EFFECT OF BORATE RAW MATERIAL CHOICES ON THE BATCH REACTIONS OF ALKALI-LEAN BOROSILICATE GLASSES

摘要

Borosilicate glasses are of utmost importance in a large number of commercial applications, and are among the most largely produced types of glass. The boron, integrated within the structure of these materials, confers outstanding properties to the glass and is irreplaceable for numerous glass compositions (such as low thermal expansion lab-ware or display glasses). For industrially produced borosilicate glasses, different types of borate raw materials can be chosen by the manufacturers (e.g. borax, boric acid, colemanite). The selection of the type of borate employed for the glass batch depends notably on the type of borosilicate and the exact composition of the raw material itself (e.g. the sodium-containing borax would not be used for alkali-free glasses) as well as on economic considerations. The choice of the borate raw materials may also have an impact on the melting process itself, e.g. on the melting kinetics and the evaporation processes. In this study, the influence of the choice of the borate raw materials upon the melting behavior of alkali-lean borosilicate glasses is presented. Industrial alkali-lean borosilicate glass batches were melted using High Temperature Melting Observation System and Evolved Gas Analysis setup (HTMOS/EGA). It is shown that the type of borate raw material employed has an effect on the melting and fining behavior of the glass. Notably, the influence of hydrated vs. anhydrous borate raw material (boric acid vs. boron oxide) is highlighted.