| Summary: | 碩士 === 國立高雄應用科技大學 === 化學工程系碩士班 === 93 === In this study, polymer-grafted-MWNTs were obtained via functionalizing the MWNT-bound carboxylic acid moieties to attach polyurethane (PU) to MWNT, where the carboxylic acids were first converted to acyl chloride via acylation with thionyl chloride (SOCl2). The physical properties of nanocomposites based on PU were improved via adding PU-grafted-MWNT into PU polymer.
The polymers PUD and PUT with side chains of COOH or OH were synthesized via the polyaddition reaction of 4,4’-methylenebis(phenyl isocyanate) (MDI), polytetramethylene ether glycol (PTMG) and chain extender 2,2’-bis(hydroxymethyl) propionic acid (DMPA) or 1,1,1-tris(hydroxyl methyl) propane (TMP). The results of Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H-NMR) showed the syntheses were successful.
During the functional modification process, the sp2 structures of carbon nanotubes were converted to sp3 structure gradually. The evidence, shown in Raman spectra, was that the Raman shift intensity ratio (I D-band / I G-band) of 1350 cm-1 (D-band) became larger as the acid treatment time was longer. The TEM images also showed that the carbon nanotubes were shorter after modification. The modified carbon nanotubes (PNT8 and PNT24) showed superior dispersion behavior and didn’t precipitate in water after 2 weeks.
PU-grafted-MWNTs were analyzed by FTIR, thermogravimetic analysis (TGA) and scanning electron microscope (SEM). The results of TGA show the amount of the PU grafted on MWNTs could be up to 27 %. All of the results showed the improvement of the dispersion properties of MWNTs via functional modification.
Three weight fractions (1 %, 5 %, 10 %) of PU-grafted-MWNT were added into PUD or PUT matrix via solution method. The physical properties of nanocomposites were investigated by dynamic mechanical analyzer (DMA), tensile strength test, TGA, and conductivity analysis. The results showed the nanocomposites exhibited better physical properties than those of original PU polymers.
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