Extension of Unoriented Nylon 66 Filaments. III. Superposition of Data

In an effort to understand the molecular mechanism of cold drawing, the tensile creep of unoriented nylon 66 monofilaments as a function of load has been obtained at three different combinations of temperature and moisture content. Qualitatively, an increase in either load, temperature, or moisture content will shift the creep curve to shorter times. These data can be quantitatively correlated by plotting the elongation ε against log t−a+bx+cT+c1σ/(c2+σ). Here t is time, x is % H2O, T is temperature in °K, σ is an average stress in dynes/cm2, and a, b, c, c1, and c2 are constants. The parameters b and c are identical with those previously found to apply to the moisture and temperature dependence of the elastic extension of oriented nylon 66 fibers. The free-volume theory frequently employed for amorphous polymer behavior is shown to be inapplicable since moisture sorption decreases the free volume although it quickens cold drawing. Application of dislocation concepts enables an estimate of the stress dependence of dislocation velocity to be calculated.