Colorfastness

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Also present but not essential in permanent hair colorants are nitro dyes which dye hair without oxidation. These dyes, nitro derivatives of aminophenols and benzenediamines, impart yellow, orange, or red tones. Although they have good tinctorial value, they are not as colorfast as the oxidative dyes. They also are used in semipermanent hair colorants. 

Meta.1 Complexes. The importance of Ni complexes is based on their effectiveness as quenchers for singlet oxygen. Of disadvantage is their low colorfastness and their lower ir-reflectance compared to cyanine dyes (qv) therefore they are used in combination with suitable dyes. Numerous complexes are described in the Hterature, primarily tetrathiolate complexes of Pt or Ni, eg, dithiolatonickel complexes (3). Well known is the practical use of a combination of ben2othia2ole dyes with nickel thiol complexes in WORM disks (Ricoh, TDK) (17). 

Stilbene dyes ate classed as a subgroup of azo dyes having excellent colorfastness and typical direct dye wash fastness on cotton and ate arranged iato six categories by the Society of Dyers and Colourists (2), as described ia the foUowiag. 

Higher butyryl esters, formulated with acryUc polymers, provide coatings with excellent weather resistance, good colorfastness and dispersibiUty, and good flow properties (154). Formulations for a typical automotive refinishing lacquer and a wood furniture lacquer are given in Tables 12 and 13, respectively. Low viscosity, high butyryl cellulose esters tolerate substantial amounts of alcohol solvent without appreciable increase in solution viscosity. 

Vat dyes are water-soluble ki the reduced state but extremely kisoluble ki the oxidi2ed anthraqukione state (see Dyes, anthraquinone). As an example. Figure 2 shows the soluble and oxidi2ed states for Vat Yellow 3, used as a yellow colorant ki several lenses. The water-soluble form of the dye is allowed to diffuse kito the polymer matrix for a specified amount of time. The dye is then treated with a mild oxidi2kig agent and the kisoluble form is precipitated. The tints are extremely colorfast and stable for the life of the lens however, the dyes are unstable ki the soluble form and quite expensive. 

The principal methods of measuring colorfastness have been described in detail (34). Described below are the general principles for the tests as revised in 1990. Eor detailed information in English reference should be made to the 1992 AATCC manual equivalent (35). 

Fastness to Light. The ISO test for colorfastness to light is DajlightlSO 105-B01. The textile specimen is exposed to daylight under prescribed conditions, including protection from rain, along with a series of blue wool reference samples that fade at defined, prescribed, different rates. 

The test for colorfastness to artificial light Kenon arcfading lamp test ISO 10S-B02, is identical to BOl except that the sample is exposed to xenon arc light under prescribed conditions in a closed container. 

Dry Cleaning. In colorfastness to dry cleaning, ISO 105-D01 a specimen of the textile is placed in a cotton fabric bag together with stainless steel disks and agitated in perchloroethylene (30 min, 20°C) and the effect of the shade and the color of the solvent assessed using the grey scale. 

Water Tests. In colorfastness to water, ISO 10S-E01, the test specimen is placed in contact with the chosen adjacent fabrics, immersed in water, and placed wet between glass plates and left for 4 h at 37°C. After drying, the effect on the test specimen and stain on adjacents are assessed. The test, colorfastness to seawater, ISO 10S-E02, is the same as EOl but uses 30 g/L anhydrous sodium chloride solution instead of water. To test for colorfastness to chlorinated seawater/swimming baths water, ISO 10S-E03, the specimen is immersed in sodium hypochlorite solution containing either 100, 50, or 20 mg of active chlorine per Hter at pH 7.5 for 1 h at 27°C, rinsed, dried, and assessed. 

Eor colorfastness to perspiration, ISO 10S-E04, the specimen is immersed in a solution of 0.5 g/L of 1-histidine monohydrochloride monohydrate and 5 g/L sodium chloride buffered to either pH 8.0 (alkaH perspiration test) or pH 5.5 (acid perspiration test) in a dish at 50 1 Hquor-to-goods ratio, at room temperature for 30 min. The specimen is removed and, as in the water test EOl, left for 4 h between plates at 37°C before drying and assessing both test piece and adjacents. 

In colorfastness to acid spotting, ISO 10S-E0S, drops of a solution of either acetic acid (300 g of glacial acetic acid per Hter of water), sulfuric acid (50 g of concentrated acid per Hter), or tartaric acid (100 g of crystalline acid per Hter) are spotted onto the test material, which is then dried and assessed. Colorfastness to alkaH spotting, ISO 10S-E06, is like E05 except that a solution of 100 g of anhydrous sodium carbonate per Hter of water is used. Colorfastness to water spotting, ISO 10S-E07, is like E05 but uses drops of water and assessment is made after 2 min wet and after drying. In colorfastness to hot water, ISO 10S-E08, the textile specimen and adjacents are wound around a glass rod and placed in water adjusted to pH 6 with acetic acid at 70°C... 

The test colorfastness to potting, ISO 10S-E09, is of importance for dyed wool as potting is one of the processes woven wool fabrics can be given before they are made up iato clothing. The procedure is similar to EOS except that the test conditions are 1 h immersion ia boiling water. 

Colorfastness to decatiziag, ISO 10S-E10, iavolves a specimen wrapped around a perforated cylinder and through which steam is passed for 15 min at different pressures or temperatures to represent mild or severe conditions. In colorfastness to steaming, ISO 105-E1 /, a specimen and adjacents are roUed iato a cylinder and placed ia the neck of a flask of boiling water for 30 min. 

Golorfastness to Atmospheric Contaminants. The test colorfastness to nitrogen oxides, ISO 105-G01 is to assess the fastness of the color to nitrogen oxides that may be present ia hot air that has been passed over heated filaments or from the burning of gas, coal, etc. Specimens are exposed to nitrogen oxides ia a closed container along with standards until the standards have changed to a predetermined extent. 

Colorfastness to burnt gas fumes, ISO 105-G02 is similar to GOl except that the specimen and standards are exposed to the fumes from a burning butane gas flame. Colorfastness to o2one ia the atmosphere, ISO 10S-G03, is done as GOl but uses o2one. 

In fastness to peroxide bleaching, ISO 10S-N02, the specimen is immersed ia a standard bleaching solution containing hydrogen peroxide (or sodium peroxide for viscose) where the composition of the bleaching Hquor is dependent on the fibers used ia the test specimen as are the pH and time of exposure (1—2 h). The objective of the test is to assess the colorfastness usiag typical bulk bleaching conditions for the fiber under test. 

Other tests include assessing the colorfastness to solvents, felting treatments, stoving, vulcani2iag, merceri2ing, degumming, etc. 

Colorants must provide colorfastness under the required exposure conditions of light, temperature, humidity, chemical exposure, and so on, but without reducing other desirable properties such as flow during... 

Thus, given the demands of the textile industry, a well-trained young chemist like Perkin would have been alive to the dyeing possibilities in a beautiful purple solution. After experimenting with the solution on silk, Perkin realized he had discovered a process for transforming the chemicals in coal tar into a colorfast purple dye. 

G. Klarner, M.H. Davey, E.-D. Chen, J.C. Scott, and R.D. Miller, Colorfast blue-light-emitting random copolymers derived from di-w-hexylfluorene and anthracene, Adv. Mater., 13 993-997, 1998. 

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