Float glass

0.25-5 usd/kg
Circularity potential
Very high
Strength
Medium
Production energy
Low
Stiffness
High
Embodied CO2
Low
Density
Medium

Float glass is soda lime glass produced as flat sheet, which can be further processed by bending, strengthening and laminating. It is named after the method of production: molten glass is floated on a pool of liquid tin to produce a perfectly flat and smooth sheet.

Its technical strength is far higher than its practical strength. Glass is very brittle and any imperfections (scratches or flaws, for example) act as a stress concentrator, causing premature failure when even a relatively small amount of tension is applied, such as by bending. So even though the theoretical strength is in the order of GPa, tiny imperfections reduce the strength down to around 14 MPa. The mechanical properties are enhanced with strengthening and tempering, which can raise tensile strength to 40 and 70 MPa, respectively.


Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products
Low circularity potential


Laminated glass is a composite of glass sheets with plastic interlayers, bonded under heat and high pressure. For standard glazing applications, polyvinyl butyral (PVB) is the most common interlayer type. Other types include ethylene vinyl acetate (EVA), thermoplastic polyurethane (TPU), and cast resins such as polyurethane (PU), acrylic (PMMA) and epoxy. The major advantage of laminated glass is that when broken, the pieces are held together by the plastic interlayer. As a result, it is used for automotive windscreens (windshields). For the same reason, it is used for added safety and security in buildings, such as doors and windows.

As well as providing added safety, the plastic interlayer may be coloured or printed, to enhance the colour or ultraviolet filtering properties of the glass. It can also be used to provide added acoustic insulation.


Design properties
Cost usd/kg
1-3
Embodied energy MJ/kg
20-25
Carbon footprint kgCO2e/kg
3.4
Density kg/m3
2490
Tensile modulus GPa
70
Tensile strength MPa
14-70
Shear modulus GPa
28.5
Hardness Mohs
5.5
Poissons ratio
0.22
Thermal expansion (µm/m)/ºC
8.8
Melt temperature ºC
1000
Thermal conductivity W/mK
1
Temperature min-max °C
-40 to 150
Thermal
insulator
Electrical
insulator