Problems And Suggestions Of Method Standard In Textile Inspection

　　 In the long run Textile products In the testing work, detects found some methods and standards. Actual operation There are problems in the selection of test conditions in the standard, calibration of instruments, revision of numerical values, explanation of calculation formulas, and handling of specific details in the process of detection. These problems may directly affect the consistency and comparability between the testing personnel or the inter agency testing, and even directly affect the determination of the results of the product inspection.

One Textile Test method for pilling and pilling

1.1 circular track method for test conditions of fabric pilling test

GB/T 4802.1 - 2008 "determination of fuzzing and pilling properties of textile fabrics first part circular trajectory method". The selection of test conditions in the standard is not clear, resulting in a variety of test conditions which may be selected or unconditionally selected for a piece of fabric. If the A test conditions of this standard are applicable to sportswear, the B test conditions are applicable to synthetic filament fabrics, and A and B can be used for two test conditions for sportswear made of synthetic filament fabrics. But for pure chemical short fiber fabrics and pure cotton, pure silk fabrics such as reference to the classification of the standard is unconditionally optional. Although the notes of this standard indicate that other fabrics that are not listed can be referenced by similar fabrics listed in the table or agreed on the selection of parameter categories according to the parties concerned, but different test personnel or inspection institutions may choose different test conditions, resulting in uncertainty in operation, so that the test results are not comparable. Therefore, it is suggested that a clearer and more careful classification of the type of fabric suitable for the test conditions of the standard should be avoided to avoid the above situation.

1.2 the "reference fabric" of pilling performance of the four calibrating instruments for fabric pilling.

GB/T 4802.1 - 2008 "determination of pilling properties of textile fabrics first parts: circular locus method" and "GB/T 4802.3 - 2008" determination of pilling properties of textile fabrics third part: circular track method. "Reference fabric" is made of 2~3 kinds of fabrics (from grade 1~2 to grade 4), which are used periodically or as required to compare the initial samples to determine the extent of the pilling effect of the instrument. At present, the pilling devices produced by the two pilling methods produced by the instrument manufacturers are quite different, especially the circular track pilling tester. However, there is no uniform fabric as a "reference fabric" or "standard substance" to detect pilling performance of the pilling apparatus. It is difficult to control and compare the pilling effect between different sets of pilling apparatus produced by different instrument manufacturers or even the same instrument manufacturer, and it is difficult to ensure the consistency of pilling performance between the inspection bodies. From the interlaboratory comparison results, we can see that the detection results of the pilling test items between the inspection organizations can reach 1.5 levels, which shows the seriousness of the problem.

Therefore, it is suggested that the standard substance production units should design and produce a set of standard materials as soon as possible, so as to unify the pilling performance of the pilling pits of the testing institutions and the various instrument manufacturers, so that the test results between the testing institutions can be comparable.

1.3 revision of pilling test results

GB/T 4802.1 to 4 "determination of fuzzing and pilling properties of textile fabrics" standard provides that the rating results of samples are calculated as follows: the average rating of individual personnel is the average rating of all samples, and the test result of the sample is the average rating of all personnel. If the average value is not integer, it is revised to the nearest 0.5 level.

There is no provision for revision here. When the average decimal position is exactly 0.25 or 0.75, there will be two revision results to the nearest 0.5 level, and the final result of different personnel or different institutions may be inconsistent. For example, the 3.25 amendment to the nearest 0.5 level can be revised to 3.5 or 3. In the case of test results, sample rating and the number of personnel involved in the assessment, the test results may be different from grade 0.5 only due to the unspecified stipulate rules in the standard. If the test result of the product is just at the critical value of qualified and unqualified, it may also result in the result of unqualified judgement due to the different ways of revision.

It is suggested that the way of amendment should be specified in the standard. For example, according to the standard of GB/T 8170, "the rules for the expression and determination of numeric revision rules and limit values", or referring to GB/T 8427-2008, "8.2 fastness to artificial light fastness: Xenon arc" standard in the textile color fastness test, the revision method is stipulated to evaluate the arithmetical average value of the series as the result and to be expressed in the nearest half level or integer level. When the arithmetic mean value is 1/4 or 3/4, the assessment should be taken to its adjacent high half level or level one, that is, 3.25 to be revised to 3.5 grade; and the 3.75 grade to the 4 grade. This will ensure consistency between the testing personnel and the consistency of the test results.

2 formula for elongation

FZ/T 70006-2004 "8.2.2 method for testing the elastic recovery rate of knitted fabrics".

Fixed force elongation = ""

(1)

L0 the length (original length) of the specimen plus pre tension is in millimeter (mm).

L1 - stretching length, in millimeters (mm).

The "stretch length L1" in Formula 1 has two kinds of understanding, one is the total length after stretching (including the original length), the other is the total length after drawing minus the length of L0 after adding the tension to the specimen. According to the two different understandings of "stretch length L1", the results obtained are far from being comparable. Therefore, we should try to avoid ambiguities in the standard. It is suggested that the formula be revised in a more intuitive way.

Fixed force elongation =

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(2)

L0 -- the length (original length) of the specimen plus pre tension is in millimeter (mm).

L1 - the total length of the load applied is millimeter (mm).

This can avoid ambiguity and avoid the fact that the inspector can calculate completely different values due to different understandings, which will affect the consistency and comparability of the reports.

3 the amount of desiccant in the moisture permeability test.

