Density, surface tension and viscosity of the molten Pbo-B₂O₃-SiO₂ system

The density, surface tension and viscosity of the molten PbO-B₂O₃-SiO₂ system were measured for high packaging industry. The compositional dependence of the properties has been investigated. The results were shown as follows. The density of melt increase linearly with increasing PbO content. The molar volume was estimated from the density data and its deviation from additivity was calculated. It was considered that Pb²⁺ ions may act as a network former for PbO content more than 40-50 mol%. The surface tension decreased with decreasing the ratio SiO₂/XB₂O₂, and its value increased at 30<PbO<60 mol%, showing a maximum at around 60 mol%PbO, and then decreasing with further additions. The result indicated that the surface tension was affected by [BO₃] in the region 30<PbO<60 mol%, and by PbO content in the region PbO>60 mol%, respectively. The viscosity of melt decreased linearly with increasing the PbO content. To predict the viscosity, an empirical equation between viscosity and molar equivalent weight was obtained, from which the effect of viscosity; B₂O₂=SiO₂ × 0.5 was presumed.