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

2015 ◽  
Vol 1114 ◽  
pp. 92-99
Author(s):  
Ismail H. Tavman
Keyword(s):  
Electrical Conductivity ◽  
Thermal Diffusivity ◽  
Thermal Cycling ◽  
Polymer Nanocomposites ◽  
Conductive Polymer ◽  
Young Modulus ◽  
Expanded Graphite ◽  
Filler Concentration ◽  
Melt Mixing ◽  
Natural Graphite

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.

Preparation of Expanded Graphite and Graphite Nanosheets for Improving Electrical Conductivity of Polyester Coating Films

2021 ◽  
Vol 21 (12) ◽  
pp. 5846-5858
Author(s):  
Yun Ding ◽  
Mingxia Tian ◽  
Aili Wang ◽  
Hengbo Yin
Keyword(s):  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Milling Time ◽  
Expanded Graphite ◽  
Graphite Powder ◽  
Expandable Graphite ◽  
Coating Films ◽  
Natural Graphite ◽  
Graphite Nanosheets ◽  
Volumetric Rate

Expanded graphite and graphite nanosheets were facilely prepared by the thermal expansion of expandable graphite at 800 °C and sand milling of expanded graphite in water, respectively. When the expandable graphite precursor was prepared by the oxidation and intercalation of natural graphite (5 g) using KMnO4 (6 g) as an oxidant in a concentrated sulfuric acid solution (120 mL) at room temperature (25 °C) for 8 h, the expanded graphite with a maximum volumetric rate of 317 mL g−1 was prepared after the thermal expansion of the expandable graphite precursor at 800 °C for 60 s. The oxidation extent of natural graphite with KMnO4 is crucial for the preparation of expanded graphite. The thicknesses of graphite nanosheets decreased from 8.9 to 3.2 nm when the sand milling time of the expanded graphite in deionized water was prolonged from 6 to 24 h. The prolonging of the sand milling time not only decreased the layer number of the graphite nanosheet but also increased the d002 spacing due to the shocking and shearing forces. The addition of the expanded graphite powder and graphite nanosheets in a polyester paint efficiently improved the electrical conductivity of the resultant polyester coating films.

Recent progress on improving the mechanical, thermal and electrical conductivity properties of polyimide matrix composites from nanofillers perspective for technological applications

2021 ◽  
Vol 41 (9) ◽  
pp. 768-787
Author(s):  
Victor Ekene Ogbonna ◽  
A. Patricia I. Popoola ◽  
Olawale M. Popoola ◽  
Samson O. Adeosun
Keyword(s):  
Electrical Conductivity ◽  
Polymer Nanocomposites ◽  
Recent Progress ◽  
Conductive Polymer ◽  
Matrix Composites ◽  
Thermal And Electrical Properties ◽  
Review Study ◽  
Polyimide Matrix ◽  
Conduction Polymer ◽  
Selection Of

Abstract The adoption of polymer nanocomposites in the design/manufacturing of parts for engineering and technological applications showcases their outstanding properties. Among the polymer nanocomposites, polyimide (PI) nanocomposites have attracted much attention as a composite material capable of withstanding mechanical, thermal and electrical stresses, hence engineered for use in harsh environments. However, the nanocomposites are limited to the application area that demands conduction polymer and polymer composites due to the low electrical conductivity of PI. Although, there has been advancement in improving the mechanical, thermal and electrical properties of PI nanocomposites. Thus, the review focuses on recent progress on improving the mechanical, thermal and electrical conductivity properties of PI nanocomposites via the incorporation of carbon nanotubes (CNTs), graphene and graphene oxide (GO) fillers into the PI matrix. The review summarises the influence of CNTs, graphene and GO on the mechanical and conductivity properties of PI nanocomposites. The authors ended the review with advancement, challenges and recommendations for future improvement of PI reinforced conductive nanofillers composites. Therefore, the review study proffers an understanding of the improvement and selection of PI nanocomposites material for mechanical, thermal and electrical conductivity applications. Additionally, in the area of conductive polymer nanocomposites, this review will also pave way for future study.

scholarly journals Dielectrical properties of composites LDPE+CB

2010 ◽  
Vol 64 (3) ◽  
pp. 187-191
Author(s):  
Blanka Skipina ◽  
Dusko Dudic ◽  
Dusan Kostoski ◽  
Jablan Dojcilovic
Keyword(s):  
Electrical Conductivity ◽  
Polymer Composites ◽  
Conductive Polymer ◽  
Dissipation Factor ◽  
Filler Concentration ◽  
Electrical Insulator ◽  
Conductive Polymer Composites ◽  
Wide Range ◽  
Filler Particles ◽  
Dielectrical Properties

