composite characterization of emi shielding

Composite Characterization of EMI shielding materials

CHAPTER 1

INTRODUCTION

Dept of E&E, Sir MVIT, 2009 1


1.INTRODUCTION

1.1 Introduction to EMI

EMI (Electro Magnetic Interference) is the disruption of operation of an electronic

device when it is in the vicinity of an electromagnetic field in the radio frequency spectrum

that is caused by another electronic device. EMI consists of any unwanted, conducted or

radiated signals of electrical origin that can cause degradation in equipment performance.

Interference also leads to data loss, picture quality degradation on monitors, and other

problems with PC, or problems with other devices such as television sets and radios.

EMI refers to how different sets of electronic equipment interact with each other,

usually in a negative manner. The recent advance in semiconductor devices and large scale

integration has dramatically reduced the size of electronic equipment while increasing the

probability for electromagnetic interference between the different systems and sub systems.

Today’s electronic designers must make sure their solutions work in an environment of high

EMI. It is not practical to ask new product designers to test their equipment under all

conditions and possible end-user configurations, therefore strict emissions regulations have

been established.

In the United States the Federal Communications Commission (FCC) regulates the

use of radio and wire communications. Part of its responsibility concerns the control of

electromagnetic interference. The standards for the allowed levels of electromagnetic

emissions are outlined in part 15 of FCC rules and regulations. These rules apply to almost

all electronic equipments. Under these rules, limits are placed on maximum allowable

radiated emissions in the frequency range between 30 to 1000 MHz and on the maximum

allowable conducted emissions on the AC power line in the frequency range of 0.450 to 30

MHz.

The FCC defines a computing device as “any electronic device or system that

generates and uses timing pulses at a rate in excess of 1000 pulses (cycles) per second and

use digital techniques; inclusive of telephone equipment that uses digital techniques or any

device or system that generates and utilizes radio frequency energy for the purpose of

performing data processing functions, such as electronic computations, operations,

transformations, recording, filing, sorting, storage, retrieval or transfer”.

This definition was intentionally made broad to include as many products as possible.

Thus, if a product uses digital circuitry and has a clock frequency greater than 10 KHz, it is a



computing device under the FCC definitions. This definition covers most digital electronics

manufactured today.

The computing devices covered by this definition are divided into two classes:

Class A: a computing device that is marketed for use in a commercial, industrial, or

business environment.

Class B: A computing device that is marketed for use in a residential environment,

not withstanding its use in a commercial, industrial, or business environment.

Since class B devices are more likely to be located in closer proximity to radio and

television receivers, the emission limits for these devices are about 10dB more restrictive

than those for class A devices.

1.1.1 EMI SOURCES:-

An EMI source can be any device that transmits, distributes, processes, or utilizes any form

of electrical energy where some aspect of its operation generates conducted or radiated

signals that can cause equipment performance degradation.

Figure 1 shows taxonomy of the different sources of electromagnetic interference.

Fig 1.1


Natural Broadband Incoherent

Radiated Unintentional

Man-Made

Broadband

Narrowband

Coherent

Incoherent

Coherent

Conducted

Radiated

Conducted

Radiated

Conducted

Radiated

Unintentional

Unintentional

Intentional

Intentional

Restricted


A brief description of each category is given below :-

Natural EMI sources: sources that are associated with natural phenomena. They include

atmospheric charge/discharge phenomena such as lightning. All natural sources are classified

as broadband, incoherent, radiated and unintentional.

Man made EMI sources: sources that are associated with man made devices such as

power lines, auto ignition, fluorescent lights etc.

Broadband EMI: electromagnetic conducted and radiated signals whose amplitude

variation as a function of frequency extends over a frequency range greater than the

bandwidth of the receptor.

Narrowband EMI: electromagnetic conducted and radiated signals whose amplitude

variation as a function of frequency extends over a frequency range narrower than the

bandwidth of the receptor.

Coherent broadband signals: neighboring components of the signal ( in the frequency

domain ) has a well defined amplitude, frequency and phase relationship.

Incoherent broadband signals: neighboring components of the signal ( in the

frequency domain ) are random or pseudo random ( bandwidth limited ) in phase or

amplitude.

Conducted EMI: noise signal transmitted via electrical conduction path (ie,wires,ground

planes, etc).

Radiated EMI: electric and magnetic fields transmitted through space from source to

receptor.



Intentional radiating emitters: emitters whose primary function depends on radiated

emitters. Example includes electronic licensed communication systems. These include

communication, navigation and radar systems.

Unintentional (incidental) radiating devices: devices that intentionally use

electromagnetic radiation purposes other than communication and data transfer( ie, garage

door operating systems ).

1.1.2 RECEPTORS OF EMI:

Any EMI situation requires not only an emission source but also a receptor. A receptor is also

called a "victim" source because it consists of any device, when exposed to conducted or

radiated electromagnetic energy from emitting sources, will degrade or malfunction in

performance. Many devices can be emission sources and receptors simultaneously. For

example, most communication electronic systems can be emission and receptor sources

because they contain transmitters and receivers.

Figure 2 shows a taxonomy of different receptors that are susceptible to EMI. Similar to the

emission source taxonomy, receptors can be divided into natural and man-made receptors.

Figure 1.2


Natural

ManAnimals Plants

Man-made

Communication electronic devices

Amplifiers

BroadcastNavigatorRadar

IF VideoAudio

Industrial & Consumer

ControlsBio medical InstrumentsTelephonesSensorsComputers

RADHAZ

EEDSFuels


A brief description of each category is given below.

Natural EMI receptors - Natural receptors include humans, animals, and plants.

Man-made EMI receptors - Man-made receptors can be categorized into 4 categories:

communication electronic receivers, amplifiers, industrial and consumer devices, and

RADHAZ.

Communication electronic receivers - These receivers include broadcast receivers,

communication receivers, relay communication receivers, and radar receivers.

Amplifiers - Amplifiers include IF, video, and audio amplifiers.

Industrial and consumer receptors - Industrial receptors include digital computers,

industrial process controls, electronic test equipments, biomedical instruments, and public

address systems and intercoms. Consumer receptors include radio and TV receivers, hi-fi

stereo equipment, electronic musical instruments, and climate control systems.

RADHAZ - This category includes radiation hazards to electro-explosive devices and

fuels. RADHAZ is an acronym for RADiation HAZards, the name given by the U. S.

Department of Defense to the program that is determining the extent of radiation hazards and

methods for controlling them.

1.1.3 Causes of EMI :-

The causes of EMI can be within the system called as intrasystem problem or the EMI

can occur from outside the system called as intersystem problem. A very common cause of

both intra system and intersystem problems is, a signal intended for one circuit also reaches a

circuit or circuits for which it was not intended. An electronic device should do two things:

respond only to desired signals and not respond to undesired signals. If a receiver or other

equipments respond to undesired signals, then this causes problems or EM interference. Here,

the table 1 lists a number of intrasystem EMI causes and table 2 lists a number of intersystem



EMI causes. “Emitter” is used to denote a source of electromagnetic energy while the term

“susceptor” is used to denote a device that responds to electromagnetic energy. Any item in

an emitter column can interfere with any item in a susceptor column.

