Fluorescent Labeling Of Silica Filler Network In Silicone Rubber And Its Application

In silica reinforced silicone rubber,the synergistic effect between polymer chain network and filler network results in better mechanical properties.The current network of inorganic fillers and its associated macro mechanical properties,remain in some of the phenomenological description.Therefore,it is necessary to explore simple,intuitive and authentic ways to characterize the filler network structure,and study its evolution law under stress,so as to reveal the reinforcing mechanism of inorganic nanoparticles in rubber and provide technical support for the selection of various silica modification methods and the design of high-performance filler silicone rubber.In this paper,SiO₂ was fluorescently labeled by physical adsorption and chemical grafting,and its structure and performance were analyzed.Then chemical grafting method was selected to label silica,which was used to fill in silicone rubber to prepare fluorescent silicone rubber,and laser scanning confocal microscope?LSCM?technology was used to realize the visualization of the filler network structure in silicone rubber matrix,and the effects of silica content and bound rubber content on the mechanical properties and network structure of silica rubber were studied.The specific research conclusions are as follows:?1?The structure and properties of fluorescent SiO₂ were analyzed by scanning electron microscope?SEM?,transmission electron microscopy?TEM?and fluorescence spectrophotometer.The particle size of SiO₂ increased after fluorescence labeling,among which the physical adsorption method increased by 5%and the chemical grafting method increased by 15.8%.Under the monitoring of the wavelength of 610 nm,the excitation wavelength of both was around 360 nm,indicating the success of fluorescence labeling.The fluorescence SiO₂ prepared by the physical adsorption method can maintain good fluorescence performance at 270?and in the buffer solution with pH=8-12.The fluorescence performance of SiO₂prepared by the chemical grafting method can still be detected at 300?.Under the optimum condition for visual,physical adsorption method of fluorescence labeling SiO₂ microspheres surface organics content is 5.62%and chemical grafting method fluorescent labeling SiO₂ surface organics content is 2.29%,respectively,which shows that chemical grafting method presented minimal impact on the surface of SiO₂structure.Therefore,chemical grafting method was used for fluorescent labeling of silica in the following experiments.?2?The mechanical properties and filler network structure of fluorescent silicone rubber was analyzed by using solid rheometer?DMA?,LSCM and three-dimensional reconstruction software?Avizo?.The experimental results showed that the filler visualization rate in silicone rubber is above 90%,which guarantees the authenticity of filler visualization.The statistic results show that the size of silica aggregates varies little under different content of filler.With the increase of the content of filler from 10to 60,the network connection rate from 23%to 60%,the filler network structure gradually improved,the corresponding fluorescent silicone rubber 100%tensile strength increased from 0.84 MPa to 3.57 MPa,the fracture energy increased from339.8 J/m² to 18962.5 J/m²,and the mechanical properties gradually increased.Comparing the network connection rate with the tensile energy,it can be seen from that the fillers filled with the silicone rubber filler network form a percolation filler of30 parts each.?3?The effects of bound rubber on mechanical properties of silicone rubber were studied by LSCM,scanning probe microscope?SPM?and DMA.The experimental results show that the network connection rate is 60%-68%,the visualization rate is more than 90%,and the filler network structure changes rarely.With the increase of the storage time of the mixed rubber from 1 day to 45 days,the content of the bound rubber in the fluorescent silicone rubber increased from 22%to 27%,and the corresponding 100%tensile strength increased from 2.71 MPa to 3.90 MPa.Therefore,the research on the visualization of filler network structure by fluorescent labeling shows that the 100%tensile strength of silicone rubber increases with the increase of the storage time of the mixed rubber,but this process does not cause the change of packing network structure.