Bend Test Determinations of Various Polymer Coatings

Objectives: The purpose of this activity is to:

• test coating bendability by the bend test.
• determine which coatings have the best and worst bendability property.
• compare bendability properties of coatings to other properties.

Materials:

• Coating samples in their original containers
• Heavy Duty aluminum foil
• Cylinders of various diameters from your teacher
• for exaple:

  Diameter in(mm)	Object
  1(25)	30mL syringe
  3/4(19)	white board marker
  1/2(12.7)	sharpie marker with added tape
  3/8(9.5)	pen
  1/4(6.4)	pencil
  1/8(3.2)	#3 allen wrench

Safety:

Manufacturers provide instructions for the use of their products, and these instructions should be followed completely. Protective gloves and lab coats should be used when preparing and handling the glass slides with coatings, and safety glasses should be used at ALL times.

Procedures:

1. Obtain one aluminum foil panel of each coating from your teacher. Record important information from the label on the container.
2. Place the test panel over the largest diameter.
3. Using a steady pressure with your fingers, bend the panel approximately 180° around the diameter.
4. Remove and examine the panel immedialtely for cracking visible to the unaided eye.
5. If cracking has not occurred, repeat the procedure using successively smaller diameter objects on another area of the foil until either cracking occurs or the smallest diameter has been used.
6. This procedure can be applied as a “pass/fail” test by determining whether cracking is produced by a specified diameter size.
7. The resistance to cracking value for a coating is taken as the diameter greater than that at which cracking occurs. So, the last diameter where cracking does NOT occur.
8. Record the objects and their diameters used in the test.
9. Record the value at which cracking occurs and the value before it cracks.
10. Record all data and report your findings to the class as directed by your teacher.

Conclusions:
Obtain reported data from all of the other lab groups in your class as directed by your teacher. Compare and contrast the data. What conclusions can you draw from the data?

Why is bendability important? Where would you use stiff or flexible coatings? Why?

Compare the results of the bendability test to other physical characteristics that you have already observed.