The reason of thermal cracking of coated glass
There is no rupture of the coated glass under normal use, and most of the rupture of the coated glass belongs to thermal stress cracking. In the strong sunlight, the glass absorbs the radiant energy in the sun, converts it into heat energy in the glass body, so that the part of the glass is relatively heated and is in the state of thermal expansion. The glass edge in the aluminum frame structure can not be affected by the same solar radiation Or shadow effect, uneven heat dissipation, resulting in the uneven distribution of the overall temperature of the glass, resulting in internal thermal stress, thermal expansion of the glass area of the glass edge of the tensile stress, the tensile stress beyond the border area tensile strength, will lead to glass rupture, which Kind of phenomenon called glass thermal stress rupture.
As the coated glass heat absorption is more significant, the difference between the absorption of solar radiation energy caused by greater glass temperature difference, thermal stress cracking more. In contrast, for the window, the curtain wall of the coated glass occurs this phenomenon more than for the hidden wall. In the following, the characteristics, causes and prevention of thermal stress rupture of coated glass are further discussed.
1, the characteristics of thermal stress rupture: broken line and the edge of the glass at right angles, from the glass edge or corner began to occur, and from the glass or corner about 50mm split into two or more, the shape of irregular twists and turns, Extends in the middle, and usually forms an arc in the middle of the glass.
2, coated glass body absorption: the glass after coating processing, the chemical properties of the basic no change, but its physical properties have greatly changed, especially optical and thermal properties. Coated glass on the solar radiation energy absorption rate is much larger than ordinary transparent glass and body coloring glass, the general coated glass solar radiation energy absorption rate is ordinary transparent glass, body stained glass several times, so under the same conditions of use, coated glass Endotherm is much more than ordinary glass, the temperature is much higher, that is, the temperature difference between the different parts of the glass is much larger. Therefore, for the coating of these advantages of the glass, in the installation process, to take different measures than ordinary glass to ensure the safe use of coated glass.