Chemical functionalization of graphene oxide for improving mechanical and thermal properties of polyurethane composites

Graphene oxide (GO) was chemically functionalized to manufacture polyurethane (PU) composites with improved mechanical and thermal properties. In order to achieve a well exfoliated and stable GO suspension in organic solvent, 4, 4′- methylenebis(phenyl isocyanate) and polycaprolactone diol – two monomers used to synthesize polyurethane – were employed to functionalize GO sequentially. The obtained functionalized GO (FGO) could form homogeneous dispersions in DMF solvent and the PU matrix, as well as provide a good compatibility with the latter. The most efficient improvement in mechanical properties was achieved when 0.4 wt% FGO was added into the PU matrix, corresponding to increases in the tensile stress, elongation at break and toughness by 34.2%, 27.6% and 64.5%, respectively (compared with those of PU). Regarding the thermal stability, FGO/PU 1 wt% showed the largest enhancement, with T2% and T50% 16 °C and 21 °C higher than those for PU, respectively. A significant improvement in both mechanical properties and thermal stability of FGO/PU composites should be attributed to homogeneous dispersion of FGO in the PU matrix and strong interfacial interaction between them.