Detailed interpretation of PH value
The pH value refers to the hydrogen ion concentration index, which is the ratio of the total number of hydrogen ions in the solution to the amount of the total substance. It is a value indicating the acidity or alkalinity of the solution, that is, the negative value of the common logarithm of the hydrogen ion concentration contained. The pH value of fabric products refers to the measurement of the pH value of the water extract of fabric products. Since the promulgation and implementation of the mandatory standard GB 18401 “National Basic Safety Technical Specifications for Fabric Products”, the pH value of fabric products, as an important safety performance indicator of fabric products, has been a quality indicator that various regulatory agencies focus on testing. It is also an indicator that frequently fails to meet standards. one. In recent years, consumers have become more and more concerned about the inherent quality of fabric workwear products that directly contact the skin. In recent years, judging from the results of spot inspections by national and local quality supervision departments, the problem of unqualified pH has always been high and has almost become a problem. The “old problem” of fabric quality is whether the pH value indicator is within the specified range, which has attracted great attention.
The dangers of excessive PH value of fabrics
The pH value of normal human skin is between 5.5-6.5, and the chemical reaction is weakly acidic. The sweat and oil secreted by the sweat glands and sebum of the skin themselves have a pH value. If the external pH value is consistent with the normal needs of the human body, Excessive pH difference in feces will cause people’s physical discomfort and many skin diseases. The pH value test of fabrics is based on this demand. If the pH value deviates from the standard value, resulting in inappropriate acid-base workwear, the natural barrier on the surface of the skin will be destroyed. The neutral to acidic skin of the human body will be irritated, causing a burning sensation, breeding bacteria, and causing disease. Therefore, the country has formulated standards such as GB 18401, which stipulates that the pH value of category A infant fabric products should be in the range of 4.0 to 7.5, the pH value of category B fabric products that directly contact the skin should be between 4.0 and 8.5, and the pH value of category C indirect contact with the skin should be between 4.0 and 8.5. The pH value of fabrics that come into contact with the skin should be in the range of 4.0 to 9.0, when the human body is comfortable to wear.
Reasons for unqualified PH value of fabrics
There are many reasons why the pH value of fabrics exceeds the standard. If the various dyes and finishing aids used in the printing, dyeing and finishing processes of fabrics are not fully washed or neutralized, and during the washing process Adding various finishing agents without standard control will cause the pH value of the final product to exceed the standard. To sum up, there are several reasons:
1. In order to reduce costs, companies arbitrarily reduce production processes and do not fully wash or neutralize acid and alkali on products that have been colored, finished, or treated with extraordinary processes, resulting in high pH or On the low side.
2. Production companies use some low-price, unstable-quality direct dyes and coatings for coloring and printing. After the products produced using these dyes are neutralized by weak acids and weak alkali, the products will become dark, have no luster, and may even change their hue or leave an unpleasant smell. Therefore, in order to keep the products bright and shiny, some companies know that the pH value of the products is too high and do not neutralize it, resulting in substandard product quality.
3. Some small businesses lack technical talents in printing and dyeing. Staff in important positions have not received systematic professional training. Some even rely on experience to decide the number of times of washing and the amount of acid and alkali added. How many. The pH value of the fabrics produced is unstable, and the phenomenon of unqualified pH value is prominent.
4. Some corporate laboratories lack necessary testing equipment and simply use pH test paper for testing. Studies have shown that pH test paper is only suitable for detecting the pH of solutions with large electrolyte concentrations. The pH value of fabric extracts is generally close to neutral, and the electrolyte concentration of the solution is very low, so it is not suitable to use pH test paper for measurement.
5. The impact of operational errors by enterprise test personnel. Testing the pH value of fabrics is a test operation with very high requirements on instruments and test conditions. Test temperature, sampling quality,
Extraction time, pH meter calibration, etc. will all affect the pH value measurement results of fabric products.
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