Composite Films of Waterborne Polyurethane and Few-Layer Graphene—Enhancing Barrier, Mechanical, and Electrical Properties

Abstract

Graphene has excellent mechanical, thermal, and electrical properties. Graphene can serve as potential reinforcement in polymer-based nanocomposites. In order to achieve this goal, graphene has to be distributed homogeneously and dispersed throughout the polymer matrix, establishing a strong interface with the polymer. Solution mixing is an interesting method for the preparation of homogeneous nanocomposites, in particular when using environmentally friendly solvents such as water. The major difficulty met in the production of graphene/polymer composites concerns the preparation and stabilization of graphene in aqueous suspension. In the present work three different graphite-based materials, with different crystallinity and purity grades, were exfoliated in aqueous solution of an amphiphilic pyrene derivative, forming few-layer graphene (FLG). The FLG prepared was dispersed in waterborne polyurethane (WPU) to produce composite films. The composite films were produced by solvent casting and spray coating, forming free-standing films that were characterized in terms of its distribution of FLG through the composite, its permeability to water vapor, its electrical resistivity, and its mechanical properties. The studies demonstrated the influence of different factors on the composite film properties such as the use of graphite vs. FLG, the FLG lateral dimensions, and the FLG composition and composite preparation method.

Ternary Nanocomposite System Composing of Graphene Nanoplatelet, Cellulose Nanofiber and Jatropha Oil Based Waterborne Polyurethane: Characterizations, Mechanical, Thermal Properties and Conductivity

“…In addition, the negative charge on GNP surfaces is so weak due to the minimal amount of carboxyl groups, therefore self-exfoliation to a single layer is not efficient [31,32]. This trend was also in agreement with findings of other researchers [21,[33][34][35]. The schematic diagram of electrostatic repulsion force and distribution of CNF and GNP is presented in Figure 5.…”

“…Since WBPU comprising of water and PU particle, GNP still faces a problem to be well dispersed even though it was dispersed in acetone prior addition into WBPU solution. Long duration of time for curing process provides enough timeframe for GNP to restack [22,33].…”

Functional Piezoresistive Polymer Composites Based on CO2 Laser-Irradiated Graphene Oxide-Loaded Polyurethane: Morphology, Structure, Electrical and Piezoresistive Properties

“…Furthermore, in the region, laser-irradiated leather comprised nanosheets and patches of an irregular shape forming a network that is several microns thick. The appearance outside the groove wall was the same as that generally observed below the percolation threshold for polymer composites containing isolated graphene sheets and platelets [ 40 , 41 ].…”

Graphene/polyurethane nanocomposite coatings – Enhancing the mechanical properties and environmental resistance of natural fibers for masonry retrofitting

“…The non-coated yarns reached their saturation point after 3 h immersion, while the coated yarns showed almost 0 % weight gain after that period. The saturation level of the coated hemp and flax was approximately 10 % weight, and was reached above 6 h of immersion and maintained still until 24 h. Although neat WPU is not strongly hydrophobic, the addition of the 2D high-aspect ratio GNPs will decrease the permeability to water due to their hydrophobicity and 2D morphology that induce a barrier effect [15]. Additionally, the nanocomposite coating may provide a restraining barrier to the fibers' swelling, limiting the access and space for the accommodation of water molecules within the hydrophilic parts in fiber lumen [10].…”