Intrasystem EMI Causes

Table 1.1

Emitters Susceptors Generators Navigational instrumentsComputers Computers

Radar transmitters Radar receiversRadio transmitters Radio receivers

Intersystem EMI Causes

Table 1.2

Emitters Susceptors Aircraft Aircraft

Radar transmitters Radar receiversLightning strokes Computers

Motors Navigational instruments

1.1.4 Effects of EMI:

The effect of EMI can cause malfunctioning or distraction of an electronic circuit.

The effect of EMI can be seen all around us. EMI effects result from both intra system and

intersystem problems.

Intersystem problems includes :

Radar interference with aircraft navigation systems.

Mobile radio interference with TV receivers.

Aircraft radio interference with shipboard systems, etc.

Intrasystem problems includes :

Interference from an automotive ignition system to a radio receiver within the

car.

Leakage of radar transmitter energy into the radar receiver.

Interference caused by the magnetic field of the tape drive to low level digital circuits

within the computer system, etc.



1.2 EMI SHIELDING:-

The purpose of shielding is to confine radiated energy to the bounds of a specific

region or to prevent radiated energy from entering a specific region. Shields may be in the

form of partitions and boxes as well as in form of cable and connector shields. In all cases

shield can be characterized by its shielding effectiveness, which is the number of decibels by

which the shield reduces the shield strength as the result of its being in place. Shielding

effectiveness is dependant not only on the material of which the shield is made, and its

thickness, but also upon frequency, the distance from source to the shield and the quantity

and shape of any shield discontinuities.

1.2.1 Use of Polymers for EMI shielding:-

Polymers are complex and giant molecules and are different from low

molecular weight compounds like, say, common salt. To contrast the difference, the

molecular weight of common salt is only 58.5, while that of a polymer can be as high as

several hundred thousands. These big molecules or ‘macro-molecules’ are made up of

smaller molecules. The small molecules, which combine to form a big molecule can be of

one or more chemical compounds. To illustrate, imagine a set of rings of the same size and

made of the same material. When these rings are interlinked, the chain formed can be

considered as representing a polymer from molecules of the same compound. Alternatively,

individual rings could be of different sizes and materials, and interlinked to represent a

polymer from molecules of different compounds.

The interlinking of many units has given the polymers its name, poly meaning ‘many’

and mers meaning ‘part’ (in Greek). Some of the polymer materials which can be used for

EMI shielding are ABS ( Acrylonitrile butadiene styrene ), PC (polycarbonate), PVC

( Polyvinyl chloride ) , HDPE(high density polyethylene), etc….

1.2.2 Acrylonitrile butadiene styrene (ABS) :

Chemical formula ( (C8H8· C4H6·C3H3N)n).



ABS is derived from acrylonitrile, butadiene, and styrene. Acrylonitrile is a synthetic

monomer produced from propylene and ammonia; butadiene is a petroleum hydrocarbon

obtained from the C4 fraction of steam cracking; styrene monomer is made by

dehydrogenation of ethyl benzene - a hydrocarbon obtained in the reaction of ethylene and

benzene.

ABS is a common thermo plastic used to make light, rigid, molded products such as

piping (for example plastic pressure pipe systems), musical instruments (most notably

recorders and plastic clarinets), golf club heads (used for its good shock absorbance),

automotive body parts, wheel covers, enclosures, protective head gear, buffer edging for

furniture and joinery panels, toys.

For the majority of applications, ABS can be used between −25 and 60 °C as its

mechanical properties vary with temperature. The cost of producing ABS is roughly twice the

cost of producing polystyrene, ABS is considered superior for its hardness, toughness, and

electrical insulation properties. However, it will be degraded (dissolve) [when exposed to

acetone. ABS is flammable when it is exposed to high temperatures, such as a wood fire. It

will "boil", then burst spectacularly into intense, hot flames.

Typical ABS Applications

- Automotive Applications

- Electrical/Electronic Applications

- General Purpose

- Appliances

- Housings

- Business Equipment

- Appliance Components

- Automotive Interior Parts

Dept of E&E, Sir MVIT, 2009

Advantages of ABS Disadvantages of ABS

- Flame Retardant

- Heat Resistance, High

- Impact Resistance, Good

- Flow, Good

- Limited weathering resistance

- Moderate heat, moisture and

chemical resistance

- Relatively high cost

- Flammable with high smoke

generation

9


1.2.3 Polycarbonates (PC):

Polycarbonates are a particular group of thermoplastic polymers. Polycarbonates received

their name because they are polymers having functional groups linked together by carbonate

groups (-O-(C=O)-O-) in a long molecular chain. They are easily worked, moulded and

thermoformed; as such, these plastics are very widely used in the modern chemical industry.

Their interesting features (temperature resistance, impact resistance and optical properties)

position them between commodity plastics and engineering plastics. Their plastic

identification code is 7. Polycarbonate can be synthesized from bisphenol A and phosgene

(carbonyl dichloride, COCl2).

Disadvantages:

Polycarbonate (PC) has few disadvantages like low durability against organic solvents

and alkaline chemicals, as well as high melt viscosity. In case of polycarbonates, shielding

effectiveness is low and there is no electromagnetic compatibility (EMC) shielding. Although

polycarbonate has high impact-resistance, it has low scratch-resistance and so a hard coating

is applied to polycarbonate eyewear lenses and polycarbonate exterior automotive

components. Polycarbonates are more expensive.

Applications of PC :

The price of polycarbonates restricts its use to mainly engineering applications.

The engineering applications include;

Equipment housings.

Outdoor lighting fixtures.

Exterior automotive components.

Nameplates and bezels.



1.2.4 Polyvinyl chloride (PVC) :

Polyvinyl chloride ( IUPAC Poly (chloroethanediyl) ) commonly abbreviated PVC, is the

third most widely used thermoplastic polymer after polyethylene and polypropylene. In terms

of revenue generated, it is one of the most valuable products of the chemical industry.

Around the world, over 50% of PVC manufactured is used in construction. As a building

material, PVC is cheap, durable, and easy to assemble.

It can be made softer and more flexible by the addition of plasticizers, the most

widely used being phthalates. Polyvinyl chloride is produced by polymerization of the

monomer vinyl chloride (VCM). Since about 57% of its mass is chlorine, creating a given

mass of PVC requires less petroleum than many other polymers.

With the addition of impact modifiers and stabilizers, it becomes a popular material

for window and door frames. By adding plasticizers, it can become flexible enough to be

used in cabling applications as a wire insulator. It is not recommended for use above 70°

Celsius although it can be taken to 80° C for short periods.

