This standard method A refers to the international standard ISO 9073-4-1989 "Textiles - Nonwovens Test Methods - Part 4: Determination of Tear Resistance". Metal Key Chain,Key Chain,Round Opener Keychain Souvenir Coin,keychain Co., Ltd. , http://www.nsmetalware.com
1 Subject content and scope of application This standard specifies two methods for determining the tear strength of nonwoven fabrics, A method - trapezoid method, B method - drop hammer method.
Method A - Trapezoidal method Suitable for all types of nonwoven fabrics.
The B method-drop weight method is only applicable to the measurement of the tearing strength of a thin nonwoven fabric having a mass of 120 g/m 2 or less.
2 Reference standard
Standard atmosphere for humidity control and test of GB 6529 textiles
GB 8170 numerical rounding rules 3 A method - trapezoidal method
3.1 Principle
A strip sample with a trapezoidal shape is drawn, and a slit of a certain length is cut as a tear starting point in the trapezoidal short side, and then the trapezoidal sample is clamped along the clamping line in the upper and lower jaws of the strength testing machine, The sample is subjected to a continuously increasing load, causing the sample to tear along the slit and gradually expanding until the sample is completely torn.
3.2 Instrument
3.2.1 The constant velocity traction type (CRT) strength testing machine can be used, and the constant velocity elongation type (CRE) strength testing machine can also be used. In the case of an arbitration test or in the event of a dispute, the CRE type shall prevail.
3.2.2 The clamps holding the specimens shall have sufficient width to allow the width of the specimen to be fully clamped. During the test, the specimen shall not slip in the jaws.
3.3 There shall be no obvious creases and defects on the sampled samples that affect the quality of the test. Samples shall be taken at a distance of more than 1 m from the end of the cloth, and each sample shall be cut to a length of 1 m.
3.4 Preparation of samples
3.4.1 Remove 100mm from the edge of the sample and cut 10 longitudinal and transverse specimens in parallel. Generally, it can be cut more than the prescribed number for spare.
3.4.2 Size of the sample: first cut into strips with a width of 50mm and a length of not less than 200mm.
3.4.3 Use a trapezoidal template (the size of which is shown in Figure 1) to draw a trapezoidal beveled edge on the strip, ie, the gripping line, and at the center of the short side of the trapezoid, cut a length of 10 mm perpendicular to the short side. Incision.
3.5 Conditioning and testing of samples The standard atmosphere shall be pre-conditioned and humidity-conditioned according to GB 6529.
The test is carried out in the standard atmosphere specified in GB 6529, and the arbitrage test uses a secondary standard atmosphere.
3.6 Test procedure
3.6.1 Correct the gap between the upper and lower clamps by 100±1mm before testing.
3.6.2 Adjust the traction speed of the lower clamp to 100mm/min.
3.6.3 Pre-test: Select the tensile force range of the strong test machine so that the maximum value of the tear strength falls between 20% and 80% of the full scale (the constant-speed Elongation CRE test machine is not subject to this limit).
3.6.4 Formal test: Place the sample in the upper and lower clamps so that the clamping line is flush with the clamp jaw line, then tighten the upper and lower clamp screws, and pay attention to the sample in the middle of the upper and lower clamps. The symmetrical position, so that the short side of the trapezoidal sample is kept in a vertical state, and finally the strength tester is started, and the sample is completely torn, and the maximum tear strength value is recorded.
3.6.5 If the specimen slips in the jaws if the clamp screw is not tightened during the test, the test data should be excluded. Due to the difference in the manufacturing process, there may be some irregularities in the longitudinal and transverse tearing directions during the test. In case of such abnormal conditions, it should be indicated in the test report.
3.7 The results represent the average of the maximum values ​​of tear strength in the longitudinal and transverse directions, in Newtons (N), calculated to two decimal places, and one decimal place after revision according to GB 8170.
3.8 Test report
a. Test methods and instruments;
b. Sample name, code number, raw material and compounding ratio;
c. Test results: the tear strength is expressed in Newtons (N), and the coefficient of variation is expressed as a percentage;
d. Atmospheric conditions for testing;
e. Any deviation from the conditions specified in this standard and abnormalities shall be noted.
4 B method - drop hammer method
4.1 Principle An approximately semi-circular specimen is clamped on the moving clamp and the fixed clamp of the drop-type tearing device, between the two clamps, ie in the middle of the specimen - incision, using a fan-shaped pendulum The force of the vertical position falling to the horizontal position causes the moving clamp and the sample in the fixed clamp to tear rapidly.
4.2 Instrument drop weight fabric tearing strength meter.
4.3 There shall be no obvious creases and defects on the sampled samples that affect the quality of the test. Samples shall be taken at a distance of more than 1 m from the end of the cloth, and each sample shall be cut to a length of 0.5 m.
4.4 Preparation of samples
4.4.1 Cut 10 pieces of longitudinal and lateral specimens in a parallel arrangement on a sample within 100 mm of the edge of the fabric. Generally, the number of the specimens can be cut more than the specified number for the spare. .
4.4.2 The sample has a width of 92 mm, a height of 63 mm, a slit line length of 20 mm, a specified tear length of 43 mm, and a curved radius of curvature R of 43 mm. The specific dimensions and drawings are shown in Fig. 2. In addition to cutting with a template, a die can be prepared as a sample.
4.5 The humidity control and test of the sample are the same as the standard atmosphere of 3.5.
4.6 Test procedure
4.6.1 Check the level of the instrument before the test, the zero state of the pointer when no load, and make necessary adjustments. Check the height of the knife edge and the length of the slit line should meet the requirements of 20mm.
4.6.2 Pre-test: Select the appropriate range according to the actual strength, so that the test value falls within the range of 20% to 80% of the full scale value.
4.6.3 Lift the fan-shaped pendulum to the vertical position, ie the test start position, and push the pointer to the baffle, place the bottom edge of the semi-circular specimen on the center of the two clamps, then Tighten the two clamps and press the cutter handle to cut a 20mm long cut from the bottom of the specimen.
4.6.4 Press the pendulum baffle, the fan-shaped pendulum quickly falls down and swings to the right side. Because the moving clamp is connected with the pendulum, the sample is torn.