Conductive Plastics Research Articles

Open the Frontier for Effective EMI Shielding with Conductive Plastics Filler

Open the Frontier for Effective EMI Shielding with Conductive Plastics Filler

Benefits of using conductive plastics in shielding configurations to reduce radiated electromagnetic interference

Conductive plastic cabinets have become an alternative to traditional metallic enclosures to shield electronic equipment from electromagnetic interference. These materials allow a wide range of conductivities that can satisfy any particular design. In this article, the benefits of using conductive plastics in enclosure configurations have been evaluated. A design with an outer metallic layer and an inner layer of conductive dielectric can provide advantages from both materials as a conductive plastic box is lighter and its shielding properties may have advantages over metallic materials. An optimum for resonance suppression has been obtained for the hybrid structure. These shielding structures have been evaluated with the help of measurements and simulations. Shielding effectiveness and Q factor have been used to compare the capabilities of these enclosures with the metallic ones showing their benefits and possibilities. Resonance suppression and shielding levels provided by conductive plastics are discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2476–2480, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25499

Fabrication of Extrinsically Conductive Silicone Rubbers with High Elasticity and Analysis of Their Mechanical and Electrical Characteristics

Conductive plastics are attracting more and more interest in electronics due to their light weight and inability to rust, which are common problems associated with metals. The field of conducting plastics is not new. Much work has been done to impart electrical conductivity to mechanically strong polymers such as polypropylene, polycarbonate and epoxies, etc. However there is a need to fabricate more flexible and elastic conductive polymers such as conducting silicone rubbers for use in various applications. In this work silicone rubbers reinforced with conductive fillers have been fabricated for use as sensors in textiles to detect the resistance change produced by stretching or relaxing. The variations of electrical resistance have been investigated by stretching and releasing the strands of conductive rubbers as a function of time. Two types of silicone rubbers—addition cured and condensation cured—were compounded with different electrically conductive fillers, among which carbon fibers have shown the best results. The carbon fibers improved the electrical conductance of the rubbers, even in very low weight percentages. The increasing concentration of fillers decreases the elasticity of the rubber. In order to keep the original properties of silicones, the filler concentration was kept as low as possible to produce a significantly detectable signal. The fabricated compounds were analyzed for their mechanical properties by stress strain curves. Such materials find their applications in electronics, antistatic applications, sports and the automotive industry where they can be used as deformation sensors.

Thermally Conductive (TC) Plastics in LED Lamps

In section 1, an assessment is made of the typical thermal conductivities attainable in a TC-plastic followed by an examination of the trade-off between increased thermal conductivity and decreased toughness caused by increasing filler load of such a TC-plastic. Having established that currently there is a ceiling conductivity of around 25 W/mK for TC-plastics, i.e., well below the 100 W/mK TC level of metals, subsequently a basic analysis is provided on the suitability of materials with such moderate TC-levels in metal replacement. For this purpose, the ideal case of a unidirectional (1D) heat flow is considered in section 2, in section 3, a more complex case of a bidirectional heat flow is analyzed. Finally, section 4 considers the thermal performance of TC-plastics in a real 3D part, i.e., the heat sink housing of an LED lamp. More specifically, a comparison is made between the thermal performance of the housing molded in a heat conductive plastic and that of an all-aluminum housing. This comparison clearly demonstrates general validity and practical value of the conclusions drawn in sections 2 and 3 and highlights the outstanding suitability of TC-plastics for heat sinks in lighting applications. High performances STANYL TC in particular.

Conductive plastics with hybrid materials

AbstractHybrid materials of conducting polyaniline (PANi) and multiwalled carbon nanotubes (CNTs) were synthesized using an in situ polymerization method. The resulting CNTs with a thin layer of PANi coating were further compounded with polypropylene to produce electrically conductive composite material. The PANi coating was found to enhance the CNT dispersion in PP. An amphiphilic component was also used as a surfactant to further enhance the dispersion. With these methods and materials, a conductivity of 26 S cm−1 was obtained. The conductivity of the hybrid material far exceeded that of the separately compounded mixture and of that prepared of lower aspect ratio conductive materials: carbon nanofibers and carbon black. The level of conductivity qualifies the material for use in applications requiring electromagnetic interference shielding. By adjusting the PANi loading, the conductivity can be tuned down to obtain materials suitable for electrostatic discharge applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Conductivity enhancement of carbon nanotube and nanofiber-based polymer nanocomposites by melt annealing