Typical PVC applications :-

Wire and cable applications General purpose Profiles Tubing Automotive applications Medical / healthcare applications Cable jacketing.

1.2.5 COMPOSITE EMI SHIELDING MATERIAL :

In order to avoid all those disadvantages which were observed in case of ABS

(Acrylonitrile-butadiene-styrene), PC (poly carbonate), PVC (poly vinyl chloride) etc, in our


Advantages of PVC- General Purpose- Flexibility, Good- Flame Retardant- Impact Resistance, High

11

Disadvantages of PVC-Sensitive to UV and oxidative degradation.- Higher density than many plastics. - Limited thermal capability.- Heat deflection temperature is low.- Shielding effectiveness is low.


project we have used a combination of HDPE (high density polyethylene), Cenosphere and

compatibilizer as a composite EMI shielding material. We have used this combination of

materials in different ratios (composition). In each composition (ratio), three sheets (test

samples) were prepared. But, in case of last ratio ( pure HDPE case), only 2 sheets were

prepared. Therefore, totally 11 sheets were prepared by using a blending machine and a hot

press machine.

Cenosphere is used as a filler material; this filler material imparts

good electrical conductivity, mechanical strength and absorbs the

radiations. Compatibilizer used here is grafted HDPE with di-butylene

maliate, it is added to improve the compatibility between the two

immiscible polymers; it acts as a adhesion promoter. In the first three

ratios, a constant 10% of compatibilizer is used and only HDPE and

Cenosphere contents are varied as shown in the table given below. In

the fourth ratio (100:0:0), no cenosphere or compatibilizer is added to

HDPE, so it’s called as a pure HDPE case. This ratio is considered as

a reference.

85:15:10 53.5gm HDPE: 9.5gm CENO: 7gm compatibilizer

90:10:10 56.7gm HDPE: 6.3gm CENO: 7gm compatibilizer

95:5:10 60gm HDPE: 3gm CENO: 7 gm compatibilizer

100:0:0 70 grams of pure HDPE

Table 1.3

1.2.6 HDPE (high density polyethylene) :

Polyethylene or polythene (IUPAC name polyethylene or poly (ethylene)) is a

thermoplastic commodity heavily used in consumer products (notably the plastic shopping

bag). Polyethylene is a polymer consisting of long chains of the monomer ethylene (IUPAC

name ethane). Polyethylene contains the chemical elements carbon and hydrogen.

Polyethylene is created through polymerization of ethane.



The Structure of HDPE :-

HDPE is known as a linear polymer, which is a polymer molecule where all the atoms are

linked together in a long chain. Unlike its less stable cousin, LDPE, which consists of many

branching molecules, HDPE is a much denser plastic, and as such is much stronger than

LDPE. HDPE is created by a catalytic process, and is prepared from a chemical compound

known as ethylene.

1.2.7 HDPE Resistance:

Excellent resistance (no attack) to dilute and concentrated Acids, Alcohols and Bases.

Good resistance (minor attack) to Aldehydes, Esters, Aliphatic and Aromatic

Hydrocarbons, Ketones and Mineral and Vegetable Oils.

Limited resistance (moderate attack and suitable for short term use only) to Halogenated

Hydrocarbons and Oxidizing Agents.

Good UV resistance.

1.2.8 HDPE details:-

Maximum Temperature: 248°F , 120°C

Minimum Temperature: -148°F , -100°C

Autoclavable: No

Melting Point: 266°F 130°C

Tensile Strength: 32 MPa

Surface Hardness: SD65

Translucent

Rigid

Specific Gravity: 0.95

1.2.9 Classification of Polyethylene:

Polyethylene is classified into several different categories based mostly on its density;

High density polyethylene (HDPE)

Medium density polyethylene (MDPE)

Low density polyethylene (LDPE)



HDPE: is defined by a density of greater or equal to 0.941 g/cm3. HDPE has a low degree

of branching and thus stronger intermolecular forces and tensile strength. Chromium/silica

catalysts, Ziegler-Natta catalysts or metallocene catalysts can produce HDPE. The lack of

branching is ensured by an appropriate choice of catalyst (for example, chromium catalysts or

Ziegler-Natta catalysts) and reaction conditions. HDPE is used in products and packaging

such as milk jugs, detergent bottles, margarine tubs, garbage containers and water pipes.

MDPE : is defined by a density range of 0.926–0.940 g/cm3.

LDPE : is defined by a density range of 0.910–0.940 g/cm3.

HDPE is readily available in many forms such as sheet, rod and tubing for

fabrication:

Excellent for any food related products, FDA, NSF, and USDA approved for direct

contact. This material machines extremely well.

Good chemical resistance and high rigidity make it a good choice for trays and tanks.

Other uses include pipe fittings, wear plates, hinges and cutting boards.

Good impact resistance, light weight, very low moisture absorption, and high tensile

strength. Not a good candidate for gluing. Mechanical fastening is one option, but

preferably joined by hot air or nitrogen welding. Also, Ultrasonic, Laser, and infrared

welding.

JOINTING :-

HDPE Pipes offer simple, easy, quick and economical method of jointing of pipes by

Butt-Welding (Fusion Technique) and detachable insert type joints (Sockets, Bends, Tee,

Elbow etc.)

1.2.10 Advantages and Applications of HDPEDept of E&E, Sir MVIT, 2009 14


ADVANTAGES APPLICATIONS

-Light Weight

-Flexibility

-Shielding effectiveness is high

-Toughness

-Chemically Inert

-Resistance to Abrasion

-Smooth Surface

-Environmental Stress

-Corrosion Resistance

-Hygienic Safety

-Easy & Quick Installation

-Low Thermal Conductivity

-Portable water supply

-Irrigation/Agriculture

-Gas Transmission

-Industrial Effluents

-Sewage & Drainage

-Sprinkler System

-Slurry Transportation

-Chemical Industries

-Tube wells

1.2.11 Cenosphere (filler material) :-

A cenosphere is a lightweight, inert, hollow sphere comprised largely of silica and

alumina and filled with air and/or inert gases. Cenospheres are a naturally occurring by-

product of the burning process at coal-fired power plants, and they have most of the same

properties as manufactured hollow-sphered products.

1.2.12 Importance of CENOSPHERES :-

Cenospheres are utilized as a High Performance Filler Material. This filler material

imparts good electrical conductivity, mechanical strength and absorbs the radiations.



Cenospheres can replace other fillers such as: Glass Spheres, Calcium Carbonate,

Clays, Talc, and various Silicas. Cenospheres can also be utilized as an extender in many

resin applications.

Why are cenospheres called as, a “High Performance Filler material”?

LOW DENSITY: When density counts, cenospheres can be the answer with a

density ranging from 0.50 to 0.80. Compared to most ground minerals and other

resins, cenospheres are 30% - 85% lighter.

