GB/T 4710-1984 Test method for breaking strength of wool bundle fibers
Some standard content:
National Standard of the People's Republic of China
Test method for breaking tenacity of wool fibre bundles
UDC 677.31/.33
:677.017.42
GB 4710-84
This method is applicable to raw wool (wool bundles) of basically homogeneous wool and processed wool fibres (scoured wool, carbonized wool, wool tops, dyed wool, etc.).
1 Nouns and terms
1.1 Breaking strength
In the tensile test, the maximum force that the textile material or textile sample can withstand when it breaks, expressed simply in the unit of force, such as Newton, gram-force, kilogram-force, etc.
1.2 Breaking strength
The breaking strength of a fiber or yarn sample per unit fineness (before stretching) is generally expressed in combined units of grams per denier, grams per tex, grams per dry tex, Newton per kilotex, etc.
1.3 Moisture balance
Textile materials and textile samples are placed under constant temperature and humidity conditions for a certain period of time, and the exchange with moisture in the air reaches a dynamic equilibrium, and the weight reaches a constant weight. The balance of moisture content of the sample from low to high is called moisture absorption balance, and the balance of moisture content from high to low is called moisture release balance. 2 Principle
Use a constant rate of elongation strength tester to stretch the bundle fiber test sample under certain parameter conditions until it breaks. The maximum load value is indicated by an electronic device and converted into breaking strength. 3 Instruments and tools
3.1 Constant rate of elongation strength tester (CRE) The technical requirements for the strength tester are:
The error of the tester indication should not exceed 1%. a.
The error of the indicated value of the testing machine shall not exceed ±1%. b.
C. The error of the indicated clamp distance shall not exceed ±1%. 3.2 Drying
3.3 Tools
3.3.1 Balance: weigh 100 grams, graduation value 1 mg. 3.3.2 Stopwatch, small steel ruler, tweezers.
Prehumidification, humidity adjustment and standard temperature and humidity for testing 4.1 Prehumidification is to bake in a 50℃ oven for at least half an hour. If the moisture regain of the sample is lower than the standard equilibrium moisture regain, premixing is not required.
4.2 Humidification is to place the prehumidified sample at a temperature of 20±2℃ and a relative humidity of 65±3%, and weigh it after a certain period of time. When the percentage of the increase in the two weights (two weighings are two hours apart) to the previous weight is less than 0.25%, the sample is considered to have reached moisture balance.
Promulgated by the National Bureau of Standards on October 13, 1984
Implemented from May to January 1985
GB 4710-84
4.3 The test should be carried out at a temperature of 20±2℃ and a relative humidity of 65±3%. 5 Sampling and preparation of test specimens
5.1 Sampling Take representative test specimens from the batch sample as specified, see Appendix A (Supplement). 5.2 Preparation of test specimens
5.2.1 Raw wool: Take a tuft of wool weighing about 50 to 150 mg from the wool pile, with a thickness equivalent to 1 to 1.5 dry tex. Take a total of 200 tufts.
5.2.2 Wool fiber after amalgamation: Take and arrange into tufts of wool weighing about 25 to 30 mg each, for a total of 50 tufts. 5.2.2.1 If it is loose fiber, arrange the fiber into bundles by hand, comb out the short fibers, and make the fibers basically parallel and straight. 5.2.2.2 If it is wool strip, pull out the free fibers and the fibers taken out at one end of the wool strip to make one end flat. Extract the fiber from the flat end and place it on the black velvet board, overlap it several times, and form a bundle of about 30 mg. Comb out the short fibers and make the fibers basically parallel and straight. bZxz.net
Note: When evaluating the strength of weak knot wool, the actual weight of each bundle of fiber should be weighed and the natural length of each bundle should be measured. 6 Adjustment of the instrument
Adjust the level and zero position of the strength tester. 6.1
Check and adjust the position of the upper and lower clamps so that the clamping planes are in the same vertical plane and the distance between the jaws is 25 mm. 6.3
If the strength of weak knot wool is evaluated, the distance between the upper and lower clamps should be adjusted according to the length of the wool. 6.4i
Adjust the descending speed of the strength testing machine to ensure that the average breaking time of the bundle fiber is within 20±3 seconds. 7 Test steps
7.1 Preliminary test: Select the appropriate range of the strength testing machine through the test of a small number of test specimens. 7.2 Clamp the specimen into the upper and lower clamps. If it is an original hair bundle, the hair tip of the specimen must be upward and the hair root must be downward when clamping. 7.3 Start the strength testing machine until the test specimen breaks and record the strength value. 7.4 Use a sharp blade to cut off the broken fiber along the inner side of the upper and lower clamps and weigh it. 7.5 If the strength of the weak section of the hair bundle is assessed, in addition to recording the strength value, the breaking position must also be recorded (divided into three parts: hair tip, hair middle, and hair root). 7.6 During the stretching process of the fiber bundle, any test results that show obvious slippage or breakage at the jaws should be discarded. 8 Number of tests
8.1 Under the conditions of 95% probability of water and ±5% permissible strength deviation, the number of tests is determined by the following formula: n=_t2.CV2
Where: n—number of tests,
tt critical value of distribution, 1.96;
CV—coefficient of variation of breaking strength, %;
E—permissible deviation rate, % (take E=5%). 8.2 When the coefficient of variation is unknown, the number of bundles tested: 200 bundles for raw wool.
