Textile antibacterial performance testing methods and standards

The important performance index of antibacterial textiles is antibacterial property. When testing antibacterial properties, the medium concentration, temperature and humidity, pH value and test time are required to be consistent with the dressing conditions. The experimental instrument should be a commonly used instrument for microbiological experiments and can be used on textile materials of any shape. Test[1]. Among the testing methods for antibacterial properties, Japan and the United States were the first to develop them. The most representative and widely used are the American AATCC test method 100 and Japan’s industrial standards. The evaluation methods commonly used in China generally refer to the AATCC (American Association of Textile Chemists and Colorists, American Association of Textile Dyers and Chemists) standards [2] and the “SEK” approved by Japan’s JAFET (Japanese Fiber Products New Function Association) “Methods for mark certification standards [3]. In 1992, my country promulgated the textile industry standard FZ/T01021-1992 “Test Method for Antibacterial Performance of Fabrics” [4], and in 1996 promulgated the national standard GB15979-2002 “Hygienic Standard for Disposable Hygienic Products” [5]. However, the methods and standards for antibacterial performance evaluation are far from being systematic, unified, and standardized. In particular, there are still many unclear issues in the performance evaluation and product specifications of antibacterial textiles in our country, and we can only make it simple. qualitative testing.

In view of the fact that my country’s current comprehensive evaluation of antibacterial textiles cannot meet the needs of domestic production and foreign trade, this article compares the antibacterial testing methods and standards currently used in the world,

1. Selection of test strains
Microorganisms are a group of tiny organisms that exist in nature with small shapes and simple structures that cannot be directly seen by the naked eye and must be observed with the help of microscopes and other equipment. The vast majority of microorganisms are harmless to humans, animals and plants, and are even beneficial and necessary. However, there are also a small number of microorganisms that can cause diseases in humans, animals and plants [6]. Therefore, when people evaluate antibacterial properties, the selection of bacterial strains must be scientific and representative. The bacterial species listed in Table 1 are widely distributed in nature and on human skin and mucous membranes.

The tested strains [7] include bacteria and fungi. Among bacteria, Gram-positive bacteria (Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis) and Gram-negative bacteria (E. coli, Pseudomonas fluorescens) are mainly used; among fungi, molds (Aspergillus niger) are mainly used , Aspergillus flavus, Aspergillus versicolor, Penicillium citrinum, Trichoderma viride, Chaetomium globosum, Paecilomyces variotii, Blastomyces cereus) and dermatophytes (Trichophyton gypseum, Trichophyton rubrum, Trichophyton rubrum, Trichophyton violaceum, Rust Microsporum chromatin, Mycorrhizum togae, Candida albicans).

Staphylococcus aureus is a highly resistant pathogenic bacterium among asporal bacteria and can be used as a representative of Gram-positive bacteria. Bacillus megaterium is a common pathogenic bacterium among spore-like bacteria; Bacillus subtilis is easy to form spores and has strong resistance, so it can be used as a representative of spore bacteria. Escherichia coli is widely distributed and has been used in various experiments as a representative strain of common Gram-negative bacteria. Aspergillus flavus and Chaetomium globus have been included in my country’s national standards (GB2423.16-81) as prescribed strains for anti-mold tests. Some other selected molds are common molds that corrode textiles or polymer materials. Candida albicans is a common opportunistic pathogenic fungus in human skin and mucous membranes. It is sensitive to drugs and has the characteristics of a fungus. The colonies resemble bacteria but not bacteria and are different from molds. Because they have colonies that resemble bacteria, they are easy to count and observe. They are often used as Representative of fungi.

Therefore, in order to assess whether antibacterial textiles have broad-spectrum antibacterial effects, a more reasonable choice is to mix representative bacterial strains in a certain proportion for testing. For the antibacterial properties of most current antibacterial products, only Staphylococcus aureus, Escherichia coli and Candida albicans are often selected as representatives of Gram-positive bacteria, Gram-negative bacteria and fungi respectively. But in fact, it is far from enough to only use these two bacteria to represent the antibacterial properties of fabrics.

In addition, since most fungi cannot count the number of colonies, the antifungal performance of textiles is mainly evaluated by observing the growth of fungi on the sample under certain temperature and humidity conditions after a certain period of time after the sample is exposed to the fungus. assessment, and the assessment of the degree of fungal growth,The British standard BS6085-81 has just been adopted for grade assessment [8].

