Extension of Unoriented Nylon 66 Filaments

The orientation of nylon 66 filaments usually occurs by a cold-drawing process. This process has previously been described, in phenomenological terms, by the adiabatic theory of cold drawing of Muller and Jackel and Marshall and Thompson. To explain the process in structural terms, tensile creep experiments under low loads have been performed in an atmosphere of controlled temperature and humidity. The extension first increases uniformly with log time; then there is a rather sharp yield point where the extension quickly increases by a large amount. The location of the yield point on the log time scale is quite sensitive to environmental conditions. Phenomenologically, the behavior is similar to the propagation of Lüder's bands in metals. These results are not consonant with the adiabatic theory; therefore, the recent crystal defect model of nylon 66 proposed by Zaukelies has been used to suggest a qualitative explanation in terms of dislocations.