The Reason of Spontaneous Breakage of Tempered Glass

Are you curious why tempered glass sometimes explodes suddenly? Today, let's unveil this mysterious veil!

Let’s see below the reasons:

1  Thermal stress caused glass explosion

Glass exposed to direct sunlight mainly absorbs infrared light and some visible light, which are converted into energy within the glass body, causing thermal expansion of the glass body; However, the glass part inside the aluminum frame structure cannot receive the same solar radiation, resulting in uneven heating of the glass as a whole and the formation of internal thermal stress. The thermal expansion in the middle area of the glass causes tensile stress in the glass edge region, which exceeds the tensile strength of the edge region, leading to glass fracture.

2  The influence of tempering degree

Experimental results have shown that when the degree of tempering is increased to level 1/cm, the self explosion number reaches 20% to 25%. It can be seen that the higher the stress, the higher the degree of tempering, and the greater the self explosion capacity.

3  Due to improper processing or operation, glass surfaces may have defects such as scratches, cracks, and deep edges, which can easily cause stress concentration or lead to self explosion of tempered glass.

4  The temperature gradient generated along the thickness direction of glass during heating or cooling is uneven and asymmetric.

This makes tempered products prone to self explosion upon leaving the factory, and some may experience "wind explosion" during rapid cooling. If the tensile stress zone shifts to one side or surface of the product, the tempered glass will self destruct.

5   There are stones, impurities, bubbles, and uneven thickness in the glass

Impurities in glass are the weak points and stress concentration areas of tempered glass, especially if the stones are located in the tensile stress zone of tempered glass, which is an important factor leading to spontaneous breakage.

6   Installation factors

If the installation gap is small or the glass is in direct contact with the frame, it may cause compression force on the edges or corners of the glass, leading to glass cracking, etc.

7  Nickel sulfide in tempered glass

After rapid cooling, the nickel sulfide inside tempered glass transforms from the high-temperature A phase to the low-temperature B phase, resulting in an increase in volume. The nickel sulfide molecules contained in the glass continue to move, leading to the rupture of the glass, which is a normal phenomenon within the specified range.

8  Glass thickness may also cause glass to spontaneous breakage

The selection of glass thickness is very important, considering not only wind load but also thermal stress. If the glass area is relatively large and the thickness of the glass used is small, then the glass has low resistance to bending and thermal stress, and is highly prone to self explosion.