| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 96 === In recent year, the research for antibacterial properties of silver nanoparticle application is becoming more wide spread. Nano-silver particles have higher specific surface area, chemical stability and non-toxic and non-toler. So it has significant potentiality to make antibiotic plastics of environmental protection and safety issue. In this study, nano-silver /polypropylene, nano-clay/polypropylene, and nano-silver-clay/polypropylene sheets are prepared innovatorily with the extrusion process to investigate its application on antibacterial measurment. Preparation of nano-silver /polypropylene film is performend in the biaxial oriented techniques. Therefore, the main purpose of this current study is discusse the preparation conditions and characterization of nanocomposites for antibacterial application issue.
Experimantally, this study involves with two different parts: Firstly, preparations of nano-silver/polypropylene film by oriented biaxial technique. In order to prepare a nanocomposite, polypropylene material was mixed up with nano-silver master-batches, nano-clay master-batches with melt-compounding process. After that extrusion, cooling and casting process were carried out for obtaining the nano-silver/polypropylene, nano-clay/polypropylene, and nano-silver-clay/polypropylene sheets, respectively.
Secondly, different physical and chemical identifications were conducted for investegating the nanocomposite properties. X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS) spectroscopy were performed to identify the fine structures of nano-silver master-batches. By using XANES spectra, framework of nano-silver with Ag(0) ucture was observed. The EXAFS data revealed that bonding distance of Ag-Ag is 2.87 Å and the coordination numbers is 10.59. By field emission-scanning electron microscopy (FE-SEM) analyses, spherical nano-silver particles with a diameter of 40 nm have good dispersibility in polypropylene nanocomposites. The X-ray diffraction (XRD) patterns showed nano-silver structures, and the d-spacing distance is in the range of 1.17~2.19 nm for nano-clay composites. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results showed that the melting temperature (Tm) and crystallization temperature (Tc) increase with the increasing thermal stability of nano-clay/polypropylene composites than polypropylene sheets. Therefore, the thermal stability was noticed to enhance with the addition of nano-silver or nano-clay in the polypropylene nanocomposites. Moreover, polarized optical microscopy (POM) was used to observe crystallization behaviors of polypropylene nanocomposites. By using film adhere method to study the antibacterial properties of nano-silver/ polypropylene composites were calculated. Percent reduction of two kinds of bacteria (Staphylococus aureus (ATCC 6538P) and Escherichia coli (BCRC 16081)) were observed. The results represented that the antibacterial activity is 99.9% and the inhibit activity is > 2.0. Furthermore, the results of nanomaterial and leaching procedure tests were fitted with the standard test method of food utensils, containers, and packages authorized by the Department of Health of government. No trace concentration of silver in nano-sliver composites was found and it may be not harmful to human’s health eventually.
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