| Summary: | 碩士 === 國立成功大學 === 資源工程學系碩博士班 === 95 === Introducing nano-sized inorganic metal oxide into polymers can greatly increase the hardness and abrasion resistance and improve the mechanical properties of the nanocomposites. However, it is difficult to disperse the nanoparticles homogeneously in the polymer. In this study, the nano-sized silica was modified with MEMO to increase the stability of SiO2/HDDA colloid. According to the results of FTIR and NMR spectrum, the silane adsorption behavior was dependent on the MEMO concentration. As the ratio of MEMO/SiO2 was＜0.6, hydrolysed MEMO monomers would adsorb onto silica surface and form T1 structure. The colloid stability is low due to incomplete coverage of the silane mono layer on the silica surface. If the ratio MEMO/SiO2＞0.6, MEMO monomers would condense first and then adsorb onto the surface of silica to form the T2 or T3 structure, meaning the adsorption layer would be thicker and the colloid could be more stable.
The pencil hardness of the coating only reach 4H even though the silica content increase up to 12.5wt% for the sample with nano-sized SiO2 modified with the ratio MEMO/SiO2=0.2. However, as the ratio of MEMO/SiO2 was≧0.6, a thicker silane adsorption layer can obtain, which results in increase of the pencil hardness of the coatings from 4H to 6H. In addition, all the samples with MEMO/SiO2≧0.6 show highly transparent, and little difference in universal hardness, Young’s modulus, and abrasion resistance.
The AFM and FE-SEM images show that silica particles with thin coverage layer (MEMO/SiO2=0.6) would mainly distribute on the surface of coatings but the silica particles with thick coverage layer (MEMO/SiO2=1.5) would distribute homogeneously in the coating. The unabsorbed MEMO oligomers could fill in the space between the silica nanoparticles to decrease the porosity of the coatings and make the interface between the particle and polymer indistinction.
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