Detailed interpretation of PH value
pH value refers to the hydrogen ion concentration index, which is the concentration of hydrogen ions in the solution. The ratio of the total number to the total amount of substances, a numerical value indicating the degree of acidity or alkalinity of a solution, that is, the negative value of the common logarithm of the hydrogen ion concentration contained. Textile pH value refers to the measurement of the pH value of textile water extract. Since the promulgation and implementation of the mandatory standard GB 18401 “National Basic Safety Technical Specifications for Textile Products”, textile pH value, as an important textile safety performance indicator, has been a key quality indicator tested by various regulatory agencies. It is also one of the indicators that frequently fails to meet standards. . In recent years, consumers have become more and more concerned about the inherent quality of textile and clothing 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 for textiles. The “old problem” of quality, whether the pH value indicator is within the specified range, has attracted great attention.
The hazards of textile PH value exceeding the standard
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 pH value of the outside world is If the pH difference between the human body’s normal needs is too great, it will cause people’s physical discomfort and many skin diseases. pH testing of textiles was born out of this need. If the pH value deviates from the standard value, the pH value of the clothing will be improper, which will lead to the destruction of the natural barrier on the surface of the skin. The neutral to acidic skin of the human body will be irritated, causing a burning sensation, breeding bacteria, and causing diseases. Therefore, the country has formulated standards such as GB 18401, which stipulates that the pH value of Class A infant textile products should be in the range of 4.0 to 7.5, the pH value of Class B textiles in direct contact with the skin should be between 4.0 and 8.5, and the pH value of Class C non-direct contact textiles should be between 4.0 and 8.5. The pH value of skin textiles 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 textiles
There are many reasons why the pH value of textiles exceeds the standard. If the various dyes and finishing auxiliaries used in the printing, dyeing and finishing processes of textiles are not fully washed or neutralized, and if they are added during the washing process If various finishing agents are added without standardized control, the pH value of the final product will 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 acid-base the products after dyeing, finishing or special processing. and, causing the pH value to be too high or too low.
2.Manufacturers use some low-price, unstable quality direct dyes and coatings for dyeing and printing. After neutralization with weak acid or weak alkali, the products produced using these dyes will become dark, without luster, and may even change their hue or leave an unpleasant smell. Therefore, in order to maintain the bright luster of the product, some companies do not neutralize the pH value of the product even though they know it is too high, 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, and some even rely on experience to make decisions. The number of times of washing and the amount of acid and alkali added. The pH value of the textiles produced is unstable, and the phenomenon of unqualified pH value is prominent.
4.Some corporate laboratories lack the 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 textile 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 textiles is a test operation that has particularly high requirements on instruments and test conditions. Test temperature, sampling quality,
Extraction time, pH meter calibration, etc. will all affect the measurement results of textile pH value.
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