preface
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This document has been prepared in cooperation with the Technical Committee’s ISO/TC 6 (Paper, Board and pulp), SC 2 Subcommittee (Test methods and quality specifications for paper and board) and the Technical Committee of the European Committee for Standardization (CEN) CEN/TC 172 (Pulp, Paper and board), According to the Technical Cooperation Agreement between ISO and CEN (Vienna Agreement).

The third edition cancelled and replaced the technically revised second edition (ISO 12625-4:216).

The main changes are as follows:

— Includes Appendix B, which describes the method for determining the tensile modulus.

A list of all the parts in the ISO 12625 series can be found on the ISO website.

Any feedback or questions about this document should be directed to the user’s national standards body. A complete list of these institutions can be found at www.iso.org/members.html.

1 range
This document specifies test methods for the determination of tensile strength maximum tensile strength and tensile energy absorption of tissue and household paper products. It uses tensile testing equipment that operates at constant elongation.

It also provides the calculation methods of tensile index and tensile energy absorption index.

2 Normative references
The following files are referenced in the text in such a way that some or all of the content constitutes the requirements of 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 1924-2, Paper and board – Determination of tensile properties – Part 2: Constant elongation method (20 mm/min)

ISO 7500-1, Metallic materials – Calibration and verification of static uniaxial testing machines – Part 1: Tensile/compression testing machines – Calibration and verification of force measurement systems

ISO 12625-1, Tissue paper and tissue products – Part 1: Vocabulary

ISO 12625-6, Tissue paper and tissue products – Part 6: Determination of gram weight

ISO 12625-4-2022 Tissue paper and tissue products – Part 4: Determination of tensile strength, maximum tensile strength and tensile energy absorption

3 Terms and Definitions
For the purposes of this document, the terms and definitions set forth in ISO 12625-1 and below apply.

3.1 Tensile strength

The maximum tensile force per unit width that a specimen can withstand before breaking

3.2 Tensile index

Tensile strength (3.1) divided by gram weight

3.3 Maximum tensile force

The ratio of the elongation of the specimen over its initial length at the moment when the maximum tension is reached during the tensile test

Note 1: The stretch at maximum force is expressed as a percentage of the initial test span length.

Note 2: Relaxation correction is used in this procedure, and elongation is not measured until a force of (0,25 ± 0,05) N.

3.4 Tensile energy absorption

The energy absorbed when stretching a specimen under tensile force per unit surface area until fracture begins (maximum pulling moment)

[Source: ISO 12625-1:2019, 3.53.1.3]

3.5 Tensile energy absorption index

Tensile energy absorption (3.4) divided by gram weight

[Source: ISO 1924-2:2008, 3.7]

3.6 Tensile modulus M

The slope between the two points of tension on the elongation curve obtained from a constant elongation device

Note 1: In the paper industry, “modulus” refers to the tensile stiffness of paper, units of force per unit width (as opposed to true “stress” in engineering terms, i.e. force per unit area).

Note 2: This procedure is optional, but if the tensile modulus is required as a measurement for this method, it should be measured and calculated according to the procedure in Annex B.

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