Abstract: This article mainly discusses the antimicrobial mechanism of commonly used inorganic, organic and natural antimicrobial additives, analyzes the characteristics and performance of different types of antimicrobial agents, and introduces the testing and evaluation of antimicrobial and antiviral textiles.The influence of antimicrobial and antiviral finishing agent Bacmatic DM-3015N on the performance of antimicrobial and antiviral applications on fabrics is discussed.The results showing that Bacmatic DM-3015N has excellent antibacterial and anti-viral effect. Fabric and textiles finished by Bacmatic DM-3015N, more than 99% of influenza A (H1N1) and H3N2 viruses were killed within 2 hours according to third-party testing results, after 50 washes, it still has more than 95% inhibition rate for gram-positive bacteria, gram-negative bacteria and fungi.

Keywords: antibacterial; antiviral; textiles; auxiliaries; applications 

0、Preface:

Since 2020, the COIVD-19 epidemic has continued to spread in many countries around the world. As of August, more than 20 million cases of COVID-19 had been diagnosed worldwide and more than 700,000 deaths had been attributed to COVID-19.

Globally, so far there is no proven treatment for the COVID-19, personal protective equipment (PPE) is an important way to combat the spread of the virus and avoid the pandemic.

Therefore, choosing textiles with antibacterial and anti-viral protection can prevent to some extent the harmful effects of viruses on the human body.

In February 2020, Dymatic Chemical launched the antibacterial and anti-viral finishing agent Bacmatic DM-3015N, which is rapidly recognized by the market,it was proven effective by 3rd party evaluation, and has been widely used in antibacterial and anti-viral textile protection finishing. The company has been working with many customers in this field.

Antibacterial and anti-viral finishing agent Bacmatic DM-3015N is a durable antimicrobial agent that can be used in the antimicrobial treatment of cotton, polyester, nylon fabrics and non-woven fabrics. Broad-spectrum antibacterial, anti-viral, effective control of microbial growth and odor generation, widely used in clothing, towels, bedding, wet-tissues, and non-wovens.

一、Types of antimicrobial agents：

Antimicrobial agents are substances that can effectively inhibit the growth and reproduction of bacteria, fungi, viruses and other microorganisms or can kill germs. According to the composition of the antimicrobial agent structure,action mechanism and source, generally antimicrobial agents can be divided into 3 categories, inorganic, organic, and natural.

1.1Inorganic antimicrobial agents
Inorganic antimicrobial agents with its broad-spectrum antimicrobial, safe and non-toxic, heat-resistant and other advantages have attracted widespread attention and are used in various fields. In recent years, with the high-speed development of nanotechnology, many inorganic metal ions and some metal oxides in the nanoscale, showing a more powerful antibacterial effect than the conventional, to inject new vitality into the research of inorganic antimicrobial agents.

Commonly used inorganic nanoparticles include nanosilver, nano-CuO, TiO2, ZnO. Compared to organic antimicrobial agents, inorganic antimicrobial agents generally have high thermal stability, in the processing can be mixed into the fiber when the monomer copolymerization or polymerization is complete, or can be added before the melt spray.

These addition methods can make the inorganic antimicrobial agent deep inside the fiber, the antimicrobial fiber wash-resistant performance, and melt process for high temperature easy decomposition, easy carbonization of the organic antimicrobial agent is obviously not applicable. According to the principle of inorganic antimicrobial agent can be divided into metal type and photocatalytic type.

Metal type inorganic antimicrobial agents are mostly inorganic heavy metals and their salts, can be used alone in the antibacterial finishing, or through physical adsorption, ion exchange or multiple wrapping technology to load in zeolite, silica gel, phosphate and kaolin and other carriers, to achieve the purpose of long-lasting and slow-release antibacterial. The activity of metal ion bactericidal inhibition decreases in the following order: Ag>Hg>Cu>Zn. Due to the toxicity of Hg, in practical applications Ag, Cu and Zn antimicrobial agents are mainly used.

