Synthesis of graphite nanosheets/polyaniline nanorods composites with ultrasonic and conductivity

The graphite nanosheets/polyaniline (GN/PANI) nanorods composites were fabricated via ultrasonic polymerization of aniline monomer in the presence of GN, which was used as electric filling. The kind of doped acids, the concentration, and the contents of the GN were used as impact factors to the conductivity of the materials that were investigated. The structure of nanocomposites were characterized by FTIR and SEM. The results show that ultrasonic can effectively restrain the agglomerate of the aniline and come to uniformity nanorods composites. The conductivity reached to 4.8 S/cm and 22 S/cm, respectively. The thermal stability of GN/PANI nanorods composites is superior to pure PANI as shown by TG analysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Eco-Friendly Electromagnetic Interference Shielding Materials from Flexible Reduced Graphene Oxide Filled Polycaprolactone/Polyaniline Nanocomposites

Hybrid nanocomposites have the unique ability of enhancing material properties due to the existing synergistic effect of the fillers. In this study, the authors report such an eco-friendly hybrid nanocomposite comprising of polyaniline and reduced graphene oxide in polycaprolactone. The conducting polyaniline improved the processability of polycaprolactone, and the final composites were prepared by incorporating graphene oxide reduced at 200 and 600°C temperatures to the polycaprolactone–polyaniline blend. Polyaniline, polyaniline/reduced graphene oxide200, and polyaniline/reduced graphene oxide600 imparted good electrical conductivity to polycaprolactone, and the fabricated flexible polycaprolactone–polyaniline/reduced graphene oxide nanocomposites exhibited good mechanical property, increased thermal stability, and excellent electromagnetic interference shielding up to 42 dB at 13 GHz.     

Electrical conductivity and electromagnetic interference shielding effectiveness of polyaniline–ethylene vinyl acetate composites

Electrical conductivity and electromagnetic interference (EMI) shielding effectiveness at microwave (200–2000 MHz) and X‐band (8–12 GHz) frequency range of polyaniline (PAni) composites were studied. It has been observed that EMI shielding of conductive polyaniline (PAni)–ethylene vinyl acetate composites increases with the increase in the loading levels of the conductive polymer doped with dodecylbenzene sulfonic acid. The result indicates that the composites having higher PAni loading (>23%) can be used for EMI shielding materials and those with lower PAni loading can be used for the dissipation of electrostatic charge. Copyright © 2004 Society of Chemical Industry     

Stability of electrical properties of carbon black‐filled rubbers

Conducting composites were prepared by melt mixing of ethylene–propylene–diene terpolymer (EPDM) or styrene‐butadiene rubber (SBR) and 35 wt % of carbon black (CB). Stability of electrical properties of rubber/CB composites during cyclic thermal treatment was examined and electrical conductivity was measured in situ. Significant increase of the conductivity was observed already after the first heating–cooling cycle to 85°C for both composites. The increase of conductivity of EPDM/35% CB and SBR/35% CB composites continued when cyclic heating‐cooling was extended to 105°C and 125°C. This effect can be explained by reorganization of conducting paths during the thermal treatment to the more conducting network. EPDM/35% CB and SBR/35% CB composites exhibited very good stability of electrical conductivity during storage at ambient conditions. The electrical conductivity of fresh prepared EPDM/35% CB composite was 1.7 × 10⁻² S cm⁻¹, and slightly lower conductivity value 1.1 × 10⁻² S cm⁻¹ was measured for SBR/35% CB. The values did not significantly change after three years storage. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Analysis of mechanical,thermal, electrical and EMI shielding properties of graphite/carbon fiber reinforced polypropylene composites prepared via a twin screw extruder

The present research focuses on the preparation of an efficient material that acts as a deterrent to electromagnetic pollution. In this study, graphite and carbon fiber (CF) reinforced polypropylene (PP) composites (GCF) are prepared using a melt processing technique via a twin-screw extruder. The prepared composites were evaluated for mechanical, thermal, DC conductivity, and EMI shielding properties. There is a rise in the tensile strength (4.32%) and thermal stability (6.57%) of composites were recorded as compared to pure PP. The fractured morphology of the composites showed the breakdown of CF, leading to the improvement in the tensile strength of the composites. An increase in electrical conductivity was seen at maximum (GCF4) filler loading indicating 2.31 × 10^?4 S/cm which is much better than the pure PP value (2.07 × 10^?10 S/cm). The maximum value of shielding effectiveness is achieved at the maximum weight percentage of filler loading which is ?44.43 dB with a thickness of 2 mm covering the X-band (8.2–12.4 GHz).     

