Chemical Functionalization and Dispersion of Carbon Nanofibers in Waterborne Polyurethane Adhesives

Waterborne polyurethane adhesives (WBPU) reinforced with carbon nanofibers (CNFs), to make them also conductive to static electricity, were prepared and their properties were evaluated as a function of content (0.1–1 wt%). The incorporation of carbon nanofibers to waterborne polyurethane adhesives implies a great difficulty because of their tendency to form aggregates, which prevents an efficient dispersion. In this sense, it is necessary to insert functional groups on the surface of the nanofibers to improve their interaction with any polymer. In this research, the surfaces of carbon nanofibers were previously oxygenated by chemical functionalization to enhance their stability in waterborne polyurethane adhesives. The obtained results showed that the chemical treatment used to functionalize the carbon nanofillers was adequate, as well as the experimental procedure carried out for their incorporation into the polyurethane, since stable dispersions were obtained. Moreover, the addition of the nanofibers to the waterborne polyurethanes contributed to improving their rheological and viscoelastic properties, imparting an increase in the viscosity and changes in the crystallisation kinetics.