Structural, thermal and dissolution properties of MgO- and CaO-containing borophosphate glasses: effect of Fe₂O₃ addition

This paper investigated manufacture of high-durability phosphate glass fibres for biomedical applications. Five different borophosphate glass formulations in the systems of 45P₂O₅–5B₂O₃–5Na₂O–(29 − x)CaO–16MgO–(x)Fe₂O₃ and 45P₂O₅–5B₂O₃–5Na₂O–24CaO–(21 − x)MgO–(x)Fe₂O₃ where x = 5, 8 and 11 mol% were produced via melt quenching. The compositions and amorphous nature of the glasses were confirmed by ICP-MS and XRD, respectively. FTIR results indicated depolymerisation of the phosphate chains with a decrease in Q² units with increasing Fe₂O₃ content. DSC analyses showed an increase in T_g by ~5 °C with an increment of 3 mol% in Fe₂O₃ content. The thermal properties were also used to calculate processing window (i.e. T_c,ons—T_g) and another parameter, K_gl, to determine the suitability for fibre drawing directly from melt, which equals (T_c,ons—T_g)/(T_l—T_c,ons). The degradation study conducted in PBS solution at 37 °C showed a decrease of 25–47% in degradation rate with increasing Fe₂O₃ content. This confirmed that the chemical durability of the glasses had increased, which was suggested to be due to Fe₂O₃ addition. Furthermore, the density measured via Archimedes method revealed a linear increase with increasing Fe₂O₃ content.