1.What is pH?
The pH value is a measure of the acid-base intensity of a solution. It is a simple way to show the concentration of hydrogen ions (pH=-lg[H+]) in solution. Generally, the value is from 1~14 and 7 is the neutral value. The acidity of solution is stronger, the value is smaller. The alkalinity of solution is stronger, the value is bigger.
2.The significance of pH detection
The surface of human skin is weak acid with pH value 5.5~6.0. Acid environment can inhibit the growth and reproduction of some pathogenic bacteria and prevent the invasion of external bacteria, protecting the skin from infection. If pH value exceeds standard, as too acid or too alkali, the weak acid environment of human skin will be damaged, which leads to skin itches or skin allergy.
3.Principle of textile pH detection
After the textile is extracted with distilled or deionized water, use a pH meter with a glass electrode to measure the pH value of the extract liquor.
4.The reason of textile pH value exceeding standard
(1) The influence of dyes during production: The common used reactive dyes, vat dyes and sulfur dyes are working under alkali condition. Although the cloth surface can be treated well by water washing, it will be affected by the pH value of the production water.
(2) The influence of dyeing and printing process: For cotton, wool, silk, polyester, nylon and acrylic, etc., after scouring, dyeing and printing, there are residual alkali and acid chemicals and auxiliaries on the fabric, which have different pH values. After treating by water washing, soaping, acid neutralization and drying process, etc., if the amount of chemical auxiliaries is too much or water washing is not enough, the pH value of textiles will exceed standard, which influences the wearing and using performance of textiles.
(3) The influence of fabrics: The thickness of fabrics will influence cloth surface. For thin fabrics, it is easy to wash after dyeing and the pH value of cloth surface is low. For thick fabrics, it is relatively hard to wash after dyeing and the pH value of cloth surface is higher.
(4) The influence of laboratory personnel’s operating error: Different dryness and humidity of tested fabric, different extraction temperature and different extraction time, etc. will influence the measure result of pH value on cloth surface.
5.Improvement measures for textiles with unqualified pH
(1) Acid-base neutralization: If partial acid, add alkali to neutralize. If partial alkali, add acid to neutralize. Generally, it is to add acetic or citric acid and sodium carbonate.
(2) Improving the dyeing and finishing process: Intensify water washing, etc.
(3) Choose high-quality raw material and dyes.
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Post time: Nov-09-2022