Design and fabrication of electro‐conductive polymer nanocomposites with mechanical and thermal resistance

The commencement of the industrial revolution paved the way for the fabrication of flexible polymers with high‐strength metalloceramics as novel materials of all kinds. Fabricating metal–ceramic/polymer conductive composites is one such dimension followed for the present research work making use of the properties of the three components. Electroless deposition, for permanent metallic coating, was performed to coat Al₂O₃ with metallic Cu followed by the inclusion of the Cu–Al₂O₃ filler into a poly(vinyl chloride) (PVC) matrix. X‐ray diffraction and energy‐dispersive X‐ray studies predicted a prominent growth of metallic Cu crystallites onto Al₂O₃ with an increased average size and variation in elemental composition, respectively, when compared to pristine Al₂O₃. Morphological behaviour via scanning electron microscopy also envisioned uniform Cu coating onto Al₂O₃ and a homogeneous dispersion throughout the polymer matrix. When incorporated into PVC, electrical conductivity analysis highlighted a distinct variation in composite phases from insulating (7.14 × 10^?16 S cm^?1) to semiconducting behaviour (8.33 × 10^?5 S cm^?1) as a function of Cu–Al₂O₃ filler. Mechanical behaviour (tensile strength, Young's modulus and elongation at break) and thermal properties of the prepared composites also indicated a substantial improvement in material strength with Cu–Al₂O₃ incorporation. The enhanced electrical conductivity along with improved thermomechanical status with significant filler–matrix interaction permits the potential usage of such novel composites in a range of state‐of‐the‐art semiconducting electronic devices. © 2018 Society of Chemical Industry     

Comparison of pristine and polyaniline‐grafted MWCNTs as conductive sensor elements for phase change materials: Thermal conductivity trend analysis

Phase change materials (PCMs) function based on latent heat stored on or released from a substance over a slim temperature range. Multiwalled carbon nanotubes (MWCNTs) and polyaniline are important elements in sensor devices. In this work, pristine and polyaniline‐grafted MWCNTs (PANI‐g‐MWCNTs) were applied as conductive carbon‐based fillers to make PCMs based on paraffin. The attachment of PANI to the surface of MWCNTs was proved by Fourier transform Infrared analysis. Dispersion of MWCNTs in paraffin was studied by wide‐angle X‐ray scattering. Heating and solidification of PCM nanocomposites were investigated by differential scanning calorimetry, while variation in nanostructure of PCMs during heating/solidification process was evaluated by rheological measurements. It was found that after 30 min of sonication, the samples filled with 1 wt % MWCNTs have melting and solidification temperatures of 29 and 42 °C, respectively. It was also found that PANI attachment to MWCNTs significantly changes thermal conductivity behavior of PCM nanocomposites. The developed MWCNTs‐based sensor elements responded sharply at low MWCNTs content, and experienced an almost steady trend in conductivity at higher contents, while PANI‐g‐MWCNTs sensor followed an inverse trend. This contradictory behavior brought insight for understanding the response of PCMs against thermal fluctuations. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45389.     

Synthesis of polypyrrole/indium tin oxide nanocomposites via miniemulsion polymerization

Polypyrrole/indium tin oxide nanocomposites were synthesized via in situ miniemulsion polymerization of pyrrole monomer in the presence of indium tin oxide nanoparticles. Different nanocomposites were synthesized by different loadings of nano indium tin oxide. The morphology and nanoparticles distribution of the nanocomposites were characterized by electron microscopy. The results of XRD and TEM analysis showed that indium tin oxide nanoparticles were well placed in the polymeric structure of latex. FTIR analysis was used for the characterization of synthesized polypyrrole and its nanocomposites. TGA analysis was performed to investigate the thermal behavior of pristine polypyrrole and its nanocomposites. Conductivities of nanocomposites were measured by 4-point probe method and compared to the neat polymer.     

