Abstract
In response to the demand for high-performance materials, epoxy thermosetting and its composites are widely used in various industries. However, their poor toughness, resulting from the high crosslinking density of the epoxy network, must be improved to expand their application to the manufacturing of flexible products. In this study, ductile epoxy thermosetting was produced using thiol compounds with functionalities of 2 and 3 as curing agents. The mechanical properties of the epoxy were further enhanced by incorporating fumed silica into it. To increase the filler dispersion, epoxide-terminated polydimethylsiloxane was synthesized and used as a composite component. Thanks to the polysiloxane–silica interaction, the nanosilica was uniformly dispersed in the epoxy composites, and their mechanical properties improved with increasing fumed silica content up to 5 phr (parts per hundred parts of epoxy resin). The toughness and impact strength of the composite containing 5 phr nanosilica were 5.17 (±0.13) MJ/m3 and 69.8 (±1.3) KJ/m2, respectively.
Highlights
Owing to their high density in crosslinking [1], epoxy thermosetting resins feature excellent mechanical properties, thermal stability, and chemical resistance
Given that a crack initiates and its tip meets the rubber particles in an epoxy composite, the stress is concentrated on the rubber particles, leading to their cavitation followed by shear deformation; the applied energy is dissipated, and the fracture toughness of the rubber-modified epoxy is enhanced [7]
Given that clusters of fumed silica aggregates were formed with increased filler content, the density in the filler-rich phase was high in NC-4; the applied energy during the tensile test was concentrated on the fillers and not transferred to the matrix, causing fracture to occur at the low elongation
Summary
Owing to their high density in crosslinking [1], epoxy thermosetting resins feature excellent mechanical properties, thermal stability, and chemical resistance. They are widely used as the materials for light-weighted composites, as well as high-performance adhesives, sealants, and coating materials in various industries from automobile manufacturing to building construction [2,3,4,5]. Despite their merits, the brittleness of epoxy resins, stemming from the dense crosslinking, impedes their application in flexible products.
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