The addition of multi-walled carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs) to polymeric melts offers a convenient route to obtain highly conductive plastics. However, when these materials are melt processed, their conductivity can be lost. Here, it is shown that conductivities can be recovered through melt annealing at temperatures above the polymer's glass transition temperature (Tg). We demonstrate these results for both MWCNT and CNF-based composites in polystyrene (PS). The mechanism behind the conductivity increase is elucidated through modeling. It involves a transition from aligned, unconnected particles prior to annealing to an interconnected network after annealing through viscoelastic relaxation of the polymer. Such re-arrangement is directly visualized for the case of the CNF-based composites using confocal microscopy. The annealing-induced increase in particle connectivity is also reflected in dynamic rheological measurements on both MWCNT and CNF composites as an increase in their elastic moduli at low frequencies.

Conductive plastics information is freely available

Conductive plastics information is freely available

コイル材切削金属繊維を用いた導電性プラスチックの開発

Plastics are common insulators which cannot shield electromagnetic waves and can easily be charged by static electricity. To make conductive plastics, we propose a laminated coiled sheet shaving method. By winding of plastic and thin metal sheet herein simultaneously using a fabric manufacturing apparatus and cutting the ends we produce a plastic combined with metal fibers, of which plastics and metal fibers are found evenly distributed. The plastic/metal fibers thus obtained are put through a heated dice for melting and curing and are then cut into appropriate lengths to produce pellets for injection molding.Stainless steel of 3 vol% in mixing ratio was found to have a volume resistivity of approximately equal to or lower than that of the electromagnetic shields of level (100 Ω·cm). In addition, the tensile strength of the injection molding was found to be reduced within increasing the amount of metal fibers.

Effect of interfacial treatment on the thermal properties of thermal conductive plastics

In this paper, ZnO, which is processed by different surface treatment approaches, is blended together with polypropylene to produce thermal conductive polymer composites. The composites are analyzed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to investigate the surface modification of filler, their distribution in the matrix and the condition of two-phase interface. Optimized content of filler surface modifier is investigated as well. The results showed that using low-molecular coupling agent produces positive effect to improve the interface adhesion between filler and matrix, and the thermal conductivity of the composite as well. Macro-molecular cou- pling agent can strongly improve two-phase interface, but it is not beneficial at obtaining a high thermal conductivity. The blend of ZnO without modification and polypropylene has many defects in the two-phase interface, and the thermal con- ductivity of the composite is between those of composites produced by previous two approaches. The surface treatment of the filler also allowed producing the composites with lower coefficient of thermal expansion (CTE). As for the content of low-molecular coupling agent, it obtains the best effect at 1.5 wt%.

Conductive plastics for electrical and electronic applications

Plastics have become the material of choice for internals in electronic components. In these applications designers are looking for thermoplastics that dissipate charge and provide barriers to electromagnetic energy. So the challenge is to convert inherently insulating thermoplastic materials to a product that would provide antistatic or electrostatic dissipative or EMI/RFI shielding or combination of these properties. Dr Jay Amarasekera of GE Advanced Materials/LNP explains.

Polymers for chemical sensing

Chemical sensors play an increasingly important role in monitoring the environment we live in, providing information on industrial manufacturing processes and their emissions, quality control of foods and beverages, and a host of other applications. Electrically conductive plastics are being developed for many useful applications. Improvement in understanding of the physical and chemical mechanisms by which electrical conduction occurs in these materials is now leading to a new generation of chemical sensors, which are reviewed in this article.

Next stretch for plastic electronics.

The article looks at the future of plastic electronics as of August 2004. Strong, flexible, lightweight and cheap, plastics have acquired an additional attribute in recent years: the ability to function as semiconductors, forming diodes and transistors in plastic integrated circuits. Now, as the first plastic electronics products are hitting the market in displays that use organic light-emitting diodes, the stage is set for a new era of pervasive computing with polymers. A key advantage of organic transistors over silicon is their ease of fabrication. In general, organic semiconductors have lower mobility than their inorganic counterparts do, resulting in slower switching speeds. Plastic electronics will soon be coming to market in radio-frequency identification tags. In December 2003 at the annual International Electron Devices Meeting, researchers from Infineon described two different types of memory chip based on organic polymers. One can imagine fabrics made of electronic textiles with controllable properties. Such wearable computers could monitor the individual's vital signs or the surrounding environment. In November 2003 Takao Someya and his coworkers at the University of Tokyo announced the use of pentacene transistors in a flexible sheet to form a pressure-sensitive skin that could be used to give a robot a sense of touch. INSET: CONDUCTIVE PLASTICS.

