Soda-lime glasses 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 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. 

Soda-lime glass SiOj, 75% NajO, 15% CaO, 10% Easily attacked by chemicals and sensitive to thermal shocks. Transmits visible light, but absorbs UV radiation. Used mainly in windows and bottles. 

Coefficient of thermal expansion (CTE). Amatch to silicon at 35 X 10" /°C is desired for chip-on-glass mounting of peripheral circuits. It also offers decreased thermal shock resistance compared to soda-lime glass. 

Thermal Expansion. Most manufacturers literature (87,119,136—138) quotes a linear expansion coefficient within the 0—300°C range of 5.4 x 10"7 to 5.6 x 10 7 /°C. The effect of thermal history on low temperature expansion of Homosil (Heraeus Schott Quarzschmelze GmbH) and Osram s vitreous silicas is shown in Figure 4. The 1000, 1300, and 1720°C curves are for samples that were held at these temperatures until equilibrium density was achieved and then quenched in water. The effect of temperature on linear expansion of vitreous silica is compared with that of typical soda—lime and borosilicate glasses in Figure 5. The low thermal expansion of vitreous silica is the main reason that it has a high thermal shock resistance compared to other glasses. 

Soda lime Inexpensive easy to melt and shape most widely used glass Poor durability not chemically resistant poor thermal shock resistance Windows bottles light bulbs jars... 

Disadvantages. Because of their high thermal expansion, soda-lime-sihca glasses are prone to thermal shock failure, and because of their relative softness, they have limited... 

In addition to its beneficial effects in melting, the presence of small amounts of borax in ordinary soda-lime-silica glass (resulting from use of borax in the batch) imparts greater brilliance, strength, durability and thermal shock resistance. It also decreases the tendency for glass to devitrify or crystallize. 

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... 

---