Water absorption and solubility of PHBHV/HA nanocomposites

A thorough understanding of the influence of bioceramic phase on the water absorption and solubility of biomaterial is of importance in tailoring its degradation and the formation of bone-like apatite for clinical implant applications in a wet environment. The objective of this study was to characterize and quantify the water transport properties and solubility of biomaterial incorporating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and nano-hydroxyapatite (nano-HA) modified with a silane coupling agent. Solubility and transport parameters such as diffusion, permeability, and sorption coefficients were determined at three different temperatures using the weighing method. When the environmental temperature reached 60 °C, the water uptake of the nanocomposite reaches equilibrium after a normally fast absorption process, and then decreases as the immersion time is prolonged due to the solubility of the material. Moreover, this phenomenon becomes more significant with increasing the volume fraction of nano-HA. Compared to those for the base resin, the diffusion coefficients for the nanocomposite decrease, whereas the sorption coefficients and the solubility show an opposite tendency. All of the transportation parameters are temperature sensitive and obey the Arrhenius or the van’t Hoff relationship. Results from thermodynamic analysis imply that when using a high filler loading level (⩾20 vol%) the sorption of the nanocomposite is mainly dominated by a Langmuir sorption mode giving an exothermic process.