Study On Surface Functionalization Of Carbon Nanotubes And Polystyrene / Carbon Tube Composites

Multi-wall carbon nanotubes (MWCNTs) have attracted great attention in polymer reinforcement due to their extraordinary mechanical properties, electrical properties, excellent thermal stability and high hydrogen storage, therefore multi-wall carbon nanotubes have a great application potential in forming nanotube composites. Achieving a good dispersion of MWCNTs in polymer matrix is the key to fabricate composites with enhanced properties and in this passage a new mild modified Hummers method with three-stages oxidation approach was utilized. Carbon nanotubes with ultra-high content of functional groups were obtained after the modification and these tubes have a better dispersion in polar organic solvent. Compared with the effect of ultrasonication on the oxidation of MWCNT in stage Ⅱ and from the analysis of the samples from different stages, the mechanism of the oxidation was initially proposed. It was found that the oxygen content in stage Ⅱ with ultrasonication reached to 18.7at% from pristine MWCNT 2.7at% and the maximum of the oxygen content is at 24.9at% in stage III after its corresponding modification of hydrogen peroxide from the results of X-ray photoelectron spectrum (XPS). Field emission scanning electron microscopy (FESEM) and High-resolution transmission electron microscopy (HRTEM) confirmed the structure integrity of MWCNT after the oxidation process. The presence of oxygen-containing functional groups that grafted on the side walls of MWCNT were confirmed from the analysis of Fourier Transform Infrared Spectroscopy (FTIR), thermal gravity analysis (TGA) and Raman spectrum. A better dispersion of the modified MWCNT in ethanol or water was expected from a photograph, a particle size analysis and field emission scanning electron microscopy. The contact angel after the oaidation changed from 140° to 40°, which further confirmed the presence of oxygen-containing functional groups.Finally, the polystyrene composite film with different MWCNT was formed via a solution casting method and deionized water was used as coagulation bath. The effect of surfactant and different functional groups on the properties were studied. And it was confirmed that the porous structures are formed with the adding of surfactant, especially the functionalized MWCNT while the mechanical and thermal properties were affected by the presence of surfactant. The elongation at break of the composite at 5wt% hydroxy1-functionalized MWCNTs increased about 146% compared with pure polystyrene and the surface hydrophilicity increased with the adding of functionalized MWCNTs which laid the foundation for preparing the porous materials utilizing for filtration.