Preparation And Characterization Of Epoxy/Nano-Silica Hybrid Materials

Polymer/inorganic nanocomposites have attracted extensive research interests due to their unique properties. The nanocomposites combine the advantages of the inorganic materials (rigidity, high thermal stability and unique optical, electronic and magnetic properties) and the organic polymers (flexibility, dielectric, ductility and processability). They can even bring some special properties, which is different with the single material and conventional composite materials. Nano-silica is one of the most commonly used inorganic components in organic/inorganic nanocomposites, which has positive effect on heat-resistance, mechanical properties and so on. Epoxy resin is one of the most widely used thermosetting resins. It has several useful properties such as good adhesion & insulation property, excellent chemical corrosion resistance, low shrinkage, high tensile strength and modulus, and low cost. Therefore, epoxy resin becomes one of the irreplaceable materials and plays the important roles in many industrial areas, such as electrics, manufacture, corrosion resistance, aerospace, watercraft, etc. However, some drawbacks of epoxy limit its application, such as high stress, brittleness, poor heat resistance, and high thermal expansion coefficient.Based on the background and requirements above, epoxy/nano-silica hybrid materials are studied in this paper. We try to improve the compatibility and enhance the interfacial interactions between silica and the epoxy matrix, in order to increase the thermo-mechanical properties and toughness of epoxy, and obtain the epoxy/nano-silica hybrid materials with high performance of heat-resistance and toughness. The work can be divided into the following two aspects:(1) Epoxy/silica hybrid materials filled with various amounts of GPTMS and nano-silica are prepared, using DDS as curing agent, through a process that combined the advantages of both sol-gel and nanoparticle mixing to enhance the interfacial interactions between nanoparticles and polymer matrix. Thermo-mechanical properties, such as storage modulus and tanδ, thermal stability and thermal expansion coefficient of the resulting hybrid materials are studied by means of Fourier-transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The results indicated that the introduction of GPTMS not only improve the compatibility between silica and the epoxy matrix but also increase the cross-linking density of the epoxy system; meanwhile the nano-silica further reinforce the inorganic network of the hybrid system. Consequently, a kind of heat-resistant epoxy/silica hybrid material can be prepared which has the potential for electronic packaging application.(2) Poly(methyl methacrylate) is grafted from the silica surface by the method of atom transfer radical polymerization (ATRP), and a kind of core-shell particles with uniform inorganic core and well-defined polymer shell is prepared, which is mixed with the epoxy resin to form nanocomposites. The tensile strength, tensile fracture energy, storage modulus, glass transition temperature and thermal decomposition temperature of the hybrid materials are studied by means of scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Various preparation conditions, such as size of the silica particles, quantity and molecular weight of PMMA, are studied. The results indicated that the PMMA grafted silica particles can improve the toughness of the cured epoxy, which can be explained by the crack pinning mechanism and crack bridging mechanism. The tensile strength and fracture energy increase with the addition of PMMA grafted silica, meanwhile the thermo-mechanical properties and thermal stability show few changes, which is better than rubber and thermoplastic toughening.