Electrically conductive,melt-processed polyaniline/EVA blends

Mechanical blends of ethylene–vinyl acetate copolymer and polyaniline doped with dodecyl benzene sulfonic acid (PAni–DBSA) were prepared in a two-roll mill at 50°C and in a Haake internal mixer at 150°C. The effects of the blend composition and processing conditions on the electrical conductivity and mechanical properties were investigated. These blends exhibited high levels of electrical conductivity at a small amount of PAni complex. Blends prepared in a two-roll mill displayed conductivity values as high as 1 S/cm and a higher protonation degree than the pure PAni–DBSA, as indicated by X-ray photoelectron spectroscopy. Two different insulator–conductor transition points were observed in these blends. The mechanical performance decreased as the amount of PAni–DBSA increased, indicating blend incompatibility and a plasticizing effect of the DBSA. The morphology of the blends were studied by scanning electron microscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 114–123, 2001     

Preparation and Properties of High Performance Multilayered PANi/PMMA/PPG-b-PEG-b-PPG/FGHMDA Nanocomposites via in Situ Polymerization

In this attempt, novel conjugated polymer/graphite nanocomposites with exposed surface area were fabricated by in situ polymerization using polyaniline, poly(methyl methacrylate) and poly(propylene glycol)-block-poly(ethylene glycol) block- poly(propylene glycol) as matrices and functionalized graphite as a filler. Structural and morphological analysis revealed the modification of graphite as well as oxidative polymerization of numerous matrices over the surface of modified graphite ensuing multilayered nanocomposites. The increased values of T_g (59 and 103°C) obtained from thermal analysis reflect the improved thermal stability of prepared nanocomposites and exhibit better adsorption capacity (35.5cm³/g). Maximum electrical conductivity (7.4 S/cm) was also observed for multilayered nanocomposite.     

Electrical conductivity modeling of carbon‐filled liquid‐crystalline polymer composites

Electrically conductive resins are needed for bipolar plates used in fuel cells. Currently, the materials for these bipolar plates often contain a single type of graphite powder in a thermosetting resin. In this study, various amounts of two different types of carbon, carbon black and synthetic graphite, were added to a thermoplastic matrix. The resulting single‐filler composites were tested for electrical conductivity, and electrical conductivity models were developed. Two different models, the Mamunya and additive electrical conductivity models, were used for both material systems. It was determined how to modify these models to reduce the number of adjustable parameters. The models agreed very well with experimental data covering a large range of filler volume fractions (from 0 to 12 vol % for the carbon black filled composites and from 0 to 65 vol % for the synthetic graphite filled composites) and electrical conductivities (from 4.6 × 10^?17 S/cm for the pure polymer to 0.5 S/cm for the carbon black filled composites and to 12 S/cm for the synthetic graphite filled composites). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3293–3300, 2006     

Synthesis of needle‐like polyanilines

Needle‐like polyanilines were prepared in aqueous media by chemical oxidation. p‐Toluenesulfonic acid (pTSA) was used to protonate aniline (ANi) and readily made the anilinium complex. By slowly adding ammonium peroxydisulfate (APS) at 15°C, polyanilines were prepared in the micelles and grew to be needle‐like aggregates potentially useful as conductive fillers for electromagnetic interference shielding and radar‐absorbing materials. The needle‐like aggregates of protonated polyaniline prepared at 15°C and 0.5 M aniline concentration with 3 h of APS addition time showed conductivity up to 3 S/cm and a maximum aspect ratio of 26 L/D. They were observed by scanning electron microscopy to peel off partially into fibrils after washing. The needle‐like polyaniline‐pTSA complexes prepared with 0.5 M aniline concentration showed good thermal stability up to 200°C. The high conductivity of the needle‐like aggregates was ascribed to their well‐developed crystalline structures, compared with those of spherical particles. J. VINYL ADDIT. TECHNOL., 13:76–86, 2007. © 2007 Society of Plastics Engineers.     

