Copyright © 2006 American Association of Textile Chemists and Colorists
AATCC Technical Manual/2007
TM 81-2006101
Developed in 1954 by AATCC Commit-tee RA34; revised 1963, 1996 (with title change); reaffirmed 1968, 1969, 1974,1977, 1980, 1983, 1988, 1989, 2001;reaffirmed and editorially revised 2006;editorially revised 1990. Related to ISO 3071.
1.Purpose and Scope
1.1This test method determines the pH of wet processed textiles.
1.2To make a quantitative determina-tion, the chemicals which influence pH must be removed from the textile speci-men, collected as a water extract and then accurately measured by a pH meter.
2.Principle
2.1The specimen is boiled in distilled or deionized water. The water-extract is cooled to room temperature and the pH is determined.
3.Terminology
3.1bleaching, n.—elimination of un-wanted coloring matter from a textile substrate by oxidative or reductive chem-ical treatment.
3.2pH, n.—the negative logarithm of the effective hydrogen ion concentration or hydrogen ion activity in gram equiva-lents per liter used in expressing both acidity and alkalinity on a scale whose values run from 0-14 with 7 representing neutrality, numbers less than 7 increasing acidity and numbers greater than 7 in-creasing alkalinity.
3.3wet processing, n.—in textile man-ufacturing, a collective term for pro-cesses included in preparation, dyeing,printing and finishing in which the textile material is treated with a liquid, normally water, or with chemicals in solution or dispersion in a liquid.
4. Safety Precautions
NOTE: These safety precautions are for information purposes only. The pre-cautions are ancillary to the testing proce-dures and are not intended to be all inclu-sive. It is the user’s responsibility to use safe and proper techniques in handling materials in this test method. Manufac-turers MUST be consult
ed for specific details such as material safety data sheets and other manufacturer’s recommenda-tions. All OSHA standards and rules must also be consulted and followed.4.1Good laboratory practices should be followed. Wear safety glasses in all
laboratory areas.
4.2All chemicals should be handled with care.editorially
5.Uses and Limitations
5.1pH can be used to determine the suitability of wet processed textiles for subsequent dyeing and/or finishing oper-ations or to evaluate the washing and/or neutralizing efficiency following any wet processing operation.
5.2This method should be used in con-junction with AATCC Test Method 144,Alkali in Wet Processed Textiles: Total,in order to quantitatively determine the amount of an alkali present. While pH gives an indication of relative alkali or acid content, the exact amount can be masked by the presence of strong buffer-ing agents.
6.Apparatus and Materials
6.1pH meter with 0.1 unit graduations.6.2Beakers, glass, 400 mL.
6.3Buffer solutions, pH 4.0,
7.0, 10.0or others as needed.
7.Calibration
7.1Calibrate the pH meter in accor-dance with the manufacturer’s instruc-tions. Select buffer solutions for calibra-tion which are in the estimated range of the specimens’ pHs.
8.Specimens
8.1Use a 10 ± 0.1 g specimen of the material to be tested. If the weight per square yard of the fabric is excessively low, cut the sample into small pieces.
9.Procedure
9.1Boil 250 mL of distilled water at a moderate rate for 10 min. Immerse the specimen, cover the beaker with a watch glass and boil for an additional 10 min.9.2Allow the covered beaker and con-tents
to cool to room temperature. Remove the specimen with tweezers, allowing the excess liquid to drip back into the extract.9.3Determine the pH of the extract using a pH meter operated according to manufacturer’s instructions.
10.Evaluation
10.1The pH of the water-extract de-pends on the chemical treatment previ-ously given the textile, the pH of the wash water, and the efficiency of the washing operation.
10.2Normally, the pH of the water-extract will be higher after caustic boiling than after bleaching. If the textile is scoured after bleaching, the pH may be lower.10.3Textiles with high pH values may exhibit yellowing tendencies, create shade changes, alter the exhaustion and fixation of dyes, and produce a decrease in the cure of resin finishes or exhaustion of softeners.
11.Precision and Bias
11.1Precision .
11.1.1In late 1993, an interlaboratory study was completed, which included five laboratories, two operators in each,running three determinations per fabric,on four fabrics. No prior assessment was ma
de of the relative level of performance of the participating laboratories.
11.1.2Analysis of the data set (5×2×3×4=120 values) yielded compo-nents of variance as follows:Laboratories 0.1203Operators within laboratories 0.0150Specimens within
materials, laboratories,and operators
0.0188
11.1.3Table I indicates the critical differ-ences calculated using the values in 11.1.2.
11.1.4Differences between two aver-ages of N determinations, for the appro-priate precision parameter, should reach or exceed the table value to be statistically significant at the 95% probability level.11.2Bias.
11.2.1To the extent the pH meter used in this test method is capable of measur-ing values of pH that are consistent with true values of pH, the determination of the pH of the water-extract from a bleached textile, using this test method,has no known bias. During this study, no determination was made of the true value of this property by an independent, ref-eree analytical method for the purpose of establishing presence or absence of bias.
Table I—Critical Differences for Two Averages—95% Probability Level
pH of Water-Extract from Bleached Textiles N Single Operator
Within Laboratory
Between Laboratory
10.380.51  1.0920.270.43  1.0540.190.39  1.048
0.130.37  1.03
AATCC Test Method 81-2006
pH of the Water-Extract from Wet Processed Textiles

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