Various Components of Compositional Security Glass
Exterior Glass Plys
Tempered Glass (TG)
Heat Strengthened Glass (HSG)
Chemically Strengthened Glass (CSG)
Sometimes referred to as flat glass or float glass. Commonly called soda lime glass. Soda lime glass is optically clear and very flat.
However, it breaks very easily upon impact (as its M.O.R., modulus of rupture, is only around 5,000-6,000 PSI) and produces sharp pieces.
This type of glass is a safety glass (not to be confused with a security glass) and is very hard to break. It has a M.O.R in the area 36,000 PSI.
When used alone as a single ply in a window opening, this glass will “dice” into small cubes when broken.
Thus, eliminating the possibility of a person being cut by a shard of glass as it falls out of the window.
However, architecturally, house design and security applications require vision as well as safety. Laminated TG has three drawbacks:
1. When it is broken, it will dice into small cubes through the entire lite but remain in place adhered to the other ply(s).
The visibility through this lite will be greatly reduced as the break pattern of the tempered glass will affect the entire lite.
2. TG also has a great deal of distortion due to the manufacturing process. During the heating and cooling process the surface
of tempered glass is put under tension and compression thus producing a roll wave distortion of wavy images.
3. TG will have warpage when compared to annealed glass. The warpage makes the product more prone to delaminate.
HEAT STRENGTHENED GLASS
This glass is produced using the same manufacturing process that is used to produce TG.
The difference is that the HSG is not subjected to the heating and cooling process for as long period as TG. Thus laminated HSG will perform differently than TG in 4 ways.
1. HSG will have distortion but to a lesser degree than TG.
2. HSG will warp but to a lesser degree than TG.
3. HSG when laminated will have a more localized break pattern (better visibility).
4. HSG has less tension and compression in the surface of the glass when compared to TG, which means the M.O.R.
(modulus of rupture), is 12,000-15,000 PSI, significantly lower than TG. When subjected to incidental impact HSG will break more.
CHEMICALLY STRENGTHENED GLASS
Soaking annealed glass in salt a bath produces Chemically Strengthened Glass.
The ion exchange that takes place on the surface of the glass strengthens the glass significantly. This enhances the performance of this glass in several ways.
1. CSG is as optically clear as annealed glass since there is no heating and cooling process to instill roll wave distortion in the glass.
2. CSG will be as flat as annealed glass (no warpage to affect the lamination process).
3. CSG when laminated will have a localized break pattern for better visibility.
4. CSG has a high M.O.R. (modulus of rupture). It is close to that of TG 28,000 to 30,000 P.S.I.
This means that when CGS is subjected to incidental impact it will not break as readily has HSG.