tshrink

Test for Coating Shrinkage

Teacher Notes

Objectives:

Shrinkage is a concern to paint and dental adhesive manufacturers among others. Coatings should adhere to the applied substrate uniformly. This test determines the shrinkage among various coatings and serves as a comparison of different substrates on which the coatings are applied.

Applicable science concepts:

Scientific measurement. Scientific method.

Materials:

Saran Wrap
wax paper or other suitable substrates that will allow the coating to shrink when applied.
Possibly students could select their own substrate to test and then compare results with other class members.
Coatings in liquid or spray form.
Templates cut form folders with a 6 cm x 6 cm square cut in the middle of each sheet.

Safety:

Manufacturer's instructions should be followed and eye, hand , and body protection is required.

Procedures:

The substrate should be placed in a space that has minimum traffic.
Possibly this could be achieved by putting the substrate on top of newspaper, applying the coatings, and then placing the sheet of substrate in a safe place.
Coating normally dry in less than an hour but could take longer depending on the coating.
Students should take care to paint of spray only on the template and quickly remove the template once the entire square is covered.

Analysis:

Results of individual class groups can be arranged and statistical analysis performed. Our test results showed none to over 2 mm shrinkage among the various paints, epoxies, and waxes tested.

Conclusions:

The results of this test should be correlated with other tests to determine the optimum coating for a given application. Also the physical and chemical parameters should be explored and correlated with each other for a given application.