IMPROVED FLOWABILITY: With the spherical shape of cenospheres, the flow

rate will improve greatly for most applications.

LOW RESIN DEMAND / HIGH LOADING POTENTIAL: Spheres have the

lowest surface area to volume ratio achievable. With their spherical shape,

cenospheres produce far less viscosity.

LOW SHRINKAGE: Cenospheres are one of the few products in the filler industry

today that can meet the requirements for low shrinkage. When used in high volume

loadings, cenospheres can reduce shrinkage.

STRENGTH: Cenospheres are three to ten times stronger than most man-made

hollow glass spheres. Unlike glass spheres, cenospheres can produce a higher

compressive strength due to a stronger outer shell.

INERTNESS: Cenospheres can be utilized in solvents, organic chemicals, water,

acids, or alkalis while maintaining their integrity.

THERMAL STABILITY: Because cenospheres are formed in the boilers, they are

thermally stable in temperatures exceeding 1,800 degrees F.

COST EFFECTIVE: Cenospheres are 50% - 200% less expensive than man-made

hollow glass spheres. Compared to less expensive fillers, cenospheres are cost

effective based on volume loading and weight reduction.

1.2.13 Typical Properties of Cenospheres :



Chemical Properties

Silica 55% - 65%

Alumina 25% - 35%

Iron Oxide 1% - 5%

Titania 0.5% - 1.5%

Fig 1.3 Physical Properties

Size 10-350 microns

pH in Water 6.0 - 8.0

Bulk Density 0.33 – 0.46 g/cm^3

Specific Gravity 0.6 - 0.8

Compressive Strength 3000 - 5000 lbs. per square in.

Softening Point Above 1800 degrees F

Shape Spherical

Color Grey - Light Grey - Off White

1.2.14 Compatibilizer :

Any polymeric interfacial agent that facilitates formation of uniform blends of

normally immiscible polymers with desirable end properties can be called as a

compatibilizer. Compatibilizer used in our project is grafted HDPE with di-butylene maliate.

It is added to improve the compatibility between the two immiscible polymers (components).

When mixing polymers with other components, be it fillers or even other polymers,

these two or more components will not necessarily like each other. In most of the cases there

will be a repelling force and there will be very poor or even no adhesion. This will occur

while mixing or even in many cases also when trying to adhere such components. Without

mixing the components will separate.

In order to improve adhesion, adhesion promoters can be added. Adhesion promoters that are

most easy to handle are polymeric adhesion promoters, which can also be called

compatibilizers or coupling agents. They act as surfactants. For example detergent powder as



surfactant will 'compatibilise' the dirt with the water in the washing machine and facilitate the

washing cycle.

When adhesion promoters are used to increase the compatibility of two immiscible

polymers, they are called COMPATIBILIZERS. Through offering the required balance of

physical and chemical properties, the applications for polymer blends continue to grow.

Compatibilizers provide the mechanism for blending these immiscible polymers.

CHAPTER-2

EXPERIMENT DETAILS



2.EXPERIMENT DETAILS

2.1 ELECTRICAL PROPERTIES:-

The electrical properties which we are studying are:-

1. Surface resistivity

2. Volume resistivity

3. Dissipation Factor (tanδ)

4. Capacitance

5. Dielectric Constant

2.1.1 Surface resistivity:

Surface resistivity is the resistance to leakage current along the surface of an

insulating material. The electrical resistance between 2 parallel electrodes in the contact with

the specimen surface and separated by a distance equal to the contact length of the electrodes.

The resistivity is therefore the quotient of the potential gradient in V/m, and the current per

unit of the electrode length, A/m. since the four ends of the electrodes define a square, the

length in the quotient cancel and surface resistivities are reported in ohms, although it is

common to see the more descriptive unit of ohms per square. Unit of surface resistivity is

ohms. Generally for a better EMI shielding, surface resistivity of the shielding material must

be low.

ρs = Resistance (Ω) x perimeter of LV electrode (cm)

Gap between LV and guard (cm)



ρs = R x πD (Ω)

0.1

Where R = resistance (Ω)

πD = perimeter of LV electrode (cm)

Gap between LV and guard = 0.1 (cm) = 1 mm.

2.1.2 Volume resistivity:

Volume resistivity is the resistance to leakage current through the body of an

insulating material. The ratio of the potential gradient parallel to the current in a material to

the current density. In SI, volume resistivity is numerically equal to the direct-current

resistance between opposite faces of a one-meter cube of the material (ohm-m). Generally

for a better EMI shielding, volume resistivity of the shielding material must be low.

ρv = Resistance (Ω) * Area of LV electrode (cm²) Thickness of sample in cm

ρv = R (Ω) x (πD²/4) t (cm)

2.1.3 Dissipation Factor (tan ):

DF is expressed as the ratio of the resistive power loss to the capacitive power, and is

equal to the tangent of the loss angle. It is also referenced as the loss tangent (tan δ) and

approximate power factor.

When an electric field acts on any matter, it dissipates a certain quantity of electric

energy that transforms into heat energy. This phenomena is commonly known as “the

expense” or “loss” of power, meaning an average electrical power dissipated in matter during

a certain interval of time. As a rule, the loss of power in a specimen of a material or in some

product made of this material, all other conditions being equal, is directly proportional to the

square of the electric voltage applied to the specimen or the product.

The amount of power losses in a dielectric under the action of the voltage applied to it

is commonly known as dielectric losses. This is the general term determining the loss of



power in an electrical insulation both at a direct and an alternating voltage. Dielectric losses

at a direct voltage can easily be found from the equation

P = V² R

Where V is the voltage in volts,

R is the resistance of the insulation in ohm.

The losses under an alternating voltage are determined by more intricate regularities.

When considering dielectric losses we usually mean the precisely under an alternating

voltage.

2.1.4 Capacitance:-

It is that property of the system of conductors and dielectric, which permits the

storage of electrically separated charges when potential differences exist between the

conductors. The total magnitude of a free charge across each plate of ac capacitor will be

denoted by Q. Experience shows that the charge Q is proportional to the voltage (Potential

difference) between the plates of a capacitor.

Q=CV

Here, as above, V is the voltage applied to the capacitor. The factor of proportionality,

C is the capacitance of a capacitor. In SI units, farad (F) is the unit.

The capacitance of an insulated portion depends on the geometrical dimensions, the

shape of the electrode and on the material of the dielectric. Generally for a better EMI

shielding, capacitance value of the shielding material must be high.

2.1.5 Dielectric constant:

Dielectric constant the relative static permittivity of the materials under given

conditions is a measure of the extent to which it concentrates electrostatic lines of flux. It is

the ratio of the amount of stored electrical energy when a potential is applied, relative to the

permittivity of a vacuum. The relative static permittivity is the same as the relative

permittivity evaluated for a frequency of zero.

