Fluorinated Multi-walled Carbon Nanotubes and Fabrication of Polyurethane Composite Films with Hydrophobic Surface

The reaction between the hydroxyl groups on the surface of acid-treated multi-walled carbon nanotubes (MWNT) and 2-bromo-2-methylpropanoyl bromide generates ATRP initiator sites on the MWNT, and then fluorinated acrylates were polymerized from MWNT via a "graft-from" method. Fourier transform infrared spectrometry (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results indicate that the polymer was covalently attached or grafted to the Surface of MWNT. Using MWNT coated with low surface energy polymer as the filler particles, a solution-casting method was employed to prepare MWNT/polyurethane composite films. The surface of composite films was exposed to tetrahydrofuran (THF) as the etchant to obtain the rough surface with microstructures. Static contact angle tests showed the hydrophobic properties of films were enhanced by adding the MWNT, and the contact angle was increased with the content of MWNT. The MWNT grafted with fluorinated polymers showed better hydrophobic performance than the pristine MWNT at the same content, and the film hydrophobicity was greatly improved after etching by solvent. Scanning electron microscopy (SEM) was used to study the microstructures of surfaces of composite films before and after etching. Effect of MWNT on the hydrophobic properties of the composite film surfaces was in-depth studied. Our experiments demonstrated that the hydrophobic properties of MWNT surfaces could be tuned via functionalization using different surface energy materials and the fabrication of polyurethane composite films with hydrophobic surfaces could be successfully achieved.