Preparation of carbon nanotubes/waterborne polyurethane composites with the emulsion particles assisted dispersion of carbon nanotubes

A simple and effective emulsion method for the dispersion of carbon nanotubes (CNTs) in waterborne polyurethane (WPU) is reported. WPU emulsions containing reactive CNTs are synthesized by in situ polymerization. During the emulsification process, a part of emulsion particles (EPs) grow and form at the reactive sites of CNTs. The CNT bundle can be separated by the growth and formation of EPs, forming individually suspended CNTs. With the aid of EPs, CNTs can be coated by EPs and easily dispersed in emulsions. After drying, CNTs are uniformly dispersed in the WPU matrix and a low percolation threshold is achieved at 0.132 vol.% CNT content. After addition of only 1, 2, and 3 wt.% CNTs, the tensile strength is greatly improved by about 128%, 179%, and 203% from 14.8 MPa of the pure WPU to 33.8, 41.3, and 44.8 MPa, respectively.