Global Silicone Network, June 24: Due to the excellent properties of silicone rubber, such as high temperature resistance, low temperature resistance, weather resistance, food grade, physiological inertness, high air permeability, electrical insulation, flame retardancy, etc., silicone rubber products are increasingly widely used in baby products, food, medical treatment, daily necessities, industry, electronic appliances and other fields. It can be said that everyone comes into contact with silicone rubber products every day.
However, due to the special structure of silicone rubber, bacteria and mold are more likely to adhere to the surface, which may cause diseases to humans. As a new functional material, antibacterial and anti-mold silicone rubber can effectively inhibit bacteria, mold and other harmful microorganisms in the surrounding environment from adhering to the surface, and has been rapidly developed and applied in recent years.
1. Bacteria can be divided into Gram-positive bacteria and Gram-negative bacteria. Gram-positive bacteria include Staphylococcus, Streptococcus, Pneumococcus, Bacillus anthracis, Diphtheria, Tetanus, etc. They can produce exotoxins to cause disease; Gram-negative bacteria include Shigella dysenteriae, Salmonella typhi, Escherichia coli, Proteus, Pseudomonas aeruginosa, Bordetella pertussis, Vibrio cholerae and Neisseria meningitidis, etc. They can produce endotoxins to cause disease.
The testing standards for antibacterial silicone rubber mainly include the Chinese national standard "GB/T 31402-2015 Test method for antibacterial properties of plastic surfaces", the Japanese standard "JIS Z 2801-2010 Antibacterial processed products - Antibacterial test method - Antibacterial effect", and the international standard "ISO 22196-2011 Measurement of antibacterial activity of plastics and other non-porous surfaces", etc. The three standards are basically equivalent: select a Gram-positive bacterium (Staphylococcus aureus) and a Gram-negative bacterium (Escherichia coli) for testing. Use the control sample (non-antibacterial sample) and the antibacterial sample to inoculate the same bacteria and liquid volume. After 24 hours, observe the colony value of the two; calculate the antibacterial activity value and antibacterial rate. Generally speaking, it is considered that the antibacterial activity value ≥ 2, that is, the antibacterial rate ≥ 99%, is considered to have a strong antibacterial effect.
2. In a warm and humid environment or when it is in frequent contact with water, silicone rubber is prone to mold. The testing standards for anti-mold (fungal) silicone rubber mainly include the international standard "ASTM G21-15 Determination of the mildew resistance of synthetic polymer materials" or the Chinese national standard "GB∕T 24128-2018 Evaluation of the mildew resistance of plastic mildew inhibitors". The main tested species are: Aspergillus brasiliensis; Penicillium funiculum; Chaetomium globosum; Trichoderma viride; and Adenophora shortissima. After 28 days of bacterial culture, observe the mold growth on the surface of the sample. The highest and best level is level 0 for no mold growth (no mold spots at all), level 1 for trace growth (less than 10% mold spots); level 2 for slight growth (10-30% mold spots), level 3 for moderate growth (30-60% mold spots), and level 4 for severe growth (60%-full coverage of mold spots).
