This standard specifies the method for determining the zero-span tensile strength using a zero-span tensile strength tester that meets the standard requirements. This standard applies to all pulp and paper. GB/T 2678.4-1994 Method for determining the zero-span tensile strength of pulp and paper GB/T2678.4-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Pulp and paper--Determination of zero-span tensile properties
Pulp and paper--Determination of zero-span tensile properties1Subject content and scope of application
GB/T 2678.4-94
This standard specifies the method for determining zero-span tensile strength using a zero-span tensile strength tester that meets the requirements of the standard. This standard applies to all pulp and paper.
2 Reference standards
GB450 Paper and paperboard sample collection
GB465.2 Determination of tensile strength of paper and paperboard after soaking in water for a specified time GB7981 Preparation of pulp laboratory paper sheets Conventional paper sheet former method GB10739 Standard atmosphere for handling and testing of pulp, paper and paperboard samples 3 Principle
Zero-distance tensile strength test is to break a 15mm wide sample when the distance between the two clamps is 0-0.6mm, and the maximum force that all the fibers clamped on the sample can withstand. Therefore, it reflects the strength of the fiber itself. 4 Terminology
Zero-distance tensile strength refers to the maximum tensile force that a sample of a certain width can withstand when the distance between the two clamps is zero under the conditions specified in the standard test method.
5 Instrument
Zero-distance tensile strength tester can act on the sample under the specified zero-distance conditions to determine the zero-distance tensile strength. The zero-distance tensile strength tester consists of the following parts.
5.1 Horizontal clamp with adjustable spacing: - One clamp is 15mm wide and divided into two pieces, each with a protruding part at both ends, the protruding height is about 1mm, the width is 1mm, and the two pieces are 75mm long. The other clamp corresponding to this clamp is 21.5mm wide, and there is a sample table with a length of 100mm and a width of 25mm in front of it. The spacing between the two clamps can be adjusted to five levels: 0mm, 0.1mm, 0.2mm, 0.4mm, and 0.6mm. Choose one of them according to different needs.
5.2 Chuck pressure regulator: The chuck pressure range is 400~600kPa. 5.3 Result and program display: The test results are displayed on the display. 5.4 Clamping force source and indicator: The compressed air pressure range is 1000~2000kPa. Approved by the State Administration of Technical Supervision on September 24, 1994 238
Implemented on March 1, 1995
6 Sample collection and preparation
GB/T 2678.4--94
Schematic diagram of fixture
1-Pressure device; 2-Chuck; 3-Pneumatic piston; 4-Clamp adjustment device 6.1 The sample collection shall be carried out in accordance with the provisions of GB450. 6.2 The preparation of pulp sample shall be carried out in accordance with the provisions of GB7981. Cut several samples from the sample to ensure that there are 10 valid data. The sample is not allowed to have any paper defects. The two sides of the sample should be straight, and the cut should be neat and without any damage. 6.3 Sample size: The width of the sample should be 15mm±0.1mm, the length of the sample should be about 100mm, and its parallelism should be within 0.1mm.
7 Sample treatment
The sample is subjected to temperature and humidity treatment in accordance with the provisions of GB10739. 8 Test steps
8.1 Use the air pipe attached to the instrument to connect the instrument to the air source, turn on the power, and preheat the instrument for 15 minutes. 8.2 Calibration of the instrument: Reduce the pressure to less than the standard pressure (clamping pressure), and insert the sample strip into the instrument fixture. Turn the test switch to the "ON" position, press the calibration button after 10 seconds, read the force value from the display and the clamping force display and compare them, the difference should be less than 2%.
8.3 Select the standard chuck pressure: Use the pressure regulator to adjust the chuck pressure to 414kPa (60psi) (1lbf/in2=6.9kPa), measure the zero-distance tensile strength value of the sample, and then adjust the chuck pressure to 483, 552, 621, 690kPa (70, 80, 90, 100psi), repeat the test, and select the chuck pressure when the maximum zero-distance tensile strength appears as the standard chuck pressure. 8.4 Measurement
8.4.1 Test under the standard atmosphere of temperature and humidity treatment of the sample. Place the prepared sample flatly into the instrument fixture, turn the instrument test switch to the "ON" position, the fixture automatically clamps, and starts to apply traction to the sample. After the sample breaks, read the load P at break from the display, then turn the test switch to the "OFF\ position and remove the tested sample. If you need to test the force value of other clamping distances, you can use the instrument clamping distance adjustment handwheel to adjust to the corresponding distance, and the value is marked on the handwheel. Then follow the above steps to test. If the sample is a finished paper, it is recommended to test it in the vertical and horizontal directions. 239
8.4.2 Wet test
GB/T 2678. 4-94wwW.bzxz.Net
Use a special sprayer for the instrument to wet the sponge in a box. Its water content should be controlled so that no water should overflow when the special roller is rolled. Place the prepared sample on the sponge, spray the sample with a sprayer, and then gently roll it with a roller until the sample is saturated with water. If the sample has a high degree of sizing, it should be soaked in water for a certain period of time in accordance with GB465.2. The time can be specified by the relevant product standards. When rolling, press from the middle to both sides. The roller is made of rubber with a diameter of 20mm. Two rollers are installed side by side on a rack. Place the wetted sample strip in the instrument fixture with a special rack, and measure its zero-distance and short-distance tensile strength respectively, which is the wet zero-distance and short-distance tensile strength of the sample.
9 Calculation and expression of test results
9.1 The instrument display shows a pressure value. If the unit is psi (1bf/in\), use the following formula to convert (this formula is provided by the instrument).
Zt (p - po) × 3. 599 1
Zero distance tensile strength value, N/15mm;
Where: Zt—
p——Instrument reading value, Ibf/in\;
po—Instrument setting value, lbf/in2, which can be obtained by looking up the following table according to the clamp distance during the test. p value at different clamp distances.
Clamp distance d, mm
Setting value po, kPa (lbf/in2)
9.2 Calculate the zero distance tensile strength of each specimen separately, and then calculate the arithmetic mean of the 10 results. The calculation result is rounded to three significant figures.
9.3 Calculate the standard deviation and coefficient of variation of the results. 10 Test report||tt| |The test report shall include the following contents:
This standard number;
The temperature and humidity treatment conditions used;
The direction of the sample to be measured;
The clamp distance and clamp pressure when measuring the sample; if required, the standard deviation and coefficient of variation of the zero-span tensile strength results shall be reported; any test conditions that deviate from this standard. Additional remarks:
This standard was proposed by the China Light Industry General Association.
GB/T2678.4—94
This standard is under the jurisdiction of the National Technical Committee for Standardization of Paper Industry. This standard was drafted by the Paper Industry Scientific Research Institute of the Ministry of Light Industry. The main drafters of this standard are Ma Xin, Xia Lifengfeng and Ji Houli. 241
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