Pyrex glass thermal shock

Soda-lime glass Borosilicate glass 70 SiOj, 10 CaO, 15 Na O 80 SiOj, 15 BjOj, 5 NajO Windows, bottles, etc. easily formed and shaped. Pyrex cooking and chemical glassware high-temperature strength, low coefficient of expansion, good thermal shock resistance. 

Borosilicate glass (known by several trade names, including Pyrex) is used for chemical plant as it is stronger than the soda glass used for general purposes it is more resistant to thermal shock and chemical attack. 

Furnace tubes made from a number of mullite and zircon compositions were used by the author. For other tubes, an alumina of low sodium content and in another anhydrous alumina were used. These compositions gave excellent seals to Pyrex 7740 glass. A number of the seals have been in use for over a year and have been subjected to many thermal shocks. The seals themselves are clear, free from gas, and of good strength. 

Chemical insensitivity. A large number of ceramics are stable in both harsh chemical and thermal environments. Pyrex glass is used widely in chemistry laboratories specifically because it is resistant to many corrosive chemicals, stable at high temperatures (it does not soften until HOOK), and is resistant to thermal shock because of its low coefficient of thermal expansion (33 x 10 K ). It is also widely used in bakeware. 

The cheapest form is soda-glass, which is brittle and sensitive to thermal shock, but borosilicate glass, for example Pyrex or Hysil, is stronger and has a greater resistance to thermal shock. It has a wide range of application as pipes, valves, heat exchangers, and small vessels. It enables several acids to be handled in the same pipeline and has the added advantage that, since it is transparent, the interior of such equipment is clearly visible. 

Of the three commonly available types of glasses, borosilicate (Pyrex-type) glasses appear to be the most satisfactory. They combine the properties of good electrical resistance, resistance to thermal shock, and mechanical... 

For pharmaceutical packaging, borosilicate glasses are preferred to standard soda-lime-silica since they are more chemically resistant. In fact, standard glass is not completely inert since mobile alkali are leached into the contained product (Chapter 5). Therefore, low alkaline concentration glass containers have been developed. In the field of elevated temperature applications, low thermal expansion glasses are used. Pyrex glass is the most well known. Some manufacturers also tried to develop tempered containers from standard glass for the same purpose. These resist expansion until thermal shock stresses exceed the built-in residual stresses and then brittle fracture... 

Borosilicate glass contains about 80% silica, 13% boric oxide, 4% alkali, and 2% alumina. It is more heat-shock-resistant than most glasses due to its unusually small coefficient of thermal expansion (typically between 2 and 5 x 10 cm /°C for soda-lime glass it is 8 to 9 X 10 cm /°C). It is better known by such trade names as Kim ax and Pyrex. Bakeware and glass pipelines are often borosilicate glass. 

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