introduction
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International standards are drafted in accordance with the rules given in Part 2 of the ISO/IEC Directive.

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ISO 2493-1-21st “Determination of flexural resistance of paper and paperboard – Part 1: Constant deflection rate”

ISO 2493-1 was developed by Technical Committee ISO/TC 6, Paper, Board and Pulp, Sub-Committee SC 2, Test Methods and Quality Specifications for paper and board.

The first edition, together with ISO 2493-2, cancelled and replaced the technically revised ISO 2493:1992. In the revised version, ISO 2493:1992 is divided into two parts due to different measurement principles. This part of ISO 2493 describes the constant deflection rate, and ISO 2493-2 describes the Taber type tester. If required, the part can also use a smaller bending length and a lower bending Angle. Added optional calculations in index form. A precise note has been added to the informative annex A.

ISO 2493 consists of the following parts, under the general heading Paper and board – Determination of bending resistance:

– Part 1: Constant deflection rate

– Part 2: Tabor type tester

introduce
In ISO 2493:1992, two principles for determining bending resistance are incorporated into the same standard, although the two principles are very different.

One principle involves deflecting the same number of specimens with relative surfaces in the deflection direction; This part of ISO 2493 describes this principle.

Another principle uses a Taber-type tester, where the specimen is inserted and deflected to the top, and then deflected in the opposite direction without changing the specimen. This principle is described in ISO 2493-2. This method is based on TAPPI test method T 489 om-04[4].

ISO 2493-1-21st “Determination of flexural resistance of paper and paperboard – Part 1: Constant deflection rate”

1 Range
This part of ISO 2493 specifies procedures based on the two-point loading principle for determining the flexural resistance of paper and paperboard.

Note 1 See ISO 5628[1] for a detailed explanation of the two-point loading principle.

This part of ISO 2493 applies to the measurement of bending resistance in the range of 20 mN to 10 000 mN. It is not suitable for corrugated cardboard, but can be applied to components of such boards.

The bending Angle is 15° and the bending length is 50 mm.

For samples where the bending resistance is too low to measure a bending length of 50 mm, a shorter bending length of 10 mm can be used.

Important note – Results obtained using different bending lengths will not be comparable.

For a circuit board that bends 15° and tends to permanently deform, you can use a semi-bending Angle, that is, 7,5 °.

Note 2 The TABER type tester and the tester using the constant deflection principle do not give comparable results. ISO 2493:1992 is therefore divided into two parts.

ISO 2493-1-21st “Determination of flexural resistance of paper and paperboard – Part 1: Constant deflection rate”

2 Normative references
The following reference files are difficult or lacking for the use of this document. For dated references, only the cited version applies. For undated references, a new version of the reference (including any revisions) applies.

ISO 186, Paper and board – sampling to determine average quality

ISO 187, Paper, board and pulp – Standard atmospheres for conditioning and testing and procedures for monitoring sample atmospheres and conditioning

ISO 536, paper and board – Determination of gram weight

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

3.1 Bending force

The force required for a rectangular specimen with a bent end clamped, measured under the conditions specified in this part of ISO 2493

ISO 2493-1-21st “Determination of flexural resistance of paper and paperboard – Part 1: Constant deflection rate”

3.2 Flexural resistance

The average of all valid readings of the measured bending force (3.1) calculated in accordance with the provisions of this part of ISO 2493

Note 1: Flexure is expressed in Newtons or millinewtons.

3.3 Bending Length

The radial distance between the fixture and the position where the force is applied on the sample under test is constant

Note 1: See l in Figure 1.

3.4 Bending Angle

The Angle at which the fixture rotates when it moves from its initial position to the position where bending resistance is measured

ISO 2493-1-21st “Determination of flexural resistance of paper and paperboard – Part 1: Constant deflection rate”

3.5 Free Length

The total length of the specimen protruding from the fixture

Note 1: See L in Figure 1.

3.6 flexural index

Bending resistance divided by gram weight to the third power

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