Prediction of glass phase viscosity in firing traditional ceramics and porcelain tiles with waste glass powder

Abstract

The theoretical calculation of the viscosity of traditional ceramic materials is complex and models based on glass processing are generally used to estimate the viscosity of the glass phase according to its chemical composition. FactSage model considers structural information from silicate melts (glass phase), which is a different approach compared to other models. The viscosity of the melt fraction was calculated for different traditional ceramics, such as hard porcelain, technical porcelain, sanitary ware and porcelain tiles, including formulations with partial replacement of the fluxing raw material by soda-lime glass waste. FactSage model consistently indicated an increase in viscosity with higher levels of silica and a decrease in viscosity with the utilization of soda-lime glass waste in the formulations. Different responses and a nonlinear behavior were presented when varying the Na2O/K2O contents in the glass phase. The tested models presented reliable results for the processing of molten glass, but depending on the chemical composition and temperature, significant differences were observed among the values. Despite this, models that simulate the viscosity of the glass phase can help to optimize production conditions, but more investigations are needed to improve the relationship between theoretical and experimental results of viscosity.