HCl和TSA共掺杂聚苯胺/凹土纳米导电复合材料

用快速原位聚合工艺制备了盐酸(HCl)和对甲苯磺酸(TSA)共掺杂聚苯胺(PANI)/凹土(ATP)纳米复合材料.通过正交实验确定了最佳反应条件,并用紫外-可见光谱、热重-差热分析、X射线衍射、Fourier红外光谱、透射电镜等对最佳条件下所得的纳米复合材料进行了表征.结果表明:HCl和TSA的混酸环境能快速实现苯胺的聚合及聚苯胺的掺杂,所生成的聚苯胺以晶态形式包覆在凹土的表面,并在物理作用下与凹土形成了纳米核壳结构纳米复合材料;纳米复合材料中聚苯胺的包覆率为23.49%,与纯HCl和TSA共掺杂聚苯胺相比,纳米复合材料的耐热性能得到提高.     

Electrically conductive nanocomposites of polyaniline with poly(vinyl alcohol) and methylcellulose

Electrically conductive nanocomposites of HCl‐doped polyaniline (PANI–HCl) nanocolloid particles with water‐soluble and film‐forming polymers such as poly(vinyl alcohol) (PVA) and methylcellulose (MC) were prepared by the redispersion of preformed MC‐coated submicrometric PANI–HCl particles in PVA and MC solutions under sonication for 1 h and the casting of the films from the dispersions followed by drying. The submicrometric polyaniline (PANI) particles were prepared by the oxidative dispersion polymerization of aniline in an acidic (1.25M HCl) aqueous ethanol (30 : 70) medium with MC as a steric stabilizer. The particles contained 4.7 wt % MC and had a conductivity of 7.4 S/cm. They had an oblong shape of 203 nm (length) and 137 nm (breadth). Sonication broke the oblong‐shaped particles to sizes of ～10 nm in the PVA matrix and ～60 nm in the MC matrix. The electrical conductivity of these films was measured, and the percolation threshold was determined. The composites had the characteristics of a low percolation threshold at a volume fraction of PANI of 2.5 × 10^?2 in the PVA matrix and at a volume fraction of 3.7 × 10^?2 in the MC matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of conductive polylactic acid/high density polyethylene/carbon black composites with low percolation threshold by locating the carbon black at the Interface of co-continuous blends

In the current study, polylactic acid/high density polyethylene/carbon black (PLA/HDPE/CB) composites are prepared via a two-step method. A double percolation network with co-continuous structure and filler distribution at the interface is constructed to design conductive polymer composites with low percolation threshold. The controllable distribution of CB at the interface is achieved by appropriate processing procedures involved mixing sequence and mixing time by taking advantage of the migration of CB from the unfavorable PLA phase to the favorable HDPE phase. Morphology characterization reveals that when the mixing time of the added HDPE is 3 min, the formation of co-continuous structure of PLA/HDPE (60/40, w/w) is observed, and CB particles migrate to the co-continuous interface. The electrical conductivity measurement shows that such double percolation conductive network reduces the percolation threshold of PLA/HDPE/CB to 2.42 wt%. The rheological property proves the establishment of particle percolation network, and the rheological percolation threshold is determined as 1.20 wt%. The prepared PLA/HDPE/CB composite by the two-step method displays a notably low percolation threshold than that prepared by one-step simultaneous mixing. Moreover, this strategy presents a high potential application in the fabrication of conductive polymer composites involving other miscible multiphase systems.     

Electrically conductive polystyrene nanocomposites incorporated with aspect ratio-controlled silver nanowires