Conductive Plastics

Conductive Plastics

Conductive plastics launch into new markets

Composite materials based on undoped conjugated polymers and conductive filler were synthesized and their electrophysical and electrochemical properties were investigated. Conjugated polymers such as polyaniline (PANI), polyacetylene (PA) and typical polymer dielectric, polypropylene (PP) were used as matrices. Graphite and single-walled nanotubes were used as conductive fillers. The investigation of the dependencies of conductivity on filler concentration show that in contrast to PP and PANI, PA becomes conductive due to injected charge carriers from filler particles. This conclusion is supported by investigated dependencies of composite conductivity on temperature and time during aging and on cyclic voltammetry data. It was shown that a conjugated polymer matrix allows composite materials with new electrophysical and electrochemical properties to be produced.

Ceramic filled thermoplastic encapsulation as a design feature for a BLDC motor in a disk drive

Thermoplastics have made steady gains in use in a wide variety of motor applications. One of the few areas in which thermoplastics have not been effectively utilized are spindle motors. Central to the development of these applications is an understanding of the heat transfer and harmonic damping requirements of the applications and the cost/benefit relationships that exist. A simple model will be presented in which the heat transfer requirements for thermally conductive plastics can be understood and their costs can be estimated. Various filler systems and their performance will be discussed highlighting motor designs where these materials offer a competitive alternative to traditional construction techniques.

Electromagnetic shielding of plastic packaging in low-cost laser modules

Low-cost MiniDIP laser modules fabricated by plastic moulded technology filled with highly conductive materials are proposed for the evaluation of electromagnetic interference (EMI) shielding effectiveness (SE). The SE of conductive plastics was measured to be 45 dB at 30 MHz and 62 dB at 1 GHz. The laser modules have a transmission speed up to 622 Mbit/s and > 1 mW fibre output power. With these excellent SEs and good optical characteristics, such plastic MiniDIP laser modules are suitable for use in low-cost OC-12 lightwave transmission systems.

Thin-film zinc/manganese dioxide electrodes based on microporous polymer foils

Abstract Thin-film electrodes allow manufacturing of flat batteries of variable design which can be used for the development of smaller electric appliances. Substituting the metal carrier by conductive plastics leads to a considerable reduction of battery weight. Usually the electroactive materials are deposited onto the surface of the carrier. A significant improvement of the originally poor adherence between polymer foil and electroactive layers can be achieved by mechanical (surface roughening) or chemical (etching) pretreatment. Another way to form extremely thin electrodes having a thickness in the range of some ten micrometers is reported here. First, a metallic layer is deposited onto one surface of a 25 μm thin porous polypropylene foil. Subsequently, the electroactive materials are electrolytically deposited into the pores of the metallized foil providing the required conductive connection through the plastic matrix by themselves. In this case the flexibility of the polymer has a positive influence on the problem of volume change of manganese dioxide during charging and discharging, respectively, because the plastic provides flexible `mechanical struts' which act as a `binder' and therefore prevent increasing internal resistance due to contact problems. Assembling a zinc filled polymer and a manganese dioxide filled one in such a way that both metallic back-layers are in contact, a thin bipolar zinc/manganese dioxide electrode can be obtained.

鉛フリーはんだ分散導電性プラスチックにおける金属凝集粒防止対策

鉛フリーはんだ分散導電性プラスチックにおける金属凝集粒防止対策

鉛フリーはんだ分散導電性プラスチックの開発

鉛フリーはんだ分散導電性プラスチックの開発

軟磁性材料 情報処理装置のＥＭＣ動向

The EMC (Electro-magnetic compatibility) includes EMI (Electro-magnetic Interference) and electro-magnetic immunity. The EMI standards for data processing equipment is the CISPR 22 issued by the IEC(International Electrotechnical Commission). Many nations are using this standard to prevent the radio equipment, TV and wireless facilities from the interference. The immunity standard is CISPR 24. The manufacturer shall voluntarily use the immunity standard to prevent the equipment from malfunctions. In Europe, the EMC Directive uses this standard. The focal point of EMC design has been moved from the shielding to the circuits design. The most importance is the control of impedance. The simulation software is important for an efficient design. Therefore, we have developed the software so called ACCUFIELD. Data processing equipment requires new materials to correspond the increase of processor speed. The flexible EM absorbing rubber sheet is being expected as an EMC material. We forecast that the recycable conductive plastics and the steel sheet with low surface-resistance will be required as the cabinet material in the future.