Talking about the similarities and differences between the current standards for measuring the moisture regain rate of textile materials
On the Similarities and Differences of Testing Standards for Textile Materials' Moisture
Wen/Wang Jun Li Hongmei
Abstract: From the five aspects of constant weight definition, test environment, sampling, drying temperature and drying time, result calculation and numerical repair, the similarities and differences of different determination standards of textile material moisture regain rate are analyzed. According to the actual recommendations, for enterprises and Relevant testing agencies provide reference.
Key words: constant weight; correction; sampling; temperature; time
Foreword
Moisture regain/water content not only affects the weight of the material, but also affects the uniformity of the spun yarn, the weight deviation of the yarn, the processing and dyeing properties of the fiber, in order to ensure the smooth production of the enterprise and the final quality of the textile, throughout The moisture content of the fiber raw materials, semi-finished products and finished products must be determined during the processing. In addition, in the process of identifying textile fibers, analyzing the content of fiber materials, testing the quality of fiber materials, testing the quality of yarns, and testing the quality of textiles, it is also necessary to first dry the fiber materials to achieve a moisture content. Under the conditions of the specified value, the detection of other properties of the fiber is carried out. Whether it is a company or a related inspection department, it is important to master the moisture regain rate/water content detection standards for different materials.
Among the many methods of textile fiber moisture testing, China's national standard stipulates that the oven method is the basic method for arbitration inspection and textile factory quality control inspection. This paper compares the following standards from different angles: GB/T 6500—2008 “Heat method for testing moisture recovery rate of plush fiberâ€, GB/T 6102.1—2006 “Test method for oven moisture regain test methodâ€, GB/T 6503—2008 Chemical fiber moisture regain test method, GB/T 13835.4-2009 "Rabbit fiber fiber test method moisture regain rate oven method", GB/T 9995-1997 "Textile material moisture content and moisture regain rate oven drying method" (hereinafter referred to as Five standards or standard numbers represent the standard), and the difference in moisture regain/moisture rate is determined, and some suggestions are made to provide reference for enterprises and related testing departments.
1 constant weight
The five standards for the moisture regain rate / moisture content are determined by the oven method, weigh a certain amount of test sample, placed in an oven at a certain temperature to test, so that the water in the test sample evaporates until the test sample reaches Constant weight, and then calculated according to the formula. However, there are differences in the definition of constant weight in the five standards, as shown in Table 1.
Table 1 Definition of constant weight in different standards
standard encdoing | Constant weight definition | |
time interval /min | Two consecutive times, we can see that the quality difference does not exceed The percentage of quality that was seen last time | |
GB/T 6500—2008 | 10 | 0.05% |
GB/T 6102.1—2006 | 15 | 0.05% |
GB/T 6503—2008 | 10 | 0.05% |
GB/T 13835.4—2009 | 10 | 0.05% |
GB/T 9995-1997 | Obtained through preliminary tests | 0.1% |
The author believes that the definition of constant weight should be unified, that is, the time interval is 10min, and the quality difference is not more than 0.05% of the quality of the next time.
2 test environment
GB/T 6500—2008, GB/T 6102.1—2006, and GB/T 13835.4—2009 all require that the test be carried out under standard conditions. If it is in a non-standard state, the measured drying quality of the test sample should be corrected to the standard. The value under the condition; GB/T 6503-2008 in the non-standard state, the general situation of the test is not corrected, and it must be corrected during arbitration; GB/T 9995-1997 stipulates that the test is carried out in a non-standard state, depending on whether the product standard requires Corrected.
The standard state refers to the temperature (20±2) °C, humidity (65±4)%. The author statistically analyzed the influence of different types of chemical fiber and yarn in the non-standard state on the moisture regain rate. The time when the humidity changes greatly is summer and winter, so this is taken as an example.
The effect of different materials in summer on the regain rate is shown in Figure 1.
