Volatilization of boron from E-glass melts

Boron is known to volatilize from borate and borosilicate melts at high temperatures. The rate of boron loss from E-glass melts, as measured using the B–O overtone band in the infrared spectrum of this glass, has been measured at several temperatures and partial pressures of water vapor. The rate of volatilization increases dramatically with increasing partial pressure of water vapor in the atmosphere surrounding the melt at constant temperature and with increasing melting temperature at constant partial pressure of water vapor. The boron concentration decrease is accompanied with an increase in hydroxyl concentration. The net effect of changes in boron and hydroxyl concentration is an increase in glass density, refractive index, and glass transformation temperature.