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1. Antibacterial agent
According to different ingredients, antibacterial agents can be divided into three categories: natural antibacterial agents, organic antibacterial agents, and inorganic antibacterial agents. Among them, only inorganic antibacterial agents are suitable for adding to plastics to enhance antibacterial properties.
2. Inorganic Antibacterial
It mainly uses antibacterial ability of silver, copper, zinc, titanium and other metals to fix silver, copper, titanium and other metals (or their ions) on zeolite through physical adsorption, ion exchange and multi-layer coating. and other technical means, silica gel, phosphorus salt and other porous materials or layered crystalline materials, and then through a certain processing technology to make antibacterial agents, and then add them to corresponding products to obtain materials with antibacterial ability. In addition, some far infrared materials can also be used as inorganic antibacterial agents in processing.
Among inorganic antibacterial agents, silver series, copper series, zinc series and titanium series are mainly distinguished. A comparison of their characteristics is shown in table below.
Comparison of properties of four inorganic antibacterial agents
In addition, on this basis, there are silver-zinc composite systems, silver-zinc-copper composite systems, inorganic-organic composite systems, systems with negative ions, etc. .
3. Classification of inorganic antibacterial agents
When a small amount of silver ions reach microbial cells, since latter are negatively charged, they are strongly adsorbed under influence of Coulomb gravity, which disturbs electrolyte balance and kills microorganisms due to damage to cell wall. Another point of view is that silver ions penetrate cell wall and enter inside of cell and react with SH group, coagulating protein, disrupting activity of cell synthetase and causing cell to lose ability to divide and proliferate to achieve an antibacterial effect. In addition, due to catalytic action of silver ions, oxygen dissolved in air and water is converted into active oxygen, which can damage structure of cell surface to achieve an antibacterial effect.
When light containing ultraviolet rays irradiates antibacterial agent, antibacterial agent generates electrons and holes, generated electrons react with components in air to form hydrogen peroxide, and holes react with traces of moisture on surface of antibacterial agent. with formation of hydrogen and oxygen. Free radicals can decompose organic matter into CO and water, thus having an antibacterial and self-cleaning effect.
Titanium dioxide photocatalytic antibacterial agents require light to work, so they do not work when used in an internal tank.
4. Classification of contact-reactive antibacterial agents (on example of silver)
Depending on nature of media
All existing silver ion antibacterial carriers use inorganic materials such as ceramics
Titanium phosphate, zirconium phosphate, calcium phosphate, silicate, zeolite, clay mineral, silica gel, magnesium aluminosilicate, etc. cannot control pores and cannot provide slow release function.
Among them, ion-exchange type has strongest antibacterial ability. The finer particle size, higher dispersion and better antibacterial effect. Thus, use of nanopowder technology to prepare ultra-fine or nano-inorganic antibacterial agent powder will greatly improve antibacterial effect. Studies have shown that introduction of rare earth elements into inorganic antibacterial agents can activate antibacterial agents based on silver and photocatalysts, thereby enhancing antibacterial properties of materials more effectively.
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