The strength of dimethylolethyleneurea (DMEU)-treated yarns and fabrics has been studied as a function of yarn premercerization technique. Yarns, which were suitably mercerized and tensioned, possessed, after subsequent cross-linking, a strength equal to or greater than unmercerized, untreated yarn. Fabrics woven from certain of the mercerized yarns showed extraordinarily high strength retention when treated with DMEU. At a level of treatment which imparted 275-279° conditioned wrinkle recovery and a wash-wear rating of 5.0, the average percent of break and tear strength retention equalled or exceeded the same average for unmercerized, uncross-linked fabric. In one of these fabrics, the average strength retention, after cross-linking, was 96% of that prior to cross-linking. Thus, the effects of mercerization cannot be explained on the basis of a strength buildup which merely offsets subsequent losses during resin treatment. It is concluded that the strength of cotton after DMEU cotton-linking depends critically on the physicochemical state of the cotton prior to cross-linking. The results demonstrate that large strength losses are not inherent to the formation of covalent cross links in cotton cellulose and that cotton fabrics having high wash-wear performance can be produced with negligible reduction in strength properties.

A technique is described for determining the relative closing capacities, largely a reflection of swelling behavior, of fibers in the form of parallel strands of yarn packed tightly in orifices, by observation of the seepage of water through the yarn. The method has been used successfully to predict the performance of cotton yarns for the type of water-resistant fabric whose utility depends largely upon "self-sealing" by swelling. Relatively wide variations in yarn construction have been shown to have little effect on closing capacity, whereas fiber shape and size, as well as swelling properties, have pronounced effects.

Scourctl cotton yarns were acetylated by two processes: (1) by a 1 : 3 niisture of acetic anhydride and acetic acid to give a series of low-and niedium-substituted products ( P A ) ; and (2) n 1 : 1 niisture of acetic anhydritle and isopropyl acetate to give a series of mediurn-to highly-substituted products (FA). Perchloric acid was the catalyst in both processes. l'he products were stritlietl with reference to rate of esterification and changes in gross morphology, density, s-ray fiber diagram, tensile properties, and thermal behavior at various temperatures up to 230" C.Above about DS = 2, the x-ray diffraction pattern disappears. Although the gross niorphology, as viewed by electron microscopy, does not change noticeably during reaction, the density decreases progressively with substitution and is independent of method of preparation. On the other hand, breaking strength is influenced by acetylation process and increases somewhat as substitution increases.Themla1 studies disclose n plastic region in the products between 125' and 17j" C.Above that temperature crystnllization of cellulose triacctate I sets in and increases progressively with temperature to about 225' C. The plastic and crystal responses of tlie fibers are reflected in stiffness, elastic recovery, and resiliency behavior at different temperature regions..Esterification proceeds by what appears to be n diffusion-controlled reaction.The results are interpreted in terms of molcular structure.MANY studies liave been carried out o n tlie physical properties of regencrated cellulose and OII secondary and triacetatcs [22]. Sitnilarly, the properties of partially ncetylnted fibers, prodiiced by limited heterogeneous acetylation, have heen explored to a considerable extent [j, 101. However, stirprisingly little has been reported on the physical

Slack mercerization of cotton, with restretching to various degrees in the mercerizing alkali, was compared to mercerization at constant, preselected lengths as a method of yarn pretreatment. Fabrics were woven of these pretreated 2-ply yams and were crosslinked with DMEU to a wrinkle recovery of 270°-286° (W + F). In certain cases little or no loss of strength occurred during DP finishing, and the yarn-mercerized fabrics possessed greater strength after crosslinking than ordinary fabric not crosslinked at all. Moreover, after 20 launderings several of the experimental wash-wear fabrics equalled in strength the unmercerized, uncrosslinked, unlaundered fabrics prepared as controls. X-ray orientation, yarn strength, and elongation, as well as the degree of stretching during yarn pretreatment, were correlated with yarn and fabric strength after crosslinking and after fabric laundering. In yarn slack-mercerized and restretched to 91% of normal length, both the strength and the elongation after crosslinking equalled the values for unmercerized yarn before crosslinking. The same effect occurred in fabrics woven from these yarns. Evidence is presented that domains of swelled and shrunken cellulose remain in mercerized cotton fibers even after tension has been applied to orient the crystallites and straighten the fibrillar spirals of the alkali-wet cotton. The most effective yarn pretreatment, for increased strength retention after DMEU crosslinking, was slack mercerization followed by restretching to 103% of normal length. In fabrics woven of these yarns, covalent crosslinking by DMEU actually increased the durability, as measured by strength retained during multiple launderings. Yarn commercially mercerized to 102% of normal length also was highly suitable. The increased yarn length obtained in this kind of pretreatment could largely offset the cost of yarn mercerization, leaving the cost of yarn plying as the principal item of expense.