect or semi-quantitative characterization,and it has impossible to establish a precise and quantitative relationship between the microstructure of the filler network and the macroscopic performance of the composite system.Based on the above research background,this paper uses the advantages of small-angle neutron scattering?SANS?and synchrotron radiation X-ray nano-computed tomography?Nano-CT?techniques in large field of view to analyze the aggregation morphology of filler,the formation of filler network and the relationship between its structure and the degree,content and surface characteristics of filler in silica/silicone rubber composite system.The purpose is to disclose the filler network and corresponding reinforcement mechanism of filler reinforced rubber.The main work is as follows:?1?In summary,we have proposed a synergistic analysis strategy,based on in operando rheology,SANS and Nano-CT measurements to schematically explore the filler networks and corresponding reinforcement mechanism of silica with different structure degrees.Highly structured silica could effectively adsorb and immobilize the rubber molecular chains,retarding the dynamics behavior of rubber to generate more bound rubber.Moreover,highly structured silica showed shorter particle-particle distance and thicker bound layer,which leaded to more effective bridges between aggregates,hence forming stronger and more steady filler networks.Such superior filler network structure could efficiently transmit and release the stress of the external field,providing an outstanding reinforcing effect on silicone rubber.?2?Study the network structure formed by different fractions of silica filler in the silicone rubber system and its reinforcement effect.The results of the study show that when?_si<30phr,the filler aggregates are mainly dispersed in the form of isolated discontinuous in the matrix,and its reinforcing effect on the rubber matrix is mainly described by the volume filling effect.With the increase of filler content,the average particle size and distance of silica aggregate decreased,and the density and connectivity of filler network increased gradually.When the?_si?40 phr,the filler network which can bear the stress is formed.The formation of the filler network is the main reason for the remarkable improvement of the mechanical properties of the silicone rubber composite.?3?By changing the content of hydroxyl groups on the silica surfaced,two kinds of silica/silicone rubber composite systems with interface strength were designed.The low-field solid-state NMR comparison was used to study the adsorption of the filler in the two composite systems on the rubber molecular chain.It was found that the reduction of hydroxyl groups on the surface of silica weakened the interface attraction between silica and silicone rubber.Nano-CT was used to visually observe the changing rules of the three-dimensional space-connected filler network and network structure during loading-unloading in the two composite systems.It is found that the failure rate of packing aggregate and packing network in the composite system with weak interface attraction is higher under tensile action.After unloading,only the filler network structure destroyed in the composite system with strong interface attraction can be reconstructed and restored to the state before loading.The above study confirmed that a dynamic reversible bond can be formed between the silicon hydroxyl group on the surface of silica can and silicone rubber,which enhances the binding ability between silica and silicone rubber matrix,and the reversible binding between filler and silicone rubber can effectively dissipate the mechanical energy,and ultimately improve the mechanical properties of the composite.