There is currently great interest in the technological properties of conductive polymer composites because their cost-performance balance. They have a wide range of industrial applications -in anti-static materials, self regulating heaters, current overload and overheating protection devices, and materials for electromagnetic radiation shielding. Measurements of the electrical properties of polymer composites are one of the most convenient and sensitive methods for studying polymer structure. A polymer composite differs substantially from a free polymer in a wide range of properties. The presence of filler affects both the electrical, as well as mechanical properties. One of the most important characteristics of conductive polymer composites is that their electrical conductivity increases nonlinearly with the increase of the concentration of filler particles. When the concentration of filler particles reaches a certain critical value, a drastic transition from an electrical insulator to a conductor is exhibited. This conductivity behavior resulting in a sudden insulator-conductor transition is ascribed to a percolation process, and the critical filler concentration at which the conductivity jump occurs is called ?percolation threshold?. In the past few years, a lot of studies have been carried out to analyze the percolation phenomenon and mechanisms of the conductive behavior in conductive polymer composites. It has been established that the electrical conductivity of conductive polymer composites uncommonly depends on the temperature. Some of such composites show a sharp increase and/or decrease in electrical conductivity at specific temperatures. The conductive temperature coefficient (CTC) of conductive polymer composites has been widely investigated. In these work we investigated how concentration of the CB affects the dielectrical properties of the composite LDPE+CB. The ac electrical conductivity, ?ac, for such composites was measured. The temperature and frequency dependence of the dissipation factor were analyzed. It was found that the ac conductivity and dissipation factor were highly affected by the concentration of the filler.

Effects of the Mould Temperature on the Properties of Graphite/Carbon Fiber/Copper/Phenolic Resin Composites

2013 ◽  
Vol 470 ◽  
pp. 31-34
Author(s):  
Mi Dan Li ◽  
Yao Lu ◽  
Xin Guo
Keyword(s):  
Electrical Conductivity ◽  
Carbon Fiber ◽  
Phenolic Resin ◽  
Conductive Polymer ◽  
Resin Composites ◽  
Large Decrease ◽  
Mould Temperature ◽  
Compression Moulding ◽  
Natural Graphite ◽  
Conductive Polymer Composites

Natural graphite, carbon fiber and copper powder as fillers are incorporated into phenolic resin to fabricate conductive polymer composites by hot compression moulding. The effects of the preparing method and mould temperature on the density, electrical conductivity and hardness of composites are investigated. It is found that the density, electrical conductivity and hardness of composites increase as mould temperature increase from 150 °C to 180 °C. Up to 200 °C, the hardness of composite shows a large decrease. At 170 °C, the density, electrical conductivity and hardness of composites are 1.904 g/cm3, 3.43 × 103S/m and 54 HS, respectively. Oxidation action occurring in the phenolic resin could be the main reason for the large decrease of hardness as temperature increases up to 200 °C.

scholarly journals Electrical Conductivity Modeling of Polypropylene Composites Filled with Carbon Black and Acetylene Black

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Abdelhafid Merzouki ◽  
Naceredine Haddaoui
Keyword(s):  
Electrical Conductivity ◽  
Carbon Black ◽  
Percolation Threshold ◽  
Acetylene Black ◽  
Filler Concentration ◽  
Melt Mixing ◽  
Entire Concentration Range ◽  
Polypropylene Composites ◽  
Boltzman Equation ◽  
Good Agreement

Composites of polypropylene filled with carbon black or acetylene black at different concentrations were prepared by melt mixing followed by compression molding. The influences of filler type and filler concentration on the composites conductivity were studied. It was found that the percolation threshold is located at a lower concentration in composites filled with the acetylene black, than that of the composites filled with carbon black. The model of Mamunya gives a fairly good agreement in the evaluation of the conductivity of polymeric composites loaded with carbon black or acetylene black, beyond the percolation threshold. The Boltzman equation was adopted to develop a model that represents more faithfully all results obtained. The expressions of the electrical conductivity, calculated with the model developed, are in good agreement with experimental results for the entire concentration range studied in linear or semilogarithmic scale.

Characterization of Expanded Graphite/Flake-Type Graphite Filled Conductive Polymer Composites

2008 ◽  
Vol 33-37 ◽  
pp. 515-520 ◽  
Author(s):  
Kyung Seok Oh ◽  
S.I. Heo ◽  
J.C. Yun ◽  
Kyung Seop Han
Keyword(s):  
Electrical Conductivity ◽  
Particle Size ◽  
Flexural Strength ◽  
Polymer Composites ◽  
Conductive Polymer ◽  
Weight Ratio ◽  
Expanded Graphite ◽  
Graphite Flake ◽  
Conductive Polymer Composites ◽  
Dependent Behavior

Conductive polymer composites (CPCs) consisting of expanded graphite (EG), flake-type graphite (FG) and thermalsetting resin were fabricated by means of a preform molding technique. Conductive fillers, EG and FG, were mechanically mixed with the phenol resin to provide an electrical property to composites. The filler loadings were fixed at 75wt.% to obtain a high electrical conductivity. The mechanical and electrical properties of CPCs were optimized according to the weight ratio and the particle size of FG. As the weight ratio increased, the flexural strength increased, however, the electrical conductivity decreased for both cases of CPCs using different sizes of FG. The particle size was an important parameter to change the mechanical and electrical behaviors. The flexural strength was sensitive to the particle size due to the different level of densification. The electrical conductivity also showed size-dependent behavior because of the different contribution to the conductive networking.

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