Degradation properties and microstructural analysis of 40P2O5–24MgO–16CaO–16Na2O–4Fe2O3 phosphate glass fibres

•The phosphate glass consists of Q1 and Q2 species with an average chain length of 2.8.•Mechanical testing revealed that the fibres are reasonably durable.•Degradation rate for the glass was between 4.9 × 10− 8 and 8 × 10− 10 g · cm− 2 min− 1.•XPS, EDX, FTIR, DSC, XRD & SEM analyses validated degradation pattern of the glass.•It suggests spalling out a very thin layer from the fibre surface during degradation.

The paper describes the physical, chemical, mechanical and thermal properties of 40P2O5–24MgO–16CaO–16Na2O–4Fe2O3 phosphate glass fibres. The initial mechanical properties of the fibres were determined to examine changes of these properties over time and also due to the variation of fibre diameter. A theoretical chain length of the fibres is calculated and that was validated using high resolution X-ray photoelectron spectroscopy (XPS) analysis. These fibres were degraded for 12 weeks in deionised water with pH adjusted to ~ 7.4 at 37 °C. Mass loss percentage, change of pH, degradation rate and the mechanical properties of the degraded fibres were determined. An XPS analysis of the 12 week degraded fibre was conducted without etching and after 40 min etching from the degraded surface. The elemental percentages of fibres degraded for different time periods were determined using energy dispersive X-ray (EDX) analysis. Scanning electron microscopy (SEM) analysis of the non-degraded and degraded fibres was also presented in order to assess changes in the fibre surface during degradation. The evolving surface of these water-soluble fibres was further characterised by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The works completely elucidated the chemical nature and degradation pattern of the bulk fibre surface of this glass composition.