Effect of glass composition on the degradation properties and ion release characteristics of phosphate glass—polycaprolactone composites

Abstract

A series of polycaprolactone and ternary-based (Na2O)0.55−x(CaO)x(P2O5)0.45 glass composites were created, each containing 20% volume percentage of glass with various calcium compositions. A short-term degradation study was carried out to investigate the physical and ion release behaviour of these composites, utilising analytical techniques such as dynamical mechanical analysis, and ion chromatography.All the composites experienced significant loss of weight and stiffness throughout the study, with the 24mol% calcium composites losing the greatest amount of weight and stiffness. The pH profile of the aqueous solutions in which the composites were placed were initially acidic, but began to neutralise mid-way through the study, with the 36mol% solution achieving the most acidic conditions. The ion release behaviour mirrored the mass loss behaviour of the glass component of the composites. The cations (sodium and calcium ions) release was comparable with the initial stages of composite mass degradation, both of which exhibited almost immediate release when placed into solution. The 24mol% composites underwent rapid rates of cation release, while the 36mol% experienced the slowest rates of release. By contrast, anion (phosphates and polyphosphates) release showed a dissimilar trend, with rapid release of the P2O7 and P3O10 occurring during the first few hours in solution, whilst the P3O9 structure released steadily during the first 48h in solution. Finally, PO4 release was at a constant rate over the duration of the study, releasing up to 300ppm from the 32 and 36mol% samples by the end of 200h. To summarise, these results show that by combining phosphate glasses with biodegradable polymer, it is possible to create composites whose rate of degradation can be controlled to meet the needs of their end application.