Investigating nonlinear viscoelastic properties of molten carbon black/poly(ethylene‐co‐butyl acrylate) composites, using fourier transform rheometry and other test techniques

Abstract

ABSTRACT:A series of molten carbon black (CB)/poly-(ethylene-co-butyl acrylate) (EBA) composites were investigated through Fourier transform (FT) rheometry and other techniques. Filler loadings were above the critical percolation value, and consequently, strongly nonlinear viscoelastic properties were observed, with, in addition, an unusual complexity of carbon black effects when compared with other systems, for instance filled elastomers. FT rheometry appears particularly sensitive to such a complexity with typical variations of torque harmonics, as dynamic torsional strain is increased at constant frequency and temperature. How CB particles are distributed in the material appears as the key to understand experimental results. Indeed, in CB-EBA composites, filler particles concentrate in amorphous regions of the polymer, which are also butyl acrylate (BA)-rich regions. At room temperature, such composites are basically dual-phase systems: ethylene segments (PE)-rich crystallites and CB-rich amorphous BA regions. Solid-state mechanical properties reflect this morphology. As temperature increases, crystallites melt down allowing a pseudofluid state to be eventually reached but the dual-phase morphology is essentially kept. It follows that, under increasing (dynamic) strain, such complex dual-phase molten systems exhibit a response that initially reflects a contribution from PE-rich regions, easier to deform than CB-rich amorphous BA regions, before the expected response of the filled BA phase is observed.

Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

“…The difference in rheological and dielectric behavior between the sample containing GnP as filler and the hybrid GnP-CB samples can be explained in the framework of the model proposed by Leblanc and Jäger [ 13 ]; Figure 11 . As nanofillers tend to aggregate in BA regions as opposed to PE regions, when subjected to nonlinear deformations, the initially percolated network is destroyed, and the nanoplatelets become oriented in the flow direction.…”

“…In contrast, however, M-screw samples appear to show a better performance in rheo-dielectric measurements compared to the extruded samples. This could suggest that in the framework of the model described by Leblanc and Jäger [ 13 ], the flow field-matrix-filler interactions during processing could be further improved.…”

“… Interpretation of the dynamic behavior of the hybrid nanocomposites studied in the nonlinear viscoelastic regime, based on the model of Leblanc and Jäger [ 13 ]. …”

“…Rheology is an important tool to characterize polymer nanocomposites in relation to understanding the underlying complex matrix-filler and filler-filler interactions and for the design of processing operations, e.g., see [ 5 , 6 , 7 , 8 , 9 , 10 ], among many others. In particular, Fourier-transform rheology has been used to determine the percolation threshold, morphological changes and microstructural interactions in percolated systems, the influence of various particle characteristics and modeling the rheological material response [ 11 , 12 , 13 , 14 , 15 ]. Changes in the strain amplitude-dependent nonlinearities’ scaling were reported for percolated systems, including a maximum peak in the third relative higher harmonic of the polycaprolactone/multi-walled carbon nanotube (PCL/MWCNT, 1D thread shape), polycaprolactone/organomodified montmorillonite (PCL/OMMT, 2D plate shape with high aspect ratio) and the polyethylene/multi-walled carbon nanotube (PE/MWCNT), but not for polycaprolactone/precipitated calcium carbonate (PCL/PCC, 3D cubic shape) [ 14 , 15 ].…”

“…Changes in the strain amplitude-dependent nonlinearities’ scaling were reported for percolated systems, including a maximum peak in the third relative higher harmonic of the polycaprolactone/multi-walled carbon nanotube (PCL/MWCNT, 1D thread shape), polycaprolactone/organomodified montmorillonite (PCL/OMMT, 2D plate shape with high aspect ratio) and the polyethylene/multi-walled carbon nanotube (PE/MWCNT), but not for polycaprolactone/precipitated calcium carbonate (PCL/PCC, 3D cubic shape) [ 14 , 15 ]. The nonlinear rheological behavior of ethylene butyl acrylate (EBA)-carbon black (CB) composites was investigated by Leblanc and Jäger [ 13 ]. Strongly nonlinear viscoelastic properties were observed, as well as an unusual complexity of carbon black influence on their viscoelastic response.…”