The pH value is a safety indicator for textiles, and the standard requires a pH range of 4.0 to 9.0. High or low pH values ​​not only affect the performance of the textile itself but may also pose certain risks to human health during use. The "National Basic Safety Technical Specifications for Textile Products" stipulates that the pH values ​​for Category A (infant and toddler products) and Category B (direct skin contact) are 4.0 to 7.5; and Category C (non-direct skin contact) are 4.0 to 9.0.

pH Testing Principle:

Boil the sample with distilled or deionized water at room temperature using a pH meter with a glass electrode. Then, extract the sample with water to measure the pH of the extracted solution. After cooling to room temperature, measure the pH using a pH meter.

Instruments and Equipment:

Testware: Erlenmeyer flask with stopper, chemically stable glass beaker, glass rod, scissors, tweezers, graduated cylinder with stopper, measuring flask, balance (accuracy 0.01g), reciprocating or rotary oscillator, pH meter

Test Procedure:

1. Reagents:

The distilled or deionized water used must be at least Grade III as specified in ISO 3696. with a pH between 5.0 and 7.5. Distilled water should be tested before first use. If it is not within the specified range, distill it using chemical-resistant glassware. If the distilled water is not Grade III, gently boil 150ml of distilled water in a beaker for (10 ± 1) minutes, isolate it from air, and cool to room temperature before use as the test water.

2. Sampling:

Weigh three portions (2 ± 0.5 g) of the sample, cut them into 5 mm x 5 mm pieces, and place them in a flask containing 100 ml of distilled water (pH 5.0-7.5). Shake the flask to thoroughly wet it. Place the flask on a shaker for 1 hour, then remove the test sample extract.

3. Calibration:

Calibrate the pH meter using three standard calibration solutions (9.18. 6.86. and 4.00). Measure the pH of the water extract (excluding the test sample) at room temperature using the pH meter.

4. pH Measurement of the Water Extract

Rinse the electrode probe with a pH of 5.0-7.5. Immerse the electrode several times in the same solution used to prepare the extract until the displayed pH stabilizes. Pour the first extract into a 25 ml colorimetric tube and immediately immerse the electrode at least 10 mm below the liquid surface. Allow the pH to stabilize and record the pH. Each sample was tested three times, and the average of the second and third test results was taken as the final result.

5. Calculation:

Measure two pH values ​​to the nearest 0.1. If the difference between the two pH values ​​is greater than 0.2. resample and retest. When two valid measurements are obtained, calculate the average.

PH testing requires strict control of experimental temperature, sample quality, extraction time, pH meter calibration, and operator error to ensure accurate test data.