ASTM D4708 Standard Practice for the Preparation of Uniform Free Films of Organic Coatings

Scope:

In ASTM D4708, the free films are required for testing physical and mechanical properties of organic coatings such as tensile and elongation, moisture vapor permeability, microbiological activity resistance and other physical qualities where the substrate could interfere.

Procedure:

In ASTM D4708, a homogenous wet coating of the test substance was applied on a release substrate to create the free films. The applied films were dried or baked, cut to different sizes for the physical property test, and finally peeled from the released substrate.

Calculations:

The permeability of free films can be calculated by using the following equation:

P = 8.64SD/d

Where, P and D corresponds to the permeability and diffusion coefficient, respectively.

Specimen size:

Applied films should be conditioned at a temperature of 23 ± 2 °C (73.5 ± 3.5 °F) and 50 ± 5%.

Conclusion:

By using standard method ASTM D4708, the fabrication of free films of organic coatings for use in determining the physical properties of coatings is covered.