conductive plastic2

8/14/2019 Conductive Plastic2

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CONDUCTIVCONDUCTIV

E PLASTICE PLASTICPresented byPresented by

Nicha TanghaNicha TanghaElect.EnggElect.Engg

77thth sem ,03/273sem ,03/273


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CONTENTS

INTRODUCTIONINTRODUCTION

RELEVANT PHYSICSRELEVANT PHYSICS

THE POLYLEDTHE POLYLED

POPERTIESPOPERTIES

APPLICATION IN VARIOUS FIELDSAPPLICATION IN VARIOUS FIELDS

LIMITATIONLIMITATION

CONCLUSIONCONCLUSION

REFERENCEREFERENCE


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INTRODUCTIONINTRODUCTIONPlastics are polymers, that is chains of many identicalPlastics are polymers, that is chains of many identicalmolecules (monomers) that are intercoupled. The reasonmolecules (monomers) that are intercoupled. The reasonthat most plastics are isolators is that their electrons arethat most plastics are isolators is that their electrons arelocalized. Each electron is firmly fixed, as it were, to itslocalized. Each electron is firmly fixed, as it were, to itsown atomic nucleus. This means that the electrons,own atomic nucleus. This means that the electrons,

carriers of the electric current, cannot move freely in thecarriers of the electric current, cannot move freely in thematerial. Conductive or semiconductive plastics, werematerial. Conductive or semiconductive plastics, werediscovered in Japan in1977. In these, the polymer chainsdiscovered in Japan in1977. In these, the polymer chainshave conjugated connections i.e. the discrete atoms arehave conjugated connections i.e. the discrete atoms areinterconnected alternately by a single and a doubleinterconnected alternately by a single and a double

chemical bond.chemical bond.


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RELEVANT PHYSICSRELEVANT PHYSICSConductive or semi conductive plastics are polymer chains withConductive or semi conductive plastics are polymer chains with

conjugated double links. The first PolyLEDs werebased onconjugated double links. The first PolyLEDs werebased onpolyphenyl-vinyl (PPY). The principle of their conductivity (or,polyphenyl-vinyl (PPY). The principle of their conductivity (or,rather semiconductivity) is best illustrated by the simplestrather semiconductivity) is best illustrated by the simplestpolymer with a conjugated structure: polyacetylene. See Figure.polymer with a conjugated structure: polyacetylene. See Figure.


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The single bond in the conjugated structure is always aThe single bond in the conjugated structure is always aa-bond, whereas the double one consists of a a-bonda-bond, whereas the double one consists of a a-bondand a n-bond, which has a different character. Twoand a n-bond, which has a different character. Twovariants of poIyacetylene that differ only in the locationsvariants of poIyacetylene that differ only in the locations

of the n-bonds are shown in Figure. These variants couldof the n-bonds are shown in Figure. These variants couldbe merged freely. The real structure is a mixture of thebe merged freely. The real structure is a mixture of thevariants in which each is represented equally. This hasvariants in which each is represented equally. This hasan important consequence: in the case of an a-bond, thean important consequence: in the case of an a-bond, theelectrons forming the bond are bonded to both nucleielectrons forming the bond are bonded to both nuclei

and therefore localized. Normally, this is also the caseand therefore localized. Normally, this is also the casewith electrons ,forming a n-bond. Because of thewith electrons ,forming a n-bond. Because of theconjugated structure, that is, a mixture , the electronsconjugated structure, that is, a mixture , the electronsare free to move along the entire chain.are free to move along the entire chain.


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This does not mean, of course, that the materialThis does not mean, of course, that the materialitself, which consists of many monomers,itself, which consists of many monomers,

becomes conductive. This occurs only whenbecomes conductive. This occurs only whenelectrons can hop from one chain of polymerselectrons can hop from one chain of polymersto another. It has been found that this becomesto another. It has been found that this becomespossible when the chains are in close proximitypossible when the chains are in close proximityof each other. The closer the chains areof each other. The closer the chains aretogether, the more mobile the electronstogether, the more mobile the electronsbecome. This is further enhanced bybecome. This is further enhanced bypurification of the material and doping it, thatpurification of the material and doping it, thatis, adding charge carriers.is, adding charge carriers.


