EMI shielding effectiveness and dielectrical properties of SBS/PAni.DBSA blends: Effect of blend preparation

This work investigates the effect of different preparation routes including mechanical mixing and in situ polymerization of aniline on the electromagnetic interference shielding effectiveness (EMI SE) over the X-band (8–12 GHz) frequency range for polyaniline doped with dodecylbenzene sulfonic acid (PAni.DBSA) filled in styrene–butadiene–styrene triblock copolymer matrix. The dc conductivity and dielectrical properties were also investigated. For all systems, the electrical conductivity, dielectric constant, and EMI SE increased with the increase in the concentration of PAni.DBSA. Blends prepared by the in situ polymerization exhibited higher conductivity and dielectric constant and better EMI SE characteristics than the physical blends with similar amount of PAni.DBSA. EMI SE value as high as −35 dB has been achieved with about 30% of PAni.DBSA prepared by the in situ polymerization. Regarding physical blends, those involving PAni.DBSA prepared by a redoping process displayed better EMI SE. For all systems under consideration, the conductivity and EMI SE bear an exponential relationship that can be represented by a master curve. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of ethylene vinyl‐acetate/polyaniline blends prepared by emulsion polymerization technique

A series of ethylene vinyl acetate‐polyaniline (98/02, 95/05, 93/07, … … 50/50) (EVA‐PAni) blends were prepared by the emulsion polymerization technique and made into sheets by the compression molding at 150°C. These sheets were characterized by electrical, physico‐mechanical, thermal, X‐ray and morphological studies. All electrical properties of EVA‐(PAni)_TSA blends increased with an increase in PAni content. The conductivity, dielectric constant and tan δ values increased from 1.34 × 10^?14 to 2.89 × 10^?2 S/cm, from 2.113 to 19.845, from 0.094 to 4.789. Tensile strength increased with an increase in PAni content up to 7% and drastically decreased above 15%, while the percentage elongation at break decreased with an increase in PAni content. TGA studies revealed that the thermal stability of PAni improved after blending with EVA. EVA‐PAni blends were found stable up to 110°C. X‐ray diffractograms of EVA‐PAni blend showed an intense peak at 26° (2θ), reflecting the influence of EVA crystallinity. Scanning electron micrographs confirmed the two‐phase morphology of the system.     

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     

Electrically conductive composites of polyurethane derived from castor oil with polypyrrole‐coated peach palm fibers

Electrically conducting fibers were prepared through in situ oxidative polymerization of pyrrole (Py) in the presence of peach palm fibers (PPF) using iron (III) chloride hexahydrate (FeCl₃·6H₂O) as oxidant. The polypyrrole (PPy) coated PPF displayed a PPy layer on the fibers surface, which was responsible for an electrical conductivity of (2.2 ± 0.3) × 10⁻¹ S cm⁻¹, similar to the neat PPy. Electrically conductive composites were prepared by dispersing various amounts of PPy‐coated PPF in a polyurethane matrix derived from castor oil. The polyurethane/PPy‐coated PPF composites (PU/PPF–PPy) exhibited an electrical conductivity higher than PU/PPy blends with similar filler content. This behavior is attributed to the higher aspect ratio of PPF–PPy when compared with PPy particles, inducing a denser conductive network formation in the PU matrix. Electromagnetic interference shielding effectiveness (EMI SE) value in the X‐band (8.2–12.4 GHz) found for PU/PPF–PPy composites containing 25 wt% of PPF–PPy were in the range −12 dB, which corresponds to 93.2% of attenuation, indicating that these composites are promising candidates for EMI shielding applications. POLYM. COMPOS., 38:2146–2155, 2017. © 2015 Society of Plastics Engineers     

Effect of pressure on the structure and electrical conductivity of cardanol–furfural–polyaniline blends

Pressure‐sensitive polymers that simultaneously present reasonable electrical conducting properties, useful thermosetting behavior, and softness are hard to develop. To combine these properties into a single material, a cardanol‐based phenolic resin was prepared and blended in situ with polyaniline (PAni). The final polymer blend was composed of a soft solid material that could not be dissolved in ordinary solvents. Samples were characterized through X‐ray scattering, Fourier transform infrared (FTIR) spectroscopy, and electrical conductivity and pressure sensitivity measurements. FTIR results indicate that the insertion of PAni into the blends did not change the chemical nature of the resin. According to wide‐angle X‐ray scattering results, PAni was dispersed homogeneously in the final polymer samples; this improved the sensitivity of the electrical conductivity to pressure variations, as confirmed through electromechanical tests. Pressure sensitivity and electromechanical analyses indicated that the produced blends could be used as pressure‐sensing materials. Among the tested materials, the blends containing 5 wt % PAni·H₂SO₄ presented the largest compression sensitivity values. Finally, it was shown for the first time through XRD analyses under pressure that PAni chains were considerably disturbed by compressive stresses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization behavior and hydrophilicity of poly(vinylidene fluoride)/poly(methyl methacrylate)/poly(vinyl pyrrolidone) ternary blends

