Flexibility Testing


BS EN ISO 1519: BS 3900-E1
BS EN ISO 6860: BS 3900-E11
ASTM D 522

 Conical Mandrel

Scope and Field of Application

BS EN ISO 1519 and BS 3900-E1 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking and/or detachment from a flexible substrate when bent around a cylindrical mandrel.

BS EN ISO 6860 and BS 3900-E11 are alternative names for the same method which is used to assess the resistance of a dry film of paint, varnish or related product to cracking and/or detachment from a flexible substrate when bent around a conical mandrel.

ASTM D 522 is a method of determining the resistance to cracking of organic coatings on sheet metal or rubber-type substrates.

When choosing a test method, you may also wish to consider the cupping test. Cupping is potentially a more severe test than the mandrel bend test. In the cupping test, deformation of the panel can be taken to the point where the metal fractures. This does not normally happen during mandrel tests.

The cupping and mandrel tests are all carried out on coatings applied to flexible substrates. If you are interested in the flexibility or other tensile properties of coatings on different substrates, you may wish to consider tensile testing.

There are no pass/fail criteria defined in the standards. This is a matter of agreement between the parties concerned.

The actual standards are copyright-protected documents and we are not able to provide you with copies. If required however, you can easily obtain copies from the British Standards Institution or the American Society for Testing and Materials.

 

Summary of Methods

BS EN ISO 1519: BS 3900-E1

This method involves the use of a set of manually operated hinges each of which incorporates a cylindrical rod (known as a mandrel) around which the coated test panel is bent. A total of 12 mandrel diameters are specified ranging from 2 to 32 mm.

After bending, the coating is examined for cracking and/or detachment using either normal corrected vision or (by agreement) a lens with x 10 magnification.

 

BS EN ISO 6860: BS 3900-E11

This method involves the use of a manually operated tool which enables a test panel to be bent around a truncated cone (known as a mandrel). The diameter of the mandrel ranges from 3.2 to 38 mm.

Before bending, the coating is cut through at 20 mm intervals: these incisions are intended to limit crack propagation

After bending, the coating is examined for cracking and/or detachment using either normal corrected vision or (by agreement) a lens with x 10 magnification. The length of any cracks formed is noted.

Given a choice between the two methods, BS EN ISO 6860: BS 3900-E11 has a number of advantages:-

BS EN ISO 1519: BS 3900-E1 does however have the advantage that the smallest mandrel specified is 2 mm. This provides a more severe test than the 3.2 mm minimum diameter of the conical mandrel.

 

ASTM D 522

This method describes the use of both conical and cylindrical mandrels.

The conical mandrel method uses the same equipment as BS EN ISO 6860: BS 3900-E11. The method of determination differs however in that the ASTM method allows for a slow bend time to measure elongation. The measurement of cracking calls for a faster bend time than the BS method and does not include the option of cutting through the coating to limit crack propagation. The ASTM cracking test is therefore somewhat mere severe than the BS method.

The cylindrical mandrel method uses different equipment to that specified in BS EN ISO 1519: BS 3900-E1. The ASTM equipment consists of a series of cylindrical metal mandrels mounted in a frame. The operator selects a mandrel and bends the test panel around it manually. The frame contains 5 mandrels ranging in size from 3.2 to 25 mm. Elongation and cracking tests can be carried out using the same bend times as for the ASTM conical mandrel.

The ASTM method allows for fewer mandrels which cover a more restricted size range than those specified in the BS EN ISO 1519: BS 3900-E1 method. It could also be argued that the BS hinged tools allow for more controlled and reproducible bending than is possible using the ASTM equipment.

 

Sample Requirements

BS EN ISO 1519: BS 3900-E1

We need coated panels with dimensions 100 x 40 x no more than 0.3 mm . The substrate may be steel, tin-plate or soft aluminium. If we are to determine the largest mandrel that causes failure, we need 15 panels for each coating. If you specify the mandrel diameter, we need 3 panels

BS EN ISO 6860: BS 3900-E11

We need 3 coated panels for each coating. The dimensions should be 150 x 100 x no more than 0.8 mm . The substrate may be burnished steel, burnished tin-plate or soft aluminium.

ASTM D 522

In order to carry out the conical mandrel test, we need 3 coated panels for each coating. The dimensions for crack testing should be 150 x 100 mm. The substrate may be any sheet metal up to 0.8 mm thick or any rubber-type material up to 13 mm thick. If elongation testing is requires the substrate must be cold-rolled steel 150 x 100 x less than 0.8 mm.

The requirements for testing using the cylindrical mandrel are the same as the conical mandrel in terms of dimensions. If we are to determine the largest mandrel that causes failure, we need 15 panels for each coating. If you specify the mandrel diameter, we need 2 panels.

If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

 

Accreditation

PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out these tests.

 

 

Please contact Peter Collins for further details.

 

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