Liquid Penetration and Absorption Capacity (Sum of Absorption in Liquid Contact and Water Vapor Transmission)
This test is used to evaluate the liquid penetration and absorption capacity of water-resistant wound dressings that are applied for more than 24 hours and primarily designed to absorb exudate and control the microbial environment.
Apparatus
1. Five clean, dry cylinders: Manufactured from corrosion-resistant materials, with an inner diameter of (35.7±0.1) mm (a cross-sectional area of 10 cm²). Each cylinder is provided with a flange at both ends and can hold 20 mL of test solution.
One end of the cylinder is an annular clamping plate with an aperture area of 10 cm². A water-resistant tape or sealant may be used in this area to prevent evaporation through the edges of the dressing. The other end of the cylinder is fitted with a metal cover plate with the same diameter as the flange, equipped with a sealing ring to ensure an effective seal with the flange. The two ends of the cover plate are clamped tightly to the flange.
2. Test Solution A: Composed of a solution of sodium chloride and calcium chloride, containing 142 mmol of sodium ions and 2.5 mmol of calcium ions per litre. The ion content of this solution is equivalent to that of human serum or wound exudate. Dissolve 8.298 g of sodium chloride and 0.368 g of calcium chloride dihydrate in deionized water in a volumetric flask, and dilute the solution to 1 L.
3. One calibrated pipette.
4. Drying oven or incubator: Equipped with forced air circulation, capable of maintaining a constant temperature of (37±0.1) ℃ and uniform air distribution, and keeping the relative humidity (RH) below 20% throughout the test.
5. Hygrometer: Capable of detecting whether the relative humidity (RH) exceeds the limit of 20%.
6. Balance: Capable of weighing up to 100 g with an accuracy of 0.0001 g.
Procedure
1. Cut a circular dressing sample to fit the test apparatus and prevent leakage. Remove the backing if the dressing is provided with one, and place the wound-contacting side of the dressing inwards against the upper flange of the cylinder.
2. Place the clamping ring on the outer surface of the dressing and fasten it securely.
3. Weigh the cylinder together with the clamping device (W1). Invert the cylinder, add approximately 20 mL of Test Solution A using a suitable pipette, fit the metal cover plate, and weigh the assembly again (W2). Repeat this procedure 4 times to prepare a total of 5 samples.
Assembled Cylinder
4. Place the assembled cylinders in the incubator.
5. After 24 hours, remove each cylinder from the incubator, allow it to equilibrate at room temperature for 30 minutes, and weigh it again (m3).
6. Remove the metal cover plate from each cylinder, pour off the liquid gently, and allow the cylinder to drain in this inverted position for (15±2) minutes. Weigh the cylinder together with all its components (including the dressing) once more (W4).
7. Repeat Steps 1 to 6 with new samples for a contact time of 48 hours.