b. 30 bundles for processed wool fibers. 9 Calculation of test results 9.1 Breaking strength: (1) Wherein: Fri GB 4710-84 - breaking strength of each hair bundle, Newton/dry tex, breaking strength of each hair bundle, gf/dtex: breaking strength of each hair bundle, gf/denier, FDi - breaking strength of each hair bundle, Newton/denier, breaking strength of each hair bundle, gf; L - straight length of each hair bundle, m; m - weight of each hair bundle, g.
9.2 Average breaking strength
Where: F
Average breaking strength, Newton/denier;
-Breaking strength of each hair bundle, Newton/kilotex, Fp-Average breaking strength, gf/denier,
Fpi-Breaking strength of each hair bundle, gf/denier; n
Number of test bundles.
9.3 Standard deviation of breaking strength
(FT:-Fr)2
Where: -—Standard deviation of breaking strength, Newton/denier; F——Average breaking strength, Newton/kilotex; Fr: -—Breaking strength of each hair bundle, Newton/kilotex; n
Number of tests.
9.4 Coefficient of variation of breaking strength
Formula: CV-
-Coefficient of variation, %
Standard deviation of breaking strength, Newton/dryte;
F Half mean breaking strength, Newton/dryte.
.(3)
(4)
·(5)
(8)
·(9)
9.5 When evaluating the breaking position of weak hair, the percentage of the number of breaks at the tip, the middle and the root of the hair to the total number of breaks shall be calculated respectively. 12
GB471084
9.6 The test result shall be calculated to the third decimal place and rounded to two decimal places. The rounding of numbers shall be carried out in accordance with the provisions of Appendix C (Supplement) "Rounding Rules for Numbers" of GB1.1-81 "General Provisions for the Preparation of Standards for Standardization of Weighting and Weighing". 10
Test report
The test report shall include the following contents:
Sample batch, source, sample number; average breaking strength, standard code, coefficient of variation; number of tests;
percentage of fracture sites at high strength,
test date, temperature and humidity conditions.
GB 4710--84
Appendix A
Recommended sampling method
(Supplement)
A.1 The test specimens shall be drawn from the same variety and batch number. A.2 Method of sampling batches
A.2.1 The number of bales of raw wool sampled is determined by the following formula: Where: t - critical value of distribution, 1.96; CV - coefficient of variation of breaking strength, %,
E - allowable deviation rate, % (take E=±5%), N - total number of raw wool bales, bales,
number of bales of batch sampled, bales.
A.2.2 The sampling quantity is shown in the table below.
Total number of incoming bales, bales
The sampling quantity of processed wool fiber, bales
The sampling quantity of raw wool, bales
Note: The number of sampling bales in the above table is determined by taking the coefficient of variation of the breaking strength of processed wool fiber as 15% and the coefficient of variation of the breaking strength of raw wool as 35%.
A.2.3 Each wool bale is sampled from two different parts, one of which must be sampled from the center of the wool bale. The weight of the batch sample is not less than 5 kg.
A.3 Randomly select representative laboratory samples from the batch sample. A.4 Mix the laboratory samples thoroughly and lay them flat on the test bench, divide them into 16 areas evenly (zoning method), and randomly select a total of 32 points from the front and back sides as test samples.
A.5 Randomly select 60 representative wool tufts from the fully mixed test samples as test samples. Additional Notes:
This standard was proposed by the Fiber Inspection Bureau of the National Bureau of Standards. This standard was drafted by the Shanghai Wool and Linen Textile Science and Technology Research Institute and the East China Textile Engineering Institute. The main drafters of this standard were Wu Ancheng and Zou Jianfang. 14
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