Studies on disulfide‐crosslinked nylon. II. Stress relaxation of disulfide‐crosslinked polycaprolactam fibers in water

Abstract

AbstractThe stress relaxation at 100% elongation in water was investigated for disulfide‐crosslinked polycaprolactam (DSPC) fibers prepared from N‐mercaptomethyl polycaprolactam. The stress decreased faster with increasing temperature and with increasing mercaptan content of the fiber. Little stress decay took place when the fiber was treated with a mercaptan‐blocking reagent. It was concluded that the controlling mechanism of the stress relaxation was the mercaptan/disulfied (SH/SS) interchange reaction. The remanent stress observed for the stress relaxation was fairly high and increased with decreasing mercaptan content of the fiber. The stress decay curve was not Maxwellian. It has been suggested that the concentration of mercaptan that could not participate in the interchange with stressed disulfide bonds increased with increasing cycles of the interchange reaction. A kinetic equation is presented and the activation energy of the SH/SS interchange reaction was evaluated as 22.3–23.9 kcal/mole. The stress relaxation of DSPC fibers in dilute β‐mercaptoethanol was also studied. The stress decreased more rapidly to almost zero and the decay curve was Maxwellian. The activation energy of the reaction was 17.1 kcal/mole. These results were compared with the stress relaxation of wool fibers.