|Bending Strength||120-200 N/mm2|
|Thermal Shock Resistance||Up to 250 Degree C|
|Mechanical Strength||Four to five times stronger than annealed glass|
|Tensile Strength||65 MPa|
|Surface Compression||Greater than 95 MPa|
|Design Stress for Architectural Purposes||50 MPa|
|Fragmentation||Small round crystals|
|Conducive for Processing||Cannot be cut after Toughening|
Toughened is glass that has undergone processes of controlled thermal treatment to increase its strength.
Toughened glass is made from annealed glass that has been heated to approximately 650C and then rapidly cooled. Due to the increased heat treatment and rapid cooling of the glass, especially between the surface and the inside of the glass, the treatment produces different physical properties. This results in compressive stress on the surface and improved bending strength of glass.
Before toughening, the glass must be cut to size or pressed to shape. This is because once it is toughened, it cannot be re-worked on. Toughened glass is widely used in a number of applications.Characteristics of Toughened Glass
- Toughened glass is four to five times stronger than annealed glass of the same size and thickness against impact.Toughened glass has higher thermal strength and can withstand a high temperature differential upto 250 DegreeC.Toughened glass is considered as safety glass. It is difficult to break and even in the event of a breakage, disintegrates into small globules, which are relatively harmless.
- Toughening does not alter the basic characteristics of glass such as light transmission and solar radiant heat properties.
- After heat treatment, the surface of toughened glass has the same resistance to surface damage as annealed glass.Toughened glass cannot be cut, drilled or altered.
- Heat soak test is recommended to be carried out on Toughened glass that is used for overhead and horizontal application, to prevent the spontaneous breakage caused due to nickel sulphide inclusion.
Strength & Safety Considerations
- Toughening increases tensile strength, thermal shock resistance and safety of normal glass. It also increases its heat withstanding capacity. Because of these properties, toughened glass is preferred in applications where strength, safety and thermal resistance are significant.
- Four to five times stronger than annealed glass
- Two to three times stronger than heat strengthened glass
- Fragments into small, relatively harmless pieces, reducing the likelihood of injury