Effect of boron oxide addition on the viscosity-temperature behaviour and structure of phosphate-based glasses

L-DOPA coating improved phosphate glass fibre strength and fibre/matrix interface

The levodopa (L-DOPA) has been reported as a promising adhesive for various materials. In this study, we utilized L-DOPA as an interfacial agent for phosphate glass fibre/polycaprolactone (PGF/PCL) composites, with the aim to enhance the interfacial properties between the fibres and polymer matrix. The PGFs were dip-coated in varying concentrations of L-DOPA solution ranging between 5 and 40 g L-1. The fibre strength and interfacial shear strength (IFSS) of the composites were measured via a single fibre tensile test and single fibre fragmentation test, respectively. It was found that the L-DOPA agent (at conc. 10 g L-1) significantly improved the IFSS of the composites up to 27%. Also, the L-DOPA coating (at conc. 40 g L-1) significantly increased the glass fibre strength up to 18%. As a result, an optimum coating level could be tailored depending on application and whether fibre strength or IFSS was of greater importance. In addition, SEM and TGA analyses were used to detect and quantify the coating agents. FTIR and XPS further confirmed presence of the coating and indicated the zwitterionic crystals of L-DOPA and the formation of a melanin-like polymer layer. The spectroscopy data also evidenced that both catechol and amine groups contributed to the interaction between the L-DOPA and the PGF surface.

Chitosan as a Coupling Agent for Phosphate Glass Fibre/Polycaprolactone Composites

This study shows that chitosan (CS) could be highly useful as a coupling agent in phosphate glass fibre/polycaprolactone (PGF/PCL) composites, as it improved the interfacial shear strength by up to 78%. PGFs of the composition 45P2O5–5B2O3–5Na2O–24CaO–10MgO–11Fe2O3 were dip-coated with CS (with a degree of deacetylation >80%) dissolved in acetic acid solution (2% v/v). Different CS concentrations (3–9 g L−1) and coating processes were investigated. Tensile and fragmentation tests were conducted to obtain the mechanical properties of the single fibres and interfacial properties of the PGF/PCL composites, respectively. It was observed that post-cleaning, the treated fibres had their tensile strength reduced by around 20%; however, the CS-coated fibres experienced strength increases of up to 1.1–11.5%. TGA and SEM analyses were used to confirm the presence of CS on the fibre surface. FTIR, Raman, and X-ray photoelectron spectroscopy (XPS) analyses further confirmed the presence of CS and indicated the protonation of CS amine groups. Moreover, the nitrogen spectrum of XPS demonstrated a minimum threshold of CS coating required to provide an improved interface.

Compositional dependency on dissolution rate and cytocompatibility of phosphate-based glasses: Effect of B2O3 and Fe2O3 addition

The unique property of phosphate-based glasses and fibres to be completely dissolved in aqueous media is largely dependent on the glass composition. This article focuses on investigating the effect of replacing Na₂O with 3 and 5 mol% Fe₂O₃ on cytocompatibility, thermal and dissolution properties of P₂O₅–CaO–Na₂O–MgO–B₂O₃ glass system, where P₂O₅ content was fixed at 45 mol%. The effect of increasing Fe₂O₃ from 3 to 5 mol% on P₂O₅–CaO–Na₂O–MgO glasses was also evaluated. The glass transition temperature, onset of crystallisation temperature and liquidus temperature were found to decrease with increasing Fe₂O₃ content and the addition of B₂O₃, while the thermal expansion values were found to decrease. The density of the glasses decreased with increasing Fe₂O₃ content. However, an increase in the density was observed by the addition of 5 mol% B₂O₃. The dissolution properties and mode of bulk glass and fibres were also examined which were found to decrease with increasing B₂O₃ and Fe₂O₃. However, it was found that the dissolution properties of the glasses containing both B₂O₃ and Fe₂O₃ were lower than only Fe₂O₃ containing glasses. The in vitro cell culture studies using human osteoblast like (MG63) cell lines revealed that the glasses containing both B₂O₃ and Fe₂O₃ maintained and showed higher cell viability as compared to the only Fe₂O₃ containing glasses. Glasses containing both B₂O₃ and Fe₂O₃ showed a pronounced effect on the dissolution rate of the glasses, which eventually improved the cytocompatibility properties of the glasses investigated.