DuPont Impact Tester

The DuPont Impact Tester tests the endurance of coated material. It does by impacting the coating with a falling weight from a specific height. The purpose of the test is to see if test specimens can resist the effect of rapid impact testing.

The purpose of the test is to verify the quality of coating. It checks the impact of falling weights from various heights. Thus, checking the damage or deformation of the test specimen. If it affects the coating, the quality of coating and other materials should be checked. Additionally, the DuPont Impact Tester is useful to paintings with coated materials.  It uses the same procedure. But uses various impact heads or needles to drop freely onto the test specimen from a certain height. After repeating this for three times on the test sample, its left to stand for an hour. Finally, the test sample is verified for cracking on the painting.

The DuPont Impact Tester has been designed to evaluate the resistance of a dry film of paint, varnish or related product to cracking or peeling from a substrate when it is subjected to a deformation caused by a falling weight, dropped under standard conditions. The DuPont Impact Tester should produce rapid-deformation as per ASTM D2794 and ISO 6272.

The terms “impact” and “impact resistance are used, but an important characteristic of the apparatus used is that it should produce rapid deformation rather than a true impact. Whereas failure is the presence of any crack or split created by the impact of the falling weight and indenter, visible to the naked eye. This includes any cracking or peeling of the surface coating; use a viewing lens if required. Or Copper sulfate solution and a white flannel-type cloth; copper deposition on test panel or iron-rust staining on cloth will occur if cracked Copper Sulfate Solution or CuSO4 is an acidic solution prepared by dissolving 10g of CuSO4.5H2O) in 90g of 1.0 N hydrochloric acid (HCI). The viewing lens is a magnifying glass with a magnification of x10.

Optional Items

Falling Weights

• 500 g (IDM-I0007-OP1)
• 1000 g (IDM-I0007-OP2)
• 2000 g (IDM-I0007-OP3)

Impact Needles

• Impact Needle - R1 /16" (IDM-I0007 -OP4)
• Impact Needle - R1 /8" (IDM-I0007-OP5)
• Impact Needle - R3/16" (IDM-I0007 -OP6)
• Impact Needle - R1/4" (IDM-I0007-OP7)
• Impact Needle - R1 /2" (IDM-I0007-OPS)

Summary of test method

The coating under test is applied to suitable thin metal panels. After the coatings have cured, a standard weight is dropped a distance so as to strike an indenter that deforms the coating and the substrate. The test can be carried out with the coated side of the panel facing upwards (i.e. towards the falling weight and indenter) or downwards (i.e. away from the weight and indenter). By gradually increasing the distance the weight drops, the point at which failure occurs can be determined. Films generally fail by cracking, which is made more visible by the use of a magnifier or, on steel, by the application of a copper sulfate solution.

DuPont Impact Tester Apparatus

The DuPont Impact Tester consists of the following:

A fall-weight apparatus, consisting of a vertical tube to guide a cylindrical weight that is dropped on an indenter resting on the test panel.

• A guide tube mounted vertically on a baseplate. A slot is cut lengthwise on one side of the tube to act as a guide for a cylindrical weight that fits inside the tube.
• A measurement system with graduations marked in millimetres, and the drop height to be set.
• A base constructed so that a thin flat panel can be inserted 50mm below the tube.
• Weights consisting of a metal cylinder made to fit inside the guide tube. A pin is fitting into one side of the weight to act as a guide by riding in the slot of the tube, to serve as a handle by which the weight can be raised and released. The mass of the weight is either 1.0kg or 2.0kg.
• Indenters made of hardened steel, with a mass of 150g. The hemispherical head having a diameter of either Ø12.7mm or Ø15.9mm. The head rests on a test panel, and the shaft is held vertically by a guide ring.
• A panel support consisting of a steel fixture with a cylindrical hole of Ø16.3mm, centred under the indenter to support the test panel.

Test Specimens

Test specimens and sample should be prepared with the following in mind:

• The substrate shall be metal, conforming to the requirements of ISO 1514.
• The panels shall be planar, free from distortion.
• The panels shall be at least 0.25mm thick (measure to the nearest 0.01mm).
• The dimension shall be such as to allow the test to be carried out on at least five different positions, not less than 40mm from each other and no less than 20mm from the edge of the panel.
• Test shall be prepared as per the above, and then coated by the method specified by the manufacturer of the product or system under test, to give the dry-film thickness required.

Conditioning

Perform the test in standard laboratory atmosphere of 23 ± 2° C and 50 ± 5% relative humidity unless otherwise required.

Test samples should also be conditioned in 23 ± 2° C and 50 ± 5% relative humidity for no less than 16 hours prior to the test. Perform the test no more than 30minutes after removal from conditioning.

Operating Instructions

1. Determine the number of samples for each specimen to be tested.
2. Measure the thickness of each specimen and coating thickness to the nearest 0.01mm using a micrometer.
3. Insert the specified or agreed upon die into the panel support holder.
4. Insert the specified or agreed upon indenter through the guide ring, and place into the top plate.
5. Place a randomly selected test panel onto the die/panel support, lifting the indenter and gently resting it back onto the test panel. The test panel can be inserted with either the coated side facing up or down.
6. Adjust the ruler so that the 0mm marker is level with the top of the indenter.
7. Gently place the specified or agreed upon weight into the guide tube from the rear, screwing in the lifting pin.
8. Adjust the height gauge to a height where no failure of the test panel is expected to occur. Tighten using the hand knobs.
9. Lift the weight using the lifting pin handle to the top of the height gauge slot.
10. Release the grip on the weight, allowing the weight to fall onto the indenter.
11. Carefully remove the test panel from the apparatus and observe the impact area for cracks in the coating. Determine the appropriate definition of failure as per specimen specifications.
12. If no cracks are evident, repeat the procedure at a greater height, increasing 25mm at a time.
13. Once visible cracks are observed, repeat the test five times at each of the following heights: height of failure, 25mm below, 25mm above. Test in a random fashion so that all impacts from one height are not made in succession or on one panel.
14. Examine the impacted areas for cracking by one of the following methods:
    i. Use a viewing lens to examine the area for cracks.
    ii. Hold a white flannel-type cloth saturated with the acidified copper sulfate (CuSO4) solution over the impacted areas for at least 15minutes. Remove the cloth and examine both the test areas and cloth for evidence of copper deposition or iron-rust staining respectively.

Test Report

Report the following for each coating tested:

• The kilogram-metres (inch-pounds) at the impact failure end point
• Whether intrusion or extrusion was used
• Diameter of the punch used
• Thickness of coating
• Substrate thickness and type of metal
• Method of panel preparation
• Atmospheric conditions under which the coated panels were conditioned and tested