Photocatalytic inorganic antimicrobial agents are a class of semiconductor inorganic oxides that can be activated by photons, TiO2 and ZnO are most popularly used. Under the action of light, these antimicrobial agents can oxidize water or oxygen into O-2 or OH and other active oxygen forms; this high-energy reactive oxygen can oxidize and destroy bacteria, fungi and viruses, and can oxidize their remains and secretions and other harmful substances into carbon dioxide and water. In addition to the broad-spectrum anti-bacterial bactericidal activity, it also has excellent deodorizing and anti-fouling effect.

1.2 Organic antimicrobial agents:
Organic antimicrobial agent because of its wide resource, low cost, simple processing technology, bactericidal performance, high efficiency, bactericidal speed and other advantages, has become the most commonly used class of antimicrobial finishing agent. However, organic antimicrobial agents are generally toxic, heat resistance and poor performance and easy to microbial drug resistance and other shortcomings. Commonly used organic antimicrobial finishing agents include quaternary ammonium salts, guanidine, halogenated phenols, halogenated amines and so on.

Quaternary ammonium salts are widely used in public health disinfection,individual protection, is considered a safe non-toxic antibacterial disinfectant. Quaternary ammonium salts are positively charged in water and bind to negatively charged bacterial cell membranes by electrostatic attraction, disrupting the normal permeation of cell membranes.

At the same time, the hydrophobic long-chain groups of quaternary ammonium salts will pierce the cell membrane and enter the cell interior,disrupting the normal metabolic process of the cell. The antibacterial activity of double-chain quaternary ammonium salt is generally higher than that of single-chain quaternary ammonium salt, when the alkyl chain is benzyl, the antibacterial activity is much higher than that of methyl quaternary ammonium salt, quaternary ammonium salt containing unsaturated alkyl chain has higher antibacterial activity than saturated alkyl chain quaternary ammonium salt.

That is, the quaternary ammonium salt antimicrobial agents with improved structure have more efficient antimicrobial performance and more broad-spectrum antimicrobial capabilities. The ability of quaternary ammonium salts to attach to fibers is mainly due to the ionic interaction of cationic quaternary ammonium compounds with anions on the fiber surface. To improve the durability of quaternary antimicrobial agents, siloxane groups can be introduced into them. The siloxane group forms a covalent bond with the hydroxyl group on the fibre, which results in long-lasting and strong adhesion to the textile surface.

Among guanidine antibacterial agents, polyhexamethylene guanidine hydrochloride (PHMB) is the most widely used, PHMB is a highly effective, broad-spectrum, low toxicity antibacterial agent, easily soluble in water, widely used in food, cosmetics and swimming pool disinfection and other fields, due to the existence of guanidine group, PHMB molecules are positively charged, easy to adsorb all kinds of bacteria, diffuse through the cell membrane and combine with the cell plasma membrane, and destroy the penetration of bacteria. equilibrium, causing their cells to rupture.

Among the halogenated phenol antimicrobial agents, triclosan is the most widely used in textiles. Triclosan is a highly effective broad-spectrum antimicrobial agent with a strong killing ability against a wide range of bacteria, fungi and some viruses (e.g. hepatitis B virus), with a minimum inhibition concentration of only 10 μg/mL. Unlike other cationic organic antimicrobial agents, triclosan does not ionize in water. Its effect on microorganisms is mainly through blocking the biosynthesis of lipids and interacting with the amino acid residues in the active site of enzymes on the membrane to achieve antibacterial and virulence effects.

Halogenamines refer to compounds containing nitrogen-halogen bonds in the molecule, which can be obtained by simple oxidation of hypohalogenated acid by compounds containing N-H bond such as amine,amide or imide groups, and are a new type of antimicrobial agent developed in recent years. It is a new type of antimicrobial agent developed in recent years. It has been widely used in water disinfection and is a safe, efficient and low-toxic antimicrobial agent. Because of the unstable N-Br bond, it is easy to be decomposed, and chloramines are commonly used in practice. The Cl atom, which is covalently bonded to the N atom, has positive electric properties and can slowly release positive chlorine ions in water. Whether it is the covalent chlorine in the halogenamine molecule or the free release of positive chloride ions have strong oxidizing properties, can kill most of the bacteria in a short period of time, also has a good killing effect on some viruses.

