Determination of Methylene Groups in Disulfide and Methylene Sulfide Crosslinks in Polycaprolactam Fibers

Recent publications from this laboratory describe some unusual properties, such as crimping and helical coiling, induced by heterogeneous, chemical crosslinking of polycaprolactam fibers. The following crosslinks are involved: [Figure: see text] It has been found that the —CH(2)—groups in these crosslinks can be hydrolyzed to yield one equivalent of formaldehyde for each equivalent of hydrolyzable methylene group. This permits the application of the chromotropic acid method for determining formaldehyde to the estimation of the number of crosslinks in the fiber, when used in conjunction with a previously reported conductometric method for the determination of sulfhydryl groups. A general method has been worked out, with special attention to sulfur-containing degradation products (of the crosslinks) that may interfere with the analysis.