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Learn what is needed to complete an accurate test with a falling weight indenter. The Gardco Universal Impact Tester, Model 172, is used in this video demonstration.

Left: The device is shown with magnets that hold the substrate to the tester. Right: An allen wrench can be used to support the combination weight/indenter to make removing the test panel simple and convenient.

SPECIFICATION REFERENCES

• ASTM D2794 "Resistance of Organic Coatings to the Effects of Rapid Deformation – Impact"; MIL-P-85582C; MIL-P-23377G; MIL-C-85285A; MIL-E-24763A (SH); NCAA 11-10 (11-6, 11-16, AND X-1); ECCA
• ASTM D4226 "Impact Resistance of PVC Building Products"
• Meets ASTM G 14 with optional accessories; call for details
• General Electric Company PLI-100 "Modified Gardner Impact Strength," 1975
• Federal Highway Administration FP-74 "Standard Specifications for the Construction of Roads and Bridges on Federal Projects" Section 633.06, Traffic Control Signs – Impact Resistance
• Model 172RF meets Proposed Revision of TT-P-2756A, Polyurethane Coating: Self-Priming Topcoat, Low Volatile Organic Compounds (VOC)
• ASTM D6905 "Standard Test Method For Impact Flexibility Of Organic Coatings"
• ASTM D5420 "Standard Test Method for Impact Resistance of Flat, Rigid Plastic Specimens by Means of a Falling Dart"

FEATURES

Many years of experience have taught that the bending and stretching of the metal base on which a coating is applied can provide valuable information about the elastic and adhesive characteristics of the coating. Several types of testing instruments, including powered elongation testers, cylindrical or conical mandrels, manual or powered indenters and falling weight indenters, have been used.

Falling weight indenters typicaly have the most impact due to the "shock" nature of the test. The design purpose of the new Universal Impact Tester, Model 172RF, is to provide a range of operating capabilites that match or exceed those of existing testing instruments. In addition, Model 172RF, with selected auxiliaries, exceeds specification ASTM D2794.

METHOD OF USE

Coatings to be tested are applied to cleaned thin metal panels (suitable panels are available from the Paul N. Gardner Company). After the coatings are properly cured and ready for test, one of the test panels is placed on the selected supporting die and magnets, or for the GE evaluation, on the flexible anvil.

The selected indenter with associated weight or the combined indenter weight is placed in the tube so that it rests on the test panel. The guide tube is then adjusted in the base so that the scale registers zero at the lifting handle or mark and/or the position of such lifting member while at rest. The weight or combined weight indenter is then raised to the desired height, noted and released. The test panel is inspected and, depending on results, the test may be repeated by releasing the weight or the combined weight indenter at a higher or lower elevation. (When using the device’s GE Flexibility Test Impactor, the usual practice is to use a fixed-height drop, as is covered under "Procedure" here).

Coating failure is determined when cracks first appear in the coating with the minimum inch-pounds of falling weight. Such failure cracks may be made more visible by the application to the test area of a copper sulfate solution (CuSO₄).

For more information about Model 172RF, view details here.