Discussion on the Method of Quantitative Chemical Analysis of Cotton Viscose Blended Products

文/瞿彩莲 董激文胡红花朱梦滢卞敏

Abstract: This paper discusses the quantitative chemical analysis methods of cotton/viscose blended products, and studies and practices the test methods of sulfuric acid soluble cotton/viscose blended products in JIS and AATCC standards, and determines the different test conditions. The actual mass correction factor for cotton fibers.

Key words: cotton; viscose; quantitative analysis; sulfuric acid method

Abstract: The article studied the quantitative analysis of cotton and viscose blend products, and compared the JIS and AATCC standard for using sulfuric acid method, and determined the quality correction coefficient of cotton fiber under different experimental conditions.

Keywords: cotton; viscose; quantitative analysis; sulfuric acid method

1 Introduction

Viscose fibers are similar in chemical properties to cotton, and each has its own physical and mechanical properties. The blending of the two can make up for the shortcomings of both parties and give full play to their respective advantages. The products not only improve the feel, luster and drape of the pure cotton products, but also retain the unique moisture absorption and breathability of the cotton fibers, which is favored by consumers. .

In the process of trade and use, fiber content is an indispensable important performance indicator, and it is also the focus of consumers when purchasing textiles. In order to improve the grade of fabrics, some garment manufacturers often intentionally increase the proportion of natural fibers in the ingredient identification, resulting in the labeling of the fiber components not in line with the actual situation. Therefore, it is of great significance to correctly test and label the textile fiber content to protect the interests of consumers, safeguard the legitimate rights and interests of producers, guarantee the quality and safety of textiles, and improve the means of legitimate competition.

All along, due to the great similarities between the chemical properties of viscose and cotton, the quantitative chemical analysis methods and test conditions of the blended products of both are highly concerned by the inspectors. At present, the domestic test is mainly based on GB/T 2910.6-2009 "Quantitative chemical analysis of textiles, Part 6 viscose fiber, some copper ammonia fiber, modal fiber or a mixture of lyocell fiber and cotton (formic acid zinc chloride method)" . However, in actual operation, the tester noticed that the formic acid/zinc chloride method often showed insufficient dissolution of the viscose, the residue was in the form of a paste, it was difficult to filter, and the test results were greatly deviated. In addition, formic acid/zinc chloride is prone to volatile toxic substances at high temperatures, and the solution preparation and the entire dissolution process also need to be strictly controlled. In contrast, the 60% (59.5%) sulfuric acid method selected in JIS L 1030-2 and AATCC 20A has a relatively good dissolution effect and a relatively simple operation method in actual detection. However, there are differences in the specific operations of the two standards, and there are large differences in the quality correction coefficients between the two. This paper studies these two standards and tries to determine a more accurate and practical test method.

2 test principle and method

2.1 Test principle

Dissolve the viscose from a known dry quality cotton/viscose mixture with 60% (59.5%) sulfuric acid, collect the residue, wash, dry and weigh, and calculate the dry quality of the mixture with the corrected mass. Percentage, and then the difference gives the mass percentage of the viscose.

2.2 Test methods

2.2.1 Sample

GB/T 3921 "Textile color fastness test soaping fastness" specified cotton standard lining cloth; GB/T 3921 "Textile color fastness test soap fastness" specified by the viscose standard lining cloth. The fabric must be cut into yarn and cut to a length of 1 cm, 0.5 to 1.5 g per sample. If necessary, the sample should be pretreated, such as degreaser treatment, desizing, and fading.

2.2.2 Instruments

Mainly include: analytical balance (accurate to 0.1 mg), oven (constant at 105 ~ 110 ° C), dryer (with color-changing silica gel), constant temperature shock water bath, vacuum pump, plugged triangular flask (capacity 250 mL), Glass sand core crucible, weighing bottle, 1000 mL measuring cylinder, 2000 mL beaker, density meter, mercury thermometer, etc.

2.2.3 Reagents

60% (59.5%) sulfuric acid: 1000 mL of concentrated sulfuric acid with a density of 1.84 g/mL was metered into the flask and slowly added to a beaker containing 1100 mL of distilled water. At 20 ° C, the sulfuric acid solution was adjusted by a densitometer. The density is between 1.4950 and 1.4982 g/mL.

Dilute ammonia: Take 20 mL of ammonia (density 0.880 g/mL) and dilute to 1 L with water.

2.2.4 Test methods and processes

Method 1, refer to the test procedure of AATCC 20A: put the weighed sample into an Erlenmeyer flask, add 59.5% sulfuric acid at a ratio of 1:100, cover the stopper, strongly oscillate for 1 min, and maintain at 15 to 25 °C. 15 min, then take out the shock, then keep it for 15 min, take out and shake again; filter the undissolved material on the pump with a known dry weight crucible, rinse with 59.5% sulfuric acid, rinse with water, then dilute with ammonia And clean and soak the residual fiber for 10 min, then rinse with cold water, drain with an air pump, put the crucible and residual material into the oven to constant weight, cool and weigh.

Method 2, refer to the test procedure of JIS L 1030-2: put the weighed sample into an Erlenmeyer flask, add the warmed 60% sulfuric acid at a ratio of 1:100, cover the stopper, and shake the flask. Shake for 10 min at room temperature, then let stand for 5 min, then continue to shake for 5 min. The undissolved material was filtered on a suction pump with a known dry weight crucible, rinsed with 60% sulfuric acid, washed with water, then washed with dilute ammonia and soaked in residual fiber for 10 min, then rinsed with cold water, with an air pump Drain, place the crucible and residual material in an oven to constant weight, cool and weigh.

3 test results

3.1 Calculation of results

The results of this test were calculated using the percentage of net dry content.

