Preparation and performance of new long-acting nano-silver antibacterial powder coatings.

Wen/Cui Jixing 1, Zhang Haiping 1, Zhang Hui 1, 2, Yu 1, Zhu Jingxu 1,2
1. Tianjin University School of Chemical Engineering, Tianjin Chemical and Chemical Collaborative Innovation Center
2. Department of Chemistry and Bioengineering, University of Western Ontario, CanadaAbstract:
In order to improve the durability of antibacterial powder coating,
studied a long-lasting antibacterial powder coating with nano-silver as the main antibacterial component, and examined the antibacterial, antibacterial durability, yellow resistance and paint film appearance of the coating. The results showed that the antibacterial powder coating had excellent antibacterial properties and durability, had an initial sterilization rate of more than 99.99% for Terrain-positive bacteria and E. coli, and was able to withstand 360 repeated wipes under 20kPa force. With the increase of antibacterial agent addition, the antibacterial performance of coating film is improved, but the degree of yellowing is

. In addition, the study also found that the addition of antibacterial agents on the paint film gloss and fog effect is small, the gloss slightly reduced, fog slightly increased.0 IntroductionPowder Coatings are widely used in the coating industry and have good prospects for development because of their similar performance characteristics and excellent environmental benefits (without VOCs) to liquid coatings. As the inhibition of bacterial growth on the surface of coatings is attracting more and more attention from end users, the demand for antibacterial coatings is increasing., as an effective antibacterial substance, has been used by humans for nearly a thousand years. Due to the instability of organic antibacterial substances, inorganic antimicrobial agents represented by silver are developing rapidly. Commercial brands of silver antimicrobials such as Zeomic, Novaron and AgION have emerged in the industry since the 1980s. In the field of scientific research, the carrier of silver has been widely studied in recent years, including silicate, clay, zirconium phosphate, silicon and so on. Among them, molecular sieve has become a hot research topic in recent years because of its large ion exchange performance.ordinary silver exchange molecular sieve is difficult to apply in powder coatings because silver ions are easily destroyed at high temperatures. This not only causes the loss of silver ions but also yellows the coating surface. In addition, the antibacterial durability of the coating film is very poor, after repeated washing several times the antibacterial effect is greatly reduced. This is due to the uncontrollable release rate of silver in the silver ion sieve system, which causes a large loss of silver and weakens the antibacterial properties of the coating film.In order to solve the above problems, this study improved the traditional silver ion exchange molecular sieve, first adding copper ions as a protective agent to prevent the destruction of silver ions, and secondly adding nano-silver to the molecular sieve loaded with silver-copper ions. Nano-silver releases silver ions in the water environment, which serve as a storage warehouse for silver ions. In addition, the antibacterial agent is wrapped in hydromassive substances, hydromassive substances can not only promote nano-silver into silver ions, but also wrap the surface, to prevent the release of silver ions too fast. Graphene is an ultra-thin nano-sheet layer, which makes the coating surface produce nano-scale spikes, microorganisms are difficult to grow on the surface, so graphene as an antibacterial aid has also been studied.1 Experiments and MethodsThis study involves several steps of antimicrobial preparation, antimicrobial and powder coating mixing, electrostectrulation spraying, and curing into film.
