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FAQs
1. What are the main properties of BOROFLOAT® 33?
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The main properties of BOROFLOAT® 33 are:
- Mirror-like surface quality
- Low linear thermal expansion
- High thermal resistance
- High chemical resistance
- Excellent transmission.
Every application has its own spectrum of requirements with regards to these various properties.
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2. Which applications can BOROFLOAT® 33 be used for today, and what markets will it be used for in the future?
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Its special physical and chemical properties make BOROFLOAT® 33 a genuinely versatile performer with a broad spectrum of uses in the following areas of application:
- Home appliances (e.g. as internal panels in pyrolytic self-cleaning ovens and vision panels in space heating appliances)
- Lighting industry (e.g. as cover panels for high-power floodlights and projectors)
- Chemical industry (linings and sight glasses for equipment)
New areas of future applications are increasingly opening up for BOROFLOAT® in:
- Biotechnology (as slides and DNA sequencers)
- Optics (filters, telescope mirrors)
- Electronics (wafers, display glass and sensors)
- Photovoltaics
- Armored glazing
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3. What is „BOROFLOAT® 33“?
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BOROFLOAT® 33 is a registered trademark of SCHOTT Company for a high quality special float glass with many possible applications. The identifier BOROFLOAT 33 is made up as follows:
"BORO" = borosilicate glass
"FLOAT" = flat glass manufactured using the float process
"33" = the thermal expansion coefficient a value,
which is 33 x 10-7 K-1
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4. What is a borosilicate glass?
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Borosilicate glass is a glass which contains a significant proportion of boric acid (boric oxide B2O3) in addition to its main component which is quartz sand (silicon dioxide SiO2). The level of the boric oxide content in the batch (the mixture of all the glass raw materials) has an equally lasting effect on the melting behavior of the glass as on all its other properties (inc. chemical resistance). In line with the wide variety of possible chemical compositions, including the addition of extra metal oxides, borosilicate glasses form a very extended family.
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5. What are the "float" and "microfloat" processes?
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The float process, which was developed and first used in practice in the 1950s, revolutionized the world of glass at the time. In the float process molten glass flows continuously from the melting tank on a bath of liquid tin. There it spreads out uniformly and then undergoes mechanical treatment to produce the required thickness. When it reaches the end of the tin bath, the glass, which has now "solidified", is removed from the surface of the metal and then annealed to relieve any internal stress. After it leaves the annealing oven the glass ribbon is cut into the required sheet sizes by an automatic cutting device.
In 1993 SCHOTT constructed the world’s first Microfloat facility for the production of BOROFLOAT® 33 in Jena (Germany).
Difference between Microfloat Process and Float Process
The difference between microfloating and floating is mainly the size of the plant.
Conventional float plants have a glass throughput of up to 1000 tonnes per day. They are used almost exclusively for the production of soda-lime glasses for use mainly for internal and external architectural glazing purposes and car windows.
A microfloat plant on the other hand has a throughput capacity of 20 to 50 tonnes of glass per day. It is used to produce special glasses such as borosilicate or alumino-silicate glasses. These differ significantly in regards to their melting properties from soda-lime glasses.
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6. What is the difference between BOROFLOAT® 33 and soda-lime float glass?
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The difference is the chemical composition:
BOROFLOAT® 33 is a borosilicate float glass with boric acid (B2O3 > 8%) as its main component in addition to quartz sand. It does not contain any alkaline earths (CaO + MgO).
Soda-lime float glass (i.e. conventional float glass or modern window glass) is a member of the alkali-alkaline-earth-silicate glass family. This glass does not contain any boron compounds. Instead it has a 12 – 16 % alkaline earth content and contains a higher proportion of alkalis (approx. 15% Na2O) than BOROFLOAT® 33.
More detailed information on the chemical composition can be found here.
Compared with soda-lime glass BOROFLOAT® 33 has
- a lower specific weight
- a higher thermal load capacity and
- a higher chemical resistance plus
- excellent transmission (= transmission of radiation, e.g. light).
BOROFLOAT® is, therefore, frequently used in special applications with extreme thermal and/or chemical demands, which conventional float glasses of the soda-lime glass family cannot cope with.
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7. What differences are there between BOROFLOAT® and PYREX®?
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a) Chemical Composition
BOROFLOAT® 33 and PYREX® 7740 differ as regards their chemical composition in the alkali ratio of Na2O to K2O and in their content of so-called oxidic minor components and impurities. These result from both the mineral composition of the raw materials and also the method of preparing the batch.
An oxidic minor component of this type is ferric iron oxide (Fe2O3), which reduces transmission in the ultraviolet range of the light. BOROFLOAT® 33 has only a third of the Fe2O3 content of PYREX® 7740. It therefore looks significantly more colorless than PYREX and is categorized as a high quality colorless glass.
b) Manufacturing Process
BOROFLOAT® 33 is manufactured using the Microfloat process. This process guarantees an excellent mirror-like surface quality.
PYREX® 7740 is manufactured by rolling and casting respectively which results in a slightly textured surface. For some applications, therefore, it requires additional surface polishing.