The relative static permittivity is represented as Єr. Dielectric constant is also defined

as the ratio of permittivity of a substance to the permittivity of free space. It is an expression

of the extent to which a material concentrates electric flux and is the electrical equivalent of

relative magnetic permeability.



Substances with high dielectric constant breakdown more easily when subjected to

intense electric fields, than do materials with low dielectric constants. Generally for a better

EMI shielding, dielectric constant value of the shielding material must be high.

For example, dry air has a low dielectric constant, but it makes an excellent dielectric

material for capacitors used in high power radio frequency transmitters.

Єr = (C*t) / (Єo*A)

Where A= area of electrode = 20*10^-4 m²

Єo= 8.854*10^-12

t = thickness of sample in m

C = capacitance in pF.

2.2 SHIELDING EFFECTIVENESS:-

Shielding can be specified in terms of the reduction in magnetic and / or electric field

strength caused by the shield. It is a measure of the reduction or attenuation in

electromagnetic field strength at a point in space caused by the insertion of a shield between

the source and that point stated in dB. In the design of a shielded enclosure there are two

prime considerations: -

1) The shielding effectiveness of the shield material itself and

2) The shielding effectiveness due to discontinuities and holes in the shield.

The shielding effectiveness of a solid shield with no seams or holes is determined and

then the effect of discontinuities and holes is considered. It is the shielding effectiveness of

the apertures that usually determines the overall shielding effectiveness of a shield, not the

intrinsic shielding effectiveness of the shield material.

Shielding effectiveness varies with frequency, geometry of shield, position with the

shield where the field is measured, type of field being attenuated, direction of incidence, and

polarization. In this project we are considering the shielding provided by a plane sheet of

moderately conducting material.

The total Shielding effectiveness of a material is equal to the sum of the absorption

loss (A) plus the reflection loss (R) plus a correction factor (B) to account for multiple

reflections in thin shields. Total Shielding effectiveness therefore can be written as

S = A + R + B dB.



The multiple reflection factor B can be neglected if the absorption loss A is greater

than 9 dB.

CHAPTER-3

PREPARATION OF TEST SAMPLES



3. PREPARATION OF TEST SAMPLES (SHEETS)

3.1 STEP 1:- BLENDING

Blending is the first step in the preparation of samples. It involves the breakdown of

molecules and incorporation of selected ingredients. Blending is basically done to develop a

uniform, homogenized well-dispersed compound.

3.1.1 Principle:

The basic principle of blending carried here is REACTIVE BLENDING. Reactive

blending is a process in which a chemical bond is formed between polymer and additives

accompanied by the chemical reaction(s) of a polymer mixture with the aid of compatibilizer.

The primary objectives of blending process are:

To obtain a uniform blend of all the ingredients with adequate dispersion of the dry

powders.

To produce consecutive batches which are in degree of dispersion and viscosity,

which is essential for consistency in processing and finished products.

Blending steps:

Viscosity reduction.

Incorporation of ingredients.



Distribution of ingredients.

3.1.2 Process:

Almost all compounding ingredients exist as powders or granules. During

incorporation stage these powders will breakdown into smaller molecules, still retaining

irregularity in structure. The polymer will flow and wet these powders. The voids will get

filled with the polymer. At this stage the blend becomes less compressible and denser. This

will lead to further breakage. The viscosity will be slightly higher than the initial value

because some polymer is getting immobilized by the irregular structure of the individual

particles. The entire process will lead to some rise in temperature. In the next stage

distributive mixing occurs concurrently with dispersion.

Blending of HDPE, CENOSPHERE (filler material) and compatibilizer (grafted

HDPE with di-butylene maliate) in the desired compositions is carried out using

BRABENDER (blending machine).

3.1.3 BRABENDER (Plasti-corder):

BRABENDER (blending machine) is rather like a very small internal blender which

has interchangeable rotors and in which the blending chamber is jacketed for operation

generally at constant temperature. The rotors are coupled to a torque meter that records

throughout the blending cycle. Blending of HDPE, CENOSPHERE (filler material) and

compatibilizer (grafted HDPE with di-butylene maliate) in the desired compositions is carried

out using this blending machine.



Fig 3.1

BRABENDER specifications are as follows:

Chamber size: 70 cubic centimeters

Rotor speed: 100rpm

Equipment and instrument:

Make: CMEI

Model: 16CME SPL

BRABENDER (Blending Machine)

3.1.4 Operating procedure:

Procedures for operating internal mixers depend on the nature of the polymer and

additives, and have often been established as a result of production experience over many

years.

Mixing is carried out at an optimum temperature of 120 degree centigrade. Firstly,

HDPE is added into the stainless steel chamber. It is allowed to melt, to obtain uniform

blending and then cenosphere and compatibilizer are added and again left to melt for

sometime. The compatiblizer [HDPE-grafted with dibutylene maliate] plays its role well in

forming an efficient bond between HDPE and Cenosphere. The compatiblizer being HDPE

grafted as well forms a thorough bond and forms a good composite.

Finally, a homogenous (uniform) mixture is obtained. Then, the obtained blended

mixture, which is irregular in shape, is compressed into sheets by using a HOT PRESS

machine.



3.1.5 Factors affecting quality of mix:

Rotor speed :

High speeds are given to rotors if the compounds to be prepared using non-reinforcing

fillers, whereas low speeds for reinforcing fillers.

Fill factor :

It is the ratio of volume of the mix to that of the volume of the chamber. A fill factor

of 65% is normally followed for reinforced system. It can be 85% for general-purpose

compounds. There should be some empty space left out in chamber for the continuous

flow of material inside the chamber.

Temperature of the mix :

The temperature of the compound inside the chamber should be maintained in the range

of 120 degree centigrade.

3.2 STEP 2 :- HOT PRESSING and COOLING



Fig 3.2

3.2.1 Hot Press Machine:

A smooth test specimen (sheet) is prepared using a hot press machine where the

blended mixture is made into a smooth sheet at a temperature of 150 degree centigrade.

Hot Press is a machine, which consists of an ammeter, voltmeter, which can be varied

and upper and lower plates. Firstly, temperature (150C) is set for both upper and lower

plates. Then, the blended mixture (which will be in irregular shape) obtained from blending

machine, is placed between these upper and lower plates and pressed. The mixture is pressed

for sometime and then cooled to a temperature of 30 degree centigrade. The cooling is done

by letting down water to upper and lower plates. Finally, smooth uniform sheets are obtained

from hot press machine.



CHAPTER-4

MEASUREMENTS OF THE TEST SAMPLES



4. MEASUREMENTS OF THE TEST SAMPLES

4.1 Measurements

The measurements of the test samples are done by using Screw gauge instrument to have a

high accuracy. Using screw gauge the thickness of the test samples is calculated.