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When an electric potential is applied across semi conductiveWhen an electric potential is applied across semi conductive

plastics, they emit light. This forms the basic of PolyLED.plastics, they emit light. This forms the basic of PolyLED.

The PolyLED is essentially a much simpler component than aThe PolyLED is essentially a much simpler component than a

transistor. Its applications include segment displays such as usedtransistor. Its applications include segment displays such as used

in mobile telephones and background lighting in liquid-crystalin mobile telephones and background lighting in liquid-crystal

displays.displays.

PolyLEDs operate with low (battery) voltage and are thereforePolyLEDs operate with low (battery) voltage and are therefore

eminently suitable for use in modern equipment.eminently suitable for use in modern equipment.

THE POLYLED


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PROPERTIESPROPERTIESSteadily increasing the length of a purifiedSteadily increasing the length of a purified

conducting polymer vastly improves its ability toconducting polymer vastly improves its ability to

conduct electricity, Their study of regioregularconduct electricity, Their study of regioregular

polythiophenes (RRPs) establishes benchmarkpolythiophenes (RRPs) establishes benchmarkproperties for these materials that suggest howproperties for these materials that suggest how

to optimize their use for a new generation ofto optimize their use for a new generation of

diverse materials, including solar panels,diverse materials, including solar panels,

transistors in radio frequency identification tags,transistors in radio frequency identification tags,and light-weight, flexible, organic light-emittingand light-weight, flexible, organic light-emitting

displays .displays .


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Unlike plastics that insulate, or prevent, the flowUnlike plastics that insulate, or prevent, the flow

of electrical charges, conducting plastics actuallyof electrical charges, conducting plastics actually

facilitate current through their nanostructure.facilitate current through their nanostructure.Conducting plastics are the subject of intenseConducting plastics are the subject of intense

research, given that they could offer light-weight,research, given that they could offer light-weight,

flexible, energy-saving alternatives for materialsflexible, energy-saving alternatives for materials

used in solar panels and screen displays. Andused in solar panels and screen displays. Andbecause they can be dissolved in solution,because they can be dissolved in solution,

affixed to a variety of templates like silicon andaffixed to a variety of templates like silicon and

manufactured on an industrial scale, RRPs aremanufactured on an industrial scale, RRPs are

considered among the most promisingconsidered among the most promising

conducting plastics in nanotech research today.conducting plastics in nanotech research today.


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Mobility of electrons increases exponentiallyMobility of electrons increases exponentiallyas the width of a nanofibril increases, Each rope-as the width of a nanofibril increases, Each rope-like nanofibril actually is a stack of RRPlike nanofibril actually is a stack of RRPmolecules, so the longer these molecules, themolecules, so the longer these molecules, thewider the nanofibril and the faster the electricalwider the nanofibril and the faster the electricalconductivity. In this way, electricity movesconductivity. In this way, electricity moves

preferably perpendicular through the rows ofpreferably perpendicular through the rows ofnaturally aligned nanofibrils.naturally aligned nanofibrils.

Charge carriers encounter fewer hurdles whenCharge carriers encounter fewer hurdles whenjumping between wider nanofibrils. So thejumping between wider nanofibrils. So the

nanostructure of our conducting plasticnanostructure of our conducting plasticprofoundly enhances its ability to conductprofoundly enhances its ability to conductelectricityelectricity


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APPLICATIONAPPLICATIONElectrical applicationElectrical application

1.1. BRUSHLESS MOTOR 2. D.C. MOTORBRUSHLESS MOTOR 2. D.C. MOTOR

3. D.C. TORQUE POTENTIOMETER 4. D.C. TORQUE MOTOR3. D.C. TORQUE POTENTIOMETER 4. D.C. TORQUE MOTOR


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ELECTRONICSELECTRONICS

APPLICATIONAPPLICATIONKeypadsKeypads

Phosphorescent rubberPhosphorescent rubber

keypadskeypads

Rubber keypadsRubber keypads


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BatteriesBatteries

In an age of massive portability in electronics,In an age of massive portability in electronics,the need for improved batteries is critical. Therethe need for improved batteries is critical. Thereis a tremendous growth in laptop computers,is a tremendous growth in laptop computers,cellular phones and personal digital assistantscellular phones and personal digital assistants(PDAs). Electronics are being put in every place(PDAs). Electronics are being put in every placetherefore, replacing heavier metal componentstherefore, replacing heavier metal components

with lightweight polymers would seem to bewith lightweight polymers would seem to behighly desirable.highly desirable.

