Evolution of self-generating porous microstructures in polyacrylonitrile-cellulose acetate blend fibres.

Polyacrylonitrile (PAN), cellulose acetate (CA) and polyacrylonitrile - cellulose acetate (PAN-CA) fibres were formed in single and binary solvents which were subjected to gyration under pressure. Fibres in the diameter range 200–2000 nm were generated using a rotating speed of 36,000 rpm and a working pressure of 3 × 10 5 Pa. Long fibre morphologies with isotropic distribution of fibre orientation were obtained from PAN polymer solutions with a concentration of 5–15 wt%. Short fibre morphologies with anisotropic distribution of fibre orientation were produced for CA polymer solutions with a concentration of 25 wt% and below this concentration polygonal beads were generated. PAN-CA fibre bundles were generated and these showed remarkable self-generating porous characteristics when the working pressure was changed from 1 to 3 × 10 5 Pa. For comparison, porous PAN-CA fibres were also generated by solvent etching and porogen leaching techniques and in these the etching time and porogen concentration influenced the pore size of the generated fibres. Fourier transform infrared and Raman spectroscopies were performed to elucidate the bonding characteristics in the fibres. Release characteristics of the porous fibrous structures were studied using vanillin as the active ingredient. A mathematical model which allows the evaluation of the fibre diameter as a function of rotating speed and working pressure is presented and this helps to understand the solvent mass transfer taking place during fibre forming. [ABSTRACT FROM AUTHOR]