| Abstract: | ![]()
The possibility of producing high-modulus nylon 6 fibers by incorporation of lithium chloride (LiCl) in the polymer prior to spinning and drawing has been examined. Samples containing 2% and 4% LiCl (w/w) together with an unsalted control were studied. Particular attention was given to optimizing the spinning process by varying the melt temperature and the draw-down. The spun fibers were subsequently drawn in a tensile testing machine at 135°C, preliminary studies having established that this was desirable for the production of high-modulus material. The influence of annealing after drawing was also examined. Drawn fiber moduli in the range 8–9 GPa were obtained, compared with ca. 5–6 GPa for unsalted material. Limited structural studies (birefringence and wide-angle x-ray diffraction) suggest that the enhancement of modulus is due to an increase in the stiffening effect of extended molecules in the noncrystalline regions. Dynamic mechanical measurements show that there is reduced chain mobility in the disordered regions of the polymer, suggesting strong polymer-ion interactions. The salt can be readily removed by washing the fibers in boiling water, with significant reduction in moduli. This militates against commercial application of the salted fibers. |
