November 2006
DEUTSCHE NORM
English price group 6
No part of this translation may be reproduced without prior permission of
DIN Deutsches Institut für Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,
©
DIN 53359:2006-11
2
Foreword
This document has been prepared by Technical Committee NA 054-04-04 AA Kunststoff-Folien und kunststoffbeschichtete Flächengebilde (Kunstleder); allgemeine Eigenschaften  of the Normenausschuss Kunststoffe (Plastics Standards Committee).
Amendments
This standard differs from DIN 53359:1957-11 as follows. a) The title has been changed.
b) The scope has been extended to include “imitation leather and similar sheet materials”. c) Normative references have been included.
d) The assessment after a predefined number of flexes has been included. e)
The standard has been editorially revised.
Previous editions DIN 53359: 1957-11
Introduction
Although the withdrawal of DIN 53359:1957-11 had previously been announced, the publication of a revised edition became necessary since the flexing test it specifies is included in the delivery conditions of a number of important customers.
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editorially
DIN 53359:2006-11
1 Scope
The test specified in this standard serves to assess the behaviour of products as in DIN 16922 when subjected to repetitive flexing (flex cracking behaviour).
The test specimens may be of type A or type B (see clause 4), although results obtained for the two types are not comparable.
Whether type A or type B test specimens are to be tested and at what temperature shall be subject to agreement.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
DIN 16906, Testing of plastic sheeting and plastic films — Sample and specimen — Preparation and conditioning
DIN 16922, Flexible sheet materials manufactured using plastics — Technological classification
DIN EN ISO 291, Plastics — Standard atmospheres for conditioning and testing
DIN EN ISO 2286-3, Rubber- or plastic-coated fabrics — Determination of roll characteristics — Part 3: Method for determination of thickness
3 Terms and definitions
For the purposes of this standard, the following term and definition applies.
3.1
flex number
the number of flexes under defined test conditions at which the first crack becomes visible on a test specimen viewed through a magnifying glass having a magnification of 6 ×
4 Samples and test specimens
4.1 Sampling and conditioning
Sampling and conditioning shall be carried out as specified in DIN 16906.
4.2 Type and number of test specimens
Out of each sample, cut five test specimens each parallel to, perpendicular to and, if so agreed, diagonal to the direction of extrusion.
Type A test specimen (for testing as in Figures 1 and 2): 20 mm × 40 mm,
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DIN 53359:2006-11
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Dimensions in millimetres
Key 1
Test specimen (20 mm × 40 mm)
Figure 1 —Type A test specimen — clamped, unflexed
Key 1
Test specimen
Figure 2 —Type A test specimen — clamped, flexed
Type B test specimen (for testing as in Figures 3 and 4): 40 mm × 40 mm
Dimensions in millimetres
Side view of test specimen
Key 1
Test specimen (40 mm × 40 mm, or 20 mm × 40 mm when folded)
Figure 3 —Type B test specimen — clamped, unflexed
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DIN 53359:2006-11
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Key 1
Test specimen
Figure 4 — Type B test specimen — clamped, flexed
5 Apparatus
5.1 Flexing machine
Testing shall be carried out with a flexing machine  having a grip travel that can be adjusted from 0 mm to 20 mm and is capable of performing 200 flexes per minute and equipped with a counter for displaying the number of flexes.
5.2 Grips
Grips shall be designed so that test specimens can be firmly clamped without their grip end faces imposing a mechanical load on the test specimen when flexed (see Figures 2 and 4). The thickness of the end faces shall be such as to exceed the dimensions of the outward fold of the test specimens.
5.3 Temperature control device
If testing in a test atmosphere other than the  standard atmosphere is agreed: a temperature control device capable of maintaining the selected temperature to within ± 2 K throughout the test.
5.4 Magnifying glass
Magnifying glass having a magnification of 6 × (e.g. magnifying glass as in DIN EN ISO 15253).
6 Procedure
6.1
Setting the test temperature
Unless otherwise agreed, perform the test in a DIN EN ISO 291 23/50-2 standard atmosphere. If a different test temperature is agreed, prior to testing condition the test specimen, clamped as in 6.3, for at least one hour at the test temperature.
6.2 Sample thickness measurement
Measure the thickness, h , of the test specimen as specified in DIN EN ISO 2286-3.
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