Ternary blends composed of matrix polymer poly(vinylidene fluoride) (PVDF) with different proportions of poly(methyl methacrylate) (PMMA)/poly(vinyl pyrrolidone) (PVP) blends were prepared by melt mixing. The miscibility, crystallization behavior, mechanical properties and hydrophilicity of the ternary blends have been investigated. The high compatibility of PVDF/PMMA/PVP ternary blends is induced by strong interactions between the carbonyl groups of the PMMA/PVP blend and the CF₂ or CH₂ group of PVDF. According to the Fourier transform infrared and wide‐angle X‐ray difffraction analyses, the introduction of PMMA does not change the crystalline state (i.e. α phase) of PVDF. By contrast, the addition of PVP in the blends favors the transformation of the crystalline state of PVDF from non‐polar α to polar β phase. Moreover, the crystallinity of the PVDF/PMMA/PVP ternary blends also decreases compared with neat PVDF. Through mechanical analysis, the elongation at break of the blends significantly increases to more than six times that of neat PVDF. This confirms that the addition of the PMMA/PVP blend enhances the toughness of PVDF. Besides, the hydrophilicity of PVDF is remarkably improved by blending with PMMA/PVP; in particular when the content of PVP reaches 30 wt%, the water contact angle displays its lowest value which decreased from 91.4° to 51.0°. Copyright © 2011 Society of Chemical Industry     

Investigation of the electric conductivity and the electromagnetic interference shielding efficiency of SWCNTs/GNS/PAni nanocomposites

This work demonstrates the fabrications and characterizations of polyaniline (PAni) composites containing single-walled carbon nanotubes (SWCNTs), graphite nanosheets (GNS), or hybrid fillers (SWCNTs/GNS). The characterization of microstructure, examination of fracture surface morphologies, and measurement of electric conductivity and electromagnetic interference shielding efficiency (EMI SE) were performed. It was found that both the electric conductivity and the EMI SE increase with filler loading, and the nanocomposites filled with 1.0 wt.% SWCNTs/GNS possessed the highest electric conductivity of 16.2 S/cm and total EMI SE of 27.0 dB. The experimental results also show that absorption is the primary mechanism of EMI SE for all of the loadings and fillers.     

Novel poly(butylene terephthalate)/poly(vinyl butyral) blends prepared by in situ polymerization of cyclic poly(butylene terephthalate) oligomers

Blends of in situ polymerized PBT from cyclic oligomers (c-PBT) and PVB were prepared with varying compositions and compared with mechanical blends of conventional PBT and PVB. The materials were characterized by a variety of techniques including DSC, DMTA, DETA, FTIR, NMR and GPC. It was found that the in situ prepared blend of c-PBT/PVB has one glass transition temperature and shows evidence of miscibility. In contrast, the conventional blend of PBT/PVB shows incompatibility after blending. The cause of miscibility in the in situ prepared PBT/PVB blends is thought to be the formation of a graft copolymer. These results show that there are unique possibilities for in situ processing by combining polymerization of cyclic polyester oligomers with blending.     

Effect of polymer blending on the electrical conductivity of polypyrrole/copolyester composite films

Summary The effect of polymer blending on the electrical conductivity of polypyrrole/copolyester composite film was investigated. Copolyesters containing sodium sulfonate group with various main chain structures were synthesized and blended with PET. The average anionic group contents in the blend samples were controlled to be 3.5 and 6.1 mol%. The polypyrrole composite films were prepared by polymerization of pyrrole through vapor phase absorption onto the copolyester-PET blend films which contained FeCl₃. The conductivity of the blend samples containing 3.5 mol% of DMS was greater than that of the copolyester of the same DMS content when the pyrrole vapor exposure time was longer than 30 min. The blends of 6.1 mol% of DMS showed higher conductivity than the copolyesters of the same DMS amount even when the exposure time was short. The high electrical conductivity of the blend samples was thought to be due to the phase separation between PET and copolyesters in amorphous region. Received: 1 June 1998/Revised version: 5 October 1998/Accepted: 30 October 1998     

Microwave dielectric properties and EMI shielding effectiveness of poly(styrene‐b‐styrene‐ butadiene‐styrene) copolymer filled with PAni.Dodecylbenzenesulfonic acid and carbon black

