Abstract
In this study, one waterborne polyurethane (WPU) pre-polymer was synthesized by using polypropylene glycol (PPG-2000), 2,2-dimethylolpropionic acid (DMPA) and isophorone di-isocyanate (IPDI) via a step-wise reaction. Then, a series of WPU/graphene oxide (GO) nanocomposites were prepared by ultra-sonication of GO dispersion and high shear emulsification. The GO and the WPU/GO nanocomposites were characterized by the Fourier transform infrared spectroscopy (FTIR), particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), water contact angles test, atomic force microscopy (AFM), Raman spectroscopy, tensile properties test, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the WPU/GO emulsions exhibited optimal dispersion stability, the particle size of WPU/GO increased compared with that of virgin WPU. While the GO amount in the WPU/GO nanocomposites was 0.25-0.50 wt% (based on the weight of WPU resin), the GO could be dispersed homogeneously, yet the water contact angle values for the WPU/GO films were higher than that of pure WPU, an increase from 58.83 degrees for pure WPU to 61.38 degrees for the GO content of 0.25%, and 62.32 degrees for the GO content of 0.50%, respectively, showing an improvement in the hydrophobic properties. Furthermore, with the GO content increased from 0.00 (WPU0) to 0.25% (WPU1), the tensile strength of the film got 60.69% improvement from 2.90 to 4.66 MPa, whereas the GO content increased from 0.25 (WPU1) to 0.50% (WPU2), the tensile strength of the films decreased from 4.66 to 4.31 MPa, with further increasing GO content, the elongation at break of the WPU/GO films decreased correspondingly. Finally, better synergy interactions between WPU and GO were observed, and the micro-phase separation was reduced.