Strength Loss of Basalt-Based Mineral Fibers after Thermal Desizing

This study investigates the effects of desizing by heat cleaning on tensile properties of basalt-based mineral fibers. Two heat treatments, which lead to a complete removal of the sizing layer, were considered: one at low temperature (350 degrees C) for a long time (10 h) and one at high temperature (600 degrees C) for a short time (35 min). Desizing greatly affects tensile strength. High temperature and short time treatment conditions lead to the most severe strength degradation (66%). SEM micrographs reveal that failure originates from surface defects. Mechanisms responsible for strength loss were investigated by X-ray diffraction analyses, density measurements and differential thermal analyses. Strength degradation is ascribed to sizing layer removal and to thermally activated structural rearrangement of basalt.