ASTM D1146 Blocking Point of Potentially Adhesive Layers

Scope:

The blocking point of potentially adhesive material is determined using the ASTM D1146 test procedure. Because some potentially adhesive compounds are both thermoplastic and hygroscopic, this test method allows for assessing both thermoplastic and hygroscopic blocking on the same material. Because certain criteria are more stringent than others, ASTM D1146 recognizes and defines two different degrees of blocking: first-degree blocking and second-degree blocking. 

Procedure:

In ASTM D1146, two conditioned test specimens are placed, adhesive face to adhesive face, on a glass plate for cohesive blocking. Three squares of standard paper are stacked on the adhesive face of a conditioned test specimen for adhesive blocking, and a glass is placed on top. The edges of the test specimens, standard paper, and glass plate are all flush. A 0.45-kg (1-lb) weight is placed in the center of the 38-mm (1/2-in.) square area on top of the aligned specimens. Each of  the following types of tests is done in triplicate, as per ASTM D1146:

▪ Cohesive Blocking: (1) Thermoplastic (2) Hygroscopic. 

▪ Adhesive Blocking: (1) Thermoplastic (2) Hygroscopic. 

For thermoplastic blocking, the above test assemblies are placed immediately in a desiccator over an anhydrous calcium chloride solution at (38 ± 1°C) for 24 h. For hygroscopic blocking, the test assemblies are placed immediately in a desiccator at approximately 50% relative humidity and at  (38 ± 1°C) for 24 h. The test assemblies are then removed and allowed to cool to room temperature before being inspected and the degree of conformance is noted. The degree of blocking would then be categorized as free, first-degree blocking, second-degree blocking, or any other degrees of blocking agreed upon in line.

Specimen size:

The ASTM D1146 test technique employs adhesive specimens with a size of 38 mm (1 ½ inch) in square forms. 

Data:

The results of all determinations undertaken, including the critical temperature or (alternatively)  the highest temperature utilized for thermoplastic blocking/hygroscopic blocking, or any other crucial phenomenon, are reported in accordance with ASTM D1146.

Read more: ASTM D1146 Standard Test Method for Blocking Point of Potentially Adhesive Layers 

Conclusion:

The blocking point of potentially adhesive material is determined using the ASTM D1146 test procedure.