| As one of the most widely used thermosetting resins, epoxy resin has many kinds of advantages. Therefore, it becomes one of the irreplaceable materials and plays the important roles in many industrial areas, such as electrics, aerospace, watercraft and so on. However, due to viscosity of the resin glue, it is difficult to satisfy the requirement which it is used in microelectronic packaging and composites processing. What's more, some drawbacks of epoxy limit its application, such as high stress, brittleness, poor heat resistance, and high thermal expansion coefficient. Commonly we use reactive diluents to improve the process performance of epoxy resin, and they can participate in the curing reaction, and finally become one part of cross-linked cured resin structure, so they don't have much effect on the properties of cured resin. Polymer/inorganic nanocomposites combine the advantages of the inorganic materials (rigidity and high thermal stability) and the organic polymers (flexibility, dielectric, ductility and processability), so they are widely used. Nano-silica, with its high thermal stability, rigidity and modulus, is one of the most commonly used inorganic components in organic/inorganic nanocomposites, which has positive effect on many properties of polymers, such as heat-resistance, mechanical properties and so on.This paper firstly uses butyl ether (660), ethylene glycol diglycidyl ether (669) and phenyl glycidyl ether (690) reactive diluents to modify epoxy resin. The results show that, the three kinds of diluents can improve the process performance and toughness of resin, but they will reduce resin's mechanical strength; 660 could reduce the heat-resistant of resin, while 669 and 690 can increase it; Three kinds of diluents have little effect on the dielectric properties of resin, and only the resin which added 660 has lower dielectric loss tangent; The addition of 660 has little effect on the arc resistance of resin, and 669 and 690 can significantly increase resins' arc resistance, especially when the content of 690 is 3% and 6%, the arc resistance can reach to 94s and 93s, which increased by 22% and 20% compared with pure resin. When the content of 690 continues to increase, the arc resistance of resin declines and retains around 84s. According to analyzing various performances, we find that the properties of resin which added 690 are better than other two resins.Following, epoxy/silica nanocomposites are prepared by chemical mixing method, and the structure and properties of nanocomposites are analyzed and discussed by SEM, XRD and mechanical, thermal, electrical test. The results shows that nano-SiO2 particles are distributed in resin as amorphous state, and have the covalent bond union with resin after they are organize treated; Nano-SiO2 can improve the materials'mechanical properties, heat resistance and electrical properties. The material has best performance when the nano-SiO2 content is 5%, in which the initial decomposition temperature is 18.5℃higher than pure resin, the dielectric constant increase by 22% to 3.58, the arc resistance is stable around 113s and increase 47% than pure resin when the content of SiO2 is higher than 5%.Finally, epoxy/diluents/silica nanocomposites are prepared. The performance research shows that the property changes don't have much regularity, because 690 and nano-SiO2 have different effect on the properties of nanocomposites. In general, the mechanical properties of nanocomposites are better than pure resin and the resin is only modified by diluents, but can't compare with epoxy/silica nanocomposites. The tensile strength is the maximum 77.91MPa when the 690 and nano-SiO2 content is both 9%; The thermal resistant of nanocomposites is higher than the resin which is only mosified by 690 or nano-SiO2. The initial decomposition temperature is 367.8℃and is 35.5℃higher than pure resin(332.3℃); The addition of two materials can improve the arc resistance of nanocomposites, but has little effect on dielectric constant, and increase the dielectric loss.
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