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

Scope:

ASTM D1146 standard test method can determine the blocking point of a thermoplastic or hygroscopic layer or coating of potentially adhesive material. Potentially adhesive materials are those that are substantially non-adhesive but can be activated to become adhesive with the use of heat or solvents.

Test Procedure:

In ASTM D1146, two conditioned test specimens, adhesive face to adhesive face, on a glass plate for cohesive blocking were placed. Next, three squares of standard paper on the adhesive face of a conditioned test specimen were placed on a glass plate for adhesive blocking. Test specimens, standard paper and glass paper were flushed. 0.45 kg (1 lb) weight in the center of the 38 mm (112 in) square area on top of the aligned specimens was placed.  The specimen dimensions of the panel should be 75 mm in thickness and 800 mm in diameter. The fixture supporting the panel during testing can consist of any configuration. Furthermore, it should include three symmetrically arranged pivot points on a pitch circle diameter of 750 mm. The above test assemblies were placed in a desiccator over anhydrous calcium chloride at 38 ± 1°C (100 ± 2°F) for 24 hr to prevent thermoplastic blocking. Once again, the test assemblies were placed in a desiccator at 50% relative humidity 38 ± 1 °C for 24 hr to prevent hygroscopic blocking. For noting the degree of adherence, the test assemblies were removed and set aside in cool room temperature for inspection. Followed by the grades were assigned to the degree of blocking. (1) Free (2) First degree blocking (3) Second degree blocking (4) Any other blocking degrees agreed upon. The test methods with new specimens were repeated at at successively higher temperatures (in increments of 5 °C (10 °F) for thermoplastic blocking, or successively higher humidities (in increments shown with various salts) for hygroscopic blocking, until first, second, or other degree blocking is found, or until a suitably high temperature or humidity is reached.

Sample size: 

Eighteen test specimens of 38 mm (11⁄2 in). Square from suitable large specimens for each series of tests, six specimens for cohesive tests and three specimens for adhesive tests in both thermoplastic and hygroscopic blocking.

Data:

The data should be stated in SI units to be regarded as standard, no other units are included in this standard.

Conclusion: 

ASTM D1146 standard test method can determine the blocking point of a thermoplastic or hygroscopic layer or coating of potentially adhesive material.