Studies of the Drawing of Polyamide Fibers. II. The Drawing of Heat-treated Nylon Monofilaments

Abstract In order to investigate the influence of the structure of an undrawn sample on the change in physical properties upon drawing, undrawn nylon monofilaments were drawn to various draw ratios after having been heat-treated at several temperatures; some properties, such as tensile strength, shrinkage in boiling water and specific gravity, were then measured on these drawn samples. Although the minimum of tensile strength observed at the draw ratio near 2 had a tendency to disappear upon the heat-treatment of an undrawn sample, the strength did not increase in the range of a low draw ratio. When an undrawn sample was heat-treated above 150°C, a maximum appeared at a draw ratio near 2 in the plot of shrinkage in boiling water against the draw ratio. The higher the heat-treating temperature of an undrawn sample, the greater the maximum of shrinkage. The specific gravity decreased during drawing when the undrawn sample was of a rather high crystallinity, but it increased when the undrawn sample was of a low crystallinity. These results have been discussed, and it has been suggested that the polymer structure becomes most unstable at the intermediate stage of drawing.