Meaning and use
5.1 The results of this test method will indicate the relative vapor transmittance of the tape at its smallest size, usually perpendicular to the backing of the tape.

5.1.1 Compared to the thickness of the tape, the water vapor channel parallel to the glue cup interface is much larger, and the latter is usually an almost separate source of passing vapor.

5.1.2 Some tape types allow a relatively free path in the direction perpendicular to the backing or along the backing path parallel to the adhesive cup interface, thus making the adhesive the primary barrier.

5.2 If the adhesive does not continue to adhere to the cup body flange during exposure, unexpected water vapor channels may occur, then the measurement should be considered unperformed. Therefore, in wet conditions (close to test conditions), tape may not be suitable for use on surfaces such as cup flanges.

Note 1: May only be interested in tape material as a water vapor barrier. In this case, the degree of adhesion of the tape to the cup flange will make little difference, so measures need to be taken to prevent any edge effects. These will be mentioned in section 10.

ASTM D3833/D3833M-2019 Standard Test Method for Water Vapor Transport of Pressure Sensitive Tapes

Step 1: Scope
1.1 The test method covers a procedure for measuring the water vapor transmittance of a pressure sensitive tape.

1.2 Values expressed in SI units or inch-pound units shall be regarded as standard values respectively. The values specified in each system may not be exactly the same; Therefore, each system needs to be used independently and the values cannot be combined in any way.

1.3 This standard is not intended to address all safety concerns associated with its use. It is the responsibility of users of this standard to establish appropriate safety, health and environmental specifications and to determine the applicability of regulatory restrictions prior to use.

1.4 This international standard is based on internationally recognized standardization principles established in the Decision on Principles for the Development of International Standards, Guidelines and Recommendations issued by the WTO Technical Barriers to Trade (TBT) Committee.

2. Refer to the file
ASTM standard

D996 Packaging and distribution environmental terms

D3715 / D3715M pressure sensitive tape quality assurance practice

D4332 Practice of regulating containers, packaging or packaging components for testing

E96 / E96M test method for water vapor transmittance of materials

E122 Practice of calculating sample sizes to estimate average values of batch or process features with specified precision