Polymer nanocomposites consisting of electrically conductive nanofillers with high aspect ratios are widely utilized for high-performance applications such as sensors and electronics. Silver nanowires (AgNWs) synthesized through polyol reduction have been reported to show excellent electrical conductivity, hydrophilicity, and high aspect ratios. In this study, the influence of the aspect ratios of the AgNWs on the rheological and electrical properties of the fabricated polystyrene (PS)/AgNW nanocomposites was chiefly investigated. The nanocomposites were made by combining a dispersion of AgNWs with a suspension of PS particles, followed by freeze-drying the PS/AgNW mixture harnessing the latex technology. Scanning electron microscopy, UV–Vis spectroscopy, and thermogravimetric analysis were performed on the nanocomposites to investigate the morphological, optical, and thermal properties, respectively; in addition, X-ray photoelectron spectroscopy was performed to examine the hydrophilic polymer poly(vinylpyrrolidone)-capped AgNW surfaces. The rheological behavior of the nanocomposites changed from liquid-like to solid-like after the addition of AgNWs with high aspect ratios. The electrical percolation threshold of the AgNWs in the nanocomposites was determined by the aspect ratio of the nanofiller rather than by its length. Thus, the various properties of the PS/AgNW nanocomposites could be tuned by tailoring the aspect ratios of the AgNWs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47927.     

Assessment of mechanical performance,thermal stability and water resistance of novel conductive poly(lactic acid)/modified natural rubber blends with low loading of polyaniline

Biodegradable conductive polymer blends made from poly(lactic acid) (PLA), liquid natural rubber (LNR) and polyaniline (PANI) were prepared via a melt‐blending technique assisted by ultrasonic treatment. The effects of PANI at low loading (0.03 to 0.11 wt%) on the electrical conductivity and mechanical, thermal and physical properties of PLA/LNR/PANI blends were investigated. It was found that the mechanical properties of samples improved when PANI was introduced into PLA/LNR. Tensile results showed that the optimum loading of PANI was achieved at 0.07 wt% with an improvement of 8% in tensile strength compared to neat PLA/LNR. Although it was at low loading, the incorporation of PANI promoted an outstanding electrical conductivity to PLA/LNR blends. Thermal analysis of the PLA/LNR/PANI blends was conducted using differential scanning calorimetry and thermogravimetry. The thermal stabilities of the blends were improved markedly with the presence of PANI. Comparing to PLA/LNR, the incorporation of PANI component improved the resistance towards water absorption. Variable‐pressure scanning electron microscopy micrographs of PLA/LNR/PANI confirmed the good mixing of PANI with PLA/LNR and strong interaction networks among the PANI, PLA and LNR components. © 2018 Society of Chemical Industry     

Temperature and time dependence of electrical resistivity in an anisotropically conductive polymer composite with in situ conductive microfibrils

An anisotropically conductive polymer composite (ACPC) based on conductive carbon black (CB) and binary polymer blend of polyethylene (PE) and polyethylene terephthalate (PET) was successfully fabricated under shear and elongational flow fields. The PET phase formed in situ the aligned conductive microfibrils whose surfaces were coated by CB particles. This ACPC material exhibited a strong electrical anisotropy within a broad temperature range. When the ACPC samples were subjected to isothermal treatment (IT), they showed anomalous variations of the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effects. The PTC intensity was attenuated gradually with the increase of the IT time, and the NTC intensity was nearly eliminated after IT of 8 or 16 h. Beyond 16 h, the resistivity in the NTC region rose anomalously with the temperature after the elimination of NTC effect, which was the result of much transformation from the potential pathways to the intrinsic pathways due to the disordering of oriented conductive microfibrils. When the amount of potential pathways was very small, the effect of the intrinsic pathway separation surmounts that of the potential pathways, leading to the anomalous resistivity increase in the NTC region. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Interaction of dendronized polymeric nanocomposites with isomeric cyclohexanediols

Dendronized poly(diethylaminoethyl methacrylamide) (PEAM) was studied in blends containing isomeric cyclic dialcohols. Monomers and polymers were characterized by spectroscopic measurements. The phase behaviors of blends of PEAM with 1,2‐, 1,3‐ and 1,4‐cyclohexanediols (1,2‐CHD, 1,3‐CHD and 1,4‐CHD, respectively) were established. Transparent films of the blends exhibited a single glass‐transition temperature (T_g). Thermogravimetric analysis (TGA) revealed the temperature at which the polymer releases the small molecules. UV‐vis spectra of 1,3‐CHD and 1,4‐CHD derivatives showed an isosbestic point that indicated the association of the alcohols. FT‐IR measurements showed shifts in several absorption bands. The results were analyzed in terms of the side‐chain structure and the interactions involved. AFM measurements revealed differences between the polymer and the blends. Compatibilization of blends of PEAM/CHDs occurred via the formation of hydrogen bonds, although hydrophobic interactions could not be disregarded. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42267.     