2. Classification of textile antibacterial performance testing methods
The test of antibacterial performance of textiles is divided into quantitative testing methods and qualitative testing methods, with the quantitative testing method being the most important.

2.1 Quantitative testing methods
The current quantitative testing methods and standards for textile antibacterial performance include the American AATCC Test Method 100 (bacteria count determination method) TZ/TO2021-9, Quinn test method, etc.

Quantitative testing methods include fabric disinfection, inoculation of test bacteria, bacterial culture, and counting of residual colonies. It is suitable for non-leaching antibacterial finishing fabrics, but not for dissolving antibacterial finishing fabrics. The advantages of this method are quantitative, accurate and objective, but the disadvantages are long time and high cost. Figure 1 is an example of bacterial count test results [9].

2.2 Qualitative testing methods
Qualitative testing methods mainly include American AATCC Test Method 9O (Halo Test, halo method, also called agar plate method), AATCC Test Method 124 (parallel streak method) and JISZ2911-1981 (antimicrobial test method), etc.

Qualitative testing methods include inoculating test bacteria on the fabric and observing the growth of microorganisms on the fabric with the naked eye. It is based on the activity of the antibacterial agent leaving the fiber and entering the petri dish. It is generally suitable for dissolution antibacterial finishing, but is not suitable for wash-resistant antibacterial finishing. The advantages are low cost and fast speed, but the disadvantage is that it cannot quantitatively measure antibacterial activity and the results are inaccurate. Figure 2 is an example of the halo method test results [9].

3. Selection of antibacterial performance evaluation methods
Research on evaluation methods for the antibacterial properties of textiles has been carried out abroad for many years, and some representative, relatively stable measurement methods that can be repeated in multiple laboratories have been established. See Table 1 and Table 2 for details.

Most of these methods have certain limitations, and the measurement results of various methods are not strictly comparable. The advantages and disadvantages of each are very obvious. The following is an introduction to several commonly used antibacterial testing methods:

3·l AATCC-90 test method
Also known as the halo test method, it is a rapid qualitative method of antibacterial efficacy for screening antibacterial agents. The principle is: inoculate the test bacteria on the agar medium, then place it close to the sample, incubate it at 37°C for 24 hours, and then observe the bacteria with a magnifying glass. The similar reproduction conditions and the halo size of the sterile zone around the sample are compared with the test conditions of the control sample. This method can process a large number of samples at one time, the operation is relatively simple and the time is short. However, there are also some problems. For example, although it is stipulated that the test bacterial liquid should be cultured within a certain period of time, the bacterial concentration table l Antibacterial efficacy determination method [10]

Table 2 Antifungal efficacy determination method[10]

But there are no clear regulations. In addition, the width of the blocking band represents the diffusion and antibacterial efficacy, which is meaningful for comparison with standard fabrics, but cannot be used as a quantitative assessment of antibacterial activity [11].

One of the improvements to the AATCC-90 test method (spray method) is to spray a certain amount of TNT reagent on the cultured sample and observe the growth of bacteria on the sample with the naked eye. The principle of color development is that the TNT reagent is reduced by the succinate dehydrogenase of the test bacteria to generate an insoluble red pigment and appear red, thereby achieving the purpose of determining the antibacterial property. The advantage of this method is that no matter whether there is an inhibition zone in the sample, as long as there is bacterial growth on the plate, it will appear red [12].

The second improvement of the AATCC-90 test method (colorimetric method) is to add a certain amount of TNT reagent to the bacterial eluate on the sample after culture to develop color. After 15 minutes, use a spectrophotometer to measure the absorbance at 525nm to calculate The number of viable bacteria. However, the above two methods are not suitable for test bacteria without succinate dehydrogenase.

3·2 AATCC-100 test method
AATCC-100 is a volumetric quantitative analysis method suitable for the evaluation of the antibacterial rate of antibacterial textiles.
This law was proposed by the AATCC Committee in 1961 and revised in 1965, 1981, 1988, and 1993. It is one of the most widely used antibacterial testing methods in foreign countries.

The principle of this method is: inoculate the test bacteria on the test sample and the control sample, add a certain amount of neutralizing solution respectively, shake vigorously to wash out the bacteria, and measure the bacterial concentration in the eluate using the dilution plate method, and compare it with the control sample Calculate the percentage reduction of bacteria on the fabric compared to The disadvantages of this method are that there cannot be too many specimens in one test and it takes a long time; for non-dissolving samples, the antibacterial performance cannot be evaluated; the ingredients of the neutralizing solution are not specified in detail; and the bacterial solution is too rich in nutrients. It is too different from the actual wearing conditions; the container is too large and difficult to operate [13].

