Epoxy/silica nanocomposites and benefit of a gelatin interface on nanocomposite properties

Strong interfacial adhesion between phases is needed for most effective enhancement of mechanical properties. Epoxies reinforced with silica microparticles is well studied, but silica nanoparticle-reinforced studies are fewer, and many of those used commercial-grade surface-modified silica nanoparticles commercially available since 2002. Those nanoparticles appear to rely on silanol groups for bonding, but only small increases in tensile modulus, even at high nanoparticle loading, are found. Silica nanoparticles (ca. 20 nm) prepared in the presence of gelatin yield amine-rich surfaces. When added at 3 wt% to epoxy a 127% increase in tensile modulus was found. Composite fracture surfaces show generally uniform, nanoparticles (ca. 20 nm) but with occasional aggregates (ca. 100-250 nm). SEM showed many features that are associated with increased toughness but no particle cavities indicating excellent interfacial adhesion. Silica nanoparticles with amine-rich surfaces may be superior to silanol surfaces for interfacial bonding, and can be achieved using low-cost gelatin.