Low-loading oxidized multi-walled carbon nanotube grafted waterborne polyurethane composites with ultrahigh mechanical properties improvement

The uniform dispersion of oxidized multi-wall carbon nanotubes (OCNT) in waterborne polyurethane (WPU) matrix was achieved by in-situ polymerization, endowing the OCNT/WPU composite film with enhanced tensile strength, thermal stability, and excellent elongation at break. The structure of multi-wall carbon nanotubes (CNT) and OCNT was characterized by TEM, XRD, XPS, and the structure and morphology of composites were characterized by particle size analysis, SEM and FT-IR. Compared with pure WPU and OCNT/WPU composite, the breaking strength and the thermal degradation temperatures of 20 % weight loss of the OCNT/WPU composite were increased by 175 % and 353 °C, respectively. The oxygen-containing functional groups effectively improved the surface active of OCNT, making it easier for OCNT to react with polyurethane prepolymers. After addition of only 1 % OCNT, the tensile strength approaches 77 MPa while the elongation at break remains at 277 %. In addition to having outstanding chemical and mechanical properties, OCNT have a better dispersibility rate than multiwalled carbon nanotubes, which means that they will have a broader application range.