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8. How resistant is BOROFLOAT® 33 to high temperatures, thermal shock and temperature differences?
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BOROFLOAT® 33 is very heat resistant with a long-term (= 10 h) temperature loading capacity of 450 °C and a short-term (< 10 h) temperature loading capacity of 500 °C.
Because of its low thermal expansion it can easily withstand thermal shocks of 125 K - 175 K (depending on the glass thickness) and temperature differences of 90 K (1 - 100 h) and 80 K (> 100 h) respectively.
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9. What factors have an influence on its impact resistance?
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The impact resistance of BOROFLOAT® 33 is dependent, in addition to many other parameters, on the following factors:
- The way the glass is fitted
- Size and thickness of the glass
- The way it has been processed or worked (e.g. edge working, holes)
- The wear and tear the glass has suffered in use
- The type of impact
It is not possible to make any definite statement on impact resistance without knowledge of the specific use and fitting.
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10. What thicknesses and sizes of BOROFLOAT® 33 can be supplied?
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The spectrum of thicknesses available in BOROFLOAT® 33 ranges from 0.7 mm to 21.0 mm.
The standard sheet size for all thicknesses is 1150 x 850 mm. In addition a larger sheet size of 2300 x 1700 mm can be supplied in the 3.3 to 15.0 mm range of thicknesses. The 16.0 to 21.0 mm thicknesses can also be supplied in the larger 1700 x 1300 mm size.
Further details can be found here or supplied on request.
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11. What methods of working can be used for BOROFLOAT® 33?
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BOROFLOAT® 33 can be worked with all the usual methods used for glass (e.g. cutting, arrissing, grinding, polishing and drilling). In line with the glass-specific properties of BOROFLOAT® 33 special tools are required to cut it to size. Supplementary laser and water jet supported cutting plus ultrasonic drilling are also available.
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12. What methods of processing are there?
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Various methods of processing can be used for BOROFLOAT® 33 such as coating and semi-toughening:
a) Coating
Coating with composite materials can be used to vary the specific properties of BOROFLOAT® to match the requirements of a particular application. This increases its functionality:
- BOROFLOAT® M: with reflective coating
The application of appropriate interference layers (e.g. metal oxides) results in the part of the radiation of visible light responsible for the reflection being semireflected particularly well (reflection wanted).
- BOROFLOAT® AR: with anti-reflective coating
The application of appropriate interference layers results in the part of the radiation responsible for the reflection being reduced (reflection largely prevented).
Coated BOROFLOAT® 33 is supplied in the 3.3 mm thickness and 1150 x 850 mm sheet size. We will be happy to provide information about other thicknesses and sizes plus information about other coatings upon request.
b) Thermal Semi-Toughening
The resistance of BOROFLOAT® to thermal and mechanical loads is improved by thermal semi-toughening.
Thermal semi-toughening is possible in thicknesses from 3.3 to 15 mm. The maximum sheet size is 3000 x 1800 mm and the minimum edge length is 300 mm. We will be happy to provide information about thicknesses and sizes at any time on request.
BOROFLOAT can also be imprinted, sandblasted and bent. We will be happy to provide detailed information on request.
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13. How can I clean BOROFLOAT® 33?
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BOROFLOAT® glass can be cleaned with any commercially available glass cleaner. Under no circumstances should abrasive sponges, scouring powders or other corrosive or abrasive cleaners be used, as these can cause damage to the surface of the glass.
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14. How should BOROFLOAT® 33 be fitted?
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- When sizing frames and panels the different thermal expansions of BOROFLOAT® and the various frame materials plus any possible manufacturing tolerances must be taken into account.
- If it is necessary for design considerations to use compression fixing of the glass in the frame, this pressure must be applied uniformly all around the edge of the panel (no uneven pressure).
- The glass must be fitted in non-distorting frames. If it is not possible to avoid a small amount of torsion, a suitable permanently elastic gasket must be used to prevent the torsion in the frame being transferred to the glass.
- There must be no direct contact between glass and metal (or any other hard element of construction). Permanently elastic, heat-resistant materials (e.g. mineral fiber materials) are recommended as an intermediate layer between glass and metal.
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15. Where can I purchase "BOROFLOAT® 33"?
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Sales of BOROFLOAT® 33 are coordinated from SCHOTT Technical Glass Solutions GmbH in Jena (Germany). There is a closely linked network of sales companies and agencies worldwide to ensure optimum attention to customers’ requirements on a local basis.
Please send inquiries to:
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SCHOTT Technical Glass Solutions GmbH Otto-Schott-Strasse 13
07745 Jena
Germany
 | +49 (0)3641/681-4686 |
 | +49 (0)3641/28889-241 |
Home Tech
SCHOTT North America, Inc. 5530 Shepherdsville Road
Louisville, KY 40228
USA
| | +1 (502)6574417 |
| | +1 (502)9664976 |
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Contact
SCHOTT Technical Glass Solutions GmbH
Otto-Schott-Strasse 13
07745 Jena
Germany |
| +49 (0)3641/681-4686 |
| | +49 (0)3641/28889-241 |
E-mail
More contacts
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