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GB/T 24328.3-2020 English PDF (GBT24328.3-2020)

GB/T 24328.3-2020 English PDF (GBT24328.3-2020)

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GB/T 24328.3-2020: Tissue paper and tissue products--Part 3: Determination oftensile strength, stretch at maximum force and tensile energy absorption

GB/T 24328.3-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 85.010
Y 30
Replacing GB/T 24328.3-2009
Tissue paper and tissue products - Part 3:
Determination of tensile strength, stretch at maximum
force and tensile energy absorption
(ISO 12625-4:2016, Tissue paper and tissue products - Part 4:
Determination of tensile strength, stretch at maximum force and tensile energy absorption, MOD)
ISSUED ON: JULY 21, 2020
IMPLEMENTED ON: FEBRUARY 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 7
4 Principle ... 7
5 Apparatus ... 8
6 Conditioning ... 9
7 Preparation of test pieces ... 9
8 Test procedure ... 10
9 Calculation ... 10
10 Test report ... 13
Annex A (Informative) Precision ... 14
Bibliography ... 16
Tissue paper and tissue products - Part 3:
Determination of tensile strength, stretch at maximum
force and tensile energy absorption
1 Scope
This Part of GB/T 24328 specifies a test method for the determination of the tensile strength, stretch at maximum force and tensile energy absorption of tissue paper and tissue products. It uses a tensile-testing apparatus operating with a constant rate of elongation. It also specifies the method of calculating the tensile index and the tensile energy absorption index.
This Part applies to tissue paper and tissue products.
2 Normative references
The following documents are indispensable for the application of this document. For the dated references, only the editions with the dates indicated are applicable to this document. For the undated references, the latest edition (including all the amendments) are applicable to this document.
GB/T 450 Paper and board - Sampling for testing and identification of
machine and cross direction, wire side and felt side (GB/T 450-2008, ISO 186:2002, MOD)
GB/T 10739 Paper, board and pulps - Standard atmosphere for conditioning and testing (GB/T 10739-2002, eqv ISO 187:1990)
GB/T 12914 Paper and board - Determination of tensile properties - Constant rate of elongation method (20 mm/min) (GB/T 12914-2018, ISO 1924-2:2008, MOD)
GB/T 24328.1 Tissue paper and tissue products - Part 1: General guidance on terms (GB/T 24328.1-2020, ISO 12625-1:2019, MOD)
GB/T 24328.5 Tissue paper and tissue products - Part 5: Determination of grammage (GB/T 24328.5-2009, ISO 12625-6:2005, MOD)
test piece.
From the recorded data, the tensile strength, the corresponding stretch at maximum force and the tensile energy absorption can be calculated.
The test can be carried out by a vertical or a horizontal tensile strength tester. Precision data are available in Annex A.
5 Apparatus
5.1 Tensile-testing apparatus
5.1.1 General
The tensile-testing apparatus shall be in accordance with GB/T 12914. It is capable of stretching a test piece of tissue paper or tissue product of given dimensions, at a constant rate of elongation of (50 ± 2) mm/min, and recording the tensile force as a function of elongation on a strip chart recorder or any electronic device.
The elongation shall be recorded to an accuracy of ±0.1 mm. The measurement of the elongation shall start at a tension of (1.0 ± 0.5) N/m.
The force-measuring system shall measure loads with an accuracy of ±1 % of the reading or ±0.05 N, whichever is greater, and shall be calibrated and verified regularly.
5.1.2 Means for measuring the area of the force-elongation curve
The tensile-testing apparatus shall provide a means for measuring the area between the force-elongation curve and the elongation axis to an accuracy of ±2 % of the true value as determined by numerical integration of the raw data. Note: Most modern tensile testers are equipped with an electronic or electro-mechanical integrator. The area can also be determined from a graphical output of the data on chart paper using a planimeter.
5.1.3 Clamps
The tensile-testing apparatus shall have two clamps of 15 mm or 50 mm in width. Each clamp shall be designed to grip the test piece firmly along a straight line across the full width of the test piece, without causing any damage or slippage, and shall have means for adjusting the clamping force.
The clamps should preferably grip the test piece between a cylindrical and a flat surface, with the plane of the test piece tangential to the cylindrical surface. be free of creases, kinks, wrinkles, folds or other thickness variations. For finished products with dimensions or perforations which make cutting of a test piece of 150 mm impossible, cut the longest piece possible. In such cases, a test span length of (50 ± 1) mm shall be used. This deviation from the normal procedure shall be recorded in the test report.
