Encapsulation of multiwall carbon nanotube via self-polymerized polydopamine: The improvement on properties of elastomeric polyurethane nanocomposites with ultralow nanotube loadings

In this study, a facile and environmentally friendly surface modification method employing polydopamine (PDA) as a surface treatment agent for CNTs was used. It was found that the interfacial PDA layers did not only facilitate the dispersion of CNTs, but also strengthen the stress transfer from the polymer matrix to the CNTs, leading to greatly improved mechanical properties. The modification of CNTs was confirmed by FT-IR spectra and the surface morphologies of pristine CNTs and PDA-CNTs were observed by transmission electron microscopy (TEM), indicating that the surface of CNTs were uniformly coated by PDA. The influences of PDA-CNTs on mechanical properties of polyurethane (PU)/PDA-CNTs nanocomposites were examined by tensile test. We found that with only 0.1 wt% loading, the Young's modulus and tensile strength of PU/PDA-CNTs 0.1 were increased by 10% and 64%, respectively, while the elongation at break was up to 81% increment. The enhanced mechanism of PDA-CNTs was studied and discussed by comparing with the pristine CNTs reinforced PU nanocomposites. Furthermore, the thermal behaviour and thermal stability of PU/PDA-CNTs were also studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that a higher melting point of soft segments and enhanced thermal stability was obtained by incorporating PDA-CNTs into PU matrix.