Antibacterial finishing mechanism
The action units and targets of different antibacterial agents are different. The mechanism can be summarized into two categories: one is to use the cationic groups in the antibacterial agent to adsorb to the negatively charged bacterial cell wall through electrostatic interaction. They can destroy the cell wall structure, inhibit protein synthesis, and inactivate cell synthesis enzymes. They can also change the The permeability of the cell wall allows intracellular dissolved substances to leak out to achieve antibacterial effects; the second is to use the small size effect and photochemical activity of nanomaterials to generate strong oxidizing groups under photocatalytic conditions that react with microorganisms to cause bacterial death.
Antibacterial finishing methods
Based on the antibacterial mechanism of commonly used antibacterial agents, antibacterial finishing of wool fibers can be divided into inorganic metal ion antibacterial finishing, organic antibacterial finishing, natural antibacterial finishing and nanomaterial antibacterial finishing.
Inorganic metal ion antibacterial finishing
In the process of antibacterial finishing, people have long used metal salt compounds to treat fabrics and give them special functions. Wool fiber has a special structure and contains a variety of amino acid structures. The amino acid residues have polar groups such as amino, carboxyl, and hydroxyl groups that can absorb various metal ions.
Research shows that the adsorption of metal ions by wool fiber is affected by factors such as ion type, concentration, solution pH, treatment time and temperature, among which pH has the greatest impact. Taking silver ions and copper ions as an example, under acidic conditions, Ag+ and Cu2+ are mainly combined with carboxyl groups. When the pH value is lower than the isoelectric point of wool (4.2~4.8), the fiber surface is positively charged, and the electrostatic repulsion adsorption with Ag+ and Cu2+ is relatively small. Weak; when the pH value is above the isoelectric point, the surface of the wool fiber is negatively charged, and the electrostatic attraction between the two increases the adsorption amount. Under alkaline ammonia-containing conditions, silver ions and copper ions are bound to the nitrogen-containing side groups of wool in the form of silver ammonia and copper ammonia complexes, and the adsorption capacity is increased compared with acidic environments. However, in a strong alkaline solution, the keratin structure of wool changes, and the amino acid structure such as cystine residues decomposes, which affects the stability of the wool fiber. The intuitive performance is that the fiber strength decreases and the hand feels rough.
Despite this, there are still deficiencies in the bonding fastness and antibacterial durability of metal ions to wool. Some scholars have solved this problem by loading metal ions into wool fibers through cross-linking. Commonly used cross-linking agents include tannic acid and seaweed. sodium acid, etc.
Organic antibacterial finishing
At present, various organic antibacterial agents represented by quaternary ammonium salts occupy a dominant position in the market. Medicinal antibacterial agents such as quaternary ammonium salts, biguanides and imidazoles are gradually used in the antibacterial finishing of wool products.
Quaternary ammonium salt compounds can be divided into single long chain quaternary ammonium salts, double long chain quaternary ammonium salts and compound quaternary ammonium salts according to their structures. The factors that determine the antibacterial properties of quaternary ammonium salts mainly include molecular weight and alkyl chain length. According to literature reports, the molecular weight of quaternary ammonium salts increases, the charge density increases, and the antibacterial activity increases; only when at least one of the four branches of N+ has a length between C8 and C18, quaternary ammonium salts have better antibacterial activity. . Ordinary quaternary ammonium salts have poor binding force with fiber. As dissolution-type antibacterial agents, they are easy to elute and accumulate in the human body, so they have certain limitations. Therefore, some scholars modify wool fibers to improve the fiber’s adsorption capacity and binding fastness to quaternary ammonium salts.