1.3 Natural antimicrobial agents:
In the course of millions of years of evolution in nature, a large number of plants and animals have evolved their own unique defense mechanisms against microorganisms, resulting in the production of biologically active substances with antimicrobial properties, which are called natural antimicrobial agents.

Compared with organic synthetic antimicrobial agents, natural antimicrobial agents are biocompatible, can be degraded naturally, and do not cause bacteria to develop drug resistance. With the increasing demand for antimicrobial textiles, the constant pursuit of quality of life and the concern about the environmental problems caused by synthetic antimicrobial agents, the research of natural antimicrobial agents has received widespread attention.

Chitosan is a representative class of natural antimicrobial agent of animal origin, which has good inhibitory effect on many kinds of bacteria and fungi, and is derived from the removal of acetyl group by chitosan. Chitosan is the second most abundant polysaccharide in nature after cellulose and is widely distributed in the shells of shrimps and crabs and in mollusks and other organisms. The solubility of natural chitosan is poor, but after the removal of acetyl group, the resulting chitosan is exposed as an amino group, the hydrophilicity is greatly increased and the solubility is improved, so chitosan is more widely used.

The amino group of chitosan is protonated in water to form a polycation, and its antibacterial and antimicrobial action is similar to that of quaternary ammonium salt antibacterial agents, and the positively charged amino group can interact with the negatively charged bacterial surface to destroy the integrity of its cell membrane.

The active ingredients of plant source antimicrobial agents are mostly natural terpenes, alkaloids, anthraquinones, flavonoids, tannins, coumarins, and their antimicrobial scope varies. Some plant antimicrobial agents can be used as natural dyestuff at the same time, giving antimicrobial properties and also improve the fabric antioxidant, anti-UV and other properties. At present, one of the main methods to treat fabrics with natural antimicrobial agents is microencapsulation technology.

These natural antimicrobial active ingredients can be encapsulated in microcapsules, which can be coated or impregnated to adhere to the fibers, and when the microcapsules are broken by friction during use, the antimicrobial substances are slowly released.

二、Testing and evaluation of antibacterial and antiviral agents

There are many types of flora on the surface of human skin, flora and skin together constitute a dynamic balance of the micro-ecosystem, once the balance is broken, it may lead to skin infections or other diseases.Therefore, in the evaluation of antimicrobial performance, the selection of strains must be scientific and representative. Table 1 lists the most widely distributed strains of bacteria in nature and on human skin and mucous membrane.

Major strains of bacteria in nature

Item	Classify	Strains of fungus
germs	Gram-positive bacteria	Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis
	Gram-negative bacteria	Escherichia coli, Pseudomonas fluorescens
fungi	/	Aspergillus niger, Aspergillus flavus, Aspergillus metamorphosis, Penicillium oryzae, Green wood mold, Chlamydomonas globulus, Candida albicans, Microsporidium ferruginosa, Sporotrichomonas sporangia

Staphylococcus aureus is the most resistant pathogenic bacterium among the germ-free bacteria and be regard as a representative of Gram-positive bacteria. Escherichia coli is very widely distributed and is a typical representative of gram-negative bacteria.

Candida albicans is a common pathogenic fungus of human skin mucosa, sensitive to drugs, with the characteristics of fungi, colonies resemble bacteria rather than bacteria, but is different from mold, with colonies resemble bacteria, easy to count and observe, often as a representative of the fungus. Aspergillus flavus, Aspergillus niger, Trichoderma globosum is often used as a representative of mold for mold performance testing. Most of the current standard select Staphylococcus aureus, Escherichia coli and Candida albicans as the typical testing for gram-positive bacteria, gram-negative bacteria and fungi.

