Preparation Of Nano-SiO₂/epoxy Resin Via Reverse Microemulsion In Situ Polymerization

Epoxy resin is an important category of thermosetting resins and is widely used in applications such as adhesion and advanced composites due to its high mechanical and adhesion characteristics and good solvent and chemical resistance, together with its curability in a wide range of temperatures without the emission of volatile byproducts.But the cross-linked epoxy resin contains a large density and is fragile when impacted. Thus the toughness improvement has been paid extensive attention in fundamental researches and applications of epoxy resin. Due to surface structural effect and nano-size effect, nanoparticles have been used in the toughness improvement of polymers.In recent years, improving toughness of epoxy resin by composing with nanomaterials is an attractive point. However, there exists severe inorganic and organic phase separation in the improving process and this will remarkably affect properties of the materials. Therefore seeking a new synthesis method of nanocomposite is a hot topic. In the paper, a new synthesis method of nanocomposite by reverse microemulsion in situ polymerization was adopted, which overcomes the agglomeration and produces the high performance hybrid material.The main contents are as follows:The properties of reverse microemulsions using epoxy resin as oil phase was studied. Water solubilization is an important factor for the stability of the microemulsion and the hydrolysis of the TEOS. Thus in this chapter, the effects of surfactant type and content, ammonia concentration,surfactant/cosurfactant mol ratio and temperature on the water solubilization of the microemulsions using epoxy resin as oil phase, were systematically investigated.. The optimal preparation conditions were as follows: TX-100 was chosen as the surfactant with the weight percentage below 20%, ammonia concentration was 5wt%,surfactant /cosurfactant mol ratio was 0.3 and preparation temperature was 35℃.Based on the above microemulsion preparation condition, epoxy resin/SiO₂ nanocomposite was prepared. IR, SEM and tensile testing machine were used to characterize the structure and performance of the composite. The results revealed that the optimal mechanical properties were obtained at 3wt% TEOS content and 5wt% TX-100 content. Compared with neat epoxy resin, the tensile strength and flexural strength were 40wt% and 12wt% higher, respectively. With the increase of TEOS content, the viscosity of the composite first increases and then decreases. In addition, the transparency of the nanocomposite decreases with the increase of TEOS content.The SEM observation showed the morphology of the fracture surface was ductile fracture. For contrast, traditional sol-gel process and blending method are used to prepare nanocomposites, and their mechanical properties and dispersions are tested. It is found that dispersion of nanoparticles in nanocomposites prepared by the new method is much more satisfying than by traditional ones.Tensile test results show that tensile strength and flexural strength of the nanocomposites by the new method was the highest among the three methods.