The electrodes of all common batteries areThe electrodes of all common batteries aremade of metals. (Car batteries are lead,made of metals. (Car batteries are lead,flashlight batteries are nickel/cadmium, andflashlight batteries are nickel/cadmium, and

button cells are lithium.) By replacing thesebutton cells are lithium.) By replacing thesemetals with conductive polymers, the followingmetals with conductive polymers, the followingadvantages have been shown: lower weight,advantages have been shown: lower weight,lower cost, more charge/discharge cycles, lowerlower cost, more charge/discharge cycles, lowertoxicity, and improved recyclability.toxicity, and improved recyclability.


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Light-Emitting DiodesLight-Emitting Diodes

Conductive polymers have been made intoConductive polymers have been made intodevices that provide an alternative todevices that provide an alternative to

conventional backlit LCD displays. The devicesconventional backlit LCD displays. The devicestermed OLEDs(organic light-emitting diodes),termed OLEDs(organic light-emitting diodes),which use conductive polymers, are sandwich-which use conductive polymers, are sandwich-type structures where the active polymeric filmtype structures where the active polymeric filmlayer is positioned between a semi-transparentlayer is positioned between a semi-transparentanode and a back row cathode. The devicesanode and a back row cathode. The devicesemit uniformly over the entire device. Suchemit uniformly over the entire device. Suchdevices are applied in displays for cellulardevices are applied in displays for cellulartelephones, camcorders, PDAs, and numeroustelephones, camcorders, PDAs, and numerous

industrial devices needing a readout display.industrial devices needing a readout display.Their present advantages over LCD backlitTheir present advantages over LCD backlitdisplays include lower power, lighter weight,displays include lower power, lighter weight,increased durability (no glass), wider viewingincreased durability (no glass), wider viewingangle, and increased brightness; their futureangle, and increased brightness; their future

advantage of lower cost is also promising.advantage of lower cost is also promising.


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MicrotoolMicrotool

One interesting property of many conductiveOne interesting property of many conductive

polymers is that they swell when they conduct.polymers is that they swell when they conduct.This means that conductive polymers canThis means that conductive polymers canchange electrical signals into mechanicalchange electrical signals into mechanicalenergy, similar to piezoelectric materials.energy, similar to piezoelectric materials.However, in contrast to piezoelectric films,However, in contrast to piezoelectric films,

conductive polymeric films work well at lowconductive polymeric films work well at lowvoltages, thus expanding the areas ofvoltages, thus expanding the areas ofapplicability for such devices.applicability for such devices.


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MEDICAL APPLICATIONMEDICAL APPLICATIONMedical applications under evaluation or currentlyMedical applications under evaluation or currentlyusing conductive thermoplastics include:using conductive thermoplastics include:

1.1. Bodies for asthma inhalers. Because the properBodies for asthma inhalers. Because the properdose of asthma medications is critical to relief, anydose of asthma medications is critical to relief, anystatic "capture" of the fine-particulate drugs canstatic "capture" of the fine-particulate drugs canaffect recovery from a spasm.affect recovery from a spasm.

2. Airway or breathing tubes and structures. A flow of2. Airway or breathing tubes and structures. A flow ofgases creates triboelectric charges, which mustgases creates triboelectric charges, which mustdischarge or decay. A buildup of such charges coulddischarge or decay. A buildup of such charges couldcause an explosion in a high-oxygen atmosphere.cause an explosion in a high-oxygen atmosphere.

3. Antistatic surfaces, containers, and packaging to3. Antistatic surfaces, containers, and packaging to

eliminate dust attraction in pharmaceuticaleliminate dust attraction in pharmaceuticalmanufacturing.manufacturing.


