Circularity potential
Low
Strength
Medium
Production energy
Medium
Stiffness
High
Embodied CO2
Medium
Density
Medium

The addition of just 5-15% of boron – in the form of diboron trioxide (B2O3) or boric acid, (BH3O3) – to a silicate glass improves its mechanical properties, resistance to temperature and thermal shock, electrical resistivity, and resistance to chemicals. Borosilicate glass is not so straightforward to manufacture as soda lime glass, and more expensive, but has become irreplaceable in many applications, such as labware, heat-resistant cookware, solar panels and E-glass fibre for composites. It has superior strength compared to soda lime glass. It doesn’t break so easily when dropped – and when properly made without residual stresses can resist surprisingly high impacts – and can bounce off the floor.

It consumes around half of all boron mined each year. Boron is reasonably expensive – 2-5 usd/g compared to silica sand at around 0.00025 usd/g – which raises the cost of the glass compared to soda lime. While it is consumed in much less significant quantities, partly because it is more expensive, its use in glass fibre for reinforcing composites is unrivalled in terms of volume.


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


Borosilicate glass is available in many standard formats. It is blown and pressed into products, much like soda lime glass, from a molten gob. Alternatively, it is supplied as extruded tube, rod, sheet, or as a bead. Its importance in lampworked labware promotes the supply of a range of sizes and extruded profiles, which can be worked by hand to make instruments, vessels and containers. The same techniques are used to make tableware and light shades, for example. Products made from these materials are very durable and as a result can have much thinner wall sections (lighter weight) than is possible with soda lime glass.

Borosilicate glass has become known by trademark names, such as Duran, Simax and Pyrex (although the Pyrex consumer brand no longer uses borosilicate glass in North America). Tableware, vacuum cups and mugs (thermos), and cookware used in domestic and commercial settings has become iconic, partly because it is so long lasting.


Design properties
Cost usd/kg
3-5
Embodied energy MJ/kg
27-45
Carbon footprint kgCO2e/kg
1.6-2.5
Density kg/m3
2230
Tensile modulus GPa
51-64
Tensile strength MPa
80
Compressive strength MPa
900-950
Hardness Mohs
6
Poissons ratio
0.21
Thermal expansion (µm/m)/ºC
3.3
Melt temperature ºC
1252
Thermal conductivity W/mK
1.1
Temperature min-max °C
-250 to 500
Thermal
Electrical