ASTM D1146 is a standard test method to determine the blocking point of a thermoplastic or a hygroscopic layer or coating of potentially adhesive materials that are materials in a substantially nonadhesive state which may be activated to an adhesive state by application of heat or solvents. 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 (Standard Test Method for Blocking Point of Potentially Adhesive Layers) recognizes and defines two different degrees of blocking: first-degree blocking and second-degree blocking.
ASTM D1146 Blocking Point of Potentially Adhesive Layers
What is ASTM D1146?
Sample Preparation Guide
The ASTM D1146 test technique employs adhesive specimens with a size of 38 mm (1 ½ inch) in square forms.
A 0.45-kg (1-lb) weight (5.3) 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.
What are the Testing Procedure and Requirements for the ASTM D1146?
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 plate is placed on top. The edges of the test specimens, standard paper, and glass plate are all flush. 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 is then categorized as free, first-degree blocking, second-degree blocking, or any other degree of blocking agreed upon in line.
Analysis Results and Interpretation
The blocking point of potentially adhesive material is determined using the ASTM D1146 test procedure.
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.
Updated on July 24, 2026
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