Question

why do Borosilicate glass have a very low coefficient of thermal expansion compared to other type of glasses?

Answer 1

Answer :Thermal expansion is the tendency of matter to change its shape, area, and volume in response to a change in temperature. The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of thermal expansion. Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. It contains substantial amounts of silica (SiO₂; 70–80 wt%) and boron oxide (B₂O₃>8%). Borosilicate glass have low coefficient of thermal expansion (≈3 × 10⁻⁶ K⁻¹ at 20 °C). This means it will not crack under extreme temperature changes like regular glass. Its durability has made it the glass of choice for high-end restaurants, laboratories and wineries. Silicon dioxide is the glass former in the borosilicate glass system. Thanks to this, borosilicate glass has the ability to go straight from a freezer to an oven rack without cracking. For you, this means you can pour boiling hot water into borosilicate glass if you wanted to say, steep tea or coffee, without worrying about shattering or cracking the glass. Higher levels of SiO₂ increase the melting temperature as well as the working point, and reduce the coefficient of thermal expansion. Besides presence of boron trioxide also have effects on the behaviour of glass and makes it thermal shock resistant. This allows the glass to resist extreme changes in temperature.