4.1.1 SCREW GAUGE (for thickness measurement of the samples):

The micrometer screw gauge:-

The micrometer screw gauge is used to measure even smaller dimensions than the

vernier calipers. The micrometer screw gauge also uses an auxiliary scale (measuring

hundredths of a millimeter) which is marked on a rotary thimble. Basically it is a screw with

an accurately constant pitch (the amount by which the thimble moves forward or backward

for one complete revolution). The micrometers in our laboratory have a pitch of 0.50 mm

(two full turns are required to close the jaws by 1.00 mm). The rotating thimble is subdivided

into 50 equal divisions. The thimble passes through a frame that carries a millimeter scale

graduated to 0.5 mm. The jaws can be adjusted by rotating the thimble using the small

ratchet knob. This includes a friction clutch, which prevents too much tension being

applied. The thimble must be rotated through two revolutions to open the jaws by 1 mm.



Fig 4.1

Fig 4.1 The micrometer screw gauge :-In order to measure the thickness of the specimen

(sheet), the specimen is placed between the jaws and the thimble is rotated using the ratchet

until the specimen is secured. Note that the ratchet knob must be used to secure the object

firmly between the jaws, otherwise the instrument could be damaged or give an inconsistent

reading. The manufacturer recommends 3 clicks of the ratchet before taking the reading. The

lock may be used to ensure that the thimble does not rotate while taking the reading.

The first significant figure is taken from the last graduation showing on the sleeve directly to

the left of the revolving thimble. Note that an additional half scale division (0.5 mm) must be

included if the mark below the main scale is visible between the thimble and the main scale

division on the sleeve.

Fig 4.2

Figure 4.2: The reading is 7.38 mm.



In figure 4.2 the last graduation visible to the left of the thimble is 7 mm

and the thimble lines up with the main scale at 38 hundredths of a millimeter

(0.38 mm); therefore the reading is 7.38 mm.

4.1.2 Tabular column ( for thickness ) :-

95:5:10 Thickness of sheets ( mm ) Average

thickness(mm) Average thickness(cm)

1 2.201 2.174 2.187 2.1874 0.21874

2 2.141 2.193 2.225 2.1864 0.21864

3 2.074 2.087 2.114 2.0917 0.20917



1 2.08 2.11 2.15 2.114 0.2114

2 2.23 2.51 2.36 2.366 0.2366

3 1.94 1.92 1.89 1.9166 0.19166



1 2.08 2.18 2.31 2.1874 0.21874

2 2.054 2.058 2.02 2.054 0.2054

3 2.44 2.087 2.053 2.19 0.219

Pure HDPE Thickness of sheets ( mm ) Average




PURE 1 1.187 2.017 2.157 1.787 0.1787

PURE 2 1.10 2.06 2.08 1.7466 0.17466

Table 4.1

4.2 CALCULATION OF RESISTIVITY 4.2.1 Resistance Measurements using ELTEL (MODEL ADTR-2k) :-

Description :-

The ELTEL automatic Dielectric Constant, tan δ and resistivity test set, (model

ADTR-2k) is an instrument designed to measure three important parameters of a insulation

medium. Though specifically designed for testing oil and other dielectric fluids, it can be

used to test other insulating media, provided a suitable test fixture is available. By combining

the three measurements in a single unit, the entire test procedure is simplified to a great

extent, resulting in a considerable save in time.

Once the instrument is installed and test connections are made, test can be carried out

ever disturbing the test set up. Many advanced features and safety checks are built into this

instrument, making it more reliable, simple and safe instrument to operate and maintain.

This instrument is fully automatic and microprocessor controlled, it measures dielectric

constant, tan δ and resistivity of the transformer oil as well as other insulating media at set

voltages and display results.

The ADTR-2k comprises:

HV supply board

Analog board

Relay board

Interlock and ground protection board

Digital board

Key board

Power supply board

LCD panel.



The rear panel of the chassis contains the power on socket and other connectors (HV,

LV, INTLK, GND, RS232 etc).

ELTEL ADTR-2K :-

Fig 4.3

The test sample is connected to the ELTEL ADTR -2k, with the help of a electrode system

(cell) as shown below :-



Fig 4.4

4.2.2 VOLUME AND SURFACE RESISTIVITY CONFIGURATIONS:-

VOLUME RESISTIVITY:-

In this configuration type, the test specimen (sheet) is placed between the two

electrodes of a cell. A cell consists of 2 electrodes i.e. high voltage electrode and low voltage

electrode. For the measurement of volume resistivity the sheet is placed between the two

electrodes where the low voltage electrode is placed above and the high voltage electrode is

placed below. This cell is connected to ELTEL device. The device displays the readings,

which are shown in tabular column.


Volume resistivity

LV (Low voltage terminal)

Sample

Ground

HV (high voltage terminal)


Fig 4.5

Surface resistivity:

Similar procedure is followed here, the only difference is that, the sheet is placed

between the high voltage electrode, which is placed above and the ground electrode, which is

placed below. The device displays the readings, which are shown in tabular column.

Fig 4.6

4.2.3 PROCEDURE :-


Surface resistivity

HV (high voltage terminal)

LV (Low voltage terminal)

Sample

Ground


The ADTR-2K performs two different measurements: one, it measures resistance and

second, it measures capacitance and dissipation factor. We have used this instrument to

measure the resistance values.

Procedure:-

a) Measure the thickness of the material to be tested (‘t’ in mm). If the thickness is uneven

take multiple measurements and choose the highest reading for ‘d’.

b) Keep the material to be tested between the H and LG electrodes.

c) Keep the instrument OFF and make the connections for H, L and G electrodes.

d) Switch ON the instrument and raise the AC voltage gradually (500 volts).

e) Press ‘2’ from the main menu of ADTR-2K as shown in the figure below;

1 AUTOMATIC MEASUREMENT

2 MANUAL MEASUREMENT

3 VIEW RESULTS

4 SETTING

5 DATE/TIME PROPERTIES

6 BACK LIGHT

Table 4.2

f) If ‘2’ is pressed from the menu it will go to the menu which is as shown below;

MANUAL MEASUREMENT

1 AC TESTING

2 DC+ TESTING

3 DC- TESTING

Table 4.3

g) Press ‘1’ for selecting AC testing, result appears as shown in the figure below;



AC TESTING

Resistance ……………………………(Ω)

Voltage ……………………………(V)

Current ………………………...…..(A)

Power ………………………….....(m W)

Frequency …………………………......(Hz)

Table 4.4

4.2.4 TABULAR COLUMN AND GRAPH FOR 200 V : -

200V

CompositionThickness

Surface Surface Avg. Volume Volume Avg. resistance resistivity Surface resistance resistivity Volume

