Abstract
The virtual elimination of break and tear strength losses in cotton sheeting during conventional pad-dry-cure treat ments with DMEU, formaldehyde, APO, and bis(2-hydroxyethyl) sulfone has been observed. At wrinkle recovery angles of 270-300° (W + F), the tearing and breaking strength retention, or the average of these, in yarn-mercerized fabric were often equal to the values for untreated unmercerized fabric. Yet the cross-linking of unmercerized fabric produced 33- 55% losses in breaking strength and 45-68% losses in tearing strength. Moreover the scoured fabrics, yarn-mercerized and unmercerized, were nearly identical in strength prior to cross-linking. The experimental fabrics, woven of yarn only partially restretched after slack-mercerization, possessed higher elongation when cross-linked than did unpretreated cross linked fabric.
Since strength losses during cross-linking can be varied or nearly eliminated without changing the wrinkle resistance ob tained, strength losses and wrinkle recovery are evidently produced by separate and, in some cases, independent cross-link mechanisms. Work of others indicates strength and elongation losses in conventional cross-linking processes are due to the spiral structure of fibrillar windings in the secondary wall of the cotton fiber. The fibrils cannot unwind fully and equally under stress after being cross-linked. Present findings suggest conditioned wrinkle recovery, as imparted here, arises in more elementary structural units, such as cross-linked microfibrils, where tensioning has little effect.
The possibility that a strength maximum can occur in cotton at optimal levels of cross-linking is re-examined, in view of evidence that swelling and tensioning pretreatments, as well as polymer inclusion during cross-linking, can alter the amount and type of cross-linking already present in cotton because of hydrogen-bonding and crystallinity.
Keywords
Get full access to this article
View all access options for this article.