Moisture Barrier Property Test of Medical Dressing

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A dressing is a sterile pad or compress applied to a wound to promote healing and protect the wound from further harm. A dressing is designed to be in direct contact with the wound, as distinguished from a bandage, which is most often used to hold a dressing in place. Many modern dressings are self-adhesive.

Traditional dressing uses natural gauze as material, which has a lot of defects e.g. it is liable to be stuck to the wound and may cause infection due to the growth of microbe. Today, modern dressings include dry or impregnated gauze, plastic films, gels, foams, hydrocolloids, alginates, hydrogels, and polysaccharide pastes, granules and beads. They all provide different physical environments suited to different wounds. Oxygen and water vapor can permeate through the dressings easily meanwhile the particulate matter and microbe in the external environment can be kept away from the wound. ‘

The medical dressings should have high water vapor permeability which is good to the healing of the wound. Therefore, it is necessary for the manufacturers to strengthen the tests of water vapor permeability of the medical dressing. This article provides a simplified test method of water vapor permeability of medical dressing for your reference. The test specimens are medical dressings made of foamed polymer and the testing instrument is Labthink’s W3/031 Water Vapor Transmission Rate Tester.

Figure 1. Medical Dressings

Figure 2. W3/031 Water Vapor Transmission Rate Tester

Currently, there are mainly two categories of test methods for water vapor transmission rate i.e. gravimetric method (also known as cup method and divided into dry cup method and wet cup method) and sensor method (including electrolytic sensor method, infrared sensor method and humidity sensor method). Labthink’s W3/031 Water Vapor Transmission Rate Tester uses gravimetric method. Under a certain test temperature, a constant humidity difference is generated between two sides of the test specimen. The water vapor permeates through the specimen and into the dry side. By measuring the weight changes of the test dish in different time, water vapor transmission rate and other parameters can be obtained.

The tests can be performed according to the following procedures.

(1)    Cut 3 pieces of specimens from the sample material with sample cutter. The diameter of the specimen should be 74mm.

(2)    Mount the specimens in 3 test dishes respectively. Then invert the test dish and make sure the distilled water contact directly with the specimens.

(3)    Place the test dishes on dish support inside the test chamber. Close the glass door of the testing instrument.

(4)    Set specimen name, specimen thickness, test temperature (38℃), test humidity(90%RH) and other test parameters.

(5)    Turn on the gas supply and click Start Test to start the tests.

(6)    The test results will be displayed automatically after tests.

For more details about W3/031 Water Vapor Transmission Rate Tester, please visit www.labthink.com

About Labthink Instruments Co., Ltd:

Labthink Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China and operated in Boston, U.S.A.