Moisture Permeability Test of PE Film Used for Disposable Baby Diaper

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A diaper (herein referred to disposable diaper) is a type of underwear that allows the wearer to defecate or urinate without the use of a toilet, by absorbing or containing waste products to prevent soiling of outer clothing or the external environment.

Disposable baby diaper usually has a layered construction which allows the transfer and distribution of urine to an absorbent core structure where it is locked in. Basic layers are an outer shell of breathable polyethylene film or a nonwoven and film composite which prevents wetness and soil transfer, an inner absorbent layer of a mixture of air-laid paper and superabsorbent polymers for wetness, and a layer nearest the skin of nonwoven material with a distribution layer directly beneath which transfers wetness to the absorbent layer.

This article discusses the significance of sufficient moisture permeability of the PE film used for the outer shell of the diaper and provides a simplified test method of the moisture permeability. If the PE film is of low moisture permeability, the moisture cannot be expelled and the diaper may not be able to maintain the dryness of baby’s bottom and thus may cause skin problems such as red buttocks and eczema, etc. Therefore, it is quite important for the diaper manufacturers to test and control the moisture permeability of PE film used for outer shell of the diaper.

Figure 1. Disposable Baby Diapers

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). The testing instrument used in the tests mentioned in this article is Labthink’s W3/030 Water Vapor Transmission Rate Tester which adopts gravimetric method. The test specimens are provided by one diaper manufacturer.

The tests were performed in the following procedures.

(1)   Cut 3 pieces of specimens from the surface of the provided samples. The diameter of the specimen should be 74 mm.

(2)   Mount the 3 specimens in 3 test dishes respectively. Place the test dishes on the dish supports and move them into the test chamber. Close the door of the instrument.

(3)   Set test temperature, humidity, specimen thickness and other specimen parameters and test parameters in the software system. Then click Test to start the test.

(4)   The system will calculate and display the test results automatically.

The diaper manufacturers can determine whether the PE film they used in their products meet relative requirements and may change raw materials according to the test results obtained in the moisture permeability tests mentioned above.

For more details about W3/030 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.