Electrical, thermal, and viscoelastic properties of graphene nanoplatelet/poly(butylene adipate‐co‐terephthalate) biodegradable nanocomposites

Abstract

Graphene nanoplatelets (GNPs) were dispersed in poly(butylene adipate‐co‐terephthalate) (PBAT) by melt‐blending. Scanning electron micrographs showed good dispersion of GNPs in PBAT at low concentrations while at higher loadings, the platelets became physically in contact forming conductive pathways. Electrical conductivity of PBAT was enhanced markedly with GNP addition with a distinctly faster rate for GNP loadings higher than 6 wt % because of formation of conductive networks. Interestingly, thermal stability of PBAT was also found to increase for GNP loadings above 6 wt %. Dynamic viscoelastic properties of the nanocomposites exhibited significant enhancement with increasing GNPs. In particular, storage modulus showed less frequency dependency in the low frequency region leading to a percolation threshold of between 6 and 9 wt %, above which time–temperature superposition principle failed. Steady shear measurements revealed that GNP incorporation increased the zero‐shear viscosity markedly and intensified the shear thinning behavior. Carreau model well described the shear viscosity of all the compositions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43620.

Rheology and 3D Printability of Percolated Graphene–Polyamide-6 Composites

“…The greater increase in G’ can be attributed to the filler’s more pronounced influence on the elastic response of PA6 than its viscous response, thus the materials were becoming more solid-like (where G’ > G”). Increasing moduli with increasing graphene concentration has been widely reported in several graphene–polymer composites including those with PA6 [ 12 ], PLA [ 28 ] and poly (vinylidene fluoride) (PVDF) [ 29 ] matrices. In the mentioned works, graphene concentrations of as low as 0.5%· w / w were studied.…”

“…Furthermore, the moduli of specimens with GNP content of 6.0%· w / w and higher appeared to approach a plateau at low frequencies, with GC17.0 displaying the most distinct plateau. Decreasing frequency dependence and the appearance of a plateau at low frequencies can be attributed to the increasing influence of interactions between adjacent GNP particles as a result of the formation of interconnected structures [ 28 ]. Thus, the observations indicate the formation of a percolated network of GNP at concentrations of 6.0%· w / w and higher.…”

“…The formation of percolated GNP networks can manifest as changes in viscoelastic behaviour due to the network’s restrictions on polymer chain mobility [ 12 ]. Besides the observation of moduli crossover, rheological percolation can be observed in the change in the slope (α) of the log G’–log ω plot in the terminal frequency region [ 28 ]. A change in behaviour of α will correspond to a change from liquid-like to solid-like behaviour.…”

“…Increasing the GNP content to 6%· w / w and higher increased the η* at low frequencies, with more significant shear-thinning behaviour at higher frequencies and the disappearance of the Newtonian plateau in the low-frequency region. The increase in the η* at low frequencies can be ascribed to impeded polymer chain mobility as a result of increased filler-matrix interactions when the GNP concentration increased [ 28 ]. The disappearance of the Newtonian plateau is indicative of the formation of continuous GNP networks [ 30 ].…”

Microwave Attenuation of Graphene Modified Thermoplastic Poly(Butylene adipate-co-terephthalate) Nanocomposites

“…The platelets in Figure 3c have a void surrounding, which is the GNP-matrix interphase, differentiating the platelets (light grey) from the sharp edges of the matrix. Morphology of PBAT/GNP nanocomposites and dispersion state of the nanoplatelets in the polymeric matrix have been studied in more detail in a report on the rheological behaviour of these nanocomposites [53].…”