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Borosilicate Glass |
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All Prodcuts manufacturer by Tensil brand products listed in this catalogue are manufactured from borosilicate glass (unless otherwise specified). |
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Standards |
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Borosilicate glass which meets the specifictions of the following standards: |
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| BS ISO 3585, DIN 12217 |
Type 3.3 borosilicte glass |
| ASTM E-438 |
Type 1 class A borosilicate glass |
| Us Pharmacopoeia |
Type 1 borosilicate glass |
| European Pharmacopoeia |
Type 1 glass |
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Chemical composition |
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Borosilicate Glass has the following typical composition
(per centage by weight): |
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| SiO2 = |
80.6% |
| B2O3 = |
13.0% |
| Na2O = |
4.0% |
| Al2O3 = |
2.3% |
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Physical properties |
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| Coefficient of Expansion (20oC - 300oC) |
3.3 x 10-6 K-1 |
| Density |
2.23 g/cm3 |
| Refractive index (Sodium D line) |
1.474 |
| Dielectric Constant (1MHz, 20oC) |
4.6 |
| Specific hear (20oC) |
750J/KGoC |
| Thermal conductivity (20oC) |
1.14WmoC |
| Poisson's Ratio (25oC - 400oC) |
0.2 |
| Young's Modulus (25oC) |
6400 kg/mm2 |
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Chemical resistance |
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Borosilicate glass has a very high resistance to attack from water, acids, salt solutions, halogens and organic solvents. It also has a modereate resistance to alkaline solutions. Only hydrofluoric acid, hot concentrated a phosphoric acid and strong alkaline solutions cause appreciable corrosion of the glass |
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Hydrolytic resistance |
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For many applications it is important that laboratory glassware has a high hydrolytical resistance; e.g. during sterilisation procedures, where repeated exposure to water vapour at high temperatures can leach out alkali ions. Borosilicate glass has a relativerly low alkali content and consequently a high resistance to attack by water. It meets the following standards (determined by the glass grain method).
Hydrolytic resistance according to ISO 719 (98oC) - class 1
Hydrolytic resistance according to ISO 720 (121oC) - class 1
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Acid resistance |
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Glasses rich in silica are less likely to be attacked by acids. Borosilicate glass has approximaterly 80% silica and is execptionally resistant toacids (except hot concentrated phosphoric acid and hydrofluoric acid). The acid resistance borosilicate glass meets the requirement of ISO 1776 and class 1 requirements of DIN 12116. |
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Alkali resistance |
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Alkaline solutions attack all glasses and borosilicate glass can be classified as reasonably resistant. The alkali resistance of borosilicate glass meets class 2 requirements as defined by ISO 695 and DIN 52322. |
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Temperature resistance |
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Borosilicate glass has excellent thermal properties due to its high softening point and low coefficient of expansion (3.3 x 10-6 K-1). The maximum recommended working temperture for glassware manufactured from borosilicate glass is 500oC (for short periods of time only). Special care should be taken at tempertures above 150oC to ensure that both heating and cooling are achieved in a slow and uniform manner. |
