Conducting Polymer Blends Research Articles

Limit current surges with +TC resistors

The characteristics and design of positive temperature coefficient (PTC) resistors, which are used in current-limiting circuits that do not isolate completely the protected circuit from its power source, are described. The way in which the PTC resistor, a conductive polymer blend of specially formulated plastics and various conductive materials, works is outlined. As an example of the specification process for a PTC circuit protector, the use of a conductive polymer PTC resistor to protect an outlet circuit in a personal computer used for connecting a keyboard is considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multiple percolation in conducting polymer blends

A method is introduced to control the percolation in conducting polymer blends with a desired low content of the conducting polymer, which is due to phase separation. An explanation is also presented for the low conductivity threshold and the high conductivity critical exponent in terms of a new concept of multiple percolation

Conducting polymer blends: polypyrrole and poly(vinyl methyl ketone)

Blends of polypyrrole (PPy) and poly(vinyl methyl ketone) (PVMK) have been prepared both chemically and electrochemically. Hydrogen bonding between PPy and PVMK has been verified by IR spectroscopy. No significant change in conductivity occurs on stretching the blends over 200%. PPy/PVMK blends prepared chemically and electrochemically exhibit threshold conductivities near 10% PPy. X-ray diffraction spectra suggest that crystallinity does not vary with PPy concentration in the blend. Conductivity vs temperature and conductivity vs moisture are reported as measures of environmental stability

Electrically conductive polymer blends comprising polyaniline

Electroactive polymer blends comprising polyaniline (PANI) as conductive constituent and poly(methyl methacrylate) (PMMA), polystyrene (PS) and methyl methacrylate-butadiene-styrene (MBS) copolymer as a thermoplastic constituent (TC) were prepared by using various techniques:in situ by oxidative polymerization of aniline in aqueous dispersions of the TC; by, coagulating of latex of TC in the acidic dispersions wherein PANI has been preliminary obtained; and by dry blending. It was shown that highest conductivity values revealedin situ prepared PANI/PMMA blends, where the intermolecular interactions between the constituents were suggested to be stronger than in the other systems studied.

EMI shielding measurements of conductive polymer blends

Shielding efficiencies for a number of blends containing a variety of conductive fillers, including intrinsically conductive polymers, have been measured in the near field with a dual-chamber box and in the far field with a transmission line fixture. Although all samples satisfied the classical good-conductor approximation, most of them exhibited a crossover from being electrically thin (thickness skin depth) over the frequency range of interest, 1 MHz to 3 GHz. The theoretical relations for both near-field and far-field shielding which are prevalent in the literature do not accurately describe this region of crossover. The authors have derived expressions which describe the behavior accurately over the entire range of interest. Far-field shielding efficiencies as high as 70 dB at 1 GHz were measured for purely organic composites consisting of an intrinsically conductive polymer, polyaniline, dispersed in a thermoplastic matrix. >

Electrically conductive polymer composites and blends

AbstractIncreasing utilization of the electrical properties of polymeric blends and composites has prompted our renewed interest in developing a general working relationship which can explain the electrical properties of polymer composites and blends in terms of processing characteristics, morphology, and compositions. Here, we restrict our attention to the following two‐component systems: (1) two component systems with conductive particulate inclusions (e.g. carbon black) embedded in a continuous polymeric matrix, and (2) two component polymer blend systems with one conductive polymer (e.g., polyether copolymer) dispersed in another continuous polymeric matrix. The following processing aspects related to the electrical property of particulate filled composites are discussed: (1) critical concentration of rigid conductive fillers, ϕc, and (2) redistribution of conductive fillers upon processing. An equation based on the crowding factor of concentrated suspension rheology and Janzen's particle contacts percolation is proposed to describe the relationship between ϕc, and the maximum packing fraction of conductive fillers. The relationship is used to explain the influence of particle morphology on conductivity, and the conductivity difference in the high shear and the low shear region of a processed polymer composite part. Furthermore, some qualitative guidelines for blending a low conductivity polyether copolymer to achieve an overall balance of antistatic and mechanical properties of polymer blends are also discussed.

Heterogeneous conducting polymeric systems: dispersions, blends, crystalline conducting networks — an introductory presentation

The preparation and properties of fully organic heterogeneous conducting systems are briefly presented. The comparison of specific properties of mechanical blends of conducting crystals with inert polymers, of conducting latices in film-forming polymers, of conducting polymer blends and reticulate doped polymers (RDPs) is shown. Several advantages of RDPs include very low percolation threshold, bulk, surface and highly anisotropic conductivity, transparency and optical anisotropy. The latter composites are obtained by well-mastered casting technologies, thus a wide range of applications including those expected for conducting latices in film-forming polymers is possible.

Highly electrically conducting polymer blends

Heterocyclic polymers such as polythiophene and polypyrrole have received a great deal of attention due to their high electrical conductivity and good environmental stability [1-5] . However, they possess poor mechanical propert ies and processibility. In recent years, several at tempts to overcome these drawbacks have been made [6-9] , in particular a method of blending with conventional polymers. However, mechanical blending in melt state is undesirable because the conductivity of the polymer decreases due to thermal effect during processing. Furthermore, a high concentrat ion of conducting polymer is required to make a conduct ion path. We have developed a novel method to prepare conducting polymer blends. The most attractive feature of this method is that polymerization of pyrrole occurs after fabrication and the construct ion of conducting networks can be controlled by the polymerization conditions.

