Spontaneous Glass Fracture
Examination of damaged tempered glasses using SEM/EDX

The properties of glass are not merely influenced by their chemical composition. The production method itself can also have an impact on the produced glass. So-called tempering can significantly increase the impact resistance compared to normal flat glass. During the tempering process, the glass is heated to over 660 ° C. This special glass is the so-called single-pane safety glass. Tempered single-pane safety glasses are often used for particularly demanding tasks such as horizontal storage. However, sometimes, even years after installation spontaneous cracks and fracture can occur in tempered glass. The optical image of a spontaneous fracture already provides the glass expert with valuable information about the cause of the damage. However, a clear determination of the cause usually requires more precise analyses of the damaged tempered glasses using techniques such as SEM/EDX. Tascon has been analyzing glass for over 20 years and is regularly confronted with the damage caused by spontaneous glass fracture. In addition to the pure analysis, we also accompany you in legal disputes and make our expertise available.

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Spontaneous Glass Fracture
Detection of particle composition

Spontaneous fracture can often be recognized by their appearance, the so-called butterfly effect. Figure 1 shows the optical image of such a butterfly effect. In the center of the picture, a particle inclusion is visible as the starting point for the spontaneous fracture.

A closer examination of the particle using scanning electron microscopy (SEM, figure 2) provides information about its diameter (approx. 200 µm) and morphology. In addition, the differences in brightness clearly visible in the backscattered electron image (figure 2) demonstrate a material contrast between the particles and the toughened glass.

Bilder des DefektsThe areas marked in the backscattered electron image were therefore used to determine the elemental composition of particles and glass more precisely with energy dispersive X-ray

The areas marked in the backscattered electron image were therefore used for the more precise determination of the elemental composition of particles and glass by means of energy-dispersive X-ray analysis (EDX). Figures 3a and b show the results of this analysis. The clear Ni and S signals show that nickel sulfide is the main component of the particle. Nickel sulfide particles can be introduced into glass panes through contaminations in the glass melt. Due to phase transformations and thermal expansion, these particles can lead to stresses and, in the worst case, are able to fracture glass panes even after years. In order to avoid such glass fractures after installation, modern toughened safety glass panes are subjected to a so-called hot storage test before they are delivered. Panes that pass this test show a significantly reduced probability of spontaneous fracture later. Nevertheless, the combined SEM-EDX analysis in the example above clearly identified the damage mechanism of the spontaneous glass fracture. This made the subsequent settlement of the damage considerably easier.

Tascon - your partner for the analysis of spontaneous glass fracture

Have you been affected by spontaneous glass fracture and want to get to the bottom of the incident? Then Tascon is the right address: We support you in discussions with customers and suppliers. We also offer expert statements in the event of legal disputes. Get in touch with Tascon and get advice today without any obligation.

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