CONTINUOUS PLASTICIZED MELT-EXTRUSION OF POLYACRYLONITRILE HOMOPOLYMER

In this work, it is shown that polyacrylonitrile (PAN) powder which had been plasticized by propylene carbonate (PC) could be 'melted' and extruded continuously into filaments. The 'molten' extrudate solidified on-line as a result of cooling, without the need for coagulation. In this respect, PAN-PC solutions behaved differently when compared with other solutions commonly used in the wet-spinning of PAN fibres. Spontaneous solidification on cooling meant that the filament could be wound-up on a take-up system without the need to pass it through a coagulation bath. The solidification occurred as a result of the rapid crystallization of the PAN from the propylene carbonate solution. The X-ray diffraction pattern of the solidified filament (which contained 40-50 wt% of solvent) was different from that of the dry PAN powder, indicating that a different polymorph had been formed. Drawing of the filaments, however, led to the normal hexagonal polymorph. A PAN:PC (50:50 by wt) 'melt' had a shear viscosity comparable with that of a conventional thermoplastic such as extrusion-grade polyethylene. The plasticized melt showed shear-thinning behaviour.