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4.ESD housings to provide Faraday cage4.ESD housings to provide Faraday cageisolation for electronic components inisolation for electronic components in

monitors and diagnostic equipment.monitors and diagnostic equipment.5.EMI housings to shield against interference5.EMI housings to shield against interference

from and into electronics.from and into electronics.

6.ECG electrodes manufactured from highly6.ECG electrodes manufactured from highlyconductive materials. These are x-rayconductive materials. These are x-raytransparent and can reduce coststransparent and can reduce costscompared with metal components.compared with metal components.

7.High-thermal-transfer and microwave-7.High-thermal-transfer and microwave-absorbing materials used in warming fluidsabsorbing materials used in warming fluids


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LIMITATIONLIMITATION

Conductive polymers do not conduct electricity atConductive polymers do not conduct electricity atthe same speed as silicon chips. Polymers are,the same speed as silicon chips. Polymers are,therefore, limited to those applications where grosstherefore, limited to those applications where grossor relatively slow changes occur.or relatively slow changes occur.

The conductive polymers are still much weaker inThe conductive polymers are still much weaker inmechanical strength when compared to metals,mechanical strength when compared to metals,although the polymers are better than silicon-basedalthough the polymers are better than silicon-baseddevices. Also, the polymer materials are softer anddevices. Also, the polymer materials are softer andtherefore, more likely to be damaged by scratchingtherefore, more likely to be damaged by scratchingand abrasion when compared to metals.and abrasion when compared to metals.


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Lastly, polymeric devices are mostly conductiveLastly, polymeric devices are mostly conductivein only one or two dimensions, whereas metalsin only one or two dimensions, whereas metalsare fully conductive in three dimensions; that is,are fully conductive in three dimensions; that is,they are anisotropic conductors. Thethey are anisotropic conductors. Thedimensionality restriction of the polymersdimensionality restriction of the polymers(anisotropy) is because polymers are linear or,(anisotropy) is because polymers are linear or,occasionally, planar structures, and theoccasionally, planar structures, and the

delocalized electrons follow the shape of thedelocalized electrons follow the shape of thepolymer network. Designers need to be aware ofpolymer network. Designers need to be aware ofthis difference in directional conductivity. It canthis difference in directional conductivity. It canbe a problem but, in some applications, it mightbe a problem but, in some applications, it mightalso be an advantage to have a significantlyalso be an advantage to have a significantly

reduced conductivity in a specific direction. Inreduced conductivity in a specific direction. Infact, anisotropic conductors are used in manyfact, anisotropic conductors are used in manyapplications in electronics, including inexpensiveapplications in electronics, including inexpensivedigital watchesdigital watches


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CONCLUSIONCONCLUSIONSurely conductive polymers are exciting developments.Surely conductive polymers are exciting developments.As they become more common, they have become partAs they become more common, they have become partof many products with which we are already familiar andof many products with which we are already familiar andwill certainly enable many advances in future products.will certainly enable many advances in future products.

Some researchers have embarked on a study ofSome researchers have embarked on a study ofconductive polymers as a new method for storingconductive polymers as a new method for storingelectronic information, perhaps optically. These could beelectronic information, perhaps optically. These could bedeveloped into very fast storage and retrieval devices.developed into very fast storage and retrieval devices.Others see conductive polymers as light-detectingOthers see conductive polymers as light-detecting

devices that could be configured into large arrays fordevices that could be configured into large arrays formilitary and commercial applications .military and commercial applications .


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REFERENCESREFERENCESDe Gaspari, John, New alternatives InDe Gaspari, John, New alternatives In

Conductive Plastics, Plastics Technology,Conductive Plastics, Plastics Technology,

November 1997, p. 13-15.November 1997, p. 13-15.

Moore, Samuel K., Just One WordMoore, Samuel K., Just One Word

Plastics, IEEE Spectrum, SeptemberPlastics, IEEE Spectrum, September

2002, p. 55-59.2002, p. 55-59.

www.google.comwww.google.com


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