Development of a Dyed Verification Standard Development of a Dyed Verification Standard

Color fastness is important for satisfactory performance of textiles in use. Successful color fastness testing relies on accurate interpretation of published test methods, and control of laboratory conditions. The accuracy of testing may be checked by the use of a verification standard, which should produce known results if the test is carried out correctly. The AATCC does not have a verification standard for two of its most often-used colorfastness tests: Method 15 (Colorfastness to Perspiration) and Method 61 (Colorfastness to Laundering). A survey of dyes in the Colour Index was used to select candidate disperse, direct and acid dyes on the basis of their fiber suitability, fastness, availability, and hue. The dyes were applied individually to cotton or nylon as appropriate, and their fastness to perspiration and laundering assessed. The results were used to plan combinations of dye, which were applied to a nylon-cotton blend. Once again, fastnesses of the dyeings were assessed. In a final step, the combination dyeings showing the most appropriate (i.e. borderline pass/fail) levels of fastness were subjected to the variations in the test method conditions to see which responded most strongly to such variations The combination comprising of Direct Blue 80 (0.2% owf), Disperse Red 60 (0.5% owf) and Acid Red 299 (0.2% owf) performed well as verification fabric for colorfastness to laundering. This combination did not perform well as a verification for colorfastness to perspiration; such a fabric will need to be developed separately.


LIST OF TABLES
The coloration of textile products has been practiced since ancient times. Today, the majority of textile items are colored by dyeing or printing. Colorfastness is the resistance of a material to changes in any of its color characteristics, transfer of its colorant(s) to adjacent materials, or both as a result of exposure to any environment that might be encountered during the processing, testing, storage or use of the material. Hence, colorfastness is an important deciding factor in evaluating the quality of a colored textile. (AATCC, 2015) Colored textiles should exhibit satisfactory colorfastness to agents such as light, laundry, crocking, chlorine, and perspiration based on their intended end use. Agents such as acids/alkalis, oxidizing/reducing agents, dry-cleaning solvents, burnt gas fumes, heat, oxides of nitrogen, ozone, and chlorinated water, may cause color changes in textiles, and fastness to those agencies also may be required and determined by testing.
When consumers put these colored textile products to use they are expected to be fast to common agents such as laundering, perspiration, light, and crocking. A product that fails to perform satisfactorily results in degrading the brand image as well as a huge loss for the company and the manufacturer. Hence, rather than wait for poor fastness to reveal itself during use by the ultimate consumer, its likely occurrence may be predicted by standardized test methods. Committee on the Standards for light perspiration and washing described four series of washing tests based on the severity of laundering. Two series of standards, one in blue and one in red, were selected to provide a pass/fail result. (Tordoff, 1984) In 1942, tests showed that the dyed standards were not satisfactory. In fact, they were developed only to show the permissible loss in color under a particular test only to facilitate the judgment of results. (Tordoff, 1984) The colorfastness test to laundering for dyed or printed cotton followed by AATCC With the introduction of gray scales, the use of dyed standards declined, although verification or control fabrics continued to be included in some tests. In 1982, an AATCC subcommittee focused on developing a standard dyed-comparison fabric to reduce variance in the colorfastness to hypochlorite bleach test. (Clark, 2001) Standards for colorfastness to chlorinated swimming pool water, and atmospheric contaminants also were developed, but the use of these standards was dropped as the results were not satisfactory.  wash cycles are considered as average, making colorfastness to laundering a significant factor in the performance of a colored textile. (Muthu, 2015) AATCC test method 61 developed in 1950 by AATCC Committee RA60 has been continually revised to reflect changes in laundry practices and detergent formulation. The test has 5 test conditions to mimic a range of laundry conditions.
Most apparel is subject to perspiration when worn, making colorfastness to perspiration another important aspect to determine the quality of clothing. In AATCC test method 15, colorfastness to perspiration, a colored fabric is wetted with a simulated acidic perspiration solution, subjected to fixed pressure of 8 lbs and allowed to dry at slightly elevated temperature. The test method suggests the use of an in-house colored textile of known colorfastness producing mid-range of staining as verification.
However, as discussed earlier, using an in-house fabric may not give the exact idea of the accuracy of the test procedure. the supply of a consistent product less certain. Sulfur dyes were thus not considered further. Azoic dyes are classified as "ingrain dyes" since as the colorant is formed in the fiber by a reaction between intermediate compounds. (Perkins, 1996) As the colorant formed in the fiber is extremely insoluble, it is fast to laundering, making this class unsuitable for the development of verification standard. Similarly, vat dyes are water-insoluble pigments that are applied after conversion to a water-soluble salt using an alkaline reducing agent, which after application are re-oxidized to insoluble pigments, imparting exceptional colorfastness properties. (Perkins, 1996) Hence, vat dyes were ruled out from the study. Reactive dyes, as the name suggests, react with the fiber and become fixed, they have excellent fastness to washing because of the high strength of the covalent bond. (Perkins, 1996) The reaction is not 100% efficient, however, and achieving such fastness requires extensive rinsing to remove the dye that has not reacted with the fiber: if this does not happen, the unfixed dye will bleed in use and fastness might be poor. However, for this project, controlling the level of fixation to generate a known degree of fastness would be difficult. Direct dyes are economical, simple to apply and provide bright shades but with typically moderate to poor fastness to laundering. Of all the dye classes for cotton, direct dyes represent the most suitable class for this study. (Perkins, 1996) Acid dyes are anionic and applicable to fibers containing free amino groups that protonate under acid conditions, hence their name. Nylon is a polyamide, has such free amino groups and is routinely dyed with acid dyes. The color fastness of acid dyes ranges from good to excellent, giving a selection of dyes that can generate the required levels of staining for this project. Disperse dyes are useful for hydrophobic thermoplastic fibers. Their primary application is on polyester, but nylon, acetate, and acrylics can also be dyed using disperse dyes. The wash fastness of disperse dyes varies with the fiber to which they are applied. For the project, it is useful that their fastness on nylon is low. (Perkins, 1996) Therefore, after considering various dye classes and the fibers for which they are suitable, cotton and nylon were chosen as fibers, and a combination of direct, acid and disperse dyes would be most appropriate.
A verification fabric is used to validate test results on a regular basis by various testing firms, and results over time might need to be compared. Ensuring dye availability in the long run therefore is of utmost importance for a successful verification fabric. The availability of dyes was determined by examination of the 1991 AATCC Buyer's Guide, to find dyes listed generically that were produced at that time by ten or more manufacturers. Dyes with questionable environmental or health effects were eliminated from consideration on the basis of possibility of future restricted. Yellow colors are difficult for visual assessment and were avoided. Additionally, the same generic dye produced by different manufacturers or different lots can perform differently in terms of colorfastness, hence, the dyes used in the study were used from same brand and lots. The six dyes found to fit these criteria are the following along

