Effect of nano TiO2 particle size on mechanical properties of cured epoxy resin

Mechanical properties of toughened epoxy resin with two nano particles sizes of TiO2 (17 nm and 50 nm) at different weight fractions (1%, 3%, 5% and 10%) were investigated and compared to that of submicron particles at 220 nm. The composites were characterized by tensile, flexural, pull-off and abrasion tests, followed by X-ray photoelectron spectroscopy and scanning electron microscopy of the fracture surfaces. The investigated epoxy depicted high performance epoxy systems formulated with low molecular weight epoxy resin and diethyltoluenediamine as a curing agent.Results indicate an enhancement in the epoxy composite mechanical properties due to the addition of small fraction of TiO2 particles. Highest tensile stress values were found at 3 wt.% for 17 nm and 50 nm particles and at 5 wt.% for 220 nm particles. The maximum flexural properties were found at lower TiO2 fraction of 1 wt.% only. The flexural behavior of the epoxy composite was not improved by further addition of the filler. The enhancement of modified epoxy with the smaller nano particles size showed a better resistance to weight loss. It is suggested that the amount of particles present and its size affect the matrix deformation and as a result, the quality of interface in the composite. A relation between tensile and flexural stress as function of the toughened particle size was found.