Preparation And Characterization Of Polyester And Polyamide Functionalized Multi-walled Carbon Nanotubes

Carbon nanotubes(CNTs)are one of the most outstanding discoveries in the field of chemistry and materials.The unique properties of CNTs make them promising for wide range of applications,including high-strength composites,conductiors and semi-conductiors,energy storage and electro-mechanical actuators,and so on. Hooever,these applications are hindered by the poor compatibility of CNT with the matrix in composites.Earlier CNTs composites were prepared by physically mixing multi-walled carbon nanotubes(MWNTs)and polymers.CNTs are easily drawn out from matrix due to the weak interface bonding between polymers and CNT surface to improve the interaction force between CNTs and matrix.Methods of solution casting, electro-spinning and surfactant-assisted processing are developed for the fabrications of CNTs-polymer composites.However,the measured mechanical properties are still lower than theoretically predicted.It is expected that polymer chains are grafted onto MWNTs used as additives in bonding to polymer matris,the mechanical and electrical properties of the hybrid material would be siginificantly enhanced.An in situ process was used to prepare poly(1,3-propylene glycol-hexanedioic acid)-functionalized carboxylate carbon nanotubes(PHCNTs)and poly (1,3-propylene glycol-hexanedioic acid)-functionalized hydroxyl carbon nanotubes (PHHCNTs)using carboxylate multi-walled carbon nanotubes(MWNT-COOH)and hydroxyl multi-walled carbon nanotubes(MWNT-OH),1,3-propylene glycol and hexanedioic acid as reactants respectively.The functionalized MWNTs were characterized using Fourier Transform Infrared Spectroscopy(FTIR),Transmission Electronic Microscopy(TEM),Thermogravimetric Analysis(TG)and Differential Scanning Calorimetry(DSC).The effects of concentrations of CNTs and catalyst on the non-isothermal crystallization of PHCNTs and PHHCNTs were studied.The results showed that the structures of all the synthesized compounds agree with the pre-designed structure.The polyester linked to the surface of MWNT-COOH and MWNT-OH respectively.The average thickness of polyester on the surface of MWNT-COOH and MWNT-OH was 3 and 2 nm respectively.The chain length of polyester decreased with the increase of the content of MWNT-COOH and MWNT-OH.Avrami equation is effective in describing the non-isothermal crystallization of PHCNTs and PHHCNTs.The catalyst and cooling rate have little effect on the crystallization mechanism of PHCNTs and PHHCNTs. Hoffman degradation reaction was used to prepare amido multi-walled carbon nanotube(MWNT-NH₂).Acyl chloride multi-walled carbon nanotube(MWNT-COCl) and amide multi-walled carbon nanotube(MWNT-CONH₂)formed as intermediates in the process of preparation of MWNT-NH₂.The MWNT-NH₂,MWNT-COCl and MWNT-CONH₂ were characterized using FTIR,TG,x-ray diffraction(XRD)and Raman spectroscopy.Then an in situ process was used to prepare PA66-functionalized carboxylate multi-walled carbon nanotubes(NFMWNT)and PA66-functionalized amido multi-walled carbon nanotubes(NACNTs)using adipic acidhexamethylene diamine salt,MWNT-COOH and MWNT-NH₂ as reactants respectively.The NFMWNT and NACNTs were characterized using FTIR,TEM,XPS,TG,DSC,XRD and Dynamic Themomechanical Analyzer(DMA).The results indicated that the PA66 chains reacted with MWNT-COOH and MWNT-NH₂.The average thickness of PA66 on MWNT-COOH and MWNT-NH₂ are 2 nm and 2.5 nm respectively.The dissolubility of NFMWNT and NACNTs in formic acid was improved.The chain length of PA66 on the surface of CNTs is decreased with the increase amount of MWNT-COOH and MWNT-NH₂.The onset decomposition temperature(T_i)and temperature at maximum weight loss rate(T_p)elevates as the content of MWNT-COOH in some ranges.The storage modulus of NFMWNT and NACNTs increases with the content of MWNT-COOH and MWNT-NH₂.The a₁ crystal grain sizes of NFMWNT increased but that of NACNTs decreased with the increase of the amount of MWNT-COOH and MWNT-NH₂ respectively.