Conducting composites of polyaniline doped with dodecylbenzenesulfonic acid (PAni.DBSA), carbon black (CB) and poly(styrene‐b‐styrene‐butadiene‐b‐styrene) (STF) as supporting matrix were prepared by in situ polymerization. The influence of components and composition (% w/w) on the electromagnetic properties (dielectric constant ε′ and the dielectric loss ε″) and electromagnetic interference shielding effectiveness (EMI‐SE) of the materials were evaluated with a waveguide, using a microwave network analyzer from 8.2 to 12.4 GHz (X‐band). It was found that CB presence generates adverse effects on PAni.DBSA yield during synthesis, as it can be seen by X‐ray diffraction and TGA analyses. The type of PAni.DBSA formed modifies the composites properties. Dielectric constant, loss factor, and EMI shielding increase with conductive filler loading. Both the fillers, individually and in combination, increase the properties; however, the effect is not additive in nature. POLYM. ENG. SCI., 52:2041–2048, 2012. © 2012 Society of Plastics Engineers     

Electroactive mixtures of polyaniline and EPDM rubber: Chemical,thermal, and morphological characterization

A new route for blending polyaniline (PAni) and EPDM rubber was devised with maleic anhydride as a compatibilizer precursor. Rubber matrices containing ammonium peroxidisulfate and dodecyl benzene sulfonic acid were cast from organic solvents. Exposure to the monomer vapors allowed the chemical polymerization of aniline. The influence of PAni and the compatibilizer on the thermal properties, chemical structure, electrical conductivity, and morphology of the mixtures was observed with differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, in situ conductivity measurements, and optical microscopy. The micrographs showed a good distribution of the PAni complex in the matrix. The use of approximately 2 wt % compatibilizer resulted in chemical interactions between maleic anhydride and the PAni complex formed with dodecyl benzene sulfonic acid, which could enhance the compatibility between the polymers. The obtained blends reached relative electrical conductivity values of up to 9 × 10^?3 S cm^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 535–547, 2003     

Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

Novel polymer nanocomposites comprising of MnO₂ nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10^-16S/m to 4.5 × 10^-5S/m (3.2 × 10^-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region.     

New polyaniline(PAni)-polyelectrolyte (PDDMAC) composites: Synthesis and applications

Conducting and electroactive polymer blends of polyaniline (PAni) with polyelectrolyte, poly(diallydimethylammoniumchloride) (PDDMAC) have been synthesized by an in situ polymerization method and the resulting composites have been characterized by FT-IR, UV–Vis, XRD, AFM and electrochemical techniques. The blends are conducting and electroactive with even lower loadings of PAni and can be cast as films. The conductivity of the cast films containing 0.04–1.5 wt% PAni ranged from 4.5 × 10⁻⁶ to 42 × 10⁻⁶ S/cm. Some of the composites are tested for their corrosion inhibition property for pure iron in 1 M HCl solutions and were found to be active inhibitors.     

Effect of composition on the properties of PEM based on polybenzimidazole and poly(vinylidene fluoride) blends

Inadequate performance, short term durability and high cost of polymer electrolyte membrane (PEM) are the major roadblocks that need to be resolved for successful commercialization of high temperature PEM fuel cell. In this report, we investigated the viability of previously developed miscible blend membranes of polybenzimidazole and poly (vinylidene fluoride) (PBI/PVDF), as potential PEMs. In addition, we have carried out several advanced analytical techniques such as dynamic mechanical analysis (DMA), ¹³C CP-MAS solid state NMR (SS-NMR) and wide-angle X-Ray diffraction (WAXD) to prove the miscible behavior of the polymer pair. Sub-ambient temperature DMA studies confirmed the miscible behavior of PBI/PVDF blends at different compositions based on single T_g criterion. SS-NMR and WAXD showed the presence of interactions between the functional groups of the polymers and their dependence on blend composition. Thermogravimetric analysis of phosphoric acid (PA) doped and undoped blend membranes confirmed the improved thermal stability of the membranes compared to neat PBI. The membranes exhibited excellent oxidative stability than pristine PBI membrane. The swelling ratio and volume after dipping in PA was found to be significantly low in the blend membranes owing to the hydrophobic nature of PVDF. Among the blends prepared, 90/10 and 75/25 membranes showed higher proton conductivity than PBI, attributed in part, to electronegativity of fluorine and crystallinity of PBI in PA that activate proton transport. The results demonstrated the potential usefulness of the blend membranes as PEM in fuel cell.     

