ISO 2493-1-221 “Paper and board – Determination of flexure – Part 1: Constant deflection rate”

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

The first version, 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 a constant deflection rate, and ISO 2493-2 describes the Taber type tester. The part can also use a smaller bend length and a lower bend Angle if desired. Added optional computations 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 tester

ISO 2493-1-221 “Paper and board – Determination of flexure – Part 1: Constant deflection rate”

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 direction of deflection; This part of ISO 2493 describes this principle.

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

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

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

This part of ISO 2493 is suitable for measurement of bending resistance in the range 20 mN to 10 000 mN. It does not work with corrugated board, but it can work with components of such board.

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 with different bending lengths will not be comparable.

For boards that tend to permanently deform when bent at 15°, a semi-bending Angle of 7,5 ° can be used.

Note 2Taber type tester and tester using the principle of constant deflection cannot give comparable results. Therefore, ISO 2493:1992 is divided into two parts.

2 Normative references
The following reference documents are not available or available for use in this document. For dated references, citation-only versions apply. For undated references, the 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 to bend a rectangular specimen with one end clamped, measured under the conditions specified in this part of ISO 2493

3.2 Flexural resistance

The average of all valid readings of the measured bending force (3.1) calculated as specified in 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 of force applied on the sample under test is constant

Note 1: See l in Figure 1.

3.4 Bending Angle

The Angle of rotation of the fixture as it moves from its initial position to the position where bending resistance is measured

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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