Flexural stress effect on mechanical and mechanochemical properties of soda lime silicate glass surface

As a means to elucidate the mechanical stress effect on the durability of soda lime silicate (SLS) float glass, a thin glass plate under flexural stress was investigated with X-ray photoelectron spectroscopy (XPS), specular reflectance infrared (SR-IR) spectroscopy, nanoindentation, and tribo-testing. A lab-built four-point bending rig was employed to create compressive or tensile stress (around 40 MPa) on the air-side surface of SLS glass. XPS analysis showed that electric field-induced sodium ion migration is greatly enhanced in both compressive and tensile stress surfaces. The SR-IR analysis of the Si-O-Si stretch mode revealed that the structural distortion of the silicate network appears to be larger under compressive stress than tensile stress. The elastic and plastic responses of the SLS surface to nanoindentation were significantly altered under the flexural stress conditions even though the magnitude of the flexural stress was less than 0.7% of the applied indentation stress. Compared to the stress-free surface, the resistance to mechanochemical wear at 90% relative humidity deteriorated under the compressive stress condition, while it just became more scattered under the tensile stress condition. Even though the applied flexural stress was very small, its impact on chemical and structural properties could be surprisingly large. Combining all results in this study and previously published works suggested that the changes observed in nanoindentation and mechanochemical wear behaviors may be associated with the strain in the Si-O bonds of the silicate network.