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Chemical composition and physical properties of high borosilicate glass
Borosilicate glass is a special type of glass with excellent heat resistance and chemical stability, widely used in laboratory vessels, optical equipment, medical devices, and other fields. Its unique properties stem from its special chemical composition and microstructure.
1、 Chemical composition
The main components of high borosilicate glass include:
Silicon dioxide (SiO ₂) (70-80%) – forms the glass network skeleton, providing mechanical strength and chemical inertness.
Boron oxide (B ₂ O3) (10-15%) – reduces thermal expansion coefficient and enhances resistance to sudden temperature changes.
Sodium oxide (Na ₂ O) and potassium oxide (K ₂ O) (5-10%) – used as fluxes to lower the melting temperature.
Trace additives (such as Al ₂ O3, CaO) – further improve chemical stability and mechanical properties.
Compared with traditional soda lime glass, high borosilicate glass has significantly increased boron content, giving it unique physical properties.
2、 Core physical characteristics
Ultra low thermal expansion coefficient (3.3 × 10 ⁻⁶/℃)
Only one-third of ordinary glass, it can withstand sudden temperature changes from -30 ℃ to 400 ℃ without breaking.
After direct heating and immersion in ice water, it remains intact (such as in the rapid cooling and heating experiment of laboratory beakers).
Excellent chemical stability
Acid and alkali resistant corrosion (except hydrofluoric acid and hot concentrated phosphoric acid), non reactive with most chemical reagents.
Widely used to hold strong acids (such as concentrated sulfuric acid), organic solvents (such as acetone), etc.
Excellent mechanical performance
The Mohs hardness reaches 6.5, and the scratch resistance is better than that of ordinary glass.
The bending strength is more than twice that of soda lime glass, and it is more resistant to mechanical impact.
Optical and Thermal Properties
Transmittance>92% (visible light range), suitable for optical instruments.
The thermal conductivity is 1.2 W/(m · K), and the temperature distribution is more uniform during heating.
3、 Why are these features important?
Laboratory safety: Temperature resistance to prevent containers from bursting due to sudden temperature changes.
Long term stability: Chemical inertness ensures that experimental data is not contaminated by containers.
Economy: The service life can reach more than 5 times that of ordinary glass.
High borosilicate glass achieves a perfect balance of strength, heat resistance, and chemical stability through precise composition ratios, making it an irreplaceable material in modern science and industry.
