Blocking develops in film processing and storage when layers of smooth film are in intimate contact with nearly complete exclusion of air. Temperature, or pressure, or both, can induce or change the degree of adhesion of the surfaces.

The procedure of this test method closely simulates the operation of separating film in some end-use applications.

1.1 This test method yields quantitative information regarding the degree of blocking (unwanted adhesion) existing between layers of plastic film. It is not intended to measure susceptibility to blocking.

1.2 By this procedure, the film-to-film adhesion, expressed as a blocking load in grams, will cause two layers of film with an area of contact of 100 cm² to separate. The test method is limited to a maximum load of 200 g.

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Note 1—This test method is similar to ISO 11502 Method B, but is not technically equivalent.