PH value is a safety indicator of textiles, and the standard requires a PH value of 4.0 to 9.0. A high or low pH value not only affects the performance of the textile itself, but may also cause certain harm to human health during the use of the textile. The PH value standards stipulated in the “National Basic Safety Technical Specifications for Textile Products” are Category A (infant products), Category B (direct contact with the skin) PH value is 4.0—7.5; Category C (indirect contact with the skin) PH value is 4.0 —9.0.
PH value testing principle:
Boil the sample with distilled or deionized water using a pH meter with a glass electrode at room temperature. Use water extraction to measure the pH of the textile water extract. After the solution is cooled to room temperature, use a pH meter to measure its pH value.
Instruments and equipment:
Test utensils: stoppered Erlenmeyer flask, chemically stable glass beaker, glass rod, scissors, tweezers, measuring cylinder with stoppered glass, measuring flask, balance (accuracy 0.01g), reciprocating or rotary oscillator, pH meter tester
Testing process:
1. Reagents:
The distilled or deionized water used must be at least level three specified in ISO 3696, with a pH value between 5.0 and 7.5. The distilled water used should be tested the first time it is used. If it is not within the specified range, chemical-resistant glassware should be used for distillation. If the distilled water is not Grade 3, gently boil 150ml of distilled water in a beaker (10±1) minutes, isolate it from the air, cool it to room temperature and prepare it as test water.
2. Sampling:
Weigh 3 samples (2±0.5g), cut them into small pieces of 5mm*5mm, put them into a flask containing 100ml of distilled water (PH value 5.0-7.5), shake the flask to fully immerse it Wet, place the flask on the oscillator and shake for 1 hour, then take out the extraction liquid of the test sample.
3. Calibration:
Calibrate the pH meter using three standard calibration solutions (9.18, 6.86, 4.00). Use a pH meter to test the pH value of the water extract (excluding test samples) at room temperature.
4. Measurement of pH value of water extraction
Rinse the electrode probe with a pH value of 5.0-7.5 and immerse the electrode several times in the same solution used to prepare the extraction solution until the displayed pH value is stable. , pour the first part of the extraction solution into a 25ml colorimetric tube, immediately immerse the electrode at least 10mm below the liquid surface and let it sit until the pH value reaches a stable value and then record the value. Each sample is tested three times, and the average of the second and third test results is taken 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 two valid measurements are obtained, calculate the average.
For pH value testing, the experimental temperature, sampling quality, extraction time, calibration of the pH value meter, and operating errors of the experimental personnel must be strictly controlled to ensure the accuracy of the test data.
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