| Summary: | 碩士 === 朝陽科技大學 === 應用化學系碩士班 === 98 === In this study, polylactic acid / pristine carbon nanotubes or modified carbon nanotubes nanocomposites were prepared by a melt blending method. In order to increase the compatibility between multi-walled carbon nanotubes (CNTs) and polylactic acid (PLA), the surfaces of CNTs were chemically modified. In this study, CNTs were first pre-treated using acid solution (HNO3) to functionalize the CNTs surface with carboxylic groups (-COOH), form the acid-treated carbon nanotubes (CNT-COOH). Subsequently, the stearyl alcohol was grafted onto carboxylic groups with the assistance of dehydrating agent, N,N’-dicyclohexyl-carbodiimide (DCC), then we can obtain the modified CNTs (CNT-C18). The CNT-C18 can be dispersed in organic solvents, such as DMF, THF, and chloroform. Furthermore, the modified carbon nanotubes and PLA were mixed by solution method, and a small amount of ester-exchange agent was added, so that modified carbon nanotubes can be grafted onto PLA chains to enhance mechanical and physical properties of the composites. Finally, the PLA/CNTs nanocomposites were then prepared through melt-blending method. The thermal behaviors, morphology, mechanical properties, conductivity of resultant PLA/CNTs nanocomposites were investigated.
The results show that excellent dispersion of nanotubes in the PLA matrices was achieved. Moreover, an improvement in thermal properties was also observed. Nanocomposite with the addition of 3wt% modified carbon nanotubes and ester-exchange agent modified carbon nanotubes composites, the increments of storage modulus (E'') at 40oC were 77.4% and 88.0%, respectively. And the increments of loss modulus (E'') at glass transition temperature (Tg) were 43.8% and 75.6%, respectively. In the aspect of conductivity, the surface resistivity of the PLA nanocomposites decreased from 5.30×1012 Ω/cm2 to 8.58×10-2 Ω/cm2 after addition of 3wt% ester-exchange agent modified carbon nanotubes. Such modified carbon nanotubes nanocomposites are highly efficient for anti-static purpose, even electrostatic discharge or anti-EMI purpose, which can be applied in electronic materials.
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