GB/T 465.2-2008 English PDF (GBT465.2-2008)

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GB/T 465.2-2008: Paper and board -- Determination of tensile strength after immersion in water
GB/T 465.2-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 85.010
Y 30
Replacing GB/T 465.2-1989
Paper and Board - Determination of Tensile Strength
after Immersion in Water
(ISO 3781:1983, MOD)
ISSUED ON: AUGUST 19, 2008
IMPLEMENTED ON: MAY 1, 2009
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Terms and Definitions ... 4 
4 Principle ... 5 
5 Instruments ... 5 
6 Sample Collection, Preparation and Processing ... 5 
7 Test Procedures ... 5 
8 Result Expression ... 6 
9 Test Report ... 7 
Appendix A (informative) Comparison of Chapter No. between this Part and ISO
3781:1983 ... 8 
Appendix B (informative) Technical Differences between this Part and ISO
3781:1983 and the Causes ... 9 
Paper and Board - Determination of Tensile Strength
after Immersion in Water
1 Scope
This Part of GB/T 465 specifies the method of determining the tensile strength of paper
and board after being immersed in water for a specified time and uses this to measure
the wet strength of paper and board.
This Part is applicable to various types of paper and board with wet strength
requirements.
2 Normative References
Through the reference in this Part of GB/T 465, the clauses of the following documents
become clauses of this Part. In terms of references with a specified date, all the
subsequent modification sheets (excluding the corrected content) or revised versions
are not applicable to this Part. However, the various parties that reach an agreement
in accordance with this Part are encouraged to explore the possibility of adopting the
latest version of these documents. In terms of references without a specified date, the
latest version is applicable to this Part.
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, ISO 187:1990)
GB/T 12914 Paper and Board - Determination of Tensile Properties (GB/T 12914-2008,
ISO 1924-1:1992, ISO 1924-2:1992, MOD)
3 Terms and Definitions
The following terms and definitions are applicable to this Part of GB/T 465.
3.1 Wet Tensile Strength after Immersion for X Hours
Wet tensile strength after immersion for X hours refers to the maximum tension that
the paper or board can withstand before it breaks after being immersed in water for a
certain time under the specified test conditions.
3.2 Wet Strength Retention after Immersion for X Hours
If it is a sample with quite strong water absorption, it is recommended to merely wet
the central part of the sample; maintain both ends dry. Generally speaking, bend the
sample into a ring; immerse the central part of the sample in water; when the water
evenly touches the full width of the sample and exceeds its upper surface, the wetted
length, including the central part of the sample, shall be at least 25 mm, but not greater
than 50 mm. After immersing the sample in the water for the specified time, take out
the sample; gently absorb the water on the surface of the sample.
7.2 Quickly place the sample, which has been immersed in water and with the surface
water absorbed, on the tensile strength tester, so as to determine its tensile strength.
Generally, there shall be respectively 10 samples in the vertical and horizontal
directions for the determination of wet tensile strength.
If the tensile strength retention rate is determined, then, the determination of dry tensile
strength shall also take 10 samples respectively in the vertical and horizontal directions.
In terms of papers with extremely low wet tensile strength, multi-layer samples shall
be used for the determination, and respectively 10 results shall be determined in the
vertical and horizontal directions.
8 Result Expression
8.1 The average value of the determined wet tensile strength after immersion shall be
expressed in (kN/m) and accurate to three significant figures. If multi-layer samples
are used for the determined, then, calculate in accordance with Formula (1):
Where,
P---the wet tensile strength of each layer after immersion in water, expressed in (kN/m);
S---the wet tensile strength of multiple layers after immersion in water, expressed in
(kN/m);
n---the number of layers being determined.
8.2 The wet tensile strength retention rate after immersion shall be expressed in (%)
and accurate to one decimal place. It shall be calculated in accordance with Formula
(2):
Where,