Methods for evaluating the antimicrobial properties of textiles are mainly divided into two categories: qualitative and quantitative.

The qualitative methods mainly include halo method (agar plate method, agar flat dish diffusion method), parallel scribing method and so on. The quantitative methods mainly include quinine method, absorption method, shake flask method, transfer method, transfer printing method, and so on.

The methods used for the different standards, the nature of the methods, and the antimicrobial effects are mainly listed in below table.

The halo method is the most common qualitative test method, which is adopted by AA TCC90, JIS L 1902 and GB/T20944 .1, etc. The principle is to inoculate the test strain on agar medium and then adhere to the specimen, incubate it for a certain period of time, observe the reproduction of the bacteria and the size of the halo in the sterile area around the specimen, and compare it with the standard control specimen.

Standard number	Method name	Nature of methodology	Effectiveness evaluation
AATCC 90	hoopla	Qualitative	Width of inhibition ring
AATCC 100	absorption method	Quantitative	Rate of bacteriostatic and bactericidal
AATCC 147	parallel delineation	Qualitative	Width of antibacterial tape
JIS L1902	hoopla	Qualitative	Width of inhibition ring
	absorption method	Quantitative	Antibacterial value, Sterilization value
	transference (printing)	Quantitative	Bacteria reduction value (inhibition value)
ISO 20743	absorption method	Quantitative	antimicrobial value
	the law of transference	Quantitative	antimicrobial value
	transference (printing)	Quantitative	antimicrobial value
GB/T 20944.1	Agar Petri dish diffusion method (inhibition loop method)	Qualitative	Width of inhibition ring
GB/T 20944.2	absorption method	Quantitative	Inhibition value, inhibition rate
GB/T 20944.3	oscillation	Quantitative	bacteriostatic rate
FZ/ T 73023	hoopla	Qualitative	Width of inhibition ring
	Improved quinine law	Quantitative	bacteriostatic rate
	absorption method	Quantitative	bacteriostatic rate
	oscillation	Quantitative	bacteriostatic rate

AA TCC 147 is a relatively quick and convenient qualitative test of the antimicrobial effectiveness of textiles by parallel scribing. Appendix D.6 of FZ/ T73023-2006 is based on the Quinn method of the US and with certain modified. It is a relatively simple and fast test method for bacterial and some fungal tests. It is suitable for soluble or non-soluble antimicrobial textiles with good water absorption and light color.

The bacterial liquid absorption method is suitable for soluble antimicrobial fabrics, or non-soluble antimicrobial fabrics that are more absorbent and require less frequent washing. Typical examples of this method are AATCC100, JIS L1902, FZ/T73023 Appendix D7, GB/T20944.2 and ISO 20743 Method A.

Shake flask method is an evaluation method of antimicrobial performance of non-soluble antimicrobial products. It is to put the sample and control sample into the triangular flask with certain concentration of bacterial liquid, oscillate for a certain time at the specified temperature, determine the concentration of bacteria in the flask before and after oscillation for a certain time, calculate the inhibition rate, and evaluate the antimicrobial effect of the sample. The representative methods include: FZ/ T 73023 -2006 Appendix D8, GB/ T 20944 .3.

The transfer method is a kind of filtering the test bacteria and nutrient broth through the filter membrane together, then put the wetted test sample on the filter membrane with test bacteria, put a weight on the sample to exert a certain pressure, transfer the test bacteria to the sample, and elute immediately and after incubation respectively, so as to evaluate the antimicrobial performance of the fabric. The method is applicable to test the antimicrobial properties of antimicrobial processed textiles that are in the dry state during consumption.

There are two main ways to express the antimicrobial effect: percentage and logarithm.