Synergetic improvement in electromagnetic interference shielding characteristics of polyaniline-coated graphite oxide/γ-Fe2O3/BaTiO3 nanocomposites

Polymer nanocomposites were prepared by in situ polymerization of aniline with graphite oxide (GO), γ-Fe₂O₃, and BaTiO₃ as electromagnetic interference (EMI) shielding materials. GO, γ-Fe₂O₃, and BaTiO₃ nanoparticles were incorporated in the nanocomposites to improve the electromagnetic properties. The nanocomposites showed the significant improvement in both EMI shielding efficiency (SE) and thermal property due to the thermal conductivity of GO, the magnetic effect of γ-Fe₂O₃, and the electric effect of BaTiO₃. The EMI SE of nanocomposites was improved due to the synergetic effect of reflection and absorption of electromagnetic interference by GO, γ-Fe₂O₃, and BaTiO₃ additives.     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Electrical and Electromagnetic Interference (EMI) shielding properties of hexagonal boron nitride nanoparticles reinforced polyvinylidene fluoride nanocomposite films

The hexagonal boron nitride nanoparticles (h-BNNPs) reinforced flexible polyvinylidene fluoride (PVDF) nanocomposite films were prepared via a simple and versatile solution casting method. The morphological, thermal and electrical properties of h-BNNPs/PVDF nanocomposite films were elucidated. The electromagnetic interference (EMI) shielding properties of prepared nanocomposite films were investigated in the X-band frequency regime (8–12 GHz). The EMI shielding effectiveness (SE) was increased from 1 dB for the PVDF film to 11.21 dB for the h-BNNPs/PVDF nanocomposite film containing 25 wt% h-BNNPs loading. The results suggest that h-BNNPs/PVDF nanocomposite films can be used as lightweight and low-cost EMI shielding materials.     

Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

This work focus on the development of polymeric blends to produce multifunctional materials for 3D printing with enhanced electrical and mechanical properties. In this context, flexible and highly conductive materials comprising poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) filled with carbon black-polypyrrole (CB-PPy) were prepared by compression molding, filament extrusion and fused filament fabrication. In order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability, blends composition was optimized and different CB-PPy content were added. Overall, the electrical conductivities of PVDF/TPU 50/50 vol% co-continuous blend were higher than those found for PVDF/TPU 50/50 wt% (i.e., 38/62 vol%) composites at same filler content. PVDF/TPU/CB-PPy 3D printed samples with 6.77 vol% filler fraction presented electrical conductivity of 4.14 S m⁻¹ and elastic modulus, elongation at break and maximum tensile stress of 0.43 GPa, 10.3% and 10.0 MPa, respectively. These results highlight that PVDF/TPU/CB-PPy composites are promising materials for technological applications.     

Understanding of intermolecular interaction in PVDF/PTW blends: Crystallization behavior,thermal, and dynamic mechanical properties

Poly(vinylidene fluoride) (PVDF)/ poly(ethylene–butylacrylate–glycidyl methacrylate) (PTW) blends were directly prepared by melt blending and the interaction and properties of PVDF/PTW blends were explored systematically. The crystallization behavior, thermal stability, dynamic mechanical property, and morphological features of PVDF/PTW blends with different ratios have been studied by XRD, attenuated total reflection Fourier transform infrared spectroscopy, differential scanning calorimeter analysis (DSC), thermal gravimetric analysis (TGA), dynamic mechanical analysis, and polarized optical microscopy (POM). The results showed that the crystalline structure of neat PVDF was dominantly α‐phase crystalline and the incorporation of PTW had no effect on the crystalline structure of PVDF in the PVDF/PTW blends. And T_g of PVDF in PVDF/PTW blends shifted to higher temperature compared with that of neat PVDF, indicating the weak interaction between PVDF and PTW, which was corresponding to DSC and TGA results. An increase in the coarseness and ring‐band spacing observed from POM further substantiated the weak interaction between PVDF and PTW. This work provided a way for preparing improved properties of PVDF/PTW blends for the coating material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43908.     

Generation of microcellular foams of PVDF and its blends using supercritical carbon dioxide in a continuous process

Use of supercritical carbon dioxide (scCO₂) as a blowing agent to generate microcellular polymer foams (MPFs) has recently received considerable attention due to environmental concerns associated with conventional organic blowing agents. While such foams derived from amorphous thermoplastics have been previously realized, semicrystalline MPFs have not yet been produced in a continuous scCO₂ process. This work describes the foaming of highly crystalline poly(vinylidene fluoride) (PVDF) and its blends with amorphous polymers during extrusion. Foams composed of neat PVDF and immiscible blends of PVDF with polystyrene exhibit poor cell characteristics, whereas miscible blends of PVDF with poly(methyl methacrylate) (PMMA) yield foams possessing vastly improved morphologies. The results reported herein illustrate the effects of blend composition and scCO₂ solubility on PVDF/PMMA melt viscosity, which decreases markedly with increasing PMMA content and scCO₂ concentration. Morphological characterization of microcellular PVDF/PMMA foams reveals that the cell density increases as the PMMA fraction is increased and the foaming temperature is decreased. This study confirms that novel MPFs derived continuously from semicrystalline polymers in the presence of scCO₂ can be achieved through judicious polymer blending.