Soda-lime glass

Soda-lime glass, even soda-lime glass, soda lime silicate glass, soda-lime glass or normal glass is the most common type of glass and belongs to the group of alkali Erdalkalisilikatgläser. It is the typical ground glass is used for manufacturing container glass, flat glass. For clear differentiation from hard glass (crystal glass) soda-lime glass is also known as soft glass. It has good chemical properties and is suitable for products that must withstand a usually short term chemical exposure and limited thermal stress (eg pipettes, culture tubes ).

Manufacturing and composition

Soda-lime glass is prepared by adding silica sand, soda and lime are melted together at about 1,200 ° C. This results in a silicate glass, whose main components are silicon dioxide ( SiO2, 71-75 %), sodium oxide ( Na 2 O, 12-16 %) and calcium oxide is formed ( CaO, 10-15%) is. In addition, other components may also be present which influence, for example, the color of the glass or its sensitivity to glass corrosion. The glass is in comparison to special glasses little resistance: acids and alkalis mainly attack the surface of soda-lime glass, and even water dissolves small amounts of glass components out of the surface. A criteria for the chemical resistance of a soda-lime glass is the ratio of silica to sodium oxide and calcium oxide. The composition should be as the formula

Correspond to the s indicates the number of moles of silica, and n is the molar ratio of sodium to calcium oxide. The chemical structure of soda-lime glass resembles a silicate network, whose bound states, but not the long-range order with the crystalline state are comparable.

Properties

Soda-lime glass has a density of about 2.5 g/cm3.

The thermal expansion coefficient of soda-lime glass is 9:10 -6 / K. It is therefore sensitive to fluctuations in temperature. Uneven heating occur in the glass on voltages that can lead to breakage. Therefore, soda-lime glass is not used in applications where temperature changes occur (eg in laboratories ).

Depending on the thickness of the glass transmittance of normal glass is 83-90 %. The thermal conductivity of soda-lime glass is 0.8 to 1.05 W / ( m · K). The refractive index is between 1.5 and 1.6.

The mechanical properties of glass and products made from it must be adapted for many applications. The security requirements in the construction and especially the automotive industry led to the development of toughened glass, an invention of the French glass company Saint- Gobain, which in 1930 applied for a patent. This so-called safety glass bursts excessive stress in a number of small fragments, which are comparatively harmless.

Use

Soda-lime glass is quantitatively the most important type of glass dar. It forms the basis for the production of bottles, food packaging, drinking glasses and flat glass (eg, mirror and window glass).

Soda-lime glass is used in some areas, especially in the automotive industry, as laminated safety glass, which was invented in 1909 by French chemist Edward Benedictus, by joining two pieces of glass by an intermediate layer of resin to a glass laminate.

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