Why does the coating with bactericidal preservatives still deteriorate(一）
Why does the coating with bactericidal preservatives still deteriorate? Most of the antiseptic preservatives used in coatings on the market are non-ionic. This kind of antiseptic fungicide is a large consumption. With the acceleration of bacterial reproduction, antiseptic fungicides will gradually be consumed, and the concentration will gradually decrease; At the same time, bacterial reproduction may change the PH value of the paint environment, and the bactericidal effect of the anti-corrosion fungicide added in the paint will also be weakened.
So, how do cationic antiseptic disinfectants kill bacteria? Before we start, let's say the pH value of the paint, generally 8.5~9, the pH value of most bacterial breeding environment is 3 ~ 4, and the nature of the surface charge of the bacterial cells in the water is controlled by the pH value, that is, when the pH value of the water is lower than the isoelectric point of the bacteria, the surface of the bacterial cells is positively charged, and vice versa.
Therefore, the general water and finished coatings are close to neutral or alkaline, so the surface of bacterial cells is negatively charged. The bactericidal principle of cationic antiseptic is mainly that the groups contained in it are positively charged in aqueous solution, which can be adsorbed on the surface of microorganisms to form microgroups, and gradually penetrate into the lipid layer and protein layer of microbial cytoplasm, thereby changing the permeability of the cell membrane and making the cell contents extravasate, resulting in microbial death;
At the same time, it can coagulate proteins, denature enzymes and structural proteins, destroy the metabolic system of microorganisms, and finally kill bacteria. After this round of sterilization, the cation is not consumed and can continue to play a role in killing.
Why does the coating with bactericidal preservatives still deteriorate? Precisely because antiseptic preservatives are not foolproof. Therefore, the choice of antiseptic should be careful.
First, do a compatibility test on the selected antiseptic and fungicide to see if it meets your paint system
Secondly, do a safety test on the selected antiseptic and fungicide, whether it is safe, for the surrounding equipment and personal safety.
Finally, the selected antiseptic fungicide should be rigorously tested to see if it can maintain antiseptic and bactericidal properties under bad circumstances.
In summary, the key to avoiding deterioration and odor of water-based coatings is to prevent bacterial contamination and anti-corrosion fungicide failure from production to packaging, storage and transportation. In addition to the selection of anti-corrosion fungicides, the production process of water, equipment cleaning and packaging cleanliness is also very important.
