Principle Of Measurement Of Fastness To Alkali, Acid Perspiration
Specimens of the Textiles in contact with adjacent fabrics are treated with two different solutions of acid and alkali immerse it for 30 minutes and the removed.The materials are uniformly squeezed and placed under a specified load for 4 hrs in between the two acrylic sheets of per spirometer for 4 hours.Then the samples are removed from the plates, stitches are removed on three sides of the samples, then dried and compared for the shade variation in the gray scales for assessment of shade variations.
As human perspiration may be acid or alkali two solutions are prepared.
Freshly prepared, containing the following chemicals per liter
- 0.5 g of Sodium chloride (NaCl) and
- 5g of disodium hydrogen orthophosphate dodecahydrate
Freshly prepared, containing the following chemicals per liter:
5g 1- histidine monohydrochloride monohydrate
5g of sodium chloride and 5g of sodium dihydrogen orthophosphate dihydrate
This solution is brought to pH 5.5 with acetic acid solution.
Preparation of Test Specimens:
If the textile to be tested in the form of fabric, place a specimen 10 x 4 cm in size between two 10x 4 cm pieces of the two kinds of adjacent fabrics and sew along one of the shorter sides to form a composite specimen. Two such composite specimens are required.
Wet one of the composite specimen thoroughly in the alkaline solution using a liquor to specimen ratio of 50:1 and allow it to remain in the solution at room temperature for 30 minutes. press and move it from time to time to ensure good and uniform penetration of the liquor.Pour off the liquor and wipe the excess liquor of the specimen between two glass rods.
Then place the composite specimen between two glass or acrylic resin plates under a force of 5.1 kgs (as the specimen is 10 x 4 cm in size ) in a per spirometer. Keep the per spirometer in the air oven at 37 + /- 2 ○C for hours.
Open out the composite specimen by breaking the stitches on all the sides except one of the shorter sides.Dry the three parts in air at temperature not more than 60°C
With the three parts in contact only at the remaining line of stitching.
Treat the second composite in acid solution as noted above instead of an alkaline solution. Evaluate the change in color of the treated test specimens and the degree of staining of the two pieces of adjacent fabric with help of the gray scale and assign the ratings, taking care to first cool the test specimens and the adjacent fabrics to room temperature. In the case of doubt in the rating given by an observer, the accesses menu should be done by at least three observers and the overall average rating should be reported.
Figure 3.10 per spirometer
Similarly another set of gray scale for staining
The test specimen is evaluated for staining and then ratings are accessed.