Gel Spinning Characteristics of Ultra-high Molecular Weight Polyethylene and Study on Fibre Structure before Drawing

Monofilaments precursor of linear ultra-high molecular weight polyethylene (UHMWPE) were produced by gel spinning at controlled conditions. The rheological behaviour of UHMWPE solution (gel) was studied in paraffin oil at 175°C with deformation rates in the range 600-11000 S·1 which was in good agreement with power law model. The effect of paraffin concentration of the extraction bath was determined on the amount of paraffin remained in the precursor fibre and on the extraction time. The desorption behaviour of paraffin/UHMWPE system is in accordance with Flory-Huggins model. The precursor fibre structure and its morphology before drawing process is a determining parameter in drawability and properties of the produced fibre. Thus, the effects of processing conditions such as spinning speed, spinneret geometry, and temperature of the region between the die and the quench bath were investigated on the crystallinity of the precursor fibre. High deformation rates (y a ) caused by decreasing the die diameter or increasinq the spinning speed result in more macromolecular orientation- and increased degree of crystalHnity. Significant recrystallization or crystal perfection took place during the solvent extraction step which increased the melting point of the precursorfibre from 11S,SOC to 147°C.