7.3 Number of test pieces
Cut 10 test pieces from one sample and 10 test pieces in the cross direction for the selected specimens, making a total of at least 20 test pieces from each sample.
8 Test procedure
8.1 Ensure that the tensile-testing apparatus (5.1) is calibrated and check the zero position of the recording device. Check that the clamps are aligned to meet the requirements in 5.1.3.
8.2 The elongation rate between the clamps shall be kept constant at (50 ± 2) mm/min.
8.3 Place the test piece in the clamps so that any observable slack is eliminated but the test piece is not placed under any significant strain. The test piece shall not be clamped with a tension greater than 5 N/m.
8.4 Do not touch the test area of the test piece between the clamps with the fingers. Align the test piece as parallel as possible to the pulling direction, tightly clamp the test piece and initiate the test.
8.5 Record all readings, except for test pieces that break within 5 mm from the clamping line, until 10 valid results are available for each direction. If more than 20 % of the test pieces break within 5 mm of the clamping line, reject all the readings. Inspect the apparatus for conformity with the specifications and take the appropriate remedial measures.
8.6 If it is necessary to report the tensile index of the test piece, the grammage of the test piece shall be determined according to GB/T 24328.5.
9 Calculation
9.1 General
Calculate and report the results separately for the machine direction and for the cross direction from Formula (1) to Formula (6).
Where:
A - the mean stretch at maximum force in %;
ε - the mean elongation at maximum force in millimetres (mm);
l - the length of the test piece between the clamps, before elongation, in millimetres (mm).
Report the result to the first decimal place.
9.5 Tensile energy absorption
Determine the area under the force-elongation curve up to the point of
maximum tensile force and calculate the tensile energy absorption from
Formula (4):
and the mean tensile energy absorption, ̅, from Formula (5):
Where:
Z - the tensile energy absorption by a test piece during the test until maximum force, in joules per square metre (J/m2);
̅ - the mean tensile energy absorption in joules per square metre (J/m2); E - the work, in millijoules (mJ), equivalent to the area under the
force/elongation curve;
w - the initial width, in millimetres (mm), of the test piece (standard width is 15 mm or 50 mm);
l - the initial test length, in millimetres (mm), of the test piece (standard 100 mm); n - the number of single values of the tensile energy absorption.
Report the mean tensile energy absorption to the first decimal place.
9.6 Tensile energy absorption index
Calculate the tensile energy absorption index, lZ, using Formula (6):
Annex A
(Informative)
Precision
A.1 General
A.1.1 The qualified laboratories of the Comparative Testing Service of the Confederation of European Paper Industries (CEPI-CTS) conducted a
comparative test on 2 tissue paper products. The data for tensile strength are presented in A.2. The data for stretch at maximum force are presented in A.3. A.1.2 The repeatability and reproducibility results from the test are reported in Table A.1 to Table A.4.
A.1.3 Precision data for tensile energy absorption is not available at the moment. A.1.4 The calculations were made according to ISO/TR 24498 and TAPPI T
1200 sp-07.
A.1.5 The repeatability standard deviation reported in Table A.1 and Table A.3 is the "pooled" standard deviation, which means that the standard deviation is calculated as the root-mean-square of the standard deviations of the
participating laboratories. This differs from the definition of repeatability in ISO 5725-1.
A.1.6 The repeatability and the reproducibility limits are estimates of the maximum difference of the data, which is obtained from the tests of two similar materials in the similar test environment, under a 95 % confidence interval. These estimates may not be valid for different materials or different test conditions. Repeatability and reproducibility limits are calculated by multiplying the repeatability and reproducibility standard deviations by 2.77. The
repeatability standard deviation and the within-laboratory standard deviation are identical. However, the reproducibility standard deviation is not the same as between-laboratories standard deviation. The reproducibility standard deviation includes both the between-laboratories standard deviation and the standard deviation within a laboratory, viz.:
𝑠௥ଶ = 𝑠௪௜௧ℎ௜௡ ௟௔௕ଶ 𝑠ோଶ = 𝑠௪௜௧ℎ௜௡ ௟௔௕ଶ + 𝑠௕௘௧௪௘௘௡ ௟௔௕ଶ
Note: 2.77 = 1.96 √2, provided that the test results have a normal distribution and that the standard deviation, s, is based on a large number of tests.

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