A study of oriented conductive composites with segregated network structure obtained via solid‐state processing of UHMWPE reactor powder and carbon nanofillers
Abstract:FederationReinforced electrically conductive polymer composites based on ultra-high molecular weight polyethylene reactor powder and filled with various amounts of carbon black, graphite nanopowder, and multiwalled carbon nanotubes were studied. The composites were obtained via compaction of a mechanical mixture of the filler and the polymer reactor powders. This was followed by uniaxial deformation of the material under homogeneous shear conditions. The resulting composites possessed high tensile strength (up… Show more
“…The layer thickness of 100 nm was taken from the thickness of conductive layer formed around UHMWPE grains in solid-state processed UHMWPE/MWCNT composites with 1% volume fraction of the filler, thoroughly investigated in the previous work of the authors. 14 Figure 3.(a) Volume element constructed for deformation tests and conductance calculations with imitated periodic boundary conditions, where the white dashed square contours the investigated sub-volume (“inner” volume), to which the deformation was applied and conductance of which was calculated later; (b) side view of the volume element; and (c) a close-up view of finite element mesh used in simulations, where blue and red color indicate edges of the matrix cubic elements, and purple indicates truss elements representing the MWCNT segments (dashed arrows symbolize constrains of the MWCNT node by the matrix nodes that are created during the embedding). MWCNT: multi-walled carbon nanotube.…”
Section: Methodsmentioning
confidence: 99%
“…Additionally, as it was shown earlier, the presence of filler does not significantly affect the process of strengthening through orientation, making it possible to obtain flexible electroconductive materials with high tensile strength. 14,16…”
Section: Introductionmentioning
confidence: 99%
“…7,13 Formation of segregated structures and investigation of their properties are of special importance for nanocomposites based on ultra-high-molecular-weight polyethylene (UHMWPE) as a matrix. 14,15 This is due to a limited number of processing methods available for that type of polymer, which results from the high viscosity of the UHMWPE's melt. One of the most popular methods of obtaining UHMWPE-based composites is a mechanical mixing of matrix polymer powder with nanofiller, followed by sintering at temperatures above melt temperature of polyethylene (PE).…”
In this work, the correlation between electrical conductivity and uniaxial deformation of a material with highly segregated distribution of conductive filler is studied. Multi-walled carbon nanotubes are used as a model filler. A numerical model that can be used to predict changes in conductive microstructure made of multi-walled carbon nanotubes in response to uniaxial deformation of material is proposed. The model takes into account the ability of nanotubes to assume various conformations and orientations during deformation. Numerical simulations are conducted for uniformly distributed multi-walled carbon nanotubes providing confinement of the filler in a two-dimensional film structure with high volume fraction of the filler. The embedded element method to conduct realistic and computationally efficient simulation of multi-walled carbon nanotube behavior during deformation of the composite material is implemented. Finally, the results of numerical simulations of changes in electrical conductivity of composite during deformation are compared with the experimental data to prove the correctness of assumptions used in the model.