Microstructure,Thermal Conductivity,and Electrical Properties of In Situ Pressureless Densified SiC–BN Composites

The microstructure, thermal conductivity, and electrical properties of pressureless densified SiC–BN composites prepared from in situ reaction of Si₃N₄, B₄C, and C were systematically investigated, to achieve outstanding performance as substrate materials in electronic devices. The increasing BN content (0.25–8 wt%) in the composites resulted in finer microstructure, higher electrical resistivity, and lower dielectric constant and loss, at the expense of only slight degradation of thermal conductivity. The subsequently annealed composites showed more homogeneous microstructures with less crystal defects, further enhanced thermal conductivities and electrical resistivities, and reduced dielectric constants and losses, compared with the unannealed ones. The enhanced insulating performance, the weakened interface polarization, and the reduced current conduction loss were explained by the gradual equalization of dissolved B and N contents in SiC crystals and the consequent impurity compensation effect. The schottky contact between graphite and p‐type SiC grains presumably played a critical role in the formation of grain‐boundary barriers. The annealed composites doped with 8 wt% BN exhibited considerably high electrical resistivity (4.11 × 10¹¹ Ω·cm) at 100 V/cm, low dielectric constant (16.50), and dielectric loss (0.127) at 1 MHz, good thermal conductivity [66.06 W·(m·K)^?1] and relatively high strength (343 MPa) at room temperature.     

Highly filled graphite polybenzoxazine composites for an application as bipolar plates in fuel cells

Highly filled graphite polybenzoxazine composites as bipolar plate material for polymer electrolyte membrane fuel cell (PEMFC) are developed. At the maximum graphite content of 80 wt % (68 vol %), storage modulus was increased from 5.9 GPa of the neat polybenzoxazine matrix to 23 GPa in the composite. Glass transition temperatures (T_g) of the composites were ranging from 176°C to 195°C and the values substantially increased with increasing the graphite contents. Thermal conductivity as high as 10.2 W/mK and electrical conductivity of 245 S cm^?1 were obtained in the graphite filled polybenzoxazine at its maximum graphite loading. The obtained properties of the graphite filled polybenzoxazine composites exhibit most values exceed the United States department of energy requirements for PEMFC applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3909–3918, 2013     

Microstructure,thermal and electrical properties of polyaniline/phenolic composite aerogel

Phenolic aerogel was first fabricated by sol–gel polymerization and freeze-drying method. Then, it was soaked into aniline solvent for 1 day. Ultimately, polyaniline/phenolic (PANI/RF) composite aerogel was obtained after the aniline molecules inside the phenolic aerogel were polymerized into polyaniline. The microstructure, thermal and electrical properties of the composites were investigated. The experimental results showed that polyaniline wires adhere to the surface of the micro holes skeleton which can be observed from the SEM images. Thus, polyaniline wires will form much smaller network inside the RF network, exhibiting an interpenetrating 3D network structure. In addition, compared with RF aerogel, PNAI/RF aerogel had maintained the thermal performance well, which showed mildly decline in heat-resistance and increase in heat conductivity, respectively. What’s more, it exhibited superior electrical performance (good specific capacitance) as compared with that of RF aerogel which is non-conducting, In general, PANI/RF aerogel with low heat conductivity (0.021 W/mK), high electrical conductivity (0.12 S/cm) and specific capacitance (280 F/g) exhibited more excellent comprehensive performance than single RF aerogel.     

Electrical conductivity and thermal properties of acrylonitrile‐butadiene‐styrene filled with multiwall carbon nanotubes

Composites of Acrylonitrile‐butadiene‐styrene (ABS) and multiwall carbon nanotubes (MWNTs) have been prepared via solution‐blending. The electrical conductivity of these composites is analyzed. The MWNT‐filled ABS shows percolation point of the electrical conductivity at low filler loadings (1–2 wt%). The micro‐structure of the composites is also analyzed by scanning electron microscopy showing that the nanotubes are dispersed quite homogeneously in the polymer‐matrix. The thermogravimetric analysis is used to study the thermal degradation of ABS/MWNTs composites in nitrogen. MWNTs tend to destabilize the ABS matrix in the 220–450°C degradation regions but improve the thermal stability in the 425–850°C regions. With further addition of MWNTs, the features of the destabilization in the 220–450°C degradation region did not change much but in the 425–850°C degradation process, the MWNTs reinforced stabilization and the quality of the char residue of amorphous carbon deposition was improved. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Preparation and performance of PANI–PVA composite film doped with HCl

