Preparation of Antibacterial Color-Coated Steel Sheets

Hindawi Publishing Corporation International Journal of Photoenergy Volume 2012, Article ID 436963, 7 pages doi:10.1155/2012/436963 Research Article Preparation of Antibacterial Color-Coated Steel Sheets Guoliang Li, Bing Peng, Liyuan Chai, Si Wan, and Lei Jiang School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China Correspondence should be addressed to Bing Peng, Received 15 September 2011; Revised 23 January 2012; Accepted 23 January 2012 Academic Editor: Gongxuan Lu Copyright © 2012 Guoliang Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A simple method to fabricate antibacterial color-coated steel sheet was presented. The Ag-loaded TiO2 was well dispersed in steel coil coating coupled with some special additives, such as plasticizer, wetting dispersant, and flow agent, and finally became the part of coil coating without any negative influence on the properties of final products. The best process parameters were obtained by substantive trial experiments. Ag-loaded TiO2 with the addition of 2% (w/w) in steel coil coating not only improved antibacterial efficiency of the antibacterial color-coated sheet by reaching 99.99%, but also greatly increased the degradation percentage of methyl orange to 88% without decreasing physical properties. The antibacterial color-coated sheets are expected to be used as antimicrobial products in the construction industry considering its low cost and high effectiveness in inhibiting the growth of bacteria. 1. Introduction The menace of infection caused awareness around the world by the suddenly globally spreading epidemic disease, such as avian influenza [1], SARS, H1N1, and other unexpected multiplication of germs or other bacteria that pose serious health problems [2, 3]. Great deals of antibacterial products appeared in the cases of antibacterial ceramics [4–7], antibacterial glasses [8–10], antibacterial textiles [11–13], antibacterial plastics [14–16], antibacterial stainless steels [17–20], and so forth. These applications mainly involve the methods of adding antibacterial agents into the overall substrate, modifying the surface of substrate, or directly coating the antibacterial agents. However, the development of antibacterial products in a wide range of areas was still hindered due to the low effective utilization rate of the antibacterial agents, the high cost, and the poor binding force, which existed between antibacterial agents and the substrates restrict. In this paper, the antibacterial agent was firstly poured into the coil coating before being made into the antibacterial color-coated sheet. Sequent research findings demonstrated that antibacterial agents presented a comfortable dispersive distribution on the surface of colorcoated sheet, which could remarkably reduce the cost by attributing to the less addition of antibacterial agents and the simple manufacturing technological process. It was also found that the binding force among the antibacterial agents and substrate got much stronger than ever due to the integration of antibacterial agents into the coil coating. Served as one category of antibacterial agent, titanium dioxide is the most preferred material to be served as pigment. Unfortunately, the antimicrobial activity of pure TiO2 is merely valid when it is irradiated under UV light. In addition, the low electron transfer rate to oxygen and high recombination rate of electron-hole employed in UV light impose further limits to the effective photocatalytic sterilization rate of TiO2 [21–23]. These drawbacks strongly restricted the practical applications of TiO2 as an effective and promising antimicrobial material. Silver (including Ag ions and Ag nanoparticles) is a well-known and effective inorganic antimicrobial material that has been applied in many fields. However, the high-cost and dark color are two notable obstacles during its applications as large-scale antimicrobial coatings [24–26]. Nevertheless, Ag can act as both an antimicrobial auxiliary agent and a sink for electrons and redox catalyst that may enhance the overall photooxidation ability of TiO2 [27–30]. Thus, it is reasonable and rational to combine Ag with TiO2 during antimicrobial coatings production. This study focused on the manufacture of antibacterial color-coated sheet using Ag-loaded TO2 as antibacterial agent. The antibacterial agent was firstly poured into steel 2 International Journal of Photoenergy Ag-loaded TiO2 Coil coating, diluent Additives Paint grinder Baking and curing Paint filter Roller coating Antibacterial color-coated sheet Figure 1: Preparation flowsheet of antibacterial color-coated sheet. coil coating with some additives and made into the antibacterial coil coating. And then, the antibacterial color-coated sheet was manufactured in a normal process. It delivered a technology of less addition of antibacterial agents and simple procedure. 2. Experimental 2.1. Materials. Ag-loaded TiO2 was purchased from Jingui Group (Chenzhou, China). The grain size was 48 nm and the Ag particle size was 10 nm. Coil coatings (including polyester topcoat and epoxy priming paint) and diluents (the main components were ethyl acetate, butyl acetate, benzene, toluene, acetone, ethanol, butanol, etc.) were provided by Center Group (Changshu, China). The additives including plasticizer, wetting dispersant, and flow agents were purchased from Yongyan Ltd. (Shanghai, China). Petri dishes. A 5 cm × 5 cm sample was cut from the antibacterial color-coated sheets for bacterial culture and the surface of all samples was cleaned with absolute ethanol soaked tissue paper before antibacterial test. The samples were placed in separate Petri dishes on top of the predeposited LB. A clean soda-lime glass piece was used as a control sample. After placing the antibacterial color-coated sheets samples, a thin layer of LB was further deposited on top. These plates were kept for 1 h for complete gelation of the agar, and after that quantitative solution of E. coli was evenly spread over each gel plate in the respective Petri dishes. The plates were incubated for 24 hours to allow the completion of bacterial growth. The bacterial colonies formed in each plate were observed and the bacterial number on each sample was counted with colony counting method. The antibacterial efficiency of the color-coated sheet was calculated in Antibacterial efficiency = 2.3. Antibacterial Properties Testing. Antibacterial properties of products were tested according to “Antibacterial Coating—Antibacterial Performance Test Method, the appendix A of “the People’s Republic of China Chemical Standard HG/T 3950-2007”. In the tests, nutrient agar media (Luria Broth, LB) was prepared in water by mixing tryptone, NaCl, agarose gel powder and yeast extract in the volume pe (...truncated)