Textile Research Journal

The "blocking friction" model by Grosberg et al. has been applied to experimental results of loop bending recovery by Stuart et al. The failure is demonstrated and ex plained qualitatively. Then the "continuous" frictional-plasto-elastic model by Olofsson is applied together with a hypothesis of "form conservation" whose general importance is further discussed in the Appendix. The agreement with experiments is demonstrated to be most satisfactory.

Nylon 6 and poly(ethylene terephthalate) monofilaments were subjected to various levels of twist inserted under constant load. X-ray diffraction patterns of the twisted filaments were obtained and the axial dispersion of the crystalline regions was estimated from the azimuthal spreading of the equatorial diffraction arcs. The experimentally obtained values were compared with those calculated by assuming that the fiber under goes a uniform deformation. The data show that the crystalline orientation does not follow the macroscopic twist imparted to the filament. The discrepancy is largest at small twist angles, indicating that at this stage the twist is taken up primarily by regions that do not give rise to coherent x-ray scattering. At higher twist angles, there is indi cation that a tilting of crystallographic planes accompanies the reorientation of the crystallites. The effect of crystallite disorientation on the properties of the fibers is discussed.

Graft copolymerization reactions of methyl, ethyl, butyl, hexyl, and lauryl methacrylates and 1,3-butylene dimethacrylate with fibrous cotton cellulose were initiated by the simul taneous irradiation procedure, using ⁶⁰Co γ-radiation. The fabric properties of the poly(alkyl methacrylate)—cotton copolymers (methyl, ethyl, butyl, and hexyl) were determined at two degrees of grafting. The flex abrasion resistance of the poly(hexyl methacrylate)—cotton copolymer at 37% add-on of polymer was more than ten-fold that of the cotton fabric control. The flat abrasion resistance of the poly(ethyl methacrylate) —cotton copolymer was ten-fold greater than that of the fabric control. Examination of electron microphotographs of thin sections of the copolymers embedded in aqueous polyvinyl alcohol indicated that layer opening of the fibrous structure occurred during graft copolymerization and that the degree of layering and size of the opening was related to the molecular weight of the monomer being reacted. The radiochemical yields of the reactions ranged from 4,600 to 44,000 molecular actions per 100 eV at a dosage of 0.5 MR.

The effects of fiber parallelization and drafting tenacity were investigated on several cottons. The average drafting tenacity was directly related to the total amount of hooks present before drafting. When one cotton was processed through eight drawings, the total amount of hooks and drafting tenacity after each process were logarithmically related to the number of processes, with a decrease in slope occurring for each property after the fourth drawing process. When the majority hooks trailed at first and second drawing, fiber parallelization increased over the conventional drafting direction. Post- combing drawing does not reduce the amount of hooks significantly. A linear relation ship exists between hooks in roving and hooks in the sliver fed to the roving frame.

Eleven N-arylcarbamylated celluloses were prepared by a pad-cure treatment of cotton with phenyl N-arylcarbamates as isocyanate generators. Add-ons up to 8.5% were obtained by impregnating the fabric with a dimethylformamide (DMF) solution of the phenyl carbamate and curing at 180-200°C for 4-5 min. The extent and efficiencies of these cotton cellulose reactions were observed by means of add-ons, nitrogen contents, and change in pickup of acid dyes. The activating aryl substituents were dialkylamino, methoxyl, methylthio, and methyl electron-donating (+E) groups. N-pyridylcarbamates were also used. The modified cotton fabrics exhibited improved rot resistance and those containing amine groups had ion-exchange properties.

