pH value is a very important quality indicator for textiles, which is GB18401-2010 The mandatory implementation indicators of the “National Basic Safety Technical Specifications for Textiles”, unqualified pH value is also a common quality problem in the process of textile processing, production and trade, which has attracted more and more people’s attention. This article will discuss with you how to conduct textile processing. pH control.
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The definition of pH value:
pH value is the acidity and alkalinity. Human skin is slightly acidic. Under such environmental conditions, it can prevent the invasion of germs. Therefore, if the pH value of textiles is slightly acidic, Or neutral is good for protecting human health; on the contrary, if the pH value of textiles is too high or too low, it will destroy the balance and resistance of the skin, causing skin allergies or inducing infection and leading to the invasion of germs.
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Requirements for pH limit values:
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Sources of abnormal pH:
Mainly due to insufficient pH control of textiles during the dyeing and finishing process, insufficient acid neutralization after wet treatment, or incomplete cleaning, which can easily cause dyeing with abnormal pH. The whole process is mainly It is alkali reduction, polyester printing washing, reactive printing washing, cotton desizing, scouring and mercerization, etc.
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Comparison of different measurement methods of textile PH value:
(1), Chinese standards (GB/T 7573-2009)
Weigh 3 samples of 2±0.05g and cut them into 5×5 mm small pieces, put them into a flask containing 100 ml distilled water, shake the flask to fully soak the sample, place the flask on the oscillator for 2 hours ± 5 min, and directly measure the water extract with a pH meter at room temperature (not (including fabric), perform three tests on each sample, and take the average of the second and third sample results as the final result, accurate to 0.1.
(2), European Union Standard (EN). 1413-1998)
Weigh 3 samples of 2±0.05g and cut them into 5×5 mm pieces, put into a flask containing 100ml potassium chloride solution (0.1mol/L) or 100ml distilled water, shake the flask to fully soak the sample, place the flask on the oscillator for 2 hours, shake at room temperature Use P The H meter directly measures the pH value of the water extract (excluding fabrics). Each sample is tested three times, and the average of the results of the second and third samples is taken as the final result, accurate to 0.1. 3), Japanese Standard (JIS L 1096-1999)
Weigh 5±0.1g sample, cut it into 1×1mm small pieces, boil it in 50ml distilled water for 2 minutes, put the sample in the flask, shake the flask to fully soak the sample, and let it stand at room temperature for 30 minutes. Remove the sample, and when the temperature of the water extract reaches 25±2°C, directly measure the pH value of the water extract with a pH meter, accurate to 0.1.
(4), American standards (AATCC 81-2001)
Weigh 10±0.1g sample, cut it into small pieces, boil it in 250ml distilled water and keep it for 10 minutes, put the sample in the flask, shake the flask to fully soak the sample , continue boiling for 10 minutes, cool to room temperature, remove the sample, and directly measure the pH value of the water extract with a pH meter, accurate to 0.01.
PH value of cotton fabric water extract under different measurement standards:
【Friendly reminder】
From the above test standards and different test results of the same sample, we can see that there must be standard requirements for testing!
Question: Why are the same sample After multiple tests, the results Is there a difference?
Answer: This may be due to errors in testing equipment, operation and environment, as well as errors in testing distilled water. Therefore, it is recommended that fabric manufacturers go to a regular testing agency for testing.
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Check pH How to deal with unqualified fabrics or garments? Generally, the pH of the fabric is re-adjusted through the principle of acid-base neutralization. If the pH is unqualified, it may be too alkaline. There are many kinds of acids that can be used to adjust it. , common ones are glacial acetic acid and lemon There are two types of acids. Glacial acetic acid is volatile and has a pungent smell. Citric acid is more stable in adjusting the pH. Therefore, it is generally recommended to use citric acid to adjust the pH. However, attention should be paid to controlling the dosage. Excessive amount will affect the feel and easily cause yellowing
Example:If the measured pH value of the fabric is 9-10, you can adjust the pH value of the citric acid aqueous solution to 4-5, then soak it for 10 minutes and let it dry. Before sending to customers, formal inspection and structural testing will be carried out to confirm that they are qualified to reduce trade risks.
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Methods for controlling pH value:
Only by analyzing the reasons for unqualified pH value and prescribing the right medicine can we effectively reduce the unqualified rate of textile pH value:
(1) Fabric enterprises Strengthen the quality awareness of relevant quality control personnel and the study and training of textile standards, and correctly understand the requirements of textile pH. Garment processing companies must also select appropriate fabrics and accessories based on the garment’s own requirements and safety categories, and provide accurate requirements and standards to fabric suppliers. Only by paying attention to the source and conducting quality control can we avoid trade disputes caused by unqualified pH.
(2) Relevant personnel of dyeing and finishing enterprises should take the initiative to learn ecological textile safety knowledge, be familiar with standard requirements, take the initiative to pay attention to the inherent quality of printing and dyeing products, optimize production processes, and take the initiative to improve technical levels.
(3) Inspection agencies or corporate laboratories should conduct testing strictly in accordance with inspection standards to ensure that the inspection data is fair and accurate, avoid testing data errors caused by improper operation and other human factors, and truly control product quality.
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