Pyroresistivity in conductive polymer composites: a perspective on recent advances and new applications

Conductive polymer composites (CPCs) with pyroresistive behaviour are of interest for a wide variety of applications such as safe batteries, resettable fuses, temperature sensors and self‐regulating heating devices. Due to their ease of processing, low density, tunable electrical properties, good oxidation resistance, and good flexibility and toughness, CPCs have become the preferred choice of pyroresistive materials in a number of applications. The pyroresistive behaviour of CPCs can be tuned to satisfy the specific requirements of different applications. In this perspective paper, recent progress in the use of pyroresistive CPCs is reviewed. In particular, various factors influencing their performance are discussed and compared, in connection with the associated application, with a special focus on reproducibility and positive temperature coefficient intensity levels. Some of the remaining challenges are identified, together with future prospects in this evolving field. © 2018 Society of Chemical Industry     

Anisotropic alignment of nickel particles in a magnetic field for electronically conductive adhesives applications

Anisotropically conductive adhesives were developed by magnetic alignment of conductive nickel particles in a non-conductive epoxy matrix. Conductivity occurs in the direction of the magnetic field applied to the adhesive film. The effects of magnetic and conducting nickel filler type (i.e. powders, filaments, flakes, and fibers), resin viscosity, and the magnitude of aligning magnetic field on the electrical properties of the resulting anisotropic adhesive were investigated. The electrical resistance of the anisotropic adhesive was measured using the four-point probe method. The resistance of the filled adhesive decreased with increasing viscosity and the intensity of the magnetic field.     

Structure and magnetic properties of CoFe2O4/SiO2 nanocomposites obtained by sol-gel and post annealing pathways

The influence of the CoFe₂O₄ nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe₂O₄/(100−x)SiO₂ nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe₂O₄ nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe₂O₄ nanoparticles have spherical shapes and size in the 6–35 nm range. The Mössbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe₂O₄ nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.     

Structure and crystallization behavior of Nylon 66/multi-walled carbon nanotube nanocomposites at low carbon nanotube contents

Multi-walled carbon nanotubes (MWNTs) were modified with poly(hexamethylene adipamide) (also known as Nylon 66) via a controlled polymer solution crystallization method. A “nanohybrid shish kebab” (NHSK) structure was found wherein the MWNT resembled the shish while Nylon 66 lamellar crystals formed the kebabs. These Nylon 66-functionalized MWNTs were used as precursors to prepare polymer/MWNT nanocomposites. Excellent dispersion was revealed by optical and electron microscopies. Nitric acid etching of the nanocomposites showed that MWNT formed a robust network in Nylon 66. Non-isothermal DSC results showed multiple melting peaks, which can be attributed to lamellar thickness changes upon heating. The crystallite sizes L₁₀₀ and L₀₁₀ of Nylon 66, determined by WAXD, decreased with increasing MWNT contents. Isothermal DSC results showed that crystallization kinetics increased first and then decreased with increasing MWNT contents in Nylon 66. This study showed that the effect of MWNTs on Nylon 66 crystallization is twofold: MWNTs provide heterogeneous nucleation sites for Nylon 66 crystallization while the tube network structure hinders large crystal growth.     

