Supercritical CO2 sorption kinetics and thymol impregnation of PCL and PCL-HA

J. IVANOVIC, S. KNAUER, M.A. FANOVICH, S. MILOVANOVIC, M. STAMENIC, P. JAEGER, I. ZIZOVIC, R. EGGERS

JOURNAL OF SUPERCRITICAL FLUIDS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 107 p. 486 - 498

0896-8446

The potential of supercritical carbon dioxide (scCO2) processing of polycaprolactone (PCL) and polycaprolactone-hydroxyapatite (PCL-HA) composites for obtaining functional porous scaffolds at moderate temperatures (35?40 °C) was analyzed and quantified. The effect of scCO2 sorption kinetics on the swelling, foam morphology and thermal behavior of the PCL and PCL-HA composites was studied. Sorption isotherms were determined using magnetic suspension balance at 10?30 MPa and 35?40 °C. Influence of the pressure, HA amount (10?20%) and procedure for HA powder preparation on the sorption kinetics was discussed. Supercritical solvent impregnation (SSI) of PCL and PCL-HA with thymol was investigated as environmentally friendly way to produce functional scaffolds with controlled microstructure. Moderately high pressures (13?17 MPa) and 10% of HA were proven to be favorable for creation of the PCL scaffolds with satisfying foam microstructure (mean pore size ∼200?300 μm), filler distribution and thymol impregnation yields (12?18%). This was due to the satisfactory high scCO2 solubility (0.25?0.30 g/g) and mass transfer rate (∼10−10 m2/s) in the polymer phase as well as its great plasticizing effect (−ΔTm = 26.4?27.4 °C). Higher saturation of the polymer phase with scCO2 (0.30?0.55 g/g), filler amount (20%) and thymol solubility in scCO2 (>5.5 g/kg) at pressures above 20 MPa resulted in decreased mass transfer rate and SSI efficiency.