Textile Research Journal

The results of swelling treatments which go beyond mercerizing at ordinary temperature indicate that there is an upper limit to the swelling of cotton, with increased luster as the objec tive. If this is exceeded, as it is with strong sulfuric acid or zinc chloride, and probably is with mercerization with caustic below 0°C, the luster is decreased, because the surface of the indi vidual fiber is roughened.

Drastic shrinkage of yarn volume, combined with film formation and disappearance of fuzz, can leave the fabric very sheer and transparent, attributes often correlated with luster. Me chanical action on the plastic cellulose, or on films of cellulose or hydroxyethyl cellulose de posited from solution, can give increased luster through flattening and mechanical stabilization in the flattened form. These cellulose-affecting treatments tend to leave the fabric stiff, if they go beyond normal mercerizing.

Other additive finishes act on luster either through film formation or by stabilizing mechani cal effects and controlling fabric structure. The more flexible thermoplastic resins can, with mechanical smoothing, produce an increase in the physical measurement of luster. However, this effect is less than that of mechanically smoothing the fabric without the thermoplastic resins, so the chief advantages lie in the other effects of these finishes, such as possible greater stability of the mechanical finish with the resin present.

In the higher ranges of luster, the eye can discriminate between luster arising from film formation or flattening, and the type of luster arising from yarn and fabric structure and from mercerizing.

The discovery that synthetic resins could be used to improve the crease recovery of cellulosic fabrics was made on a rather empirical basis more than 25 years ago. Since that time much has been learned about synthetic resins, textile fibers, and their combination in the creaseproofing process. Yet many questions remain unanswered. This paper discusses some of the aspects of the subject that are still controversial: (A) Differences between cotton and rayon and the rea sons therefor. Factors considered include tensile strength, tear strength, abrasion resistance, permeability of the fibers, resistance to acid hydrolysis. (B) A brief commentary on attempts to make cotton more like rayon. (C) Mechanism of crease recovery, with emphasis on the ques tion of covalent crosslinking vs. resin formation. (D) Other aspects of crease resistance, em phasizing subjective characteristics such as fabric hand.

The discussion throughout is more expositional than argumentative; that is, the problems are explained, with no attempt at resolving them. A few conjectures are made where feasible.

Native cellulose dissolves in cuprammonium hydroxide solution, but, when it is crosslinked, it becomes a space polymer and is insoluble in this reagent. A method of detecting alkali-stable crosslinks in cotton is presented—the sample to be tested is shaken with cuprammonium hy droxide solution for 17 hr. If it dissolves completely, cellulose chains are not crosslinked, but, if it is partially insoluble, crosslinking is indicated. Partially insoluble cellulosic material appears in the cuprammonium hydroxide as granules that are easily detected visually.

Cellulose was reacted with compounds which contained one or more groups that are reactive toward cellulose. In all cases the cellulosic derivatives made from cellulose and compounds that could crosslink it were partially insoluble in cuprammonium hydroxide. The compounds that were not capable of crosslinking cellulose produced derivatives soluble in cuprammonium hydroxide.

Cotton was made insoluble in cuprammonium hydroxide by reacting it with formaldehyde, glyoxal, chloroethylsulfuric acid, α,γ-glycerol dichlorohydrin, a mixture of α,β- and α,γ-glycerol dichlorohydrin, tetrakis (hydroxymethyl) phosphonium chloride, compounds containing two or more N-methylol groups, 1,4-disulfato-2-butyne, and potassium (disulfatoethyl) amine. Aminized cotton, which is soluble in cuprammonium hydroxide, was made insoluble by cross linking it with either formaldehyde or tetrakis (hydroxymethyl) phosphonium chloride.

Suitable cotton yarn or cloth mercerized without tension shrinks and its elastic properties are changed. Either yarn or fabric in its "shrunk" form shows greater than normal elongation, approximately in accordance with the amount of shrinkage that it has undergone. Either, also, tends to have increased elasticity. This feature is especially notable at low loads in open-weave fabrics, which usually have considerable stretchability after shrinking. Such elasticity is illus trated by a semielastic and conforming cotton gauze bandage which is in successful commercial production. This type of shrunk material, in heavier goods, appears adaptable to other uses, such as base fabrics for coating when elasticity is a required property of the coated fabric.

The mechanism of cyanoethylation of cotton is discussed, and it is shown that for best effi ciency the pick-up of sodium hydroxide must not exceed 15% of the weight of the cotton. Measurements of physical properties show that any increases in the breaking strength or elon gation of yarns are results of changes in frictional forces. The physical properties of cyano ethylated fabrics reflect the properties of the yarn and are also dependent on fabric construction. Extremely high resistance to flat abrasion is obtained with high cyanoethyl substitution.

The density of cyanoethylated cotton is shown to be linearly related to the nitrogen content, and the spread of values obtained has been found to give an estimate of the uniformity of treatment.

Cyanoethylated cotton can be dyed by methods developed for polyacrylonitrile fibers such as those employing acid dyes in the presence of cuprous ion, and the dyed samples so produced are suitable for cross sectioning for microscopic examination. The intensity of dye color can be used as a measure of the amount of cyanoethylation.

Flame-resistant cotton fabrics have been prepared by treatment of the fabric with an aqueous emulsion of an organic polymer, prepared from bromoform and triallyl phosphate. The finish is durable to repeated laundering, and when applied with proper plasticization to fabrics of 8-9-oz weight does not materially change other textile properties. The treatment may be applied on conventional textile finishing equipment.