Contact Angle Measurements ASTM D5946

Understanding Contact Angle Measurements ASTM D5946

Polymer films are widely used for various applications such as creating graphics on automobile instrument panels and consumer electronics. In some cases, these films require a secondary treatment, such as corona treatment, to improve surface adhesion. ASTM D5946 is a standard test method that uses water contact angle measurements to determine the effectiveness of corona-treated polymer films.

The test procedure involves inserting a strip of the test material into a Goniometer, which is a device used to measure contact angle. A single drop of deionized water is applied onto the test specimen using a syringe, and the gauge on the end of the Goniometer is used to measure the angle between the material and the edge of the drop. The test material is cut into 15 mm (0.5") strips that fit in the Goniometer, and the specimen thickness should not be greater than 2.5 mm.

The test result is an angular measurement in degrees, which can be converted into surface energy for purified DI water utilizing a table in ASTM D5946. The water contact angle is an indirect measurement of the surface's ability to accept and hold a coating. By measuring the contact angle, the test can determine the effectiveness of corona treatment in improving the adhesion of a surface coating to a polymer film.

This test method is useful in assessing the quality of surface treatment for polymer films and can help ensure that the surface is prepared correctly for subsequent coatings. It is important to note that this test method does not measure the actual adhesion strength of a coating on the polymer film, but rather provides an indirect measurement of the surface's ability to accept a coating.