Influence of Swelling and Mowosubstitution On the Strength of Cross-Linked Cotton

The reduction in the wear resistance of cotton fabrics in wrinkle-resistant, wash-and- wear, and durable press garments is shown to be related to the lowering of fiber, yarn, and fabric toughness resulting from concentrated cross-linking of limited regions of the cellulose polymer network. Various approaches which have been suggested for improv ing over-all toughness in cotton fabrics are reviewed and discussed. A new concept is presented for achieving major improvements in tensile strength, elongation, tear strength, toughness, flexing resistance, and surface abrasion resistance of wrinkle- resistant cotton fabrics. This concept involves the swelling of cotton fibers to increase the sites for chemical reactions, introduction of bulky, plasticizing side groups, and, finally, cross-linking the distended polymer network to achieve more uniformly placed cross links than is possible in existing methods. Preliminary experimental data are presented for several cases which help to support the above concept. Both by sequential swelling, substitution, and cross-linking and also by one-step reaction with fiber-reactive swelling agents, it is demonstrated that substantial improvements may be obtained in all or some of the various fabric mechanical properties. Studies are described on the characterization of the swelling effect of various organic structures and on the synthesis of cellulose-reactive monofunctional and polyfunctional swelling analogs. Aqueous solutions of increasing concentrations of such compounds are shown to produce variously shaped swelling-concentration curves. When cross-linking swellable, substituted cotton fabrics, much less strength and toughness reduction is produced than is normally obtained in unmodified cotton. Some esterifica tion reactions, however, themselves produce some strength loss prior to cross-linking and need to be improved. Others, such as carbamylation, ethoxylation, and grafting have given higher strength retention. In some cases, substantial increases in both flex and surface abrasion resistance have been produced. This work is continuing in attempts to synthesize the most efficient monofunctional and difunctional cellulose swelling and reactive pair of reagents.