P ₁ = (1)

P ₂ = 100-P ₁ (2)

Where: P ₁ - the percentage of net dry content of insoluble fiber, %;

P ₂ — the percentage of net dry content of dissolved fiber, %;

m ₀ — dry weight of the sample before dissolution, g;

m ₁ — dry weight of the residue after dissolution, g;

d—Quality correction factor of insoluble fiber in reagent treatment.

Calculation of d value: The pure cotton sample is subjected to the same test method and process to obtain the reciprocal of the ratio of the dry fiber dry weight to the original weight, namely:

d = (3)

Where: m ₀ - dry weight of the sample before dissolution, g;

m ₁ - dry weight of the sample after dissolution, g.

3.2 data record

3.2.1 Determination of d value in two test methods

Ten samples of about 1 g were prepared from the cotton standard lining cloth, and dissolved in a sulfuric acid solution according to the two methods described in 2.2.4. The actual mass correction coefficient ( d value) of the cotton fiber was calculated. 1.

Table 1 Actual quality correction factor of cotton fiber

Sample	method one			Method Two
	Dry weight of sample before dissolution	Dry weight of sample after dissolution	d value	Dry weight of sample before dissolution	Dry weight of sample after dissolution	d value
1	0.8651	0.8503	1.0174	0.9352	0.9119	1.0256
2	0.7984	0.7817	1.0213	0.8753	0.8575	1.0208
3	0.9103	0.8865	1.0269	0.8964	0.8758	1.0235
4	0.9571	0.9444	1.0135	1.0348	0.9996	1.0352
5	1.0153	0.9884	1.0272	1.1098	1.0748	1.0326
6	0.9652	0.9405	1.0263	0.9752	0.9502	1.0263
7	0.8863	0.8680	1.0211	0.9341	0.9114	1.0249
8	0.8465	0.8306	1.0192	0.8769	0.8504	1.0312
9	0.9237	0.9072	1.0182	0.9015	0.8738	1.0317
10	0.9964	0.9779	1.0189	0.9931	0.9637	1.0305
average value	/	/	1.02	/	/	1.03

3.2.2 Comparison of two test methods for testing cotton/viscose content

The two standard lining cloths were separately disassembled into yarns, and manually mixed into different proportions of cotton/viscose mixed samples. The accuracy test was carried out by the above two methods ( d values ​​were 1.02 and 1.03, respectively), and the obtained data are shown in Table 2.

Table 2 Comparison of the accuracy of the two methods

3.3 Analysis and comparison of results

It can be seen from the data in Table 1 that the damage of a pair of cotton fibers is small. The second method of cotton fiber damage is more serious.

It can be seen from the data in Table 2 that the absolute error between the six tests of Method One is relatively large, especially when the viscose content is high, so the stability of Method 1 is relatively poor; and the test of Method 2 is 6 times. The difference between them is not obvious and is significantly better than method one.

It can be seen from Table 2 that the cotton fiber content obtained in the first method is higher than the actual value, indicating that the method does not sufficiently dissolve the viscose. In fact, the testers noted that since the method only oscillated for 1 min at the beginning, end and middle of the test, it was likely that the viscose was not sufficiently dissolved and the data obtained could not accurately reflect the actual content. In the second method, the cotton fiber content obtained by the test is relatively close to the actual value.

In addition, the testers found from experience that there are some differences in the d values ​​of different cotton fabrics. The value of d is specified in the JIS L 1030-2 standard: when the cotton is not refined, the d value is 1.03; when the cotton is refined, the d value is 1.01. Therefore, in the actual detection process to obtain a more accurate content value, it is necessary to explore and accumulate experience of cotton fiber d values ​​in different states in the early stage, so as to select the appropriate d value in the calculation.

4 Conclusion

1 ) Tests have shown that 60% (59.5%) of the sulfuric acid method is a more feasible method for quantitative analysis of cotton/viscose content. For fabrics with standard interlining, the quality correction factor of cotton fiber with reference to AATCC 20A method is 1.02. The quality correction coefficient of the cotton fiber according to the JIS L 1030-2 method was 1.03.

2 ) The test data shows that the data error measured by the method of JIS L 1030-2 is smaller than the error obtained by referring to the AATCC 20A method, and is very close to the true value. Therefore, the method is currently applied to detect cotton/viscose by chemical dissolution method. One of the ideal methods of content.

3 ) From the perspective of safety and operability, 60% (59.5%) sulfuric acid reagent preparation method is relatively simple, there is no toxic substance volatilization, and the test results can be provided in a short time, which has high application value. .

4 ) At present, when the national standard tests the fiber content, most of them refer to the ISO standard test method, but some of the methods have not been fully applied or proved to be the best method. On the contrary, there are some other countries' testing standards, such as AATCC standard, JIS standard, BS standard, etc., but some methods with high operability and high accuracy are proposed. It is necessary for the inspectors to continuously summarize and analyze in practice to seek the most. Good solution.

references:

[1] GB/T 2910.6-2009 Quantitative chemical analysis of textiles - Part 6: Viscose fibres, certain copper ammonia fibres, modal fibres or mixtures of lyocell fibres and cotton (formic acid zinc chloride method) [S].

[2] AATCC Test Method 20A-2010 Fiber Analysis : Quantitative [S].

[3] JIS L 1030-2 : 2006 Test method for blending ratio of fibre products - Part 2: Fibrillation ratio [S].

[4] Liang Guowei. Discussion on Quantitative Test Method of Cotton and New Regenerated Cellulose Fiber Blended Products[J].China Fiber Inspection,2007(1):34-35.

[5] Li Bo, Zhu Hongliang. Discussion on the detection method of fiber content in cotton/viscose blended fabrics[J].China Fiber Inspection, 2008(09):54-57.

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