Biguanide salts were originally used as medical chemicals and were the main components of many disinfectants. They were later gradually used in food, cosmetics, textiles and other fields. ICI has developed the biguanide structure as an antibacterial agent for textiles. Its main component is polyhexamethylene biguanide hydrochloride (PHMB). Unlike traditional quaternary ammonium salts, polyhexamethylene biguanide hydrochloride (PHMB) is safe. Sex has been widely accepted by people, and many scholars have confirmed its biological non-toxicity. Polyhexamethylene biguanide hydrochloride has good chemical activity. The positive charge electrostatically adsorbs to the groups in the wool fiber, and forms a film on the surface of the wool and deposits internally. With the assistance of the cross-linking agent, PHMB-cross-linking agent can be formed. The joint agent-wool system has better antibacterial and durable properties and can also improve some physical properties of wool fiber.
Natural antibacterial finishing
Refined natural antibacterial agents extracted from animals and plants have good environmental compatibility and antibacterial activity, mainly including chitosan, ε-polylysine and lysozyme. Among them, chitosan has become a natural antibacterial agent that is currently attracting attention due to its safety, non-toxicity and simple source.
Under acidic conditions, the amino acids absorb acid and transform into positive amino ions, and chitosan becomes a positively charged polymer polysaccharide. This is not only the main reason for the antibacterial effect, but also provides the possibility for electrostatic adsorption with wool fibers. However, similar to most other cationic antibacterial agents, such a combination cannot achieve a long-lasting antibacterial effect. Many scholars have modified or compounded chitosan to improve the antibacterial effect of chitosan antibacterial agents, including quaternization, guanidination, carboxyalkylation modification or compounding with nano-titanium dioxide, nano-silver, etc.
ε-Polylysine is an antibacterial agent prepared through chemical synthesis or microbial fermentation by simulating biological structures. ε-polylysine forms a positively charged cationic polymer in solution. With the catalytic cross-linking effect of transglutaminase (MTG), ε-polylysine can be grafted to wool fibers. The amide group in MTG reacts with ε-polylysine and lysine residues and primary amino groups in wool fiber, thereby forming a stable covalent cross-link between the two.
Lysozyme comes from a wide range of sources, including animalIt can be isolated and extracted from � and plants. It is in a free state in aqueous solution and is difficult to combine with wool fibers. The stability and controllability of lysozyme can be improved with the help of the immobilized enzyme process, and the free enzyme is “fixed”, which is necessary for lysozyme to be used for antibacterial finishing of wool. link. Huang Dong, Shao Xiaojuan and others used MTG-catalyzed cross-linking of lysozyme to directly fix lysozyme on wool fibers and impart antibacterial properties to the fabric.
Nanomaterial antibacterial finishing
Nanomaterials are used in many fields due to their unique surface effects, size effects and photochemical activity. Researchers have integrated nanomaterials such as nanosilver, nanotitanium dioxide, and nanosilica into wool fibers to achieve antibacterial and anti-UV effects. Among them, the antibacterial mechanism of nanometal oxides is different from traditional cationic antibacterial agents. Under photocatalytic conditions, nanometal oxides undergo electronic transitions and generate positively charged holes. The electrons and holes interact with oxygen in the environment to generate strong oxidizing radicals. The slugs react with microorganisms, causing their death. The antibacterial mechanism of nanosilver is the joint action of metal ion dissolution mechanism and photocatalytic mechanism.
Conclusion
Currently, the types of antibacterial agents on the market are still limited, and some antibacterial agents are not widely accepted due to issues such as biological toxicity. The development of domestic antibacterial agents started late and is still in its infancy. Many reports on new antibacterial agents are only in the laboratory stage and are difficult to adapt to large-scale production. The antibacterial finishing of wool should always focus on the requirements of broad-spectrum sterilization, low biological toxicity, durability and maintaining the original style, and develop in the direction of environmental protection, comfort and efficiency. While scholars are paying attention to the antibacterial properties of antibacterial agents, they should also focus on solving the problem of the combination of antibacterial agents and fibers. In the future, new antibacterial agents will surely add color to people’s lives with the advantages of simple finishing process, long-lasting antibacterial performance, good biocompatibility and improved fabric wearing properties. Further reading: https://www.china-fire-retardant.com/post/9373.html
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