preparation of antimicrobial agents, silver ions and some copper ions are added to molecular sieves by ion exchange. Nano-silver is added to the deionized water solution of polyethylene pyridoxine (PVP), and the ultrasonic vibration is made into nano-silver suspension, which has a particle size of about 50nm. The nano-silver suspension is then mixed with a molecular sieve after ion exchange, stirring 1h at room temperature. Prepare a hydromassin solution, and mix sodium methyl cellulose, sodium seaweedate and polyacrylamide (PAM) at a ratio of 6:3:1 to 80 degrees C to make a solution. The nano-silver molecular sieve mixture is then added to the hydromassive substance solution, stirred into a thick slurry, dried and ground in the oven, to obtain the final antibacterial agent. Mix the antibacterial agent with the powder coating in a certain proportion. Static spraying (40kV, 40μA) to 6cm×7cm aluminum plate, film thickness control in 45 to 55 m. The powder coating spray plate melts and cures 10min at 180 degrees C to obtain a flat coating film. Each test was conducted in 3 parallel experiments, with the control group coating powder coating without antibacterial agents. The composition of antimicrobial agents can be found in Table 1.analysis using a scanning electron microscope (Thermo Fisher Phenom XL). The color analysis of the surface uses the color analyzer (WF32) of Shanghai Jia standard. Membrane thickness measurement using membrane thickness meter (Germany QNix1500), antibacterial performance test using ASTM E2180-07 test standards, test strains using E. coli ATCC25922. Each test of antibacterial resistance is measured with a terracometer (hash DR3900) at 600nm to ensure consistent initial bacterial concentration. Durability measurement carried out a continuous washing process, each wash is as follows: use 20mL water wet surface, then add 0.5g detergent, use a wiper sponge with 10 to 20kPa pressure repeatedly wipe the surface 60 times, and finally with 50mL water to clean the surface.2 Results and discussion
2.1 the physical appearance of antimicrobial agents due to the addition of nano-silver and hydro-water-related materials for wrapping, molecular sieve appearance has changed a lot, Figure 1 can clearly see that the surface of the molecular sieve covered with a large amount of nano-silver, and the phenomenon of hydro-water-related materials wrapped occurred.the initial antibacterial properties of 2.2 antimicrobial agents antibacterial plate antibacterial effects can be found in Figure 2.figure 2 shows a significant change in the number of bacteria in the control group, with an increase of about 2 orders of magnitude. The number of antibacterial plate bacteria has dropped significantly, especially at 6h, the sterilization rate reached more than 99.99%. Although six antimicrobial agents showed approximate antibacterial properties, it can be seen that the addition of graphene is conducive to improving the pre-antibacterial effect (in the case of 1h, the number of bacteria added to graphene antimicrobial agents is less than the test group without graphene). After passivation treatment, nano-silver is more easily dispersed in the solution, but from the antibacterial effect of coating film, there is no obvious difference in passivation.the durability of 2.3 antimicrobial agents
the changes in antibacterial board antibacterial properties after continuous washing can be seen in Figure 3.test results from durability show that six antimicrobials change significantly when washed to the 6th time, and a large number of bacteria begin to appear at 6h.for 6 different antimicrobial agents, the addition of nano-silver increases the durability of the coating film. Comparing antibacterial agents 1 and 2, 3 and 4, 5 and 6, you can see that nano-silver after passivation treatment works slightly better, but not obviously, compared to antimicrobial agents 1, 3 and 2, 4, graphene can be found to add, slightly improving durability Comparing antimicrobial agents 3, 5 and 4, 6, the number of bacteria in antimicrobial agents 3 and 6 was reduced in the case of 6h wash cycles, which proved that the initial antibacterial resistance was not much different, but the durability decreased with the decrease of nano-silver addition. 2.4 Effect of antimicrobial addition on paint film performance As can be seen from Figure 4, the number of bacteria in 4h is reduced to zero at 5% and 8%, while the number of bacteria added at 2% is reduced to zero until 6.5h bacteria are added. In addition, with a small amount of addition, the number of bacteria even increases at the initial moment, which is also a manifestation of weakening antibacterial properties. Therefore, it can be seen that in a certain range, the increase in the amount of antibacterial agents can enhance the antibacterial effect, but when the amount of addition continues to increase from 5% to 8%, the antibacterial increase is not much. addition of copper ions will weaken the yellowing of silver ions, the degree of yellowing will increase with the increase of additives. As shown in Figure 5, the color change value of the coating film increases rapidly with the increase of antibacterial agent addition, which approximates the linear relationship.
2.5 antimicrobials on coating gloss and fog (Haze) . Figure 6 shows that the coating film gloss was reduced after the addition of antibacterial agents (5%). Both nano-silver and graphene reduce the gloss of the coating film, i.e. the antibacterial agents containing nano-silver and graphene have the lowest film gloss. With the increase of nano-silver addition, the coating film gloss decreases. addition of nano-silver and graphene to Haze has caused some changes, and the antibacterial coating fog value of graphene is slightly greater than that of non-graphene coating film. However, on the whole, the difference between 6 antibacterial plate coating film and non-antibacterial coating film is small. 3 Conclusion
Through this study, the following conclusions can be drawn:
(1) the nano-silver antibacterial agent wrapped in hydromassive substances has excellent antibacterial effect, 6h inner surface no bacteria;
(2) nano-silver antibacterial agent has excellent antibacterial durability, washing to the 6th antibacterial effect only weakened (each wash includes repeated 60 wipes);
(3) nano-silver addition decreased film durability decreased;
(4) with the increase of antibacterial agent addition, coating performance increased, but the degree of yellow change also increased;
(5) added antibacterial agents on the coating film gloss and fog degree has little effect, gloss slightly reduced, fog slightly increased.
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