(cm) (*10^13 Ω) (*10^13 Ω) resistivity (*10^13 Ω) (*10^13 Ωcm) resistivity

85:15:100.219 0.03149 2.37

2.366670.0914. 1.88

1.970.2054 0.03458 2.6 0.09588 2.110.219 0.02835 2.13 0.0935.3 1.93

90:10:100.2114 0.0237 1.78

1.98330.086 1.84

1.8840.2366 0.02159 1.62 0.0907 1.7340.19166 0.0338.9 2.55 0.0882 2.083

95:05:100.21874 0.02102 1.584

1.9806670.08524 1.762

1.46760.21864 0.03107 2.342 0.08132 1.6850.20917 0.02674 2.016 0.0442 0.956

Pure HDPE0.1787 0.02053 1.54

2.1550.08721 2.207

1.88850.17466 0.0368 2.77 0.0606 1.57

Table 4.5

Surface Resistivity v/s % of Cenospheres and Volume Resistivity v/s % of Cenospheres

at 200V :-



surface resistivity Vs % of cenosphere at 200V

0

0.5

1

1.5

2

2.5

0 2 4 6 8 10 12 14 16

% of cenosphere

surf

ace

resi

stiv

ity

200V

Fig 4.7

Volume resistivity Vs % of cenosphere at 200V

1.7

1.75

1.8

1.85

1.9

1.95

2

0 2 4 6 8 10 12 14 16

% of cenosphere

Vol

ume

resi

stiv

ity

200V

Fig 4.8

OBSERVATION :-



From these graphs we can observe that, with the increase in percentage of filler

content (cenosphere), both surface and volume resistivity values are increasing. Generally for

a better EMI shielding, the EMI shielding composite materials must have low surface and

volume resistivity. Here, composite material with 5% of cenosphere (filler material), is

showing least value of surface and volume resistivity.

4.2.5 TABULAR COLUMN AND GRAPH FOR 500 V: -

500V

CompositionThickness

Surface Surface Avg. Volume Volume Avg. resistance resistivity Surface resistance resistivity Volume

(cm) (*10^13 Ω) (*10^13 Ω) resistivity (*10^13 Ω) (*10^13 Ωcm) resistivity

85:15:100.219 0.0195 1.47

1.1381.57 33.1

38.240.2054 0.0108 0.814 2.03 42.80.219 0.015 1.13 1.88 38.83

90:10:100.2114 0.09 6.7858

6.597660.898 19.05

16.440.2366 0.086 6.48 0.57 12.090.19166 0.088 6.635 0.77 18.18

95:05:100.21874 0.074 5.57

3.910.613 12.86

11.07330.21864 0.0248 1.87 0.431 9.040.20917 0.057 4.29 0.523 11.32

Pure HDPE0.1787 0.017 8.06

8.1756.98 178.65

186.54540.17466 0.011 8.29 7.6 194.44

Table 4.6



Surface Resistivity v/s % of Cenospheres and Volume Resistivity v/s % of Cenospheres

at 500V:-

surface resistivity Vs % of cenosphere at 500V

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16

% of cenosphere

su

rface r

esis

tivit

y

500V

Fig 4.9

Volume resistivity Vs % of cenosphere at 500 V

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

% of cenosphere

volu

me

resi

stiv

ity

500V

Fig 4.10

OBSERVATION :-



From these graphs we can observe that, with the increase in percentage of filler

content (cenosphere), both surface and volume resistivity values are increasing. Generally,

for a better EMI shielding, the EMI shielding composite materials must have low surface and

volume resistivity. Here, composite material with 5% of cenosphere (filler material) is

showing least value of surface and volume resistivity. Hence, composite material with 5%

cenosphere (95:5:10) is a better EMI shielding material, compared to other compositions.

4.3 CAPACITANCE AND DISSIPATION FACTOR

MEASUREMENT:-

TETTEX INSTRUMENT:-

This instrument is used to measure the capacitance and dissipation factor of the

shielding material. This instrument gives a accurate values of capacitance and tan δ. It uses a

4 capacitance bridge arrangement to measure the capacitance and tan δ values. The main

advantage of this bridge are its simple operation, its high accuracy for dissipation factor

measurements and its high sensitivity also for low test voltages. The scope of supply is that

precision measuring system for dissipation factor tan δ and capacitance type 2822. it uses

only one power cable, line voltage is from 115V to 220V, 50Hz or 60Hz. The caonnecting

cables are included with the test cells.



Fig 4.11

The capacitance and dissipation factor of the samples are tested by using a instrument

known as Tettex instrument.

Though tanδ & Єr can be measured by ADTR-2K, we are not using it because the

error caused by ADTR-2K is very high.

So Capacitance and Dissipation factor are measured by using Tettex instrument.

Later Єr is calculated by using a formula.

Єr = ( C * t ) / (Є0*A).



Where; Є0 = 8.854*10^-12 .

Єr = dielectric strength (dielectric constant).

A = area of the electrode = 20*10^-4 m².

. C = capacitance in Pf.

t = thickness of the samples in m.

The main advantages of this bridge are, its simple operation, its high accuracy for

dissipation factor measurements and its high sensitivity.

4.3.1 DESCRIPTION :-

Tettex bridge (instrument) is an instrument used to measure the electrical properties like

capacitance and dissipation factor (tan ). It consists of HV (high voltage) and LV (low

voltage) electrodes between which specimen (sheet) will be placed, a temperature control unit

in which temperature is set to 27C and voltmeter which is set to 500V ( for C and tan

measurements at 200V, voltmeter is set to 200 V ), at a pressure of 2 N/cm^2. This bridge

also consists of a galvanometer, which is set to show null deflection and ‘precision tan and

C bridge’ in which C (capacitance) and tan values are varied in order to obtain balance

condition and then readings are taken. For each specimen, minimum of 3 readings are taken.

This measuring bridge has been developed particularly for testing liquid and solid

insulants. Its design is based on the fact that dielectric tests of insulants require a broad

measurement range for the dissipation factor tan δ. The tan δ measurement range of this

bridge reaches from 1.10^-5 to 10. The bridge can also be used for normal capacitance

measurements in the range of 9 to 10,000pF.

The main advantages of this bridge are its simple operation, its high accuracy for

dissipation factor measurements and its high sensitivity. And it is also used for low-test

voltages.



4.3.2 TABULAR COLUMN AND GRAPH:-

Capacitance and tan δ values at 200V & 500V : -

Table 4.7

Fig 4.12


Sl.No, Sample

200V 500V

CapacitanceTan δ

CapacitanceTan δ

(pF) (pF)

1 pure HDPE 3.56 0.0018 12.58 0.0019

2 95:05:10 4.86 0.032 22 0.034

3 90:10:10 4.76 0.026 19.69 0.029

4 85:15:10 4.56 0.02 18.73 0.017

45


OBSERVATION :-

From the graph we can observe that, with the addition of filler material (cenosphere),

capacitance value is initially increasing. Later, with the increase in filler content

(cenosphere), the capacitance value is gradually decreasing . Generally, for a better EMI

shielding, the EMI shielding composite materials must have high capacitance value. Here,

composite material with 5% of cenosphere (filler material) is having high capacitance value.

Hence, composite material with 5% cenosphere (95:5:10) is a better EMI shielding material,

compared to other compositions.

