Graphene nanoplatelets and chemical crosslinker enhanced water-based polyurethane elastomer nanocomposites

In this work, graphene nanoplatelets (GNP) and water-based crosslinker (WCL) were systematically employed to reinforce water-based polyurethane (WPU) matrix, offering strong enhancement in mechanical and thermal properties. It should be noted that unfunctionalised GNP as used in this study is known to be incompatible with water-based systems. Therefore, dispersing GNP in water-based elastomers (WBE) such as WPU was one of the problems addressed in this work by employing a novel water-bath technology. In addition, WCL was synergistically employed with GNP for the first time as a reinforcement in WPU. The research presents robust enhancement in mechanical properties realised through thorough static and dynamic mechanical analysis. With GNP/WPU and GNP/WPU/WCL nanocomposites achieving ∼13 – 25% and ∼2.5–fold enhancement in modulus respectively across loadings of 0.05 – 1 wt% at low-strain, which is extremely crucial for high-performing elastomers. Interestingly, the effective toughening in mechanical properties achieved via GNP-alone was realised without loss in elongation, contrary to the result obtained for WCL-infused nanocomposites. As the unfunctionalised GNP showed only a slight crosslinking effect, in contrast to the huge crosslinking observed for the WCL-infused nanocomposites. Hence, the GNP-alone reinforced nanocomposites appear to offer effective recycling potential over those of WCL-infused nanocomposites, which is highly desirable for sustainable industrial applications. Understandably, through detailed analysis undertaken in this investigation employing state-of-the-art techniques such as Raman spectroscopy and scanning electron microscopy (SEM), this work has provided in-depth knowledge on the interaction of GNP and WCL with the WPU matrix. As well as their effects on elastomeric nanocomposites fracture-mechanisms, and structure-property relationship, which are desirable for wide-scale industrial applications. • Unfunctionalised GNPs were successfully integrated in WPU matrix, with and without a crosslinker, with uniform dispersion • Both GNP and WCL increase the strength and modulus of WPU by comparable levels • WCL integration contributed to reduction in elongation, but GNP does not • WCL and GNP together increase the strength beyond each individually • GNP provides mechanical enhancement without crosslinking the WPU, hence, can be recycled more easily than crosslinked WPU