Materials and Equipment
Materials: •

Millileters required = %owf X Weight of fiber / % solution strength
The dyebath for direct dyes was prepared with dye solution, and 10% owf sodium chloride. The bath was then transferred to a canister with the pre-wetted cotton cloth was run in Ahiba Polymat dye machine with temperature rising at 4˚F per minute and is maintained at 180˚F for 60 minutes. The bath was then cooled to 120˚F, the samples removed, rinsed and dried.
Acid dyes were applied to texturized nylon in a bath containing the required amount of dye solution, ammonium sulfate (5% owf) and acetic acid (1g/l). The dye bath was made up to 125mL with water, the pH was measured, and adjusted if necessary to pH 6 with acetic acid or ammonia. Pre-wetted nylon samples were added and dyeing carried with temperature increased to 212˚F at 5˚F per minute, maintained at 212˚F for 60 minutes, with subsequent cooling to 120˚F. The dyed samples were then removed, rinsed, and dried.
Disperse dyes were applied to same texturized nylon fabric used for acid dyes using a bath containing 1g/l StarLev WWB, 2g/l monosodium phosphate and the required amount of dye dispersion. The samples were dyed with the same temperature profile as used for the application of acid dyes, after which the samples were rinsed and dried.
The various dyed samples were then tested for colorfastness to laundering using AATCC TM 61 1A and 2A conditions. They were also tested for colorfastness to perspiration using AATCC TM 15. The stains on the multifiber strip present in these tests were evaluated using the spectrophotometer. The dyeings which produced stains on one or more fibers on a multi-fiber strip in desired range of 3-4 gray scale reading were selected for use in combination in the next phase.
Phase 2: Selection and application of combination of dyes Combinations included one of each class of dyes selected in the previous stage. The dyes in the combinations were selected so that the dyes from each class were of different hues. The depth of shade of these dyes was selected based on Phase 1 results.
These combinations were applied to the 50-50 nylon-cotton (ny-co) blend. Two additional combinations were dyed using depths of shade (0.3%owf) that were not included in the first phase.  The three-dye combinations were applied to the 5 grams of 50-50 nylon-cotton in a single dye bath using batch dyeing. The required amount of each dye solution was measured into a dyebath prepared with 1g/l StarLev WWB, 1g/l monosodium phosphate, 5% owf ammonium sulfate, and 10% owf sodium chloride. The pre-wetted fabric was added and dyed using the procedure used for disperse dyes in phase 1.
The dyed samples were then tested for colorfastness to laundering and perspiration using AATCC TM 61 (1A and 2A), and AATCC TM 15 and data for staining and color change was collected using a spectrophotometer. The data was used to select one or more suitable combination with wide range staining on two or more multi-fiber components with two mid-range staining for further testing.   Table 4, 5, and 6 respectively. Acid dyes yielded mid-range staining on mostly nylon and cotton fibers in shades 1%, 2%, and 4%. The disperse dyes exhibited mid-range stains on acetate, nylon, and wool in shades 0.5% and higher. Direct dyes produced stains mostly on cotton and wool: 3-4 gray scale reading were achieved mainly with lower shades of 0.1%, 0.2%, and 0.5%. Acid and disperse dyes, with color change readings varying from 5 to 4, did not fade as much the direct dyes for which the color change rating was from 4 to as low as 2. The more severe test conditions of AATCC TM61 2A resulted in heavier stains than were found from AATCC TM61 1A. The required staining range occurred in three lower shades in case of disperse dyes on all fibers except acrylic, with one or two readings below the mid-range staining. Direct dyes drew mid-range staining mainly on cotton in shades 0.1% and 0.2%. The acid dyes performed differently: C.I. Acid Orange 116 in shades 1% and up resulted in stains mainly on acetate, cotton, and nylon ranging from as low as 1 to 3.5 gray scale reading. C.I. Acid Red 299 at 0.2% and 0.5%owf produced a desirable range of staining, with darker shades producing heavier stains on one two or more fibers. Acid and disperse dye did not show severe color change (a minimum reading of 4) while direct dyes exhibited poor fastness regarding color change as they did in AATCC TM61 1A. In AATCC TM15 (Colorfastness to Perspiration) the disperse dyes on nylon displayed mid-range staining on two or more fibers, notably in the case of Disperse Blue 56 in shades 0.5% owf and higher. Disperse Red 60 at 0.2% owf and higher stained acetate and nylon in the desired mid-range. Both direct dyes at 0.5% owf and higher stained the cotton on the multi-fiber strip severely, with gray scale ratings ranging from 2 to 0.
However, lower shades resulted in a range of staining on all fibers except acetate and polyester which had no staining. All shades except 0.1% of Acid Orange 116 yielded stains primarily on acrylic and; also, resulted in staining on cotton and nylon in case of higher shades of 2% and 4%. Acid Red 299 demonstrated good fastness to perspiration and only stained at higher concentrations of 2% and 4%. The color change readings resembled the previous two tests results; only direct dyes exhibited evident color change ranging from 4.5 to 2 gray scale reading.

