NOTES ON ANALYTICAL PROCEDURES Textile Finishes and Fiber Identification Stains B R A H A M NORWICK', Beaunit Mills, Cohoer, N. Y.
IT HAS been
The fibers based upon cellulose can be treated to give test dyeings in all the available shades.
recognized that dye mixtures such as the Hahn stains and the more versatile Davis and Rynkiewicz modification ( I ) are not entirely adequate for the identification of treated rayon fibers likely to be encountered in processed fabrics. The presence of added substances in the yarn, as well as the chemical and physical history of the fabric, frequently results in peculiar alterations of test dyeing properties. Under such circumstances, once the yarns are known, anomalous dyeing may serve to determine'the finish or the extent to which processing has been carried. When the treatment is known, the shade obtained may be of value in control, once one has established a set of standards; this is illustrated in Table I, which indicates the influence of causticizing upon subsequent test dyeing with the Davis and Rynkiewicz stain.
Cotton, dried with formaldehyde and a trace of acid, moistened with ammonia, and then heated either in an oven or in an organic liquid such as lauryl alcohol, quickly loses its ability to pick up blue and shows first reddish shades and then yellows. Drying cotton with glyoxal gives similar results. The presence of melamine, even if unreacted-that is, in a state where it is extractable with water-as it might be if em loyed for inhibiting the gelatinizing action of concentrate$ sulfuric acid upon cotton, cause8 the latter to pick up yellow. Drying wscose with glyoxal yields a yarn which dyes a pale yellow. The common creaaeproof and shrink-resisting urea-formaldehyde finish gives yellow shades: one interesting sample of plainweave spun rayon showed a test dyeing yellow on one face and lavender on the other, due to the use of dry cans contacting and reacting the resin on only one face of the fabric. Incomplete and uneven desizing, which may be manifested in a variety of ways, such as a slight uneven luster or dullness, or variable tear strengths and air permeabilities, can be rapidly detected on known fabrics of nylon, viscose, and acetate, since the common size materials stain a deep, contrasting blue. I n such cases, and with mixed fibers, examination of the dyed sample under a low-power microscope may be a source of further information about the condition of the material. There is a relation between the extent of alteration of, test dyeing properties and the effective treatment, but this is generally true only over short ranges, and even there one will find in commercial treatments that interferences uncontrollable by the analyst are of such magnitude that in general only qualitative information can be obtained. Appreciating this fact, however, for satisfactory qualitative tests, the analyst has considerable leeway, following the Davis and Rynkiewicz staining suggestions.
Effect of Caustic Treatment upon Subsequent Dyeing
Table 1.
25' C.
Concentration of Caustic 1 -%-
Time Min. 0.5 1
5
0.5 1
5
Greenish yellow Greenish yellow Greenish yellow Lavender Lavender Lavender
25%. 25* C.
5%-
25O C.
50' C.
5OOC.
Acetate Greeniah Greenish yellow yellow Green Greenish yellow Blue Green Lavender Lavender Lavender
Green
Viscose Blue Blue Violet
Green
Greenish yellow Greenish yellow
Violet Violet Dark blue
Dark blue Dark blue Dark blue
In testing samples which have had unknown treatment, one must first consider the primary color components which go to make up the shade obtained. The possible significance of the various colors is not easily limited, but the probabilities, especially when considered along with the particular type of fabric under examination, are indicated in Table 11. Table I11 indicates how one may make further subdivisions in such a typical treatment as sizing. The various families of finishes may be distinguished by test dyeing before and after special treatments: enzymes for prot,eins, 5% sulfuric acid a t a boil for urea-formaldehyde resins, alcoholic extraction for cationic softeners. f
LITERATURE CITED
(1) Davis, H . L., and Rynkiewicz, H. J., IND. ENQ.CHEM., ANAL ED., 14,472 (1942).
Priority Assistance to Laboratories Conditions under which priority assistance is given to laboratories were clarified March 6 by the issuance of Preference Rating Order P-43 as amended. Any person who carries on scientific or technological investigation, testing, development, or experimentation in his business is considered to operate a laboratory in buying material for these purposes, even though he does not have a separate department or organization for such activities. Priority ratings assigned by the order may be used to get materials for development of products designed primarily for future civilian markets only if such activities will be carried on without diverting any manpower, technical skill, or facilities from war work. Laboratories may not use AA-1 preference rating for activities connected with future civillsn needs. Restrictions on the quantity of aluminum that may be obtained under the order are removed. Priorities assistance assigned under P-43 may be used for construction jobs costing not more than $500 without applying for permission to start construction under L-41. Procedure for obtaining controlled materials has been simplified, and the allotment number V-9 is used in place of MRO-P-43.
Present addreaa, Aberdeen Proving Qround, Md.
Table II. Color Components Blue Cuprammonium cotton Vinyon Sizes Cationic materials Attacked viscose Attacked acetate
Yellow Aoetate Nylon Wool Heavy oiling Melamine Aldehyde reaine
Red ViaCOE0 Attacked wool Aldehyde resins
Table 111. Alkali- and Water-Soluble Sizes Blue Starches Protein adhesives Cellulose ethers Polyvinyl alcohols
No Color Natural gums Natural resins Alkyd resins
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