On the basis of absorbing domestic and foreign experience, after a large number of experiments and improvements, a systematic quantitative testing method system has been formed, which can meet the needs of testing the antibacterial performance of different antibacterial textiles. That is, improved AATCC-l00, the key points are as follows:

Change the sample of the AATCC-100 method from a circle with a diameter of 4.8cm to a square with a side length of about 1.8cm, and put it into a 3OmL or 50mL Erlenmeyer flask with a lid. Use 0.85% ice-cold saline (0-4°C) instead of AATCC broth to dilute the inoculum. Dilute the bacterial strain from about 108-109cfu/mL to 1×105-2×105cfu/mL to prepare an inoculum liquid. Use 20mL, 0.85% ice-cold physiological saline instead of neutralizing agent to wash the sample [14].
Use the following formula to calculate the antibacterial activity and bactericidal activity of the sample:
The number of viable bacteria in the blank control sample after 18h – the number of viable bacteria in the sample after 18h
Antibacterial rate = ————————————— ×100%
The number of viable bacteria in the blank control sample after 18h

The number of viable bacteria in the blank control sample at ‘0’ – the number of viable bacteria in the sample after 18 hours
Sterilization rate = ————————————— ×100%
When ‘0’, the number of viable bacteria in the blank control sample

This method can perform antibacterial testing on both dissolving and non-dissolving samples, and the nutrients of the culture medium are suitable for the use conditions of the fabric [12].

3·3 Shaking bottle method
The Shake Flask method, also known as the Shake Flask method, is a method developed by Dow Corning in the United States to overcome the shortcomings of the AATCC-100 method to evaluate the antibacterial performance of non-dissolving fiber products. In order to enhance the contact between the sample and bacteria, this method puts the sample into a stoppered Erlenmeyer flask containing phosphate buffer solution, moves the bacterial solution into the flask and shakes it vigorously for 1 hour under certain conditions. Take 1mL of the test solution and place it on the culture medium. Bacteria reproduce for a certain period of time, check the number of colonies and compare it with the blank sample to calculate the bacterial reduction rate [15].

The advantage of this method is that it can be applied to most samples, such as powdered, hairy or feathered clothes, uneven fabrics, etc. Even non-dissolvable samples in aqueous solutions can be used to evaluate their antibacterial properties. [16]. The disadvantage is that the diluent lacks nutrients required for microbial proliferation and does not meet the wearing conditions; the culture time is short and the test bacteria can hardly proliferate, which is too different from the daily dressing time; in addition, the shaking temperature is 25°C, which is not an optimal culture temperature [15 ]��

The shaking bottle method is more accurate for testing hydrophilic fabrics. Although it can also test fabrics with poor water absorption, the accuracy is not very high. For fibers that do not absorb water at all, especially yarn-like objects or powdery or block-like objects, the reproducibility is not ideal. According to the advantages of the oscillating flask method, it is improved. The key points are as follows: the bacteria are grown from about 108- 1O9cfu/mL is diluted 10 times each time to 1.5×lO5~3.5×lO5cfu/mL. Use AATCC broth for the first dilution, and phosphate buffer from the second to the last dilution to prepare the inoculum solution. In addition, when making 10-fold serial dilutions, use 0.85% ice-cold physiological saline instead of beef broth [14].

3·4 AATCC-30
AATCC-30 is an evaluation of the anti-fungal and anti-corrosion properties of textile materials. The resistance of textile materials to mold and rot was determined to evaluate the effectiveness of fungicides on the antimicrobial properties of textile materials [18]. It is divided into soil burial method, agar plate method and humidity bottle method. The soil burial method refers to burying a sample (with a certain size) in mud for a certain period of time and then measuring the fracture strength of the sample. This method uses the fracture strength lost after the sample is buried in the soil to characterize its anti-fungal ability.

The agar plate method is used to evaluate the ability of fabrics to resist such bacteria. This method is to evenly drop a certain amount of aqueous solution dispersed with Aspergillus spores on an agar plate containing culture medium, then place a sample disc treated with a non-ionic wetting agent on it, and evenly drop a certain amount of it on the sample disc. The above aqueous solution is placed at a certain temperature for a period of time, and then the growth of mold on the sample is observed. It is characterized by the mold area on the sample disk.