Results of Phase 2
Phase 1 showed that shades of 0.1%, 0.2%, and 0.5%owf of all six dyes were suitable for testing in combination to produce candidate verification standards. Ten combinations planned with selected dyes in varied shades listed in Table 2 were planned so that each contained all three dye types, the hues of which were different.
The  Red 60, and Acid Red 299 ("Series 2") elicited a wider range of staining than Series 1 combinations, with stains mostly on acetate, cotton, and nylon. Combination 2D specifically stained all five fibers of the multi-fiber strip; the staining rating ranged from 2.5 to 4.5. Combinations 2E and 2F produced staining similar to that of 2A and 2B. The staining of combination 2C did not offer a wide range of gray scale reading for staining.     Modifications in the test condition produced changes in staining readings compared to the readings collected under standard conditions. The staining rating of acrylic in the third phase was 4.5, versus 4 in Phase 2. Combinations 2E and 2F also showed variation in one and two fibers staining respectively. As explained above, it is clear from the ΔEGS values that this variation derives from stains that are borderline between two gray scale points.
The greatest variations in staining were found in combinations 2D and 2F.
Combination 2F displayed most variation in the stains with a change in test conditions on cotton and polyester, the staining readings for cotton and polyester collected under standard test conditions vary from the readings observed in Phase 2. Hence, the fluctuations caused are questionable. The fluctuation in staining caused by variation of test conditions for combination 2D occurs in several fibers of the multifiber strip.
Additionally, combination 2D shows a clearer increase or decrease in ΔEGS values than was found from the 2E dye combination.
The findings from Phase 3 shows that the combination 2D performed as a verification In the first phase, the dyes were applied separately to cotton and nylon fabrics at a range of concentrations. The fastness of those individual dyeings was tested. Those results identified appropriate concentrations of the dyes for subsequent phases of the work.
In the second phase, these concentrations were applied to a nylon-cotton blend fabric, and the fastness of the resulting dyeings to the three tests was assessed. Three combinations, 2D, 2E, and 2F, provided a wide range of staining in AATCC TM 61 1A and 2A, while none did in AATCC TM 15. Further research hence was determined to be conducted on 2D, 2E and 2F combinations for AATCC TM 61 1A and 2A tests.
In the third phase, the three selected combinations were subject to variations of temperature, liquor volume, percentage powder detergent of total volume, the number of steel balls, time and sample size in the test method. Combination 2D comprising Direct Blue 80 (0.2% owf), Disperse Red 60 (0.5% owf) and Acid Red 299 (0.2% owf) produced staining results that displayed most fluctuations from those of the standard conditions as test conditions were changed ΔEGS values changed clearly when each of the variables was altered. This combination is thus suggested as a suitable verification fabric for TM 61 in its staining of multifiber adjacent materials.
The data collected for color change of the test specimen in TM 61through 2 were inconsistent. Similarly, in Phase 3, the gray scale rating for color change did not show an apparent increase or decrease with the change in test conditions. Further work is suggested to determine the reasons for the inconsistency before color change can be a factor in the use of this dye combination on a verification fabric. None of the combinations gave a broad range of stains when subjected to AATCC TM 15. As suggested by the results from Phase 2, the test AATCC TM 15 would require a separate dyed verification standard.