AATCC100, FZ/T73023 and GB/T20944.3 use percentage for antimicrobial activity, JIS L 1902 and ISO20743 use logarithmic value for antimicrobial activity, and GB/T20944.2 uses percentage and logarithmic value for antimicrobial activity. FZ/ T 73023 – 2006 classifies antimicrobial knitwear into three antimicrobial grades: Grade A, Grade AA and Grade AAA according to the number of washes and the corresponding antimicrobial performance (inhibition rate).

2.2 Testing of antiviral effects:
On August 19, 2014, ISO officially released the “Textile Anti-Virus Testing Standard” (ISO 18184-2014) This standard specifies the test methods for the anti-viral properties of textiles (including woven and knitted fabrics, fibers, yarns, etc.).

In this standard, viruses include.

(i) An enveloped virus,the influenza virus, which can cause respiratory illness in humans.
(ii) A non-enveloped virus, catomavirus, which can cause gastrointestinal illness in humans. It is important to emphasize that the results of a test for one virus cannot be transferred to other viruses due to individual sensitivity.

The methods used to characterize the viral infection values are the viral spot method and the TCID50 method.

ISO18184 uses antiviral activity rate and antiviral activity value to characterize the effect of antiviral, specific operation methods are: antiviral processing samples and control samples without antiviral processing quantitatively absorb a certain amount of virus suspension, 0 contact time immediate elution, and in the specified temperature and humidity conditions after a period of time to elute, the eluate for virus plate counting, calculation of residual in the Number of viruses on samples.

Finally, the rate of antiviral activity of the antiviral fabric was calculated by comparing the number of viruses on the sample at zero contact time with the number of viruses remaining on the antiviral processed fabric after a period of contact time.

The antiviral activity rate or activity value of an antiviral fabric is calculated by comparing the number of viruses on the control fabric without antimicrobial processing after a contact time and the number of viruses remaining on the antiviral processed fabric after a contact time.ISO18184 classifies the antiviral effect, and the antiviral activity value Mv≥3.0 indicates excellent antiviral effect; 3.0>antiviral activity value Mv ≥2.0, indicating an effective antiviral.

Standard number	Method name	Effectiveness evaluation
ISO18184-2014	Determination of anti-viral activity of textiles	Antiviral activity value, antiviral activity rate

  The Japanese Committee for Industrial Standards also published a test standard for textile antiviral activity in 2017, JIS L1922-2016 Textiles. Determination of antiviral activity of textiles. The test is similar to ISO 18184-2014 in terms of methodology and testing for antiviral effect.

3.Antibacterial and antiviral applications on textiles

The research and development team of Dymatic Chemical has achieved a series of breakthroughs in 2019 both in cooperation with relevant scientific institutions, including the evaluation of the clinical application effects of antiviral agents, additives emulsification technology, textile application process, and finished product wash-durability.

In February 2020, Dymatic Chemical launched Bacmatic DM-3015N, an antibacterial and anti-viral finishing agent, which was quickly recognized by the market. In the field of textile hygiene finishing, including antibacterial and anti-odor, mite, mildew, mosquito prevention, etc., Dymatic Chemical has formed a series of targeted products to meet the individual needs of different customers.

Including antibacterial hygiene finishing agent Bacmatic DM-3012, anti-mite antibacterial finishing agent Bacmatic DM-3013D, anti-mildew agent Bacmatic DM-3030N, anti-mosquito finishing agent Bacmatic DM-3031N, silver ion antibacterial agent Bacmatic DM-3011N, natural antibacterial agent Bacmatic DM-3015T and so on.

3.1 Antibacterial and antiviral principle of Bacmatic DM-3015N:
Antibacterial and anti-viral finishing agent Bacmatic DM-3015N is a complex of quaternary ammonium salt and other antibacterial components, is a durable antimicrobial agent, can be used in cotton, polyester, nylon fabrics and non-wovens for antibacterial treatment.

Bacmatic DM-3015N has broad-spectrum antibacterial function, and its antibacterial mechanism is to bind with the negatively charged acidic phosphatidylglycerol (PG) on the surface of bacterial cell membrane through the super strong cationic active group, leading to the change of membrane permeability and thus dissociation. At the same time the polymer’s suitable molecular chain length and the high match of the bridging length of the polar negatively charged groups on the cell membrane surface can further enhance its anchoring and destruction effect, which ultimately leads to the dissolution and death of the bacterial contents.

