Tempered glass thermal shock resistance

Properties Rupture modulus up to 50,000 psi, d 2.5, thermal shock resistance 900C, highest continuous-use temperature 700C. Glass ceramics lie between borosilicate glasses and fused silica in high-temper-ature capability. 

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... 

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