pH-value of aqueous extract
DIN EN ISO 3071 specifies a method for determining the pH value of textiles. A defined amount of the textile is added to a defined volume of saline water and then the pH of the aqueous extract is measured using a pH meter.
The pH-value is a concentration measurement of H3O+ (acidic) and OH- (basic) ions. In neutral water, the pH-value is 7, at this point the concentration of the two ions is equal. The lower the pH-value, the more acidic the water; the higher the value, the more basic. The conversion is made via the negative decadal logarithm: A pH change of 1 corresponds to a 10 x higher or lower ion concentration. Since the skin has a natural acid protection and has a pH-value of about pH 6, a pH-value between 5 and 7 is considered optimal for textiles. Alkaline textiles (pH value > 8) can irritate the skin just as much as very acidic textiles (pH value < 4).
To determine the pH-value, the acidic and basic ions are extracted from the textile in saline water (a defined amount of salt is added to the water prior the extraction because conductivity is indispensable for the measurement). After the extraction, the pH-value of the extract is determined. The process can be applied to textiles of all fibres and all shapes, whereby very voluminous fibre types such as cushion fillings or nonwovens can make extraction difficult. Water-repellent finishes can also falsify the measurement.
At CTL® GmbH we determine the pH-value between pH 2 and pH 13. As a rule, these limits are not exceeded or undercut in textiles.
Deviations in the pH-value may be corrected by washing.
At the beginning, we clarify the scope of testing, the goal of the tests and, if applicable, the project requirements with the customer.
We prepare a quotation based on the scope of testing and the requirements
The order is clear and as soon as the test sample is received in the laboratory, we get straight to work with the sample.
The results are available in the form of a test report. In addition to the pure test result, an overall assessment according to legal, general or customer-specific requirements is possible.
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