Attacking the spine proteins NA (neuraminidase) and HA (hemagglutinin) on the coronavirus envelope denatures them, while destroying the negatively charged lipid envelope, exposing the RNA and accelerating its degradation, ultimately resulting in rapid virus inactivation.

3.2 Application:
Bacmatic DM-3015N is cationic, can not be used with anionic adhesives, OBAs in the same bath, for polyurethane, resin and other chemicals needs to be used in the same bath, should test the compatibility before production, Bacmatic DM-3015N can be used with cationic silicone softener, water repellent agent in the same bath, does not affect the hand feel, but high dosage of silicone softener may affect the durability, it slightly affect the water-repellent effect. The amount of water-repellent agent should be adjusted before use to meet the requirements.

Functions	Examples of categories	Dosage (owf.)
Anti-bacterial and anti-odor finish for fabrics	Towels, clothing	2 ~ 4%
Antibacterial finishing of home textiles	Table sets, tablecloths, bath towels, shower curtains	2 ~ 3%
Antibacterial and antiviral protection	Mask, gloves, protective clothing	4 ~ 8%
fungal protection	Underwear, socks	3 ~ 4%

The dosage of Bacmatic DM-3015N is 2-8% (owf.), and the temperature is adjusted according to the cloth species and process, generally 120-160°C for heat-setting. The recommended dosage of Bacmatic DM-3015N for different applications is listed above.

3.3 Application performance:

Antibacterial textiles should not be worn to destroy the micro-ecological environment of the human skin mucosa as a premise, if long-term use of textiles dissolved in a large number of antibacterial drugs, a variety of microorganisms on the skin have been killed, the micro-ecological balance of the skin will be destroyed, it will pose a threat to human health and safety. Therefore, people wear daily antibacterial textiles for a long time, should not be confused with medical antibacterial fabric products, one-sided emphasis on the sterilization (or antimicrobial) effect.

Third-party test results show that the DM-3015N finishing of cotton fabric, inhibition loop width of 2.5mm, in full compliance with safety requirements. (National standard GB/T31713 requirements of sterilization ring width <5 mm).

Fabric treated with Bacmatic DM-3015N has good safety, complies with GB/T31713 antibacterial textile safety and health requirement, the acute oral toxicity of SPF level KM mouse LD50 value is higher than 5000mg/kg.BW, is non-toxic, harmless to humans. The results of the acute skin irritation test on New Zealand rabbits were as No irritation.

Treat fabric with 30g/L of Bacmatic DM-3015N, and test the antibacterial effect, after 50 washes, the antimicrobial effect is in line with FZ/T 73023-2006 standard AAA requirements, and the actual test inhibition rate is more than 98%, much higher than the standard requirements.

strains of fungus	Tested inhibitionrate%	Standard Required inhibition rate%
Staphylococcus aureus ATCC6538	98	≥ 80
Candida albicans ATCC10231	99	≥ 60
Escherichia coli 8099	98	≥ 70

item	Anti-viral activity value	Antiviral activity rate/per cent
antiviral effect	3.03	99.91

Padding 60g/L Bacmatic DM-3015N, test in accordance with ISO 18184-2014 textile antiviral activity of the determination of standards to test the anti-virus effect of finished fabric, test results are shown in above table, anti-virus activity value of 3.03, indicating that the anti-virus effect of the fabric is very good.

四、Conclusion 
Bacmatic DM-3015N has excellent antibacterial anti-virus effect, broad-spectrum antibacterial anti-virus, high safety, no stimulation to skin, there are more than 99% of the influenza A H1N1, H3N2 virus killed within 2 hours, after 50 washing, gram-positive bacteria, gram-negative bacteria, fungi still have 95% of the above bacteriostatic rate.