Wet and dry density measurements were made on a wide variety of wash-and-wear cotton fabrics and some interpretations of these values are given. Methylenated cotton was selected for more extensive fundamental study because of the simplicity of the formaldehyde cross link and the fact that formaldehyde can be reacted with cotton under greatly different conditions. Formaldehyde was used to cross link cotton print cloth at various degrees of fiber swelling by reacting in systems ranging from completely aqueous to anhydrous using hydrochloric acid as catalyst. The amount of water in the system at the time of reaction is related to the extent of fiber swotting. The extent of swelling at the time of cross-linking and the extent of cross-linking influence wet density, which may be considered to be a measure of the water swellability of a fiber. Cross-linking tends to fix or stabilize a fiber in a given state of swelling: the stabilization is more effective when the cross-linking is done in nearly anhydrous systems. The state of swelling at the time of cross-linking modifies moisture regain, water of imbibition, dyeabitity, and wet and dry wrinkle recovery. There seems to be an optimum water content in the reaction system at the time of cross-linking for maximum dry and wet wrinkle recovery. As the water content in the reaction system is increased beyond the optimum, the amount of dry wrinkle recovery becomes much less than wet wrinkle recovery. This phenomenon leads to vastly different wash-and-wear ratings of fabric.A mechanism is presented diagrammatically to explain wet and dry wrinkle recovery. The mechanism is based upon hydrogen-bond cross links, covalent-bond cross links, and the position of the two types of cross links.AL.'FHOUGH wrinkle resistant cotton fabrics have heen known for about 30 years, many of the basic principles for imparting wrinkle recovery are not too well understood. The wrinkle recovery and washand-wear characteristics of a textile are affected by its construction and by the construction of the yarns of which it is composed. However, the properties of the fiber which make tip the yarn and fabric have, perhaps, an even greater influence on wrinkle recovery and wash-and-wear properties. Cross-linking within the fiber seems to have been accepted by most researchers as the hasic requirement for wrinkle recovery. It provides an excellent way of changing many of the properties of cotton fiber. The physical properties of cross-linkeci goods are quite well known, but the principle of producing physical changes with -----.-----.. cross links within the microstructure of the fiber, which is actually responsible for the fiber properties, is not too well defined. Differences have been observed between the wrinkle recovery of cotton fabrics finished by the pad, dry, and cure process and the wrinkle recovery of fabric finished while swollen in mercerizing strength alkali solution. The first of these processes, which is often thought of as reacted in the collapsed state, imparts wet and dry wrinkle recovery....

Two processes for producing wash-wear cotton fabrics by treatment with formaldehyde are described. One of these processes consists of reacting the fabric in a wet swollen condition in an aqueous solution of formaldehyde and hydrochloric acid. This fabric has good wet wrinkle recovery only and is therefore referred to as the Form-W process. It has good strength retention and is suitable for line-drying after washing. The other process consists of reacting the fabric in a wet, partially swollen condition in a solution of acetic acid,. water, hydrochloric acid, and formaldehyde. It is referred to as the Form-D process because the fabrics have good dry (as well as wet) wrinkle recovery. These fabrics are suitable for either line-drying or tumble-drying. It is very important in both processes that the fabrics be well mercerized if adequate strength is to be re tained. Softeners also improve the tearing strength. Laboratory and pilot-plant appli cations are described, and data on the physical properties of the fabrics presented. Reaction rates of the Form-D process at various temperatures are given. Also, preliminary work on other solvents and catalysts is discussed briefly. Cross-linking with formaldehyde at various degrees of fiber swelling is discussed briefly from a theoretical standpoint.

A new group of polymers made by reacting tris(1-aziridinyl)phosphine oxide, referred to as APO, or tris(1-aziridinyl)phosphine sulfide, referred to as APS, with tetrakis-(hydroxymethyl)phosphonium chloride, referred to as THPC, are good permanent-type flame retardants for cotton. All three of the compounds are water-soluble crystalline materials. The application of APO-or APS-THPC resins to textiles consists of padding fabric in an aqueous solution of the compounds, drying the fabric, curing it at about 140° C. for about 5 min. to polymerize the compounds, and then rinsing the fabric to remove any unpolymerized material.About 8% of the resins in 8-oz. cotton twill or sateen is adequate to make the fabric pass the vertical flame test before or after 15 launderings with synthetic detergents, followed by an acid fluoride sour after each laundering. The flame resistance is also very durable to boiling alkaline soap solutions.The properties of fabric treated with these new polymers are, in general, excellent. The hand and strength of the fabric is only slightly different from that of untreated fabric. The flame-resistant fabrics are resistant to rot and mildew.SEVERAI. permanent-type flame retardants for cotton have been developed at the Southern Regional Research Laboratory [2, 4, 5, 6, 8, 10 ~ . Although it is helieved that all of these represented improvements over those currently available for commercial use, none of our flame retardants are completely satisfactory. Because of the importance of this prol)-lem from a military and civilian point of view, our studies on name-retardant finishes for cotton are being continued.One of the flame retardants reported recently is based upon a TH PC resin {8}. It is formed by the copolymerization of tetrakis ( hydrox )'111ethyl ) pho~-phonium chloride, THPC, with a methylolmelamine and urea. It has received attention from a number r of textile finishers and is now being used for fini,hing both cotton and viscose rayon. Finishing fabrics with the TH PC resin is reasonally simpte: it con sists in padding fabric through an aqueous solution of the monomers, then drying and curing to potymerize the name retardant inside the cotton fiber. Two flame retardants which contain bromine have been reported by members of Southern Regional Research Laboratory. These are formed by making a telomer of triany!phosphate and bromoform in onecase [4 and a tetomer of a!ty!phosphonitritate and bromoform in the other case {5). The polymers are prepared in aqueous emulsion. They are applied to fabric in essentially the same manner as TIII'C resins.Two additional name retardants were reported that are for111ed ty combining about one part of either of the aqueous emulsions of the telun~ers with about three parts of TI [PC resin-forming monomers fi, 10 J . The resulting emutsions are also applied to fabric by the same technique used to ahply the 'I' E 1 I'C resin.The purpose of the present paper is to present our most recent and interesting flante retardants which are based upon resins made by react...

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