Figure 1 Comparison of summer materials with different materials or not
Note: 1 - cotton fiber; 2 - cotton yarn 100%; 3 - cotton yarn 100%; 4 - cotton yarn 100%; 5 - cotton yarn 100%;
6——100% cotton yarn; 7——100% cotton yarn; 8——100% cotton yarn; 9——100% cotton yarn; 10——cotton/acrylic fiber 65/35;
11 - cotton / acrylic 65 / 35; 12 - acrylic / wool 77 / 23; 13 - acrylic / wool 77 / 23.
It can be seen from Fig. 1 that the larger the official regain rate, the greater the influence of the correction coefficient on the regain rate.
The influence of the winter material correction on the moisture regain rate, the author only selected the specially treated viscose material for test analysis according to Figure 1, the results are shown in Table 2.
Table 2 Comparison of viscose material correction or regain rate (winter)
material code | Corrected moisture regain rate /% | Corrected moisture regain rate /% | difference/% |
1 | 18.70 | 18.77 | 0.07 |
2 | 18.41 | 18.50 | 0.09 |
3 | 16.16 | 16.24 | 0.08 |
4 | 16.26 | 16.34 | 0.08 |
From Figure 1 and Table 2, it is concluded that whether the non-standard atmosphere is corrected to the standard atmosphere, and the regain rate is quite different, which will be related to trade settlement and other issues. For the accuracy, reliability and comparability of the data, the author suggests that in addition to the constant a of polyester and polypropylene, it can be corrected, and other materials, especially for textile materials with good moisture absorption properties, should be corrected.
3 test preparation
3.1 GB/T 6500—2008 “Test method for moisture regain of plush fibers†oven method
The standard stipulates: combed camel velvet, carded cashmere (50g/piece), washed wool, bristled velvet, tops (80g/piece), should be quickly and immediately within 1min after the sample container is opened. The sample was adjusted to the specified mass and the mass before baking was recorded to the nearest 0.01 g.
3.2 GB/T 6102.1-2006 "Original cotton moisture regain test method oven method"
The standard stipulates: quickly take the sample from the sample container, peel off the cotton layer on the sample surface, take out the middle part, weigh 50g test sample with the balance to the nearest 0.01g, and each test sample should not exceed 1min. From sampling to weighing, the storage time should not exceed 24h.
3.3 GB/T 6503—2008 “Test Method for Regain of Chemical Fibersâ€
The standard stipulates that: chemical short fibers shall be taken as test samples in accordance with GB/T 14334-2008 "Sampling Methods for Chemical Fiber Short Fibers". The chemical fiber filament test samples were combined and wound (make sure each package was taken), and 2 samples were cut, 60g/piece. Number of trials: 2 or more per batch. Storage time does not exceed 24h.
3.4 GB/T 13835.4-2009 "Rabbit fiber test method for moisture regain oven method"
The standard stipulates that the sample should be quickly taken out from the sample container, and 50 g of the test sample should be weighed to the nearest 0.01 g with a balance, and each test sample should not exceed 1 min. A total of 8 test samples.
3.5 GB/T 9995-1997 "Determination of moisture content and moisture regain of textile materials - oven drying method"
This standard does not specify how to sample, but simply states:
Samples are taken according to relevant product standards or related protocols; sampling should be representative and prevent any changes in moisture in the sample; each sample is required to be adjusted to the required weight within 30 s during the sampling process.
3.6 Recommendation
The author makes recommendations from sampling methods, sampling quantities and number of trials through repeated operations.
3.6.1 Sampling method
Loose fiber: Take the center of the package.
