Specific properties of special glasses and their production by the example of borosilicate glass.

Conventional glass breaks under heat or mechanical efforts. Special glasses, in contrast, are more high-quality, resistant, and made for special purposes. These properties make them an important material in chemistry and diagnosis as containers and substrates or as packaging in the pharmaceutical industry.

Borosilicate glass, for example, is resistant to acids, alkalis and organic substances. It also has a very high melting point and low sensitivity to temperature changes. The reason for this is in its low thermal expansion coefficient.

The special properties of the borosilicate glass are in its composition. The glass is made to 80% of SiO₂; the remaining part are boron trioxide (B₂O₃) with up to 13% and alkalis. Such highly quartz containing glass mixtures require a high melting temperature. The melting point can usually be lowered with alkalis. Since the borosilicate glass has a low alkali content in the glass composition, the melting temperature still is above 1650°C.

The process temperature must not drop uncontrolledly in any of the production steps, since this may lead to devitrification. The melting tanks are lined with heat-resistant refractory materials that may also be used in contact with glass. For places that are not exposed to glass contact, such as the feeder roof, SCHUPP^® offers MolyTec heating panels. MolyTec combines intermetallic heating elements made of molybdenum disilicide (MoSi₂) and insulation shapes of polycrystalline mullite/alumina wool (PCW) in heating systems ready for installation and permits controlled and precise heating up to an application temperature of 1550°C (depending on geometry).

For the electrically heated melting crucibles, SCHUPP^® offers molybdenum disilicide heating elements (MoSi₂). MolyCom^®-Ultra heating elements are particularly long-lived and permit application temperatures up to 1750°C. In the alkali-containing atmospheres, we recommend heating elements with a thicker SiO₂protection layer in order to protect the heating elements, the furnace and the products to be melted.

The perfect thermal stability, thermal shock resistance and low heat conductivity of insulation materials of polycrystalline mullite/alumina wool (PCW), as well as the high surface load and long service life of MoSi₂-heating elements offer an outstanding combination for the very specific requirements of the glass industry.

With the high-quality SCHUPP^®-products, you can achieve a clear increase of energy efficiency of your glass melting system. Thus, we develop and implement the optimal and at the same time economically efficient solutions together with our customers.