Single-step process for transparent conductive ZnO:Ga films with uniform ultrahigh haze by oblique angle deposition

Increasing the haze of front electrodes of solar cells while retaining high optical transmittance is beneficial for increasing the power conversion efficiency. However, conventional methods of fabricating hazy films require additional etching steps or materials. Moreover, depositing large-area transparent conductive oxides with uniform ultrahigh haze is challenging. Here, we combine the oblique angle deposition and the atmospheric pressure plasma jet to produce GZO with a uniform ultrahigh haze of > 80% (non-uniformity ~1.35%), high transmittance of 88% (referenced to the substrate), and resistivity of 1.96 × 10^–3 Ω cm in a single step. We show that the high haze is caused by the “pre-deposition” of adsorbed particles on the bare substrate downstream and that the upstream dummy area should be avoided for high uniformity. Unlike existing methods, our method produces uniform films with ultrahigh haze and good transmittance in a single step without additional etching/ materials or changing parameters during operation.     

Improvement in voltage,thermal, mechanical stability and ion transport properties in polymer‐clay nanocomposites

We report novel results on optimization of intercalated polymer‐clay nanocomposite endowed with desirable properties like, (i) very high ionic conductivity (～ 10^?3 S cm^?1) at room temperature, (ii) substantial improvement in voltage stability (～ 5.6 V), mechanical stability (25 MPa), and thermal stability (250°C) (iii) t_ion ～ 99% and cation transport number (t_Li+) ～ 67%: Intercalation of polymer salt (PAN)₈LiCF₃SO₃ complex into dodecylamine modified montmorillonite clay (DMMT) nanometric channels has been confirmed by X‐ray diffraction and Transmission electron microscopy analysis. Complex impedance spectroscopy suggests bulk electrical conduction in the high frequency region and electrode polarization effect at the low frequencies. The experimental value of conductivity, voltage, and mechanical stability is observed to be invariably higher in polymer nanocomposite film when compared with clay free polymer‐salt complex film. The same is true for cation transport. The optimized polymer film serves dual purpose of electrolyte and separator in energy storage devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Design of sandwich structure conductive polypropylene/styrene-butadiene-styrene triblock copolymer/carbon black composites with inherent morphological tunability

The insulator-conductor transition of conductive polymer composites (CPCs) can be ascribed to the fabrication of conductive networks, and the morphology of conductive networks plays a significant role in the electrical conductivity. This study presents CPCs with inherent morphology tunability which can be controlled by kinetic methods (i.e., mixing procedures and sequences, and polymer melt viscosity). Polypropylene (PP)/styrene-butadiene-styrene block copolymer (SBS) (50/50, in volume)/10 phr (parts per hundred of the polymer matrix) conductive carbon black (CB) composites prepared by different compounding sequences (PP/CB composites mixed with SBS, SBS/CB composites mixed with PP, and PP/SBS blend mixed with CB) are named as PC₁₀S, SC₁₀P, and PSC₁₀. With the difference between the phase morphologies, distribution, and dispersion of CB, the PP/SBS/CB composites realize seven orders of magnitude difference in resistivity. The volume resistivity (ρ_v) of PC₁₀S SC₁₀P and PSC₁₀ are 1.57 × 10¹, 1.68 × 10², and 4.88 × 10⁸ Ω m, respectively.     

P(VDF-TrFE)-based polymer nanocomposites comprising of reduced graphene oxide decorated with CoFe2O4@MCM 41 for efficient microwave absorption in X-band

Lightweight polymer nanocomposites (PNCs) dispersed with nanofiller RGO/CoFe₂O₄@MCM41, namely RCM (using hydrothermal process), have been prepared and characterized. Using the solution cast technique, PNCs {(P(VDF-TrFE)/LiTFSI/EMIMTFSI) + x wt% RCM, where x = 5, 7.5, and 10 in wt%} have been successfully synthesized. The synthesized PNCs possess good structural, thermal, mechanical, and magnetic properties because of the dispersed nanofiller within the polymeric matrix, which forms a 3-dimensional interconnected conducting network. The optimized PFE15Li50IL7.5RCM polymer nanocomposite also exhibits total shielding effectiveness (SE_T) of ~19.88 dB at 9.2 GHz for a thickness of 1.18 mm corresponding to 89.07% effective absorption (A_eff) in the X-band (8.2–12.4 GHz).