Filament/yarn: The specific requirements are selected according to the actual state of the sample. If it is a textile material with a high moisture regain rate, such as cotton, viscose, wool, etc., or a specially treated textile material, such as a plucked yarn, a surface treated with a hydrophilic material, etc., it is necessary to obtain a sample for 10 minutes. Quickly peeling inside → sampling and weighing → sealing, that is, cutting out the outer layer of 1/3 material with sharp instruments (such as blades), fixing the seal within 1min, and completing the test within 4h; if the moisture regain is low, such as polyester, etc. Sampling was performed using the hank method, but sampling was also completed within 10 minutes. After sampling, it should be quickly placed in a sealed sample container and weighed in time. The plush fiber requires the sample to take the test sample and weigh the test sample. The sample is stored in the container for no more than 8 hours. Other materials are required to be Completed within 24 hours after sampling.
Before the baking, the weighed test sample should be torn loose, and a piece of glossy paper should be placed under the tearing, and the torn debris should be put back into the test sample.
Note: For the sample with the standard moisture regain rate, the dry weight m2 should be dried first, then the humidity is adjusted for 24 hours under standard conditions, and the equilibrium mass m1 is weighed to calculate the standard moisture regain.
3.6.2 Sample size
Chemical staple fiber and cotton fiber about 50g / piece, chemical fiber filament and yarn about 60g / piece, plush fiber: combed camel velvet, carded cashmere 50g / piece, washed hair, carded yak, top 80g /, after sampling, the sample should be quickly adjusted to the specified quality within a period of not more than 1 min after the sample container is opened, and the quality before baking is recorded to the nearest 0.01 g.
3.6.3 Number of trials
The filaments are tested at least 2 times per batch, at least 3 times for the plush fibers, 8 samples for the rabbit hair fibers, and 2 times for each batch of the other types.
4 baking temperature and drying time
By comparing the five standards and trial and error, the author proposed the rapid oven drying temperature and baking time (see Table 5). Other types of ovens can increase the drying time.
Table 5 Drying temperature and drying time 1
Material name | Drying temperature / °C | Baking time / min |
Cotton fiber | 105±2 | 40 |
Rabbit hair | 105±2 | 60 |
Silk | 140±2 | 60 |
Wash hair, tops | 105±2 | 80 |
Carded camel velvet, carded cashmere, carded yak | 105±2 | 100 |
Polyester, nylon, vinylon | 105±2 | 40 |
Polyester (DTY) | 65±3 | 40 |
Acrylic | 110±2 | 60 |
Chlorine | 65±3 | 180 |
Adhesive | 105~110 | 60 |
Modal | 105~110 | 60 |
Lysell | 105~110 | 60 |
All other fibers | 105±2 | 40 |
Note 1: The bake time here refers to the time required before the first dry weight is weighed.
Test procedure: start the start button to start heating up, after the temperature rises to the set temperature, weigh the weight of the drying basket, and put the weighed and torn test sample (the sample of the loose fiber) into the drying basket to fill the sample. One-half to two-thirds of the container, close the door and start timing when the temperature rises to the set temperature.
5 result calculation and numerical repair
Different standard requirements are different, see Table 6.
Table 6 Five standard result requirements
Standard code | Moisture regain | Moisture content |
GB/T 6500—2008 | 2 decimal places | - |
GB/T 6102.1—2006 | 2 decimal places | - |
GB/T 6503—2008 | 2 decimal places | 2 decimal places |
GB/T 13835.4—2009 | 2 decimal places | - |
GB/T 9995-1997 | 1 after the decimal point | 1 after the decimal point |
6 Conclusions and prospects
1) There are differences in the definition of constant weight among the five standards. The author believes that the definition should be unified so that different enterprises and testing organizations can test the operation and improve the accuracy and reliability of the data.
2) The five standards have different requirements for the test environment and whether it is corrected to the standard state. In order to ensure the reliability and comparability of the data, the author has drawn conclusions that all should be corrected to the standard state.
3) There are differences between the five standard sampling methods and sampling quantities. The author combines the advantages and disadvantages of the five standards and puts forward suggestions in combination with actual test needs.
4) Five standards for test conditions: There is a difference between the drying temperature and the pre-baking time requirements. The author determined the test conditions required for the general rapid oven baking test.
5) The five criteria differ in the calculation of results and the revision of numerical values.
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