ASTM D7490 Contact Angle Measurements

Scope:

ASTM D7490 is important to provide data for the calculation of two components – dispersion, γ_s^d, and polar, γ_s^p – by using contact angles of two liquids. Although this procedure is exceptionally valuable in describing surfaces, assessing surface dynamic added substances, and clarifying issues, it is not intended to be a quality control or determination test.

Procedure:

In ASTM D7490 the contact points of drops of refined water and di-iodomethane (methylene iodide) are estimated on a superficial level of interest. The two qualities are then subbed into two separate articulations of the Owens-Wendt-Kaelble condition (one for every fluid). Then water contact angles are measured rapidly (within 30 s of depositing the drop). A humidity chamber is also used to reduce the rate of evaporation.

Video 01: Contact angle measurement

Specimen size:

In ASTM D7490 testing, a syringe outfitted with a No. 27 hardened steel needle, equipped for giving 100 to 200 drops from 1 mL of the liquid, is reasonable for use with water-like fluids.

Data:

The following data is calculated for ASTM D7490:

γ₁ (1+ cos θ)/2 = [(γ_l^dγ_s^d) ^½ + (γ_l^pγ_s^p) ^½] 

Where θ is the average contact angle for the test liquid on the test specimen, γ₁ is the surface tension of the test liquid in Dyn/cm, and γ^d and γ^p are the dispersion and polar components of the liquid and the solid, also in Dyn/cm.

Conclusion:

ASTM D7490 is important to provide data for the calculation of two components – dispersion, γ_s^d, and polar, γ_s^p – by using contact angles of two liquids.