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The formation of a segregated network structure (wittingly uneven distribution of a filler) is one of the most promising strategies for the fabrication of electrically conductive polymer composites at present. However, the simultaneous achievement of high values of electrical conductivity with the retention of well mechanical properties within this approach remains a great challenge. Here, by means of X-ray photoelectron spectra (XPS), near-edge X-ray absorption fine structure (NEXAFS) spectra, scanning electron microscopy (SEM), dielectric spectroscopy, and compression engineering stress–strain curve analysis, we have studied the effect of a segregated network structure on the electrical conductivity and mechanical properties of a set of polymer composites. The composites were prepared by applying graphene oxide (GO) with ultralarge basal plane size (up to 150 μm) onto the surface of polymer powder particles, namely, poly(vinyl chloride) (PVC), poly(vinylidene fluoride- co -tetrafluoroethylene) (P(VDF-TFE)), and ultrahigh-molecular-weight poly(ethylene) (UHMWPE) with the subsequent GO reduction and composite hot pressing. A strong dependence of the segregated network polymer composites’ physical properties on the polymer matrix was demonstrated. Particularly, 12 orders of magnitude rise of the polymers’ electrical conductivity up to 0.7 S/m was found upon the incorporation of the reduced GO (rGO). A 17% increase in the P(VDF-TFE) elastic modulus filled by 1 wt % of rGO was observed. Fracture strength of PVC/rGO at 0.5 wt % content of the filler was demonstrated to decrease by fourfold. At the same time, the change in strength was not significant for P(VDF-TFE) and UHMWPE composites in comparison with pure polymers. Our results show a promise to accelerate the development of new composites for energy applications, such as metal-free supercapacitor plates and current collectors of lithium-ion batteries, bipolar plates of proton-exchange membrane fuel cells, antistatic elements of various electronic devices, etc.

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The effect of the loading rate on the strength of the interface of bonds of UKN-5OOO-P carbon fibres ~ 7 #m in diameter with thermosetting (EDT-I O epoxy binder) and thermoplastic (PSK-1 polyarylene sulfone) matrices was investigated. The adhesive strength T 0 of the bonds was determined in shear ofStudying the properties of the interface between a polymer matrix and reinforcing filler under the effect of different service factors is one of the most important problems in composite science. Such studies are interesting from both theoretical and practical points of view. They would allow creating composites with defined and adjustable properties. In addition, they would make it possible to establish the mechanisms of changes in adhesive strength, compare them with the similar mechanisms of the change in the cohesive strength of the components of the system and the composites based on them, and determine their common character.The above also fully applies to the properties of the interface of bonds of polymers with fibres in different conditions of loading. However, this problem has been investigated for a very limited number of systems. In particular, it has not been investigated in general for bonds of polymers with very thin and brittle carbon fibres.We examined the effect of the loading rate on the adhesive strength of bonds of polymers with UKN-5000-P industrial carbon fibres. The fibre diameter was d = 6.8-7.1 btm and the strength was 3.5 GPa. EDT-10 epoxy binder and PSK-1 polyarylene sulfone were selected as the adhesives; the first one is a typical cross-linked binder and the second is a typical thermostable thermoplast (polyarylene sulfone was used in the form of powder).The adhesive shear strength, determined in pulling a fibre out of a layer of the polymer (pull-out method), was used as the measure of adhesion; the "three fibre" method was used [1][2][3][4][5][6][7][8]. The methods of fabrication of bonds of the carbon fibres with the polymer matrices were described in detail previously; with thermosetting matrices in [2,3] and with thermoplasts in [4].We know from studies of industrial fibres 7-20 btm in diameter that the fibre whose adhesion is determined can be pulled out of the adhesive if the thickness of the polymer layer l in which the fibre is loaded is no greater than 10-20 of its diameter: l/d< (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Otherwise, the fibre will break when the bonds are loaded, i.e., not adhesive, but cohesive failure will occur. For this reason, boron fibres 55 and 95 ~tm in diameter were used as the fibres on which the adhesive was applied and on whose diameter the average length of the adhesive bond depends in the "three fibre" method. The bonds were formed in ovens in air medium without using pressure. The temperature--time conditions of bond formation are reported in Table 1. The samples obtained were tested on an adhesiometer* which measures in a range of rates covering three orders of magnitude [2,3].