When wool fibers which have been shrinkproofed by either the KMnO₄/salt process or a dry chlorination process are examined with the optical microscope, normally, very little effect of the treatment can be seen. However, if they are straightened for the examination, a number of differences between treated and control fibers can easily be seen, especially if water is present. The principal effects are that the scales on the treated fibers, but not on the untreated, become less prominent as the fibers are straightened and that this change is much greater on the side which was the intrados of the crimp curve than on the extrados. Microscopic observation of fibers sliding on each other or over a diffraction grating also reveals effects of the treatment: the deforma tion of the scales of treated fibers is more plastic and less elastic than that of untreated and the sliding of the treated fibers is more heavily damped. From these and other observations, the conclusion has been drawn that these treatments degrade the protein inside the scales so that it becomes more viscous and less elastic, particularly when it is swollen by or dissolved in water. The epicuticle appears to be unbroken and still elastic.

These results throw some light on the well-known disagreement between different workers about the changes produced in the coefficients of friction of wool fibers by the KMnO ₄/salt treatment.

¹ In the comprehensive study of crimp recovery by Banbaji et al. [Textile Res. J. 32, 568-572 (1962)], the fiber was allowed to contract slowly and continuously. The observa tions described here refer essentially to discontinuous re covery.

The effects on cotton of esterification to low degrees of substitution have been investi gated by light and electron microscopy. Observations were made on partially esterified celluloses which included esters of acetic, palmitic, stearic, 12-hydroxystearic, linoleic, and ricinoleic acids and of the aromatic benzoic, cinnamic, naphthoic, and pkenylundecanoic acids.

The uniformity of the esterification of cellulose was followed by dyeing and swelling techniques. Refractive index measurements were used to follow changes in optical anisotropy which accompanied the chemical modification. The average refractive indices of cellulose esters containing aromatic groups were greater than those of the esters with aliphatic substituents, the greatest difference being between indices measured perpendicu lar to the fiber axis.

The normal fibrillate texture of the scoured surface appeared to become smooth upon esterification.

Fragmentation of the esters in water in a laboratory blendor produced long strands of fibrillate material intermingled with clumps of spongy or amorphous material. On de-esterification of the fragments with an alcoholic base, the structure of the material reverted to that of unesterified cotton—fibrils became distinct and, in some cases, saponification proceeded to a stage where hydrocellulose-like particles were formed. ,

Many of the esterified fibers of low degrees of substitution swelled in the conventional methacrylate embedding technique. The swelling caused the cell wall to separate into layers, and the internal structure could then be studied by examination of thin sections of these fibers with the electron microscope. By use of an alternative embedding medium, aqueous polyvinyl alcohol, in the preparation of thin sections, compact unlayered struc tures of the esterified cottons were obtained. This permitted observations of the undis turbed structure of the modified cottons. Both types of observations were used in the microscopical evaluation of cotton fibers esterified to low degree of substitution to demonstrate structural changes brought about by the esterification reaction.

This paper is concerned with the significance of stretch-textured yarn properties in relation to the character and properties of filling stretch fabrics constructed from them. The study deals with a series of commercially produced false-twist textured polyester and polyamide multifilament yarns having various filament and yarn denier combinations made under different stretch texture processing conditions. These yarns represent differ ent combinations of stretch and bulk texture and cover the range of shrinkage properties and yarn geometries usually employed in the construction of woven stretch fabrics.

Each of the false-twist textured yarns was used to construct filling stretch fabrics containing different combinations of weave type, weave texture, and warp yarn count. All of the test fabrics were commercially finished by conventional means to achieve maximum filling stretch potential and were subsequently tested to evaluate fabric stretch performance characteristics. Data obtained during the performance of this work have led to the conclusion that one can obtain a physically meaningful correlation between yam and fabric properties by considering retraction force in addition to linear yam shrinkage. fabric weave type, and fabric cover factors. Prediction of fabric stretch from the properties of false-twist textured yarns depends upon the ability of the yarn test and evaluation procedures to duplicate the loading and mechanical restraint histories experi enced by the yarn during its conversion into woven and finished fabric.

The merits of using loom-state as opposed to off-loom dimensions as a basis for computing fabric shrinkage and, hence, computing fabric stretch, are discussed.