Test method for antioxidant properties of geotextiles and related products

1 Scope This standard specifies the test methods for the oxidation resistance of polypropylene and polyethylene geotextiles and their related products. 2 Normative references The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision and parties using this standard should explore the possibility of using the latest edition of the following standards. GB/T 3923.1-1997 Tensile properties of textile fabrics Part 1: Determination of breaking strength and elongation at break Strip method GB 6529-1986 Standard atmosphere for humidity conditioning and testing of textiles GB/T 13760-1992 Sampling and testing of geotextiles Sample preparation GB/T 14798-1993 Geotextile identification mark 3 principle Ethylene was heat aged at 100°C. It is difficult to perform tensile tests on the control sample and the aged sample after heating, and compare their breaking strength and breaking elongation. 4 Instruments and equipment constant temperature non-forced ventilation oven, the oven should have adjustable vents. There is enough space in the oven for hanging the sample, and the total volume of the sample does not exceed 10% of the space volume in the oven. The set temperature should be maintained in the oven, and the temperature accuracy is±The samples at 1°C are clamped with heat-resistant clamps and hung in the oven with at least 10mm space between the samples. The distance of the sample from the oven wall is at least 100mm. 5 Samples 5.1 Sampling products must be tested after 24 hours of production, and the samples shall be taken according to the provisions of GB/T 13760. 5.2 The number and size of the samples Two sets of samples are cut from the samples, one is used as the aging sample for heat aging; the other is used as the control sample. Five samples were taken from each group vertically and horizontally. The dimensions of each specimen shall be at least 300mm x 50mm. The dimensions of each sample of the woven fabric shall be at least 300mm x 60mm. The geogrid sample shall remain a complete unit in width, and shall have at least three connection points in the length direction, and one connection point in the middle of the sample. Note: It is recommended to age several more samples as backup samples when the mechanical property test fails. 6. The humidity conditioning sample does not need conditioning before aging in the oven. Since the sample may shrink during the heat resistance test, the control sample should be placed in the oven at the same temperature for 6h. Before carrying out the tensile property test, adjust the humidity of the aging sample and the control sample according to the provisions of GB 6529. 7 Test steps 7.1 When the sample is a woven fabric, the number of yarns between 50mm in the warp and weft directions should be counted and recorded as n1 and n2 respectively. 7.2 Set the oven temperature: 110°C for polypropylene; 100°C for polyethylene °C. 7.3 When the oven temperature is stable, hang the sample clamped on the fixture inside the oven, and the samples do not touch each other. The distance between the sample and the oven wall is at least 100mm. 7.4 For the geotextile samples that play a reinforcing role, or the samples that need to be stretched for a long time in use, the polypropylene needs to be aged in the oven for 28d; the polyethylene is aged for 56d. For geotextiles used in other aspects, polypropylene needs to be aged for 14d; polyethylene is aged for 28d. The control sample should be placed in an oven at the same temperature for 6h. Record the test temperature regularly. 7.5 Determination of tensile properties When the specified time expires, take out the sample and adjust the humidity of the sample according to the provisions of GB 6529. The tensile properties were measured in accordance with GB/T 3923.1, using a tensile rate of 100 mm/min. For the woven fabric, the phase mean value was removed from both sides of the strip, the control sample was recorded as Fc, and the aging sample was recorded as Fe; the average value of elongation at break was calculated, and the control sample was recorded as ξc, and the aging sample was recorded as ξe. If the tensile test of one of the specimens is invalid, take another specimen for the test in the same direction. Note: Practical experience shows that in order to achieve better reproducibility, the following points should be noted: a) Place the sample in the middle of the oven. b) ventilation should be avoided around the oven; c) the oven and fixtures should be cleaned of residues before each test; d) thermal oxidation of polymers (eg polypropylene) may release catalytic substances. Therefore, polymers of different stabilities should not be tested in the same oven at the same time, except for geotextile composites. 8. Calculate the strength retention rate according to formula (1) for the test results, accurate to one decimal place. where: RF——Strength retention rate of the sample, %; Fe——Average breaking strength of aged samples, N;Fc——Average breaking strength of the control, N. Calculate the retention rate of elongation at break according to formula (2), accurate to one decimal place. In the formula: Rξ——Retention of elongation at break of the sample, %;ξe——Average elongation at break of aged samples, mm; ξc——Average elongation at break of the control, mm. 9 Test report The test report shall include the following contents: a) the test is carried out according to this standard; b) the identification of the sample (according to GB 14798); c) the test start date; d) the time of the aging test; e) the model of the oven used ; f) oven temperature and maximum deviation; g) effect of temperature on control; h) tenacity retention; i) elongation at break retention gauge; j) details of any deviation from this standard.
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