Structure and rheological properties of poly(vinyl alcohol)/hydroxyapatite solutions

In this study, poly(vinyl alcohol) (PVA) solutions with various hydroxyapatite content were prepared. Effect of the hydroxyapatite amount on the microstructure and rheological properties of the PVA/HA solutions was studied. Rheological behavior of the samples was examined by stress-controlled rheometer in linear and non-linear viscoelastic region. The results show that the addition of hydroxyapatite (HA) to the PVA solution greatly influences its rheology. The shear thinning exponent was used to measure the nanodispersion of solutions. It is found that n value of the PVA-9 is the highest among the solutions, which yields better hydroxyapatite dispersion. Percolation threshold was determined by analyzing the magnitude of storage modulus and slope of storage modulus at low frequency region depending on the hydroxyapatite loading. Creep-recovery experiments of PVA/HA solutions were performed in the nonlinear regime. While the creep compliances become higher by the hydroxyapatite addition, the recoverable creep compliances are strongly influenced by the addition of the nanoclay. All the results have been commented by taking the interaction between the polymer molecules and the hydroxyapatite.