Mechanical, structural, and chemical properties of unmodified and iron-modified phosphate glass fibers based on natural phosphate and kaolin clay

Abstract

Earlier research has reported that the phosphate glass fibers can be used as fertilizer with slow and controlled release of nutrient ions due to the controllable degradability in aqueous environments. In this study, two series of phosphate glasses were prepared and successfully stretched to continuous monofilaments fibers with a fixed spinning speed. The first series includes four phosphate glass fibers compositions based on natural phosphate and kaolin clay in appropriate amounts. Mechanical properties in terms of tensile strength and tensile modulus were dramatically increased with the progressive addition of kaolin clay. PCA statistical analysis carried out to study the effect of the chemical composition on the mechanical performance of fibers showed a strong correlation between Al2O3, SiO2 and Fe2O3 and K2O oxides and the evolution of tensile strength. The second series is based on the selection of the composition with significant mechanical properties to which increasing amounts of Fe2O3 oxide (3, 3.5 and 4 mol%) were added. The effect of Fe2O3 addition on surface morphology, structure, mechanical properties and dissolution behavior of fibers was studied. The results indicate that the addition of 4 mol% of Fe2O3 increased the tensile strength up to 1612 ± 177 MPa and decreased the dissolution rate of the fibers in distilled water under conditions of temperature, time and pH. These results can be explained by the formation of more covalent P–O–Fe bonds that are more resistant in aqueous media.