Fiber structure-property relationships: a disulfide-crosslinked self-crimping polyamide

A structural modification of nylon-6 fiber (polycaprolactam) was achieved by the introduction of a high density of intermolecular disulfide crosslinkages. The crosslinking process leads to an unexpected three-dimensional crimping in the dry and wet states (similar to wool), and to the formation of helical coils if swelling is carried out in a solvent capable of destroying the crystallites remaining after crosslinking. This phenomenon has not been observed previously in round cross-section synthetic homofibers. A possible explanation is advanced which attributes this crimping and coiling tendency to differential swelling caused by the varying crosslinking density across the fiber axis and to structural asymmetry resulting from the crosslinking process.