High-temperature stability of aluminosilicate glass particle pellets and its dependence on chemical composition

Abstract

Mineral wool, especially stone wool, is a sustainable, fire-safe insulation material. Its fire safety depends, amongst other factors, on its high-temperature stability (HTS), that is, its resistance to volumetric shrinking during heating. Using glass particle pellets as an analogue for mineral wool fibres, we observed a positive correlation between particle size and HTS, as well as between particle size and crystallisation temperatures, and an inverse correlation between particle size and the degree of iron oxidation upon heating. To investigate the composition dependence of HTS, we prepared two series of aluminosilicate glass particle pellets: one with varying MgO/(MgO+CaO) molar ratio (referred to as the CaO-MgO series) and another with varying MgO/(MgO+FeO) molar ratio (referred to as the FeO-MgO series). The results showed that substituting MgO for CaO resulted in decreased glass stability, a lowered onset temperature of shrinking, a reduced shrinking rate, and an increased HTS. In comparison, substituting MgO for FeO led to increased glass stability, an increased shrinking rate, and a decreased HTS. Crystallisation occurs right after the glass transition for the FeO-rich FeO-MgO samples and MgO-rich CaO-MgO samples, but a residual glassy phase remains. Upon further heating, the residual glassy phase undergoes viscous deformation, leading to a significantly reduced temperature of the final collapse of the glass particle pellets. This work provides a facile and efficient approach to studying the HTS of glass particle pellets as an analogue for mineral wool fibres.