ASTM D7027-13 Evaluation of Scratch Resistance of Polymeric Coatings and Plastics

Scope:

This test method defines a procedure to determine the scratch resistance of polymer using an instrumented scratch machine. ASTM D7027-13 is an automated test method, as the process of inducing the scratch to record the necessary data is handled by the machine. This method helps recognize the surface damage on a polymeric coating or plastic that may be experienced during its service period.

Test Procedure:

ASTM D7027-13 standard test method is performed using an automated scratch machine. The machine helps conduct controlled scratch tests on polymeric specimens. Two test modes are available: Test Mode A: the scratch applied on the specimen is subjected to a normal load from 2 to 50 N over a 0.1 m distance at a constant scratch rate of 0.1 m/s. This helps determine the critical normal load for the failure of the system. Test Mode B: the scratch is applied at 30 N normal load over a distance at a constant scratch rate. This mode is used to evaluate the scratch coefficient of friction. The scratched surface can be inspected visually or by using certain tools to analyze the surface damage.

Specimen size: 

This method can be used for various polymeric coatings.
Tensile specimens-Tensile bars with thickness between 3 and 10 mm and at least 140 mm length.
Plaque specimens-140 mm in length and 10 mm in width plaque. The thickness shall at least be 3 mm.
At least five specimens shall be tested to ensure repeatability.

Data:
The critical load for failure, Fc is calculated as follows:
Fc = d/D. (Ff – F0) + F0
Where,
d = distance measured to the failure event from the
beginning of the scratch in mm,
D = total scratch length in mm, and
Ff and F0 = final and initial applied normal loads,
respectively, in N.

Scratch coefficient = Tangential force / Normal load.