Functionalization Of Carbon Nanotubes And Its Application In Polymers

The main purpose of this thesis is to find out an effective way to solve the dispersion of carbon nanootubes (CNTs) in the polymer matrices with polar groups by means of functionalizing CNTs according to the chain structure and polar groups of the matrix we used in the investigation.CNTs were modified by means of acidification and grafting maleic anhydride in our research. The characterization of functionalized CNTs by Fourier transform infrared spectrum (FTIR), transmission electron microscope (TEM) and scanning electron microscope (SEM) showed that acidification provided CNTs a shorter length and active reaction with maleic anhydride which caused by the introduction of hydroxyl and carboxyl groups to CNTs; and maleic anhydride was successfully grafted to CNTs (the final productions were designated by f-MWCNTs, f-SWCNTs in this thesis). The comparison of the dissolve abilities between modified and pristine CNTs suggested that, once the maleic anhydride was introduced onto the surfaces of MWCNTs, the dissolve ability of MWCNTs in xylene solution was improved greatly compared to pristine CNTs, moreover the dispersion of f-MWCNTs in polyethylene terephthalate was uniform since the interfacial interaction between f-MWCNTs and PET was reinforced and the miscibility of the two components of the nanocomposite was improved greatly due to the hydrogen bond effect between PET chains and f-MWCNTs.f-MWCNTs were melting compounded with poly(ethyleneterephthalate) (PET) by using a twin-screw extruder to prepare PET/MWCNTs nanocomposites. The SEM results showed that the dispersion of f-MWCNTs was fine and the interfacial interaction between f-MWCNTs and PET was strong. The effects of f-MWCNTs on the crystallization behavior of PET nanocomposites were also studied via DSC and POM. The results showed that the nucleation effect of f-MWCNTs in PET crystallization was strong. The nonisothermal crystallization kinetics of PET with f-MWCNTs was analyzed by Jeziorny and Mo methods and the results also proved that the f-MWCNTs clearly accelerated the crystallization process of PET.In order to further study the effect of f-SWCNTs on the microstructure of polymer and explain how interaction between matrix and nanofillers works on the microstructure of composite , PP/OMM,PP/OMMT/f-SWCNTs composites were prepared and investigated. The effects of f-SWCNTs on the microstructure of PP/OMMT nano-composites were investigated by WAXD, SEM, PLM and DSC. Compared with the PP-MA/OMMT binary nanocomposite, in which OMMT was mainly exfoliated, the intercalated OMMT was mainly observed in PP-MA/OMMT/f-SWCNTs ternary nanocomposite due to the stronger interfacial interaction between PP-MA and f-SWCNT prevents more PP-g-MA enter into the interlayer of OMMT gallery during the melt process or during the cooling process the stronger interfacial interaction between PP-MA and f-SWCNTs induces the PP-MA chain segments intercalated into the interlayer of OMMT move out from the gallery, and in this condition only few PP-g-MA chain segments maintain in the interlayer, thus OMMT is mainly intercalated. The results of DSC and PLM show that the f-SWCNTs have great effect on the microstructure of PP-MA/OMMT/f-SWCNTs nanocomposite.PP/PET/f-MWCNTs in-situ microfibrillar composites were also prepared and the dispersion state of f-MWCNTs in composites was investigated by DSC and SEM. The results suggested that f-MWCNTs were mainly located in PET micro-fibrils, leading the viscosity of PET changed, which weakened the microfibrillar ability of PET. Therefore, some PET particles exsisted rather than microfiber in PP/PET/f-MWCNTs composites. Moreover the aspect ration of PET disperse phase would decrease with the increase of f-MWCNTs content.