Preparation and Characterization of Conductive Polymer Nanocomposites Based on Ethylene–Vinylacetate Copolymer (EVA) Reinforced with Expanded and Unexpanded Graphite

Abstract

Recently polymer nanocomposites are used more and more frequently in industry due to the fact that the properties of the polymers can be altered to the specific requirements by the addition of particles and fibers of different properties, shapes. Polymers are poor thermal and electrical conductors, conductive fillers such as metallic powders, carbon black, graphite, are usually incorporated into polymer matrix to produce conducting composites. In this study composites were prepared using ethylenevinyl acetate (EVA) copolymer as matrix filled with two kinds of reinforcement graphite materials: untreated natural graphite (UG) and expanded graphite (EG). Composite samples up to 29.3 % graphite particle volumetric concentrations (50 % mass concentration) were prepared by the melt mixing process in a Brabender Plasticorder. Upon mixing, the EG particles originally 5μm to 6μm in size, exfoliates in the form of nanosheets having a few nanometer thickness; they have very big surface areas with high aspect ratio ranging between 20 and 250, as evidenced by TEM micrographs. From the experimental results it was deduced that the electrical conductivity was not only a function of filler concentration, but also strongly dependent on the graphite structure. The percolation concentration of the filler was found to be (15 to 17) vol% for micro-sized natural graphite, whereas the percolation concentration of the filler in nanocomposites filled with expanded graphite was much lower, about (5 to 6) vol%. The electrical conductivity of nanocomposites was also much higher than the electrical conductivity of composites filled with micro-sized filler at similar concentrations. Similarly, the values of the thermal diffusivity for the nanocomposites, EG-filled EVA, were significantly higher than the thermal diffusivity of the composites filled with micro-sized filler, UG-filled EVA, at similar concentrations. The effect of thermal cycling on the tensile behavior of EVA composites containing 4% and 15% of UG by mass and 6% and 15% of EG by mass were subjected to thermal cycling between-25 to +60 °C. Tension tests were conducted after thermal cycling for 50 and 100 cycles. Tensile strength remained practically unchanged after thermal cycling, while the Young modulus increased appreciably with the number of thermal cycle.

Carbon Coating Influence on the Formation of Percolating Electrode Networks for Silicon Anodes

“…Specifically, we seek to understand how a 1−3 nm coating would enable electronic conductivity or facilitate fast ion transport through an amorphous carbon layer, resulting in the reported improved electrochemical performances. We note that amorphous or disordered carbons tend to have electronic conductivities 1000× lower than graphene or graphite, 23 making simple electronic pathway arguments more challenging to accept. We demonstrate through Raman mapping, electron microscopy, XPS, EIS, and zeta potential measurements that the structure of the electrodes improves with carbon coating due to a matching of the materials' surface chemistry.…”

Development of thermally conductive and high‐specific strength polypropylene composites for thermal management applications in automotive

“…A similar assumption was used earlier for predicting tensile modulus of various hybrid systems. [4,54] For all the calculations, thermal conductivity of PP, CF, and HGM were taken as 0.22 W/m K, [55] 22 W/m K, [56] and 0.153 W/m K [48] , respectively. For simplicity, the effect of MA-g-PP was not considered during the analysis.…”

A vertically paired electrode for redox cycling and its application to immunoassays

“…2(c). These results indicated that the PEDOT:PSS changed to have the property of a conductive electrode (Au: 4.1 × 10 7 S m −1 , Pt: 9.4 × 10 6 S m −1 , glassy carbon: 2.2 × 10 4 S m −1 , graphite: 2.1 × 10 3 S m −1 ) [45][46][47] at strongly acidic condition. 37,38 Additionally, the peak potential separation (ΔE p = E ap − E cp ) between the cathodic and anodic peaks of CV was observed to be decreased at strongly acidic condition from the comparison of the cyclic voltammograms of TMB.…”