This work shows studies on solubility of monomers and oxidants in scCO_2, on mass transport into important engineering polymers, and on in-situ polymerization. By supercritical impregnation and subsequent in-situ polymerization blends are obtained in a thermally gentle manner. Finally obtained data allow developing ecologically and economically justified - green - processes yielding polymeric blends with otherwise unattainable electrical properties such as tuneable electrical conductivity for electrostatic discharge control. On the way to functional textile fabrics three independent process steps were investigated separately in detail: 1) solubility of monomers and oxidants in scCO_2; 2) sorption of CO_2 into polymers / supercritical impregnation into polymers; 3) in-situ polymerization induced by oxidants (soluble ferric oxidants, iodine). Solubility studies were conducted to approach homogeneous impregnation. In case of the more volatile liquid monomers the synthetic method was applied. The solubility of pyrrole and thiophene in scCO_2 follows 'type I' behaviour for binary systems, increasing steadily with density and temperature in the range of some weight-%. Many [0]amorphous and certain semi-crystalline polymers (like PET and PA6 in this study), absorb considerable amounts of CO_2 in the supercritical state and are thus swollen. The polymer chains become more flexible and the glass transition temperature is depressed. By this lubricating effect and additionally by the high diffusivity and zero vapour pressure of supercritical fluids mass transport is significantly increased. Higher mass transport rates lead to more homogeneous solute distribution before equilibrium. Polymers are subjected to the experiments in form of fabrics or fibres. In-situ polymerization speed depends mostly on concentrations of oxidant and dopant as well as on thermodynamic conditions. The composite polypyrrole coated fabrics are characterized by optical- and electron microscopy (with EDS elemental analysis), Wide angle X-ray diffraction, thermo gravimetric analysis and via micro- ATR FT-IR.
展开▼
