Glass raw materials are more complicated, but can be divided into main raw materials and auxiliary raw materials according to their functions. The main raw materials constitute the main body of the glass and determine the main physical and chemical properties of the glass. The auxiliary raw materials give the glass special properties and bring convenience to the production process.
1. The main raw materials of glass
(1) Silica sand or borax: The main component of silica sand or borax introduced into the glass is silicon oxide or boron oxide, which can be melted into the main body of the glass during combustion, which determines the main properties of the glass, and is called silicate glass or boron accordingly. Salt glass.
(2) Soda or Glauber's salt: The main component of soda and Glauber's salt introduced into glass is sodium oxide, which can form a fusible double salt with acidic oxides such as silica sand during calcination, which acts as a flux and makes the glass easy to shape. However, if the content is too large, the thermal expansion rate of the glass will increase and the tensile strength will decrease.
(3) Limestone, dolomite, feldspar, etc.: The main component of limestone introduced into the glass is calcium oxide, which enhances the chemical stability
and mechanical strength of the glass, but too much content will cause the glass to collapse and reduce the heat resistance.
Dolomite, as a raw material for introducing magnesium oxide, can improve the transparency of glass, reduce thermal expansion and improve water resistance.
Feldspar is used as a raw material to introduce alumina, which can control the melting temperature and improve durability. In addition, feldspar can also provide potassium oxide to improve the thermal expansion performance of the glass.
(4) Glass cullet: Generally speaking, not all new raw materials are used when manufacturing glass, but 15%-30% cullet is mixed.
2, auxiliary materials for glass
(1) Decolorizing agent: Impurities in the raw materials such as iron oxide will bring color to the glass. Soda ash, sodium carbonate, cobalt oxide, nickel oxide, etc. are commonly used as decolorizing agents. They appear in the glass to complement the original color, so that The glass becomes colorless. In addition, there are color reducing agents that can form light-colored compounds with colored impurities. For example, sodium carbonate can oxidize with iron oxide to form iron dioxide, which makes the glass change from green to yellow.
(2) Coloring agent: Some metal oxides can be directly dissolved in the glass solution to color the glass. For example, iron oxide can make glass yellow or green, manganese oxide can be purple, cobalt oxide can be blue, nickel oxide can be brown, copper oxide and chromium oxide can be green, etc.
(3) Refining agent: The clarifying agent can reduce the viscosity of the glass melt, and make the bubbles generated by the chemical reaction easy to escape and clarify. Commonly used clarifying agents include white arsenic, sodium sulfate, sodium nitrate, ammonium salt, manganese dioxide and so on.
(4) Opacifier: Opacifier can make glass become milky white translucent body. Commonly used opacifiers are cryolite, sodium fluorosilicate, tin phosphide and so on. They can form 0.1-1.0μm particles, which are suspended in the glass to make the glass opaque.
Post time: Apr-13-2021