Graphene oxide decoration with ZnAl LDH and further functionalization with APTES for enhancing the toughness of polyurethane coatings

The primary goal of this study is the enhancement of the mechanical properties of polyurethane (PU) coating via introducing a hybrid sandwich-like nanofiller composed of layered double hydroxide (LDH) grown on graphene oxide. To increase the nanofiller compatibility with the PU matrix, its surface was functionalized with an amino-functional silane coupling agent(APTES). Characterization of the particles with Raman, TGA, EDX-mounted FESEM, XRD approved the prosperous synthesis and modification of the nanosheets. The untreated (LDH@GO) and silane-treated (LDHGO@Si) nanoplatelets at three loading levels (1, 2, and 3 wt%) were incorporated and the stress-strain behavior of various nanocomposites films were evaluated. The stress-strain diagrams revealed that there is an optimum content (2wt.%) for both nanosheets that causes a rise in mechanical properties. While LDH@GO could improve the toughness of the PU by 95%, the treated counterpart (LDHGO@Si) resulted in a stronger impact, leading to a 184% rise concerning unfilled PU (from 1.27 to 3.6 GPa) in toughness thanks to its better dispersion, more extensive covalent and non-covalent interactions with PU chains. DMTA results also depicted that the treated nanosheets formed a reinforced network with increased Tg and crosslinking density that can efficiently delocalize the stress under tensile pressure, resulting in promoted energy dissipation and toughness.