Talking point. Intrinsically conducting polymers: A critical stage in research strategy?

Research News/Talking Point: Is the euphoria some attach to the prospects for conducting polymers misguided? Or is it the case that the wrong approach has been adopted for the research strategy? These two questions are addressed as the first commercially available intrinsically conducting polymer blend reaches the market.

Conductive phthalocyanine polymer blends

Conductive phthalocyanine polymer blends

Synthesis and characterization of conducting polymer blends of poly(3-alkylthiophenes)

Poly(3-alkylthiophenes) (alkyl > butyl) are soluble in several common organic solvents and, furthermore, are melt-processable at temperatures below 200°C. They can be blended with thermoplastics and elastomers in the molten state using a Brabender, blow molding or extrusion molding, or they can be hot-pressed on a substrate. After doping these blends can reach conductivities as high as high as 1 S/cm. We have studied the chemical and physical properties of poly(3-octylthiophenes) (POT), including how the polymerization route affects the molar mass, how the POT content in the blends or doping time affect the conductivity and how stretching affects the conductivity of POT and its blends.

Conducting polymer blends: polythiophene and polypyrrole blends with polystyrene and poly(bisphenol A carbonate)

Preparation de melanges PT/PS, PPy/PS,PT/PC et PPY/PC pour polymerisation electrolytique du thiophene ou de pyrrole sur des electrodes recouvertes de PS ou de PC et mesure de leur conductivite en fonction de leur composition. La meilleure conductivite du melange PPy/PC est attribuee a la formation de liaisons hydrogenes, en accord avec les resultats de TGA, DSC et IR

Conducting polymer blends

We report the production and properties of electrically conducting polymer blends utilizing the melt-processability properties of high molecular weight poly(3-octylthiophene), POT. We have found that polymer blends produced by mixing appropriate amounts of POT with a variety of thermoplastic matrix polymers have excellent mechanical properties and that they can be doped to yield electrically conducting polymer blends with conductivities exceeding 1 S/cm.

Melt and solution processable poly(3-alkylthiophenes) and their blends

We report on the properties of melt and solution processable poly(3-alkylthiophenes), P3AT, and on the fabrication of electrically conducting polymer blends consisting of P3AT, specifically poly(3-octylthiophene), POT, and a thermoplastic matrix polymer made using ordinary melt processing techniques. The POT used in this work was synthesized using two different chemical polymerization techniques. Films made from as-synthesized POT powder, either by solution casting or melt processing techniques were found to be easily doped by electron acceptors to conductivities of 20–30 S/cm. Blending of POT with thermoplastics such as ethylenevinylacetate copolymer, EVA, in the molten state yields polymer blends with excellent mechanical properties that might be doped to conductivities exceeding 1 S/cm.

Proton conducting interpenetrating polymer networks

In order to improve stability and performance of the polymer electrolyte-based hydrogen sensor developed for on-line analysis, modifications to the PVA/H 3PO 4 proton conducting polymer blend were made. Water insoluble, increased bulk modulus, and higher conductivity polymer membranes have been fabricated by development of interpenetrating polymer networks that incorporate the PVA/H 3PO 4 (host) blend. The guest polymer is a three dimensional polymer network composed of methacrylic acid and methylenebisacrylamide. High protonic conductivity results from the phosphoric acid and water, the poly (methaacrylic acid-methylenebisacrylamide) contributes to the increased modulus water insolubility. Hydrogen sensors have been demonstrated using these membranes.

Electrically conducting polymer blends

A versatile technique for preparing electrically conducting polymer blends is presented which utilizes the soluble precursor approach to conducting polymer synthesis. The water-soluble polymeric sulphonium salt precursor to poly( p-phenylene vinylene) (PPV), a conducting polymer, has been used to prepare blends of PPV with polyacrylamide (PAcr). These phase-separated blends yield flexible and transparent films of good mechanical properties which can be oxidized with strong electron acceptors (e.g. AsF 5) and thereby exhibit greatly enhanced electrical conductivity. The ultimate conductivity shows an atypical gradual composition dependence, which lies between that of the pure components. These blends can also be thermally stretched in the manner reported for pure PPV. Stretching of the PPV/PAcr blends results in highly efficient PPV chain orientation and greatly augmented conductivity along the stretch axis.

Differential scanning calorimetry and complex admittance analysis of PVA/H 3PO 4 proton conducting polymer blends

The proton-conducting plymer blend of poly(vinyl alcohol) and phosphoric acid, which is incorporated into a hydrogen-specific sensor, has been modeled using a.c. impedance techniques. The presence of a separate phosphoric acid/water phase, which is responsible for the proton conduction of the film, is indicated. This is supported by differential scanning calorimetry, dielectric and conductivity measurements. Conductivity versus temperature plots show Arrhenius-like behavior rather than the free volume type behavior associated with ion transport mechanisms dependent on polymer motion.

Applications of novel proton-conducting polymers to hydrogen sensing

Ionic conducting polymer blends capable of supporting proton conduction from −40°C to 40 °C have been developed. These proton-conducting polymer blends have been used to fabricate hydrogen sensors that are capable of operating at room temperature without the need for an external supply of water vapor. Two sensor designs, both potentiostatic, are being investigated: the first uses a gaseous reference source, and the second a solid state palladium hydride reference. These sensors measure accurately the hydrogen concentration to better than 1%, have a response time of less than 6 s and are not adversely affected by most potential poisons.