Wet-Fixation DP Process—Polymer Deposition1

Abstract

When made into simulated cuffs and laundered twenty times, twill fabric given a wet-fixation treatment was found to abrade quite differently from twill finished by a pad-dry-cure process. Sections of these fabrics examined in the electron microscope revealed an even distribution of resin in the wet-fixed samples and little tendency for fibrillation from beating or washing. The expansion techniques of the SURDD applied to these sections revealed a tight bonding of cellulose layers in the wet-fixed samples. Samples from the same treatments examined in the transmission-interference microscope revealed a definite loss in internal birefringence in the wet-fixed samples and a smaller loss in the pad-dry-cure samples, revealing again a difference in degree of penetration of the resins from the two systems. In addition, with this means of viewing in which the treated fibers appear in brilliant interference colors, there was clear indication of sub stantial polymer formation inside the fibers given the wet-fixation treatment. This is possible because the refractive index of these fiber sections can be measured directly, and this technique provides an interesting avenue for future studies of resin-treated cottons of optimum performance. Both types of treated cotton were observed in replica experiments, each showing a fiber surface coating, presumably of resin, masking the surface striations of untreated cotton. Strength and elongation measurements on yarns and fibers from these same samples revealed, however, that neither treatment resulted in measurable interfiber sticking or bonding. Instead, the differences in strength and elongation noted in the fabrics were even more pronounced in the yarns and fibers of each. Only the wet-fixed samples retained a substantial portion of the original cotton fiber strength and elongation properties. If these particular changes in cotton introduced by the wet-fixation process are the main ones responsible for the enhanced performance of treated fabrics, then it appears that there may be several routes to placing resins in the right location in cotton for effective use. Vapor-phase grafting may, indeed, be an example of such a variation.

Structural Features of Cotton Treated by Pad-Dry-Cure, Mild-Cure, Poly-Set, and Wet-Fix Processes

“…This is very evident in our results, and it has been emphasized by Hollies [ 10 ] on the basis of interferencetransmission microscopy studies with high add-on fabrics.…”

“…structure (noncollapsed) in the fiber (by comparison to that cross-linked by the pad-dry-cure process). This is shown by the higher moisture regain reported by Hollies [ 10 ] and Honold [12], by the higher accessibility of periodate reported by O'Brien et al [ 14 ) , and by the rather complete expansion of thin cross sections of wet-fix cotton (either fixed-only or fixed and cured) when subjected to the methacrylate expansion technique (pad-dry-cure compositions did not expand). These expansion patterns reported by Rollins [ 18] for wet-fix cottons characterized by 4-6% add-ons are in contrast to earlier results reported by Hollies [10] for samples with substantially higher add-ons.…”

“…To facilitate the comparisons among the reactions, an arbitrary time scale has been employed with unity designating that time required for &dquo;complete reaction,&dquo; i.e., the apparent optimum extent of reaction for each process. The shapes of the curves and the final levels of bound N or add-on (Table I) [23]; 8-15°~~ add-on was employed In early studies [10,11].…”

Improved Cotton DP Through Dry-Cure Deposition of Polymers Containing Reactive Groups1

“…The absence or, at least, the very low reaction rate of these compounds in acidic aqueous solutions indicates strong solvation of the protonated species. The solvated species require elevated temperature or long time [3,4] to yield substantial quantities of polymers. The activity of the protonated species is high enough, however, to give fast polymerization even, at room temperature, when the solvating water is removed.…”

“…Prahl [6] showed correlations between physical parameters of the polymer deposit and final fabri,c characteristics. In wet polymer-deposition studies [3,4,5] (so-called wet fixation processes), the swelling of the fiber and thereby, its penetration by the monomer and the final polymer distribution are emphasized. In still another direction, the latent reactivity of the deposited polymer with the cross-linking agent is being in-, vestigated [9,10] .…”