Sotirios I. Marras

Biodegradable polymer nanocomposites: The role of nanoclays on the thermomechanical characteristics and the electrospun fibrous structure

Polymer nanocomposites, based on poly(e-caprolactone) (PCL) and organically modified montmorillonite, were prepared by the solution intercalation technique. The thermal stability of the prepared materials was analyzed by thermogravimetric analysis. Investigation of their mechanical properties revealed that incorporation of the high aspect ratio montmorillonite sheets into the matrix significantly enhanced the polymer stiffness without sacrificing its ductility. Fibrous membranes of neat and nanocomposite PCL were fabricated by electrospinning. The effect of the applied voltage, the solution concentration and the clay content of the nanocomposite materials on the final fibrous structure was investigated. The results showed that the introduction of the inorganic filler and the increase in the applied voltage from 7.5 to 15 kV facilitated the formation of fine fibers with fewer bead defects. The presence of nanoclay resulted in narrower fiber size distributions, although the mean fiber diameter was not significantly altered. The increase in the solution concentration led to the formation of more uniform fiber structures and to a slight increase in the mean fiber diameter. Furthermore, the electrospinning process affected significantly the structure of the nanocomposite material by increasing the interlayer spacing of the inorganic mineral.

Surfactant-induced morphology and thermal behavior of polymer layered silicate nanocomposites

Poly(L-lactic acid) nanocomposites were prepared by the addition of montmorillonite modified with various loadings of hexadecylammonium cation. The influence of alkylammonium on the morphology and surface charge of the clay was investigated by Xray diffraction (XRD) analysis and electrokinetic measurements, respectively. The structural characteristics of the inorganic-organic hybrids were studied by XRD, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Thermal analysis was carried out by thermogravimetric analysis (TGA) under constant nitrogen flow and under air. The results showed that high concentration of surfactant present in the clay greatly increases clays dispersibility into the matrix and this substantially improves the thermal stability of the pristine polymer.

PBSA/layered silicate nanocomposites and the role of nanoclay on their electrospun fibrous structure

Polymer nanocomposites based on poly (butylene succinate-co-butylene adipate) (PBSA) with various concentrations of organically modified montmorillonite were fabricated by the solvent casting technique. The morphology of the prepared materials was investigated by X-ray diffraction (XRD) and their thermal behaviour was analysed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Fibrous mats of pure and nanocomposite PBSA were subsequently prepared by electrospinning. Solution concentration, flow rate and applied voltage were kept constant in order to reveal the effect of the clay content alone on the final fibrous structure using scanning electron microscopy (SEM).