The humidity bottle method is to suspend the pretreated sample strip in a jar with certain ventilation, containing a certain amount of aqueous solution dispersed with a certain number of bacterial robes, and place it at a certain temperature for a period of time. This method also uses the mold area on the sample strip to characterize [17].

3·5 AATCC-147
Also known as the parallel streak method, it is a semi-quantitative experimental method for the antibacterial efficacy of textiles. It can be used to qualitatively test the antibacterial properties of antibacterially finished textile materials relatively quickly and conveniently. It can be used to determine the antibacterial ability of textiles with diffusible antibacterial agents. Replaced the cumbersome AATCC-l0O. AATCC-147 is used to evaluate the antibacterial finishing of textile materials. It is a semi-quantitative analysis of the antibacterial performance of textile materials [18].

The AATCC-147 method is to drop a certain amount of culture fluid (containing a certain number of spores of Staphylococcus aureus and other bacteria) into a petri dish containing a nutrient agar plate, so that five parallel stripes are formed on the surface of the agar. , then place the sample vertically on these culture fluid stripes, squeeze it gently to make it in close contact with the agar surface, and place it at a certain temperature for a certain time. This method uses the width of the antibacterial zone around the stripes in contact with the sample to characterize the antibacterial ability of the fabric [17].

3·6 J1SZ911 Mildew Resistance Method
This method is based on the premise that the test bacteria can decompose cellulose as a nutrient source. In antibacterial and deodorant processed fiber products, when conducting antibacterial tests on synthetic fibers, further research is needed on the bacteria that can grow on the test cloth [19].

4 Conclusion

It can be seen from various data that the antibacterial textile performance evaluation methods used by different units are different, and the antibacterial performance expression methods are also diverse and cannot be considered uniformly. Moreover, each antibacterial performance testing method is not omnipotent and has certain limitations. Therefore, a set of testing method systems should be formed, and different testing methods should be used for different objects.

5 References
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[2] Yang Ping, New AATCC Textile Conventional Item Testing Methods�Zhan[J] Printing and Dyeing, 2004, (12):32-34
[3] He Zhongqin, Basic concepts of antibacterial, deodorizing and deodorizing processing of fiber products and future research and development directions [J] Printing and Dyeing Translation, 1999, (3): 86-93
[4]FZ/T01021-1992 Test method for antibacterial performance of fabrics[S]
[5]GB15979-1995 Hygienic Standard for Disposable Hygienic Products[S]
[6] Ji Junhui Shi Weiming, Antibacterial Materials [M] Beijing, Chemical Industry Press, 2003:1-2
[7] Wang Jianping, Antibacterial fiber and antibacterial agent system (2) [J] Synthetic Fibers, 2003, (3): 5-9
[8] Jiang Tian, Application of organic antibacterial and antifungal agents in the development of antibacterial fibers [J] Textile Science Research, 2003, (3): 7-18
[9] Shen Yiding, Zhu Ping, Xin Zhongyin, etc., Light chemical additives [M] Beijing, China Light Industry Press, 2004
[10] Geshi Wang Jun and Xu Hong, new research progress on antibacterial fibers [J] Textile Herald, 2006, (3): 50-59
[11] American Association Textile Chemical Color Technical Manual.AATCC Test Method 90 [S]55;300-301.
[12] Jiang Wenxia, comments on the antibacterial efficacy evaluation methods of antibacterial and deodorant fiber products [J] Journal of Textile Science, 1999, 20(2):127-129
[13] American Association Textile Chemical Color Technical Manual.AATCC Test Method 100[S]55;304-306.
[14] Wang Junqi, Wang Youbin, Zou Haiqing, etc., Research on testing methods of antibacterial fabrics (continued) [J] Textile Standards and Quality, 2003, (1); 26-28
[15] Meng Chunli, Antibacterial and anti-odor finishing technology of textiles [J] Journal of Henan Textile College, 2004, 16(3):61-64
[16] Fiber Products Hygienic Processing Council Editor: Shake Flask Method [S] Fiber Products Hygienic Processing Council, 1985; 1-5
[17] Li Xuelian, Research on antibacterial and antibacterial and deodorant fibers (continued) [J] Shanghai Silk, 2005, (4): 1-13
[l8] Wu Xiongying, Introduction to changes in AATCC test standards in 1999 [J] Printing and Dyeing, 2000, (5): 42-44
[19]JIS Z2911-1992 Resistance test method[S]