GB/T 12704.1 - 2009 "test method for moisture permeability of textile fabrics first part hygroscopic method" principle of test is: placing a dripper and sealing glass sample in a sealed environment with specified temperature and humidity, and calculating the moisture permeability, moisture permeability and moisture permeability coefficient of the sample according to the change of the quality of the hygroscopic cup in a certain time. The standard stipulates that the dosage of desiccant in each moisture permeable cup should satisfy two conditions at the same time: 1 the mass is 35 g, and the distance between the upper surface and the specimen of the 2 desiccant is 4 mm. But in the actual test operation, these two requirements are difficult to satisfy at the same time, and can not be tested completely according to the standard. The two conditions can only be taken one. This may cause different testing personnel or different testing institutions to choose to meet the conditions inconsistent, resulting in a larger difference in test results.

According to the test principle, the moisture content is closely related to the quality of desiccant. Therefore, it is recommended that the dosage of desiccant in each moisture permeable cup should be 35 g.

4 color fastness test

4.1 test for colour fastness to rubbing

GB/T3920 - 2008, the standard for testing the colour fastness to rubbing in textile fastness test does not specify any specific test details, resulting in different processing methods between the testing bodies and the detection results. There are two main situations in testing:

One case is that after testing the rubbing fastness of some darker samples, sometimes it will encounter a deeper stain on the round edge of the friction cotton cloth. Because the standard does not specify, there may be many ways to deal with the grading: 1 do not consider the darker round edge, directly evaluate the rubbing grade of the friction center of the friction cotton cloth; 2, directly evaluate the color level of the round edge where the stain is deeper; 3, take the color content of the friction center as the chromatic series, and at the same time, consider the deep edge of the cloth to lower the grading result. In three different ways, the results of color fastness to rubbing may be different from grade 1 or even more serious. It is suggested that the rating method of frictional white cotton cloth rubbing the dark round edge should be clearly defined in the standard, and the unified assessment method should be adopted.

In another case, after testing the rubbing fastness of samples with gold and silver powder on the surface, there will be gold and silver powder on the friction cotton cloth. There may be many ways to deal with the rating: 1, remove all the gold and silver powder that is stained on the white cotton cloth and then grade it; 2, do not remove the gold and silver powder on the white cotton cloth directly; then 3 gently remove the gold and silver powder floating on the friction cotton cloth and then grade it according to the overall color. It is suggested that the sample rating method for gold and silver powder on friction cotton cloth should be specified in the standard.

4.2 water and sweat resistant test drying methods.

GB/T 5713 - 1997 "water fastness test for textile color fastness test", GB/T 3922 - 1995 "test methods for textiles Perspiration resistance" and "GB/T 3921 - 2008" color fastness test for textiles, color fastness to soaping fastness, etc., all stipulate that the lining fabric and sample should be stitched along the short side when preparing samples, but whether the specimen should be disconnected from the short side suture line after the test is finished, the operation of the lining fabric and the sample separately drying is different. For example, GB/T 5713 - 1997 stipulates: unfold the composite specimen so that the specimen and the lining will be connected only by a suture (if necessary, disconnect all the sutures) and be dried in the air which does not exceed 60 degrees C, and GB/T 3922 - 1995 and GB/T 3920 - 2008 stipulate: the expanded composite specimen shall be connected with the lining only by a suture and suspended in the air which does not exceed 60 degrees Celsius. Several standard sampling methods are the same. After the test, the drying methods are almost the same. The difference is only "if necessary, all the sutures" should be disconnected. For the sake of standard systematicness and comparability, the proposed standards should be kept as uniform as possible.

At the same time, "if necessary, disconnect all stitches" instructions are not clear enough, which may seriously affect the test results. In the past testing process, it was found that some samples of the dye in the drying process will occur swimming phenomenon. If the suture line is not opened, the lining fabric and the sample are connected. The dye will move from the sample to the lining fabric. The closer the stitch is, the more serious the stain will be. However, if the suture is taken apart, there is no such phenomenon. For different drying methods, the difference between stained series can reach 1 to 2. It is suggested that the drying methods of these color fastness standards should be uniformly stipulated, and whether the suture lines should be dismantled or not, and whether the lining fabric and samples should be dried separately. Unified operation mode.

4.3 hot pressing color fastness test

For water repellent fabrics or poorly absorbent fabrics, GB/T 6152 - 1997 "wet fastness test for textile color fastness test" is unable to absorb water evenly. When testing, some small droplets are randomly gathered on the fabric surface. Generally, the contact fabric between the lining fabric and the sample with water droplets is heavily stained, and the spots are spotted, and the reproducibility of the test results is very poor. At the same time, there is no need to check wet pressure because such fabrics will not be completely absorbent in actual use. It is suggested that water repellent fabric or poorly absorbent fabric can be evaluated without wet pressure. Only dry pressure and tidal pressure can be assessed, which can better reflect the actual situation, and the test is more reasonable.

4.4 color fastness test of light and sweat

GB/T 14576 - 2009 rating standard for light fastness test and color fastness to light fastness test for textile fastness test only provides for the use of grey card or instrument to assess the discoloration of the specimen. The rating sample for the exposed parts of the sample is not the unexposed part or the untested sample after the test. The color of the unexposed parts of the test samples may be different from those of the untested ones. Since the unexposed parts of the samples were soaked in acid or alkaline sweat after a certain period of time in the instrument, due to the blocking effect of the part, the effect may be very small. But after a certain period of time, the color of the sweat can be changed compared with the untested samples. Therefore, the difference between the exposed parts and the two different color reference samples is different. It is suggested that the rating reference sample used for evaluating the exposure area should be specified as untested sample (i.e. original sample).

summary

　　 When making the standard of the method, we should try to be considerate and careful. We should take into account the possible abnormal phenomena as far as possible, and clearly explain the way to deal with the abnormal phenomena. In this way, we can ensure that all the personnel who use this standard maintain consistency and comparability in the whole process of the test, so that they can really reach the purpose of the determination standard, so that the inspection results are authoritative and the standardization of the detection process is realized.