Mechanical properties and fracture toughness of fumed silica epoxy composites containing glycidyl terminated polysiloxanes

Abstract

Nanocomposites have received much attention as construction materials, adhesives, and sealants because of the strong interfacial interactions between nano-sized fillers and matrix. However, dispersing the nano-sized fillers in the polymer matrix is challenging because of their tendency to agglomerate. In this study, a glycidyl terminated polysiloxane (g-PDMS) was synthesized and used to disperse fumed silica (nano-sized silica aggregates) in a BPADG/D230 system. The kinetic parameters of the g-PDMS/BPADG/D230 curing were obtained through non-isothermal DSC analysis. The apparent activation energy and reaction order of the epoxy resin/D230 system were calculated to be 51.82 kJ/mol and 0.91, respectively. Next, the effect of fumed silica on the properties of the nanocomposites was investigated. Compared to neat epoxy, the maximum strength, Young's modulus, fracture toughness and fracture energy of the nanocomposite with 5 phr (parts per hundred parts of epoxy resin) fumed silica were increased by 27%, 61%, 76% and 79%, respectively. Lastly, the fracture toughening mechanisms of the nanocomposites were examined using SEM images of the fractured surfaces of single-edge notched specimens after a three-point bending test.