Strengthened electrically conductive composites based on ultra-high-molecular-weight polyethylene filled with fine graphite

Abstract

Orientation stretching is known to be an efficient method for strengthening polymer materials [1]. However, such stretching of polymer composites filled with various dispersed fillers is often accompanied by their brittle fracture even early in the deformation [2].In this work, for the first time, we described the possibility of producing strengthened oriented highly filled electrically conductive polymer nanocomposites under uniform shear conditions so that the rupture strength of these composites is an order of magnitude higher than that of non oriented composites of the same composition.We studied electrically conductive specimens of polymer composites of various compositions that were produced by filling a nascent reactor powder of ultra high molecular weight polyethylene (UHMWPE) of a nodular morphological structure (with a molecular weight of 5 × 10 6 and a bulk density of the reactor pow der of 0.058 g/cm 3 ) [1] with a commercial electrically conductive graphene nanopowder (GN) of grade AO 4 containing 60 nm thick flakes (Graphene Laborato ries) [3]. Our X ray powder diffraction studies showed that the filler is fine polycrystalline graphite with a coherent scattering length (stack height) in the crys tallographic direction [002] of ≈30 nm.The initial mixing of two fine powder components of the UHMWPE-GN system was performed mechani cally. The initial non oriented specimens of nano graphene filled polyethylene composites (PENG) were shaped as 0.5 mm thick plates obtained by compacting the material under a pressure of 200 atm at room tem perature.Uniaxial orientation of the specimens was carried out at room temperature in a special setup [2]. It pro duced a combination of compression and uniform shear of a specimen placed between plates made of a plastic Pb-Sn alloy. The specimen was extruded through a conical die of a certain diameter, which determined the strain of the material. The latter was characterized by the stretching ratio l/l 0 , where l and l 0 are the lengths of the oriented and initial non oriented composite specimens, respectively.The stress-strain curves of the produced PENG specimens were recorded at room temperature in Tin ius Olsen H1KS and Shimadzu AGS 10 universal test ing machines in the uniaxial stretching mode at a deformation rate of 0.2 min -1 . Heat treatment of the oriented specimens was performed in the heat cham ber of the Shimadzu AGS 10 testing machine.The conductivity of the composite plates and ori ented specimens was measured with an Agilent 34401A multimeter.The wide angle X ray diffraction patterns were recorded with a Bruker NANOSTAR system (CuK α radiation) with a 2D position sensitive detector. Elec tron microscopic studies of the specimens at various magnifications were made with a JEOL JSM 35 scan ning electron microscope. No metal coating was made, which allowed us to contrast conductive and nonconductive regions of the composite structure. The specimens were prepared by low temperature cleavage at liquid nitrogen temperature.The measured dependence of the electri...

A study of oriented conductive composites with segregated network structure obtained via solid‐state processing of UHMWPE reactor powder and carbon nanofillers

“…In this work, we investigate a method of production of strengthened electrically conductive materials obtained by means of room-temperature compaction and uniaxial shear deformation of the mechanical mixtures of UHMWPE reactor powder and various types of nanosized carbon particles. The efficiency of this approach was noted earlier [22,23].…”