Heat treated glass is also known as 'tempered' or 'stress-treated' glass. It is the result of a process that involves increasing the melting point of the raw material to more than double its initial value and then subjecting it to heat treatment to modify its physical properties. Tempered glass includes many different types such as shatterproof, fire-resistant, and medical/food/drug safety glasses. In recent years, due to the increased use of thermal coatings on all kinds of manufactured goods, including windows, dishes, tableware, toys, automotive, and household goods, there are now many 'tempered' glass products available in the market. This article aims at describing the different types of heat-treated glass to help potential buyers in making an informed buying decision.
Heat treated glass is a special category of toughened (also called 'strengthened') glass that undergoes a specific process that causes it to develop a high sheen. It is used for the manufacturing of thermal stress proof window panes and partitions. Heat-strengthened glass is also known as 'Float glass' (in common parlance, this term is often incorrectly termed as 'faceted glass') because it is formed into shapes (typically, oblong or triangular) by stretching the raw glass during the heat-strengthening process. The end result is a glass product with higher strength and wear resistance.
High Performance Laminated Glass: This is one of the two highest quality glasses (along with Thermoplastic) that can be classified under the category of heat treated glass. Thermoplastic refers to glass that has been specially manufactured to be more durable, less prone to cracking, and with better resistance to impact and thermal shock. Thermoplastic is usually low-melting glass, which is not as tough as heat treated glass. However, Thermoplastic does exhibit superior strength. Because the heat-strengthened glasses are laminated glass that is formed on a production line, the strength possessed by thermoplastic is superior to that possessed by other glass types.
Heat treated glass and thermoplastic are similar, yet very different in composition. Standard glass is primarily composed of B-clusion (a type of hydrogen bonding), in addition to other chemical elements such as vanadium, silicon, boron and iron. It is typically an oxide. Heat treated glass is typically made from a combination of these materials with other additional structural features. It is mixed with a lubricating agent, such as silicon hydroxyapatite (or silicon carbide) or an oil base such as methyl acrylate or ethylene propylene glycolate.
Thermoplastic and heat treated glass may have different compositions; however, both glass materials exhibit excellent electrical and optical properties. Typically, heat tempered glass may display greater hardness than standard glass, but it is still brittle. Additionally, heat toughened glass may crack more easily, although this is balanced by the relative ease in breaking the material. Standard glass tends to fracture rather easily when forced. This means that a company using standard glass may be at a slight advantage in some instances.
When it comes to strength, both types of glass are superior to annealed glass. Standard glass may not crack as easily, however, it does not develop the mechanical strength that heat treated glass does. Annealed glass develops mechanical strength during heating, which helps to increase the overall strength of the material. Heat Treated Glass does not achieve this level of development. However, the product overall is stronger than annealed glass due to a significant increase in toughness and the development of small pores in the crystalline structure through which the energy utilized during heating breaks down the bonds between the atoms.
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