Structure, viscosity and fibre drawing properties of phosphate-based glasses: effect of boron and iron oxide addition

Resorbable phosphate-based glasses have been applied as fibrous reinforcement for resorbable polymers for fracture fixation. The mechanical properties of these composites largely depend on the mechanical properties of the fibres. In this current study, four phosphate-based glass compositions were produced by replacing Na2O with B2O3 and/or Fe2O3 in the glass system P2O5–CaO–Na2O–MgO, and the P2O5 content was fixed at 45 mol%. The thermal stability of the glasses containing both B2O3 and Fe2O3 and/or FeO (P45B5Fe5 and P45B5Fe3) was significantly higher than that of the only B2O3 (P45B5)- or Fe2O3 (P45Fe3 and P45Fe5)-containing glasses. The viscosity was found to shift to higher temperature with increasing B2O3 and Fe2O3 and/or FeO content. The fragility parameters, m and F 1/2, estimated from the viscosity curve, decrease with B2O3 addition. The improved physical properties of the glasses investigated with B2O3 and Fe2O3 and/or FeO addition were attributed to the replacement of P–O–P bonds with P–O–B and P–O–Fe bonds. The presence of P–O–B and P–O–Fe bonds in the glass structure was confirmed by the FTIR analysis. It was possible to draw continuous fibres up to 3 h from the B2O3- or Fe2O3- and/or FeO-containing glasses, whereas it was difficult to pull fibre from only Fe2O3-containing glasses and the fibre pulling process was not continuous. Therefore, addition of B2O3 to the glass system enabled successful drawing of continuous fibres from glasses with phosphate (P2O5) contents of 45 mol%. It was also observed that addition of only Fe2O3 and/or FeO did not have a significant effect on the fibre mechanical properties, whilst the mechanical properties of the fibres increased with increasing B2O3.