Titanium diboride-derived nanosheets enhance the mechanical properties of polyurethane: experiments and simulation

AlB₂-type metal diborides have garnered significant attention in recent years owing to their ability to yield quasi-2D nanostructures. Titanium diboride (TiB₂), a key member of the metal diboride family, is well known for its extraordinary mechanical properties. However, the candidacy of TiB₂-based nanosheets to reinforce a polymer matrix has largely remained unexplored. In this work, we compare three kinds of TiB₂ reinforcements - the bulk form, pristine nanosheets, and functionalized nanosheets, with respect to their prospects in the mechanical reinforcement of polyurethane (PU). We find that while all fillers lead to an improvement in the mechanical properties of PU, the composite comprising pristine nanosheets exhibits the most significant enhancement. A 2 wt% loading of pristine nanosheets results in ∼80% increase in the ultimate tensile strength and toughness. Detailed molecular dynamics simulations reveal that the TiB₂ nanosheets are not only able to distribute the load effectively, but they also promote isotropic mechanical behaviour, which makes the composite stiff and strong. These insights are supplemented by inferences from the hydrogen bonding index (HBI) and degree of phase separation (DPS). This study exemplifies the rich prospects offered by the metal diboride-derived nanosheets for reinforcing polymer matrices.