Borosilicate glass , also borosilicate glass , or borosilicate glass is a very chemical and temperature-resistant glass that is mainly used for glass devices in laboratories, chemical process engineering and in the household . The good chemical resistance to water, many chemicals and pharmaceutical products ( hydrolytic class 1) is explained by the boron content of the glasses. The insensitivity to sudden temperature fluctuations is a result of the low coefficient of thermal expansion of around 3.3 × 10 −6 K −1 .
Borosilicate glass was first produced in 1887 by the German chemist and glass technician Otto Schott .
Borosilicate glass is made of
- 70% to 80% silicon dioxide (SiO 2 )
- 7% to 13% boron trioxide (B 2 O 3 ).
- 4% to 8% alkali oxides ( sodium oxide Na 2 O; potassium oxide K 2 O)
- 2% to 7% aluminum oxide (Al 2 O 3 )
- 0% to 5% alkaline earth oxides ( CaO , MgO , ...)
The name of the glass group is derived from the two components with the largest proportions.
The mechanical, optical and chemical properties of borosilicate glasses are similar. The properties of Duran are given here as an example .
|Refractive index for orange light (587 nm)||Significantly lower than flint glass|
|Abbe number||This is a typical crown glass|
|density||Around 10% lighter than window glass .|
|Modulus of elasticity|
|Relative dielectric constant||For f = 1 MHz at T = 25 ° C|
|Coefficient of thermal expansion||About 40% of the value of window glass|
|Thermal conductivity||Similar to cement|
|Specific heat capacity|
|Maximum working temperature|
|Glass transition temperature|
Borosilicate glass is almost inert to most chemicals . The abrasion of the glass is very small, but not zero. There are test methods according to: ISO 720 (hydrolytic resistance), ISO 695 (alkali resistance) and DIN 12116 (acid resistance). It is attacked by long-term exposure to hydrofluoric acid , concentrated, hot phosphoric acid and concentrated alkalis such as caustic soda .
For reasons of classification, borosilicate glass can be roughly classified into the following groups according to its oxide composition (in proportions by weight). Significant amounts of silicon dioxide (SiO 2 ) and boron oxide (from 8% B 2 O 3 ), which act as glass formers , are characteristic of borosilicate glasses . The amount of boron oxide influences the glass properties in a certain way. In addition to the highly resistant types (B 2 O 3 up to a maximum of 13%), there are others that have only a low chemical resistance (B 2 O 3 content over 15%) due to the different structuring of the boron oxide in the structure network . Therefore a distinction is made between the following subtypes.
- Alkaline earth-free borosilicate glasses (borosilicate glass 3.3)
The B 2 O 3 content in borosilicate glass is usually between 12… 13% and the SiO 2 content over 80%. The high chemical resistance and low thermal expansion of 3.3 · 10 –6 K −1 - the lowest expansion of all commercially available glasses for extensive technical applications - make it a versatile glass material. High-quality borosilicate flat glasses are used in a large number of branches of industry, mainly for technical applications that require either good heat resistance, excellent chemical resistance or high light transmission in combination with a flawless surface quality. Other typical areas of application for various forms of borosilicate glass are glass tubes, glass tubing, glass containers, etc., which are used in particular in the chemical industry.
- Alkaline earth borosilicate glasses
In addition to a SiO 2 content of around 75% and 8… 12% B 2 O 3 , these glasses contain up to 5% of alkaline earths and aluminum oxide (Al 2 O 3 ). This is a subtype of somewhat softer glasses (comparable to borosilicate glass that does not contain alkaline earth), which has thermal expansions in the range of 4… 5 · 10 –6 K −1 .
- Borosilicate glasses with high boric acid content
Glasses that also contain B 2 O 3 and 65… 70% SiO 2 as well as small amounts of alkalis and Al 2 O 3 have lower softening points and low thermal expansion. Fusion adaptation to tungsten-molybdenum alloys as well as high electrical insulation are the most important properties of these glasses. The increased B 2 O 3 content reduces the chemical resistance; In this respect, the borosilicate glasses differ largely from the alkaline earth free and alkaline earth containing borosilicate glasses. The glasses with a high boric acid content also include borosilicate glasses, which are permeable to UV radiation up to 180 nm and combine the best properties of borosilicate and quartz glass.
Borosilicate glass according to DIN 7081 is used in longitudinal sight glass fittings.
Borosilicate glass is the carrier substance for the inert storage of radioactive waste. In the melting process, glass mass and radioactive substance are mixed and filled (for example at Eurochemic in Mol (Belgium) until 1974, vitrification facility Karlsruhe (Germany) until 1990, Atelier Vitrification Marcoule in the Marcoule nuclear plant (France) until 1999, La Hague reprocessing plant in La Hague ( France) until today, Sellafield at Seascale (UK) until today).
Borosilicate glass is offered in slightly different compositions under different trade names:
- Borofloat from Schott , a borosilicate glass that, like window glass , is cast into flat panes in a float process .
- BK7 from Schott, a borosilicate glass with particularly high purity. The main areas of application are lenses and mirrors for lasers, cameras and telescopes.
- Duran from DWK Life Sciences , similar to Pyrex, Simax or Jenaer Glas.
- Fiolax from Schott; The main areas of application are containers in medicine.
- Ilmabor from TGI (2014 bankruptcy); The main areas of application were vessels and devices in laboratories and for medicine.
- Jenaer Glas from Zwiesel Kristallglas , formerly Schott AG. The main area of application is kitchen ware.
- Pyrex from Arc International Cookware , formerly Corning ; The main area of application is kitchenware, formerly also laboratory containers.
- Rasotherm from VEB Jenaer Glaswerk Schott & Genossen was widely used as technical glass.
- Simax from Pegasus Industrial Specialties or Kavalier Glaswerke , similar to Pyrex or Jenaer Glas.
- Willow Glass is an alkali-free, very thin and flexible borosilicate glass from Corning .
- Suprax by Schott (manufactured by Auer Lighting), a borosilicate glass for lenses, collimators, reflectors and sight glasses.
- DURAN properties.html , data sheet for Duran.
- Technical glasses: physical and chemical properties
- Containerglass. ACI Industriearmaturen, accessed on January 31, 2020 .
- Flow sight glass type 530. ACI industrial valves , accessed on January 31, 2020 .
- Longitudinalglass type 330. ACI Industriearmaturen, accessed on January 31, 2020 .
- Simax Borosilicate Glass 3.3 at pegasus-glass.com.
- Simax glass mass: Technical Information at simax.com.