Functionalization of multiwalled carbon nanotubes by amidation and Michael addition reactions and the effect of the functional chains on the properties of waterborne polyurethane composites

ABSTRACT A new class of hydrophilic multiwalled carbon nanotubes (MWCNTs) was prepared by amidation of carboxylated MWCNTs and then undergoing the Michael addition reactions with hydroxyethyl acrylate (HEA), acryloyl morpholine (ACMO), and acrylamide (AM), respectively. The functionalized MWCNTs were dispersible well in water showing zeta potential value of higher than −33.8 mV. After used as reinforcing filler to fabricate the waterborne polyurethane (WPU) composites, the functionalized MWCNTs showed more homogenous dispersion and stronger interfacial adhesion in/with WPU matrix in comparison with pristine MWCNTs, leading to an effective improvement in the mechanical properties, hydrophilicity and electrical conductivity of the MWCNTs/WPU composites. As fabrication of 1.5 wt % MWCNTs composite, the tensile stress was greatly enhanced by about 20.3, 22.5, and 30.1% from 13.3 MPa of the pristine MWCNTs composites to 16.0, 16.3, and 17.3 MPa for the MWCNTs‐HEA, ‐ACMO, and ‐AM composites, respectively. Varying hydrophilic moieties offered different mechanical properties and electrical conductivities to the MWCNTs/WPU composites, which is suggested to be caused by the improved compatibility and hydrogen bonds between the functionalized MWCNTs and WPU macromolecules. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 46757.