“…The layer thickness of 100 nm was taken from the thickness of conductive layer formed around UHMWPE grains in solid-state processed UHMWPE/MWCNT composites with 1% volume fraction of the filler, thoroughly investigated in the previous work of the authors. 14 Figure 3.(a) Volume element constructed for deformation tests and conductance calculations with imitated periodic boundary conditions, where the white dashed square contours the investigated sub-volume (“inner” volume), to which the deformation was applied and conductance of which was calculated later; (b) side view of the volume element; and (c) a close-up view of finite element mesh used in simulations, where blue and red color indicate edges of the matrix cubic elements, and purple indicates truss elements representing the MWCNT segments (dashed arrows symbolize constrains of the MWCNT node by the matrix nodes that are created during the embedding). MWCNT: multi-walled carbon nanotube.…”
Section: Methodsmentioning
confidence: 99%
“…Additionally, as it was shown earlier, the presence of filler does not significantly affect the process of strengthening through orientation, making it possible to obtain flexible electroconductive materials with high tensile strength. 14,16…”
Section: Introductionmentioning
confidence: 99%
“…7,13 Formation of segregated structures and investigation of their properties are of special importance for nanocomposites based on ultra-high-molecular-weight polyethylene (UHMWPE) as a matrix. 14,15 This is due to a limited number of processing methods available for that type of polymer, which results from the high viscosity of the UHMWPE's melt. One of the most popular methods of obtaining UHMWPE-based composites is a mechanical mixing of matrix polymer powder with nanofiller, followed by sintering at temperatures above melt temperature of polyethylene (PE).…”
In this work, the correlation between electrical conductivity and uniaxial deformation of a material with highly segregated distribution of conductive filler is studied. Multi-walled carbon nanotubes are used as a model filler. A numerical model that can be used to predict changes in conductive microstructure made of multi-walled carbon nanotubes in response to uniaxial deformation of material is proposed. The model takes into account the ability of nanotubes to assume various conformations and orientations during deformation. Numerical simulations are conducted for uniformly distributed multi-walled carbon nanotubes providing confinement of the filler in a two-dimensional film structure with high volume fraction of the filler. The embedded element method to conduct realistic and computationally efficient simulation of multi-walled carbon nanotube behavior during deformation of the composite material is implemented. Finally, the results of numerical simulations of changes in electrical conductivity of composite during deformation are compared with the experimental data to prove the correctness of assumptions used in the model.
“…One of the polymers that received substantial attention in the last few decades is ultrahigh-molecular-weight polyethylene (UHMWPE), which is often used as a base polymer for nanocomposites with segregated structures made of nanosized filler [ 20 , 21 ]. Due to the high viscosity of the UHMWPE melt, a limited number of processing methods are available for this type of polymer.…”
Section: Introductionmentioning
confidence: 99%
“…It was demonstrated that the presence of a filler even in a very high amount does not significantly affect the process of orientation, making it possible to obtain strong and highly flexible electroconductive materials. Nanocomposites based on this special type of UHMWPE and processed in a solid state via compression molding are characterized by an extreme segregation of the filler and by very low values of the percolation threshold [ 20 , 23 ] in comparison to the hot-molded nanocomposites. In the case of solid-state processing of polymer and MWCNT powders, since polymer melting is not involved, MWCNTs only cover polymer powder particles, mostly not penetrating their volume.…”
In this work, the piezoresistive effect for a polymer nanocomposite with a highly segregated distribution of conductive filler was investigated. As a base polymer for the investigated nanocomposites, ultrahigh-molecular-weight polyethylene, processed in a solid state (below melting point), was used. Multiwalled carbon nanotubes (MWCNTs) were used as a nanofiller forming a highly segregated structure in between polymer particles. A numerical multiscale approach based on the finite element method was proposed to predict changes in the conductive structure composed of MWCNTs in response to uniaxial deformation of the material. At the nanoscale, numerical simulations were conducted for uniformly distributed MWCNTs providing confinement of the filler to a two-dimensional layer with a high volume fraction of the filler in between two polymer particles. At the microscale, the piezoresistive response to uniaxial deformation for the three-dimensional highly segregated structure reconstructed from experimental data was investigated numerically. The embedded element method was implemented to conduct a realistic and computationally efficient simulation of MWCNT behavior during deformation of the nanocomposite. The results of numerical simulations were compared with the experimental data to prove the correctness of assumptions used in the modeling.
Process of nanoscale carbon filler migration in polymer composite melts is studied. Monotonous decrease of electrical resistance is observed for composite materials during their stay in a melted state. This is especially pronounced for composites with concentration of filler much lower than percolation threshold determined for a specific matrix/filler/mixing method combination. This phenomenon can be observed for composites based on different polymer matrices. Also, it is demonstrated that the type and geometry of the electrically conductive filler does not affect presence of the phenomena. A setup for measurement of conductance for volume and surface layer components is used. The results of electrical conductance measurements of the polymer composite melt using this setup allows to attribute the increase of composite material conductance to formation of filler enriched surface layer. To obtain information on the processes occurring at the microscopic level, molecular dynamics simulations are conducted. Variation of several simulation parameters with comparison of the results to experimental data allows to understand the macroscopic composite material conductance behavior.
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