Hyperbranched-polymer functionalization of graphene sheets for enhanced mechanical and dielectric properties of polyurethane composites

Abstract

The incorporation of graphene sheets (GSs) into polymer matrices affords engineers an opportunity to synthesize polymer composites with excellent physical performances. However, the development of high performance GS-based composites is difficult because of the easy aggregation of GSs in a polymer matrix as well as the weak interfacial adhesion between GSs and the host polymer. Herein, we present a simple and effective route to hyperbranched aromatic polyamide functionalized graphene sheets (GS-HBA). The resulting GS-HBA exhibits uniform dispersion in a thermoplastic polyurethane (TPU) matrix and strong adhesion with the matrix by hydrogen-bond coupling, which improve the load transfer efficiency from the matrix to the GSs. Thus, the GS-HBA-TPU composites possess excellent mechanical performance and high dielectric performance. It has been demonstrated that the GS-HBA composite has higher modulus, higher tensile strength and higher yield strength, and remains at nearly the same strain at break when compared with the composites with graphene oxide, ethylene diaminemodified graphene, and hydrazine reduced graphene. In addition, the hyperbranched polymer chains allow construction of a large number of microcapacitors and suppress the leakage current by isolating the GSs in a TPU matrix, resulting in a higher permittivity and lower loss tangent for the GS-HBA composite in comparison with ethylene diamine-modified graphene, or hydrazine reduced-graphene composites.

A facile approach to selective reduction and functionalization of graphene oxide and its application in fabrication of multifunctional polypropylene nanocomposites

“…For G-ODA, the appearance of new characteristic absorption peaks (ANHA, ACNA) indicates ODA has been grafted successfully onto the graphene sheet. This result is agreeable with the previous report [12]. Figure 1b compares the FTIR of GO, ODA, rG-ODA, and rGO.…”

“…Especially for polar polymers, for example, polyurethane (PU) [12][13][14], poly(butylene terephthalate) [15], and epoxy resin [16,17], because some interactions would take place between oxygen-containing functional groups on the GO surface and polymer matrix. However, the application of GO in non-polar polymers is limited because they are incompatible.…”

Simultaneously improved actuated performance and mechanical strength of silicone elastomer by reduced graphene oxide encapsulated silicon dioxide

“…Many researchers have demonstrated that the increase in k is far less than that expected using GO as the dielectric filler because of the severe disruption of the graphite structure of GO [41]. Therefore, the reduction of GO@SiO 2 /PDMS composites is required to increase the interfacial polarization ability of GO@SiO 2 .…”

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

“…3 that GO was not thermally stable. Its major mass loss appeared in the temperature range from 150°C to 300°C, associated with pyrolysis of the massive labile oxygen functional groups on its surface [33]. In contrast, the total mass loss of FGO could be divided into two major stages.…”

“…After chemical functionalization of GO with MDI and PCL, the amount of available hydrogen-bond donor groups decreased significantly, thus weakening the interlayer interactions in FGO, which contributed to the exfoliation of FGO in the DMF solvent. Meanwhile, the covalently grafted MDI and PCL on the surface of the FGO sheets could effectively prevent the graphene backbones from direct contact [33], which was also beneficial to the exfoliation of FGO in the solvent.…”