The polyaniline (PANI)–poly (vinyl alcohol) (PVA) composite film doped with HCl was prepared by adopting PVA as matrix. Effects of PVA content and film drying temperature on properties of HCl–PANI–PVA composite film were studied. A comparison was made for tensile strength, elasticity, conductivity and thermal stability of PVA, HCl–PANI or HCl–PANI–PVA. PVA film presented the highest tensile strength and elasticity (150.8?MPa and 300.0%), but its conductivity was the lowest. The conductivity of HCl–PANI–PVA was the highest (1500?S?m^?1), and tensile strength and elasticity of HCl–PANI–PVA were higher than those of HCl–PANI. The order of their thermal stability is PVA?>?HCl–PANI?>?HCl–PANI–PVA before 260°C, and the order of their thermal stability is HCl–PANI?>?HCl–PANI–PVA?>?PVA after 260°C. At the same time, the structure and conductive mechanism of composite materials were characterised and analysed through infrared and scanning electron microscopy (SEM).     

Electrical conductivity and EMI shielding effectiveness of polyurethane foam–conductive filler composites

The morphological, electrical, and thermal properties of polyurethane foam (PUF)/single conductive filler composites and PUF/hybrid conductive filler composites were investigated. For the PUF/single conductive filler composites, the PUF/nickel‐coated carbon fiber (NCCF) composite showed higher electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) than did the PUF/multiwall carbon nanotube (MWCNT) and PUF/graphite composites; therefore, NCCF is the most effective filler among those tested in this study. For the PUF/hybrid conductive fillers PUF/NCCF (3.0 php)/MWCNT (3.0 php) composites, the values of electrical conductivity and EMI SE were determined to be 0.171 S/cm and 24.7 dB (decibel), respectively, which were the highest among the fillers investigated in this study. NCCF and MWCNT were the most effective primary and secondary fillers, and they had a synergistic effect on the electrical conductivity and EMI SE of the PUF/NCCF/MWCNT composites. From the results of thermal conductivity and cell size of the PUF/conductive filler composites, it is suggested that a reduction in cell size lowers the thermal conductivity of the PUF/conductive filler composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44373.     

ASA/graphite/carbon black composites with improved EMI SE,conductivity and heat resistance properties

Composites, comprised of acrylonitrile styrene acrylate copolymer (ASA)/graphite (GR) with high electromagnetic interference shielding effectiveness (EMI SE), were fabricated by the introduction of carbon black (CB). The effects of CB on properties such as EMI SE, morphology, heat resistance, rheological and mechanical performance of the composites were characterized using a scanning electron microscope (SEM), rotational rheometer, electromagnetic shielding measuring instruments. The graphite and carbon black exhibited positive synergistic action, which promoted the complete formation of conductive networks in ASA matrix. The EMI SE and electrical conductivity of the ASA/GR/CB composites increased with higher CB loadings. In the frequency range of 30–3000 MHz, the maximum EMI SE of ASA composites with 50 % fillers reached 40 dB, but with 40 % fillers this property reached its maximum value of 50 dB. The flexural strength of ASA/GR/CB composites started to decline as CB loading exceeded 5 %. The heat resistance of the composites was improved due to the addition of CB. In this respect, the vicar softening temperature (VST) of the composites with 40 % fillers increased from 115.1 to 132.7 °C, and the VST of the composites with 50 % fillers was elevated from 125.4 to 138.9 °C.     

