Low-twist yarns made from Deltapine cotton were ethanol-extracted and chemically treated while slack. Fibers were taken from yarns treated with formaldehyde, by various procedures producing differences in swelling of the fiber structure when cross-linked; dimethylol ethyleneurea; N-methylol-N'-methylethyleneurea; and oleoyl chloride. Single fibers progressively lose strength and elongation with increasing cross links when tested at 70°F, 65% RH and when wet. Cross links introduced in the swollen fiber structure usually cause less strength loss than those introduced in the nonswollen structure. Tensile strain recovery for single fibers increases with increasing cross links. The initial are more effective than the subsequent cross links. Increased energy recovery is related to increased strain recovery. Single fibers cross-linked in slack yarns show increases in recovery with decreases in stiffness. The retention of strength and the improved ability to recover are limited to some modifications, especially under the wet conditions. Changes in mechanical properties of cottons by smooth-drying treatments are due, in part, to changes in mechanical properties of the individual fibers.

SynopsisThe graft copolymerization reaction of methyl vinyl ketone from several solvents with fibrous cotton cellulose, preirradiated to a dosage of 5.2 X 1019 eV/g with y-radiation from B°Co, was investigated. Solvents included water, methanol, N,Ndimethylformamide, and several combinations of these solvents. From water a maximum yield of copolymer product was obtained after 2 hr at 25OC. The addition of methanol to aqueous solutions of methyl vinyl ketone', in all concentrations, inhibited the graft copolymerization reaction. The addition of a small amount of N,Ndimethylformamide to aqueous solutions of the monomer increased the rate of the copolymerization reaction; however, the addition of large amounts of N, Ndimethylformamide to these solutions also inhibited the reaction. From solutions of methanol or N,Ndimethylformamide and monomer, little or no copolymerization of monomer with irradiated cellulose occurred. The copolymer products exhibited a strong infrared absorption band at 5.85 p which is characteristic of the -C=O group of the ghfted poly(methy1 vinyl ketone). Fibrous copolymer yarns exhibited increased yarn number and decreased breaking strength and average stiffness, as compared with unmodified cotton yarns.

Protection of fibrous cotton cellulose from weathering degradation and from degrada tion on exposure to high energy radiation (as measured by breaking strength retention), by substitution of benzoyl groups on the cellulose molecule, was demonstrated. It can be concluded that the presence of the benzoyl groups affected the absorption of incident energy by the cellulose molecule and/or the localization of energy within the molecule.

We have reported the substitution of aromatic groups and of substituted aromatic groups of glutosides [2,[9][10][11][12][13] and fibrous cellulose [2][3][4]6] to yield products which were resistant to degradation on exposure to high-energy, radiation. Phenyl-carbamylated glucosides were resistant to radiation-initiated degradation [11][12][13]. Also, solutions of phenyl-carbamylated glucosides exhibited fluorescent spectra with wavelengths slightly longer than those of their excitation spectra [12]. This indicated that most of the energy absorbed on excitation was emitted during fluorescence. These results suggested that cotton cellulose, reacted with phenyl isocyanate, would be resistant to radiation-initiated degradation.Cotton cellulose (about 4 g of purified Deltapine cotton [7] spun into 7s/3 yarn) was dried in '11 forceddraft oven for 1 hr at 110°C. A solution of dry pyridine containing 15 wt. % of phenyl isocyanate (about 100 g) was placed in a round-bottom flask fitted with a reflux condenser from which moisture was excluded by means of ~a CaCl2 tube. After the solution had been heated to reflux (about 130°C) the dried yarn was immersed in the solution under reflux conditions for the length of time required to give the desired degree of substitution (DS) on the cellulose. On completion of the reaction, the phenyl-carbamylated cotton yarns were washed three times with methanol at 50-60°C [8]. In one procedure, the yarns were left in the slack condition during the washing with methanol. In another procedure, the yarns were restretched to about 80% of their original length and then washed with methanol. Finally, the yarns were washed with distilled water and air-dried.The DS was calculated from the increase in weight of the original yarn. Textile tests were done according to ASTM methods [1], and other tests were done as previously described [5].The mechanical properties of phenyl-carbamylated cotton yarns (restretched before drying) are shown in Table I. If the substituted yarns were not restretched before drying, the values for the properties were decreased to values lower than those shown in Table I.