The pH value is a safety indicator for textiles, and the standard requires a pH value of 4.0 to 9.0. The high or low pH value not only affects the performance of the textile itself, but also may pose certain risks to human health during the use of the textile. The pH value standard specified in the "National Basic Safety Technical Specifications for Textile Products" is Class A (infant products) and Class B (direct contact with skin), with a pH value of 4.0-7.5; Class C (non direct contact with skin) has a pH value of 4.0-9.0. Principle of pH value testing: Boil the sample with distilled or deionized water using a pH meter with a glass electrode at room temperature, extract and measure the pH of the textile water extraction solution with water, cool it to room temperature, and then use a pH meter to measure its pH value

Instruments and equipment: test vessels with stoppered triangular flasks, glass beakers with stable chemical properties, glass rods, scissors, tweezers, measuring cylinders with stoppered glass, measuring bottles, balances (with an accuracy of 0.01g), reciprocating or rotary oscillators, pH meter testers

 

Testing process:

1. Reagent:

The distilled or deionized water used should be at least Grade III according to ISO 3696, with a pH value between 5.0 and 7.5. The distilled water used should be inspected before the first use. If it is not within the specified range, it should be distilled using a glass utensil resistant to chemicals. If the distilled water is not of third grade, gently boil 150ml of distilled water in a beaker for (10 ± 1) minutes, isolate the air, cool to room temperature, and prepare as test water

2. Sampling:

Weigh 3 samples (2 ± 0.5g), cut them into 5mm * 5mm small pieces, and place them in a flask containing 100ml of distilled water (pH value 5.0-7.5). Shake the flask to fully immerse it. Place the flask on an oscillator and shake for 1 hour before removing the extracted liquid from the test sample 3. Calibration:

Calibrate the pH meter using three standard calibration solutions (9.18, 6.86, 4.00), and test the pH value of the water extraction solution (excluding the test sample) using a pH meter at room temperature

4. Measurement of pH value in water extraction

Rinse the electrode probe with a pH value of 5.0-7.5, immerse the electrode in the same solution used to prepare the extraction solution several times until the displayed pH value stabilizes.

., Pour the first extraction solution into a 25ml colorimetric tube, immediately immerse the electrode at least 10mm below the liquid level and let it stand until the pH value reaches stability. Record this value. Test each sample three times, and take the average of the second and third test results as the final result

5. Calculation:

Measure two pH values to the nearest 0.1. If the difference between the two measured pH values is greater than 0.2, resample and retest. When the two valid measurement values are obtained, calculate the average value The pH value test must strictly control the experimental temperature, sampling quality, extraction time, calibration of the pH meter, and operational errors of the experimental personnel to ensure the accuracy of the experimental data

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