Fiber Structure—Property Relationships II: Macroscopic Deformations of Alkylene Sulfide Crosslinked Polycaprolactam Fibers

The introduction of alkylene sulfide crosslinks into oriented nylon-6 (polycaprolactam) homofiber is described. The resulting structural modifications are found to produce crimping and coiling in the dry and wet states of the fiber resembling the situation in wool. In a previous paper a similar phenomenon was reported for a disulfide crosslinked nylon-6 homofiber. The macroscopic deformations exhibited by the alkylene sulfide crosslinked fibers differ in. at least three respects from the disulfide crosslinked samples: (1) the crimp frequency is much higher and the crimp amplitude smaller, (2) in addition to crimping some helical coiling takes place even when the fiber is in the unswollen state, and (3) the extent of crimping and coiling is not decreased by gradual air-oxidation of some of the reactive groups. An explanation for this crimping and coiling previously advanced is corroborated by additional evidence provided by chemical analyses, and X-ray diffraction, birefringence, and swelling data.