Examples of antimicrobial plastics

(1) Food packaging

An antibacterial and freshness-preserving PVC, which is used as a food packaging material, is introduced. parts of diisononyladipic acid; 0.3 parts defoamer: 4 parts dihexyl adipic acid; 1 part stabilizer; 10 parts epoxidized soybean oil.

Mix above materials together and blow them into 0.008-0.02mm thick PVC sheets at 220-230°C. The result of antibacterial test of this leaf is shown in table.

Bacteria inactivation test results

(2) Antibacterial cutting board

Using synthetic rubber (NBR) and rigid polyvinyl chloride as main materials, after mixing and adding antibacterial agents, an antibacterial cutting board formed by pressing is obtained. Its formula is as follows: 24-36 parts of synthetic rubber (NBR), 1-4 parts of zinc oxide, 40-56 parts of rigid PVC, 1-4 parts of titanium, 3-8 parts of a strong hardener for synthetic materials. rubber, 0.2-0.6 parts of acid, 2-8 parts of low pressure polyethylene resin, 2-6 parts of ceramic powder, 6-10 parts of colloidal silica, 0.4-6 parts of inorganic antibacterial agent.

(3) Antibacterial household appliances (household route)

1) The process diagram is shown in figure

2) Example (antibacterial refrigerator door seal)

Add 4% antibacterial masterbatch and PVC granules to extrude refrigerator door seals. The production process is stable, appearance of product is qualified, antibacterial protection rate is 10%, and mechanical properties of product have hardly changed.

Mechanical test results of PVC refrigerator door seal

4. Verification of antibacterial effectiveness

(1) Detection of antibacterial properties of antibacterial agents

Antibacterial agents are mainly divided into two categories: antibacterial and antifungal (mold) fungi, both of which can be tested by microbial drug susceptibility testing in microbiology.

1) Dilution method. The antibacterial agent is diluted to various concentrations, bacterial strain is affected, and most inhibitory concentration of MIC of antibacterial agent on bacteria is quantified, and time of action of different antibacterial agents is different.

2) Diffusion method. Cultivated for a certain time on a nutrient medium with a quantitative concentration of bacterial solution and measure size of zone of inhibition. The incubation time of different antibacterial agents is different, determination of mold takes a long time, and size of zone of inhibition is different for different bacterial strains. For example: Escherichia coli (Escherichia coli) gram-negative bacteriostatic ring, which is commonly used to detect bacteria, is larger than 23mm and sensitive, and Staphylococcus aureus gram-negative bacteria bacteriostatic ring is larger than 24mm and sensitive. In addition, this method can be upgraded to TTC fast disc diffusion method and result can be obtained in just 1-3 hours.

5. Determination of antibacterial properties of antibacterial superconcentrate and products based on it

Antibacterial testing of antibacterial masterbatch and products based on it is relatively complex, and it is necessary to formulate different detection methods depending on different materials, different uses and different genera of bacteria.

1) Method for determining antibacterial activity

1) Cultural method. This method requires bacterial liquid to drip or spread over sample. After culturing for a certain period of time (usually 24 hours), live cup is counted to calculate antibacterial rate. This method requires strict control of nutrient temperature, humidity, pH value, time, etc. First of all, for antibacterial plastics (except foamed ones), coatings, etc., film growth method can be used. This method is developed with reference to GB 15979 and standards of Japan Household Electrical Manufacturers Association, and enterprise standard is Q/02GZS001. For antibacterial fabrics, foams, disposable hygiene products, etc., immersion culture method can be used, that is, a culture method in which bacterial solution is evenly immersed in sample and does not require a film. This method is formulated with reference to GB 15979 and incubation time is different for different materials. These two types of methods can be strictly defined byquantitatively, and antibacterial effect can be represented by accurate data, which is a method recognized at home and abroad.

2) Contact method or embedding method. In this method, sample is directly in contact with culture medium mixed with or immersed in bacterial liquid, and after culturing for various periods of time, growth of bacteria on and around sample and erosion of sample are observed. This method can be tested on samples of various materials and is also an internationally recognized method. International Standard IS0846, German Industrial Standard DIN 53793, ASTMG 22, etc. use this method to determine antibacterial activity of polymer materials, but this method has a long cycle time and is applicable to in-depth examination of materials, but as an evaluation method, product quality control cannot be quantified. Therefore, it is more suitable as a quality test method than a culture method.

3) Oscillation method. This method consists of soaking sample in a bacterial solution of a certain concentration, continuously shaking, culturing for a certain period of time, and counting number of active plates to calculate rate of antibacterial action. This method is suitable for detecting fabrics, foams, disposable hygiene products, etc. It allows you to speed up reaction and quickly identify results.

(2) Method for detecting anti-true (mold) fungus

1) Contact method. According to bacteria measurement method, sample is sticked on culture medium, a certain amount of mixed spore suspension is evenly sprayed on sample and culture surface, cultivated for a certain period of time, usually 4 weeks, regularly observed, and evaluated according to growth of bacteria to evaluate antibacterial effect. Mildew resistant materials, this method is widely used in world, ISO846, ASTMIC 21 and other standards use similar methods. It can comprehensively analyze formation of mold on material and inhibition of mold by antibacterial materials.

2) Method of influence. This method exposes sample to where mold will grow to determine rate of growth w of sample. This method provides an open environment for experimentation that is closer to natural environment. However, it is inconvenient to operate and easily pollutes environment. All national standards such as GB/T 2423.16 and GB/T4768 use this method.