The properties that antibacterial agents should possess
(1) It has efficient and broad-spectrum antibacterial properties, good antibacterial persistence, and can maintain long-term antibacterial properties of antibacterial plastics;
(2) Non toxic and odorless, no pollution to products and the environment;
(3) Good compatibility with plastics and no adverse effects on the performance of plastic products;
(4) Good color stability, does not change color during storage and use;
(5) Has good chemical stability, resistant to acid, alkali, and chemical drugs;
(6) Low price, without significantly increasing the cost of materials after use;
(7) Has high thermal stability, does not decompose or deteriorate during plastic extrusion and processing.
Overview of Inorganic Antibacterial Agents
Inorganic antibacterial agents are a new type of antibacterial agent widely used and have great market potential in antibacterial plastics. It is a type of antibacterial agent made by utilizing the bactericidal and bacteriostatic properties of metals such as silver, copper, zinc, titanium, and their ions. Among all metal ions, silver ions have strong antibacterial properties, so silver ions and their compounds are commonly used. However, the antibacterial properties of the plastic prepared by directly adding silver salt are significantly reduced, the color turns black, it is easy to precipitate when in contact with water, the antibacterial effect period is short, and the application value is low. The use of porous structures, materials that can firmly load metal ions, or materials that can form stable chelates with metal ions to carry metal ions, such as activated carbon, can improve these problems. At present, inorganic antibacterial agents are mostly made by using zeolite, wollastonite, chlorite, clay, ceramics, insoluble phosphate, soluble glass and other substances as carriers to load metal ions such as silver to produce antibacterial agents. They have broad-spectrum antibacterial properties, high heat resistance, long-term effect, and safety. They have obvious advantages in the application of antibacterial materials and are promising antibacterial agents for plastics.
#3? Overview of Organic Antibacterial Agents
Organic antibacterial agents are mainly composed of quaternary ammonium salts, biguanides, alcohols, chlorinated hydrochloric acids, (iso) thiazoles, organic halides, organometallic compounds, phenols, pyridines, imidazoles, halogenated alkyl groups, iodides, and other main components. Compared with inorganic antibacterial agents, organic antibacterial agents have been developed earlier in industrial applications, but their application in antibacterial materials such as plastics is greatly limited. However, organic antibacterial agents have their own application characteristics in certain plastics, such as faster effective antibacterial speed than inorganic antibacterial agents, better anti mold effect, better operability of adding them to plastics, and stronger color stability during storage and use. Therefore, organic antibacterial and antifungal agents play a certain role in the application of antibacterial plastics. The main varieties of organic antibacterial agents include organic silicone ammonium salts, phenolic ethers, phenols, biguanides, isothiazoles, pyrroles, organometallic compounds, imidazoles, pyridines, thiazoles, etc.
Overview of Natural Antibacterial Agents
The commonly used natural antibacterial agent at present is chitosan (chitin). Chitosan is derived from chitosan through deacetylation reaction. Chitin exists in the shells of insects and the cell walls of fungi. The annual synthesis of chitin in nature reaches billions of tons, making it the second largest natural polymer material in nature. The shell of insects is washed with acid to remove inorganic calcium, and then boiled with dilute alkali to remove protein and obtain chitin. Chitosan is obtained by deacetylation reaction of chitin in concentrated alkali. The poor thermal stability and large dosage of natural antibacterial agents are the main reasons limiting their widespread application in plastics.
Evaluation of antibacterial effect of antibacterial agents
The commonly used indicators for evaluating the antibacterial effect of antimicrobial agents are antibacterial rate and inhibition zone. The antibacterial rate can be calculated by the following formula: antibacterial rate=(number of bacteria on blank sample - number of bacteria on antibacterial sample)/number of bacteria on blank sample × 100%
The inhibition zone method is another way to measure the antibacterial effect of antibacterial agents, mainly used to determine the antibacterial effect of antibacterial agents, and is a qualitative or semi quantitative method. The method is to place the bacterial culture on a nutrient agar plate, and then
The prepared antibacterial plastic disc is placed on a plate of bacterial colonies and placed in a mold incubator. It is cultured at 36 ° C for 18-24 hours. During the cultivation, the growth of bacteria around the antibacterial plastic disc is inhibited, forming a transparent circle, known as the antibacterial circle. The size of the antibacterial circle can be obtained by measuring its diameter, which represents the strength of the tested plastic's antibacterial ability and reflects the effectiveness of the antibacterial effect.
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