Research on the improvement of the performance of composite materials by new fumed nanosilica "Rubber Technology" Li Qin
Under the same preparation conditions with the same optimal addition amount, silica enhances the mechanical properties of silicone rubber. After being reinforced with the optimal amount of pure fumed silica, the tensile strength and tear strength of silicone rubber are. In the reinforcing effect of new silica on silica gel, the tensile strength and tear strength after silica reinforcement are improved and the elongation at break is improved respectively compared with fumed silica. The reinforcing effect is similar to that of fumed silica, but its elongation at break is increased.
Combined with the microscopic characterization of nanosilica, its enhancement mechanism is analyzed. Nano-silica prepared by the pure gas phase method can form hydrogen bonds with the oxygen atoms on the polymer chain because of the hydroxyl groups on its surface, and combine with the matrix to achieve enhanced effects. However, due to the high surface energy of the nanoparticles, the agglomeration phenomenon is more serious. Moreover, the interface compatibility between inorganic particles and organic matrix is not good, and even if a silane coupling agent is added, the enhancement effect is extremely limited. Due to the in-situ modification of the surface of nanosilica particles, the surface energy of the particles is greatly reduced and matches the surface energy of silicone rubber. The two have good compatibility, a large degree of infiltration, and a large interaction area between matrix macromolecules and nanoparticles. The remaining hydroxyl groups on the surface of the nanoparticles can better interact with the oxygen atoms on the polymer chain in the form of hydrogen bonds, which offsets the fine dispersion and surface effects of the nanoparticles caused by the reduction in the number of hydroxyl groups, making the particles adsorbed. The increase in polymer chains increases the interaction with silicone rubber. When subjected to external force, the entire system is evenly stressed, so it has a better reinforcing effect on silicone rubber.
Nanoparticle-reinforced silicone rubber may have two reasons
The coating of organic components on the surface of the nanoparticle-like chain makes it better dispersible in the polymer system, increasing the remaining hydroxyl groups and the polymer The oxygen atoms in the chain have the opportunity to form hydrogen bonds to enhance the effect
The good compatibility and chain distribution of the particles and the matrix enable the nanochains and polymer chains in the composite system to be intertwined, and the organic network and inorganic The networks intersect with each other, and the composite system has both the strength of inorganic materials and the toughness of polymer materials, showing a stronger reinforcing effect.
In addition, the new silica shows superior elongation at break compared to fumed silica. This is mainly because the inorganic particle network structure of fumed silica nanoparticles is strong, which affects the relative slip motion of the polymer chains and limits the elongation at break of the material. The addition of fillers with better compatibility between new silica and matrix has little effect on the relative slip of the polymer chains. Better slip of the polymer chains increases the elongation at break of the system.
The dispersion state of fumed silica is obviously dispersed in silica gel with the help of a coupling agent. The particles are not dispersed as primary particles, and the dividing line between the agglomerate and the matrix is relatively clear, which shows the compatibility of the nanoparticles and the matrix. not good. Nano-silica has good dispersion, most of which reach the primary particle level. The particles and matrix have good compatibility, which is similar to the previous analysis results. The dispersion of nano-silica in the matrix and the compatibility in the matrix are the best. The quality of compatibility can well explain the respective enhancement effects.
The new nano-silica can be well dispersed in silicone rubber without adding coupling agent, and can have a good reinforcing effect. Compared with the system adding coupling agent, the tensile strength, tear strength and elongation at break are greatly improved. The reinforcing effect of the system is equivalent to that of fumed silica, but the processing performance of the mixed rubber is greatly improved.
Because the chain structure of nanosilica forms a structure in which the inorganic network and the organic polymer network are intertwined and intertwined in the system, it has a great effect and prevents the directional arrangement and crystallization of the polymer chain at low temperatures. The reinforced composite material can maintain good elasticity in low temperature environment. Due to their good interfacial compatibility with the matrix, nanosilica particles can be dispersed relatively finely in the system, even reaching the primary particle level, which allows the enhancement effect of nanoparticles to be fully exerted.
The morphological structure of nanosilica and the compatibility of inorganic particles and organic polymer matrix have a great influence on the reinforcing effect of silicone rubber.
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