Electromagnetic radiation shielding by composites of conducting polymers and wood

Polyaniline or polypyrrole composites with fir or oak wood have been prepared by in situ polymerization of the corresponding monomers in an aqueous suspension of wood sawdust. The percolation threshold of compressed coated particles is located below 5 wt % of the conducting component and, above this limit, the conductivity of most composites was higher than 10^?3 S cm^?1. The conductivity of composites containing ca 30 wt % of conducting polymer was of the order of 10^?1 S cm^?1, an order of magnitude lower than that of the corresponding homopolymers, polyaniline and polypyrrole. The conductivity stability has been tested at 175°C. The polypyrrole‐based composites generally lasted for a longer time than pyrrole homopolymers, also on account of the improved mechanical integrity of the samples provided by the presence of wood. The reverse order was found with polyaniline composites. The dielectric properties of the composites were determined in the range of 100 MHz–3 GHz, indicating that thick layers of composite material, ～ 100 mm, are needed for the screening of the electromagnetic radiation below ?10 dB level in this frequency range. Nevertheless, considering the potential production cost of composites and their low weight, such composite materials could be of practical interest in the shielding of electromagnetic interference. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 807–814, 2005     

Thermal stability and dynamic mechanical behavior of exfoliated graphite nanoplatelets‐LLDPE nanocomposites

The objective of this research was to investigate thermal stability and dynamic mechanical behavior of Exfoliated graphite nanoplatelets (xGnP™)‐Linear Low‐Density Poly Ethylene (LLDPE) nanocomposites with different xGnP loading content. The xGnP‐LLDPE nanocomposites were fabricated by solution and melt mixing in various screw rotating systems such as co‐, counter‐, and modified‐corotating. The storage modulus (E′) of the composites at the starting point of −50°C increased as xGnP contents increased. E′ of the nanocomposite with only 7 wt% of xGnP was 2.5 times higher than that of the control LLDPE. Thermal expansion and the coefficient of thermal expansion of xGnP‐loaded composites were much lower than those of the control LLDPE in the range of 45–80°C (299.8 × 10⁻⁶/°C) and 85–100°C (365.3 × 10⁻⁶/°C). Thermal stability of the composites was also affected by xGnP dispersion in LLDPE matrix. The xGnP‐LLDPE nanocomposites by counter‐rotating screw system showed higher thermal stability than ones by co‐rotating and modified‐co‐rotating system at 5 wt% and 12 wt% of xGnP. xGnP had a great effect on high thermal stability of xGnP‐LLDPE composites to be applied as tube and film for electrical materials. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Synthesis and characterization of novel poly(aniline-co-m-aminoacetophenone) copolymer nanocomposites using dodecylbenzene sulfonic acid as a soft template

A series of dodecylbenzene sulphonic acid (DBSA) doped poly(aniline-co-m-aminoacetophenone) copolymer composites of different compositions were synthesized in micellar solution of DBSA to obtain nanosphere morphology with enhanced processability. The plausible mechanism for the formation of poly(aniline-co-m-aminoacetophenone)-DBSA copolymer composite has been presented. These DBSA doped copolymer composites were characterized by UV–Visible, FTIR spectroscopy and XRD analysis techniques. UV–Vis absorption spectrum of the composites showed 325 and 637 nm which corresponds to the π–π* and n–π* transition. In FTIR spectroscopy a broad band around 2,924 cm^?1 corresponds to C–H vibration of DBSA indicating good agreement with the characteristic bands of DBSA. The sharp band at 1,292 cm^?1 is assigned to C–N stretching mode of vibration of N–Ph–N units. The X-ray diffraction of composites reveals that these composites are amorphous in nature. The number of diffraction peaks decreased with increase in the m-aminoacetophenone content. It indicates that these composites are amorphous in nature. Morphological studies (SEM) reveal that these composites have a spherical morphology with the average size of 100–200 nm. These composites exhibit electrical conductivity value of 0.744 × 10^?3 S/cm and enhanced solubility than polyaniline. Moreover, at the presented work, the DBSA doped copolymer composites were obtained in high yields by keeping an oxidant to co-monomer ratio of 1:1.     

Electromagnetic interference shielding of graphite/acrylonitrile butadiene styrene composites

Dispersion of graphite within the acrylonitrile butadiene styrene matrix demonstrates enhanced electromagnetic interference shielding of composites through the use of tumble mixing technique. A shielding effectiveness of 60 dB with 15 wt % of graphite has been achieved. D shore hardness data revealed a little decrease in hardness of composites with rise in graphite content. DC conductivity measurements revealed a fairly low percolation threshold at 3 wt % of graphite. The conductivity exhibited by 15 wt % composite is 1.66 × 10⁻¹ S/cm. These composites are fit for use as an effective and convenient EMI shielding material because of easy processing, better hardness, light weight, and, reasonable shielding efficiency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011