Dissipation Factor V/S % of Cenosphere at 200V & 500V is shown below :-

Fig 4.13

OBSERVATION :-


dissipation factor is initially increasing. Later, with the increase in filler content (cenosphere),

the dissipation factor is gradually decreasing. Generally, the dissipation factor is high in case

of conductors. Here, composite material with 5% of cenosphere (filler material) i.e., (95:5:10)



is showing high dissipation factor value, where as, the composite material with 15% of

cenosphere (85:15:10) is showing low dissipation factor value.

4.4 CALCULATION OF DIELECTRIC CONSTANT (Єr) :-

a) The values of capacitance of the test samples are obtained from TETTEX instrument. b) The formula for capacitance is ;

C = (Є0*Єr*A) / t F.

c) Therefore, Єr can be calculated by the formula;

Єr = ( C * t ) / (Є0*A). Where; Є0 = 8.854*10^-12 .

Єr = dielectric strength .

A = area of the electrode = 20*10^-4 m²

C = capacitance in pF.

t = thickness of the samples in m.

4.4.1 TABULAR COLUMN and GRAPH at 200 & 500V:-

Sl. No.

Sample at 200V at 500V

thickness Capacitance Dielectric constant

Capacitance Dielectric constant(cm) (pF) (pF)

1 pure HDPE 0.17676 3.56 1.35 12.58 1.26 2 HDPE+5% ceno 0.2155 4.86 1.59 22 2.68

3HDPE+10%

ceno 0.2132 4.76 1.57 19.69 2.48

4HDPE+15%

ceno 0.21438 4.56 1.55 18.73 2.26

Table 4.8



Dielectric constant Vs % of cenosphere

0

0.5

1

1.5

2

2.5

3

0 2 4 6 8 10 12 14 16

% of cenosphere

Die

lect

ric c

onst

ant

200V500V

Fig 4.14

OBSERVATION :-


dielectric constant value is initially increasing. Later, with the increase in filler content

(cenosphere), the dielectric constant value is gradually decreasing. Here, composite material

with 5% of cenosphere (filler material), that is, (95:5:10) is showing high dielectric constant

value, where as, the composite material with 15% of cenosphere (85:15:10), is showing low

dielectric constant value.



CHAPTER-5

ELECTROMAGNETIC SHIELDING EFFECTIVENESS

TEST



5. ELECTRO-MAGNETIC SHIELDING EFFECTIVENESS

TEST

5.1 Shielding Effectiveness Test

It follows the ASTM standard D 4935-99.

Shielding Effectiveness (SE) is the ability of a shield component to prevent the passage of

electromagnetic radiations. It is also defined as; the ratio of power received with and without

a material present for the same incident power.

SE = 10 log(P1/P2) dB.

P1= received power with the material present.

P2= received power without the material present.

If the receiver readout is in un its of voltage, use the following equation:

SE= 20 log(V1/V2) dB.

Where V1 and V2 are the respective voltage levels with and without a material present.

According to these equations, SE will have a negative value if less power is received with the

material present than when it is absent.

The measurement is valid over a frequency range of 30MHz to 1.5 GHz.

This test method applies to the measurement of SE of planar materials under normal

incidence, far-field, plane-wave conditions.

This test method measures the net SE caused by reflection and absorption are calculated.

In our project we are calculating from 100 KHz to 1GHz.



Fig 5.1Fig 5.1

Fig 5.2

5.2 GENERAL TEST SET UP :-

The test setup contains the following parts:-

o Specimen Holder- It is an enlarged, coaxial transmission line with special

taper sections and notched matching grooves to maintain a characteristic impedance of 50Ω

throughout the entire length of the holder.

o Signal Generator- A source capable of generating a sinusoidal signal over the

desired portion of the frequency range.



o Receiver- A device with a 50Ω input impedance capable of measuring signals

over the same frequency range as the signal generator.

o Coaxial Cables and Connectors- These are devices for connecting power

between specific components without causing interference with other components. It should

have a impedance lesser than 50Ω.

o Attenuators- These are devices used to isolate the specimen holder from the

signal generator and the receiver. Their main purpose in this system is for impedance

matching.

The test samples are prepared as below and then it can be subjected to the SE test

REFERENCE LOAD

Fig 5.3

5.3 TEST procedure:-

The samples are prepared according to the measurements given. 2 specimens are prepared

namely Reference Specimen and the Load specimen. Determine all frequencies for which

SE values are to be measured for the Reference specimen, change to the load specimen, and

then record load values at these same frequencies. Measure the received power (or voltage)

while using the reference specimen. Record the measured received values as P2 or V2 Dept of E&E, Sir MVIT, 2009 52


values at each frequency. Determine all frequencies for which SE values are to be measured.

The specimen mounting procedure requires more time and effort then changing frequency, so

it is more efficient to record values at all frequencies for the reference specimen, change to

load specimen, and then record load values at these same frequencies. This procedure can be

automated if a computer and ancillary equipment with IEEE-488 bus capability are available.

Replace the reference specimen with the load specimen. Record the measured values as P1 or

V1 values at the same frequencies.

If the recorded units are watts use the power ratio equation to calculate SE. If the recorded

units are volts, use the voltage ratio equation to calculate SE.

The procedure for inserting the specimen is a follows use a support structure to support the

specimen holder in a vertical position. Remove two nylon screws, and carefully lift off the

upper half of the holder. Place the two pieces of the reference specimen on the flange of the

bottom half of the specimen holder.replace the half of the specimen holder. Turn the holder

end for end and then reinstall the other two nylon screws. Reconnect the coaxial cables.

5.4 SE test results:-

This test was conducted in the frequency range of 100KHz to 1GHz and the following results

were obtained:-

Sample Shielding Effectiveness from 100KHz to 1GHz

Pure HDPE 1dB

HDPE with 5% Cenosphere 4dB



Table 5.1

Observation:-

The above results show. that there is no much difference in attenuation level with respect to

all compositions. However, from the results obtained we can conclude that, HDPE with 5%

cenosphere is a better EMI shielding material.



CHAPTER-6

CONCLUSION & FUTURE SCOPE



6.1 CONCLUSION:-

The above work leads to the following conclusions:-

HDPE with 5%, 10% and 15% of cenosphere as filler content and di-butylene maliate

as compatibilizer (composite materials) have been studied.

The volume resistivity of HDPE with ceno has increased with increase in ceno

content from 5 to 15%.

The dissipation factor and dielectric constant have decreased with increase in ceno

from 5 to 15%.

These samples have been evaluated for different electrical parameters like surface and

volume resistivity, capacitance, tan δ, dielectric constant and then subjected to

electromagnetic shielding effectiveness test.

It is found that volume resistivity is decreased by just 1 order in case of the composite

materials as compared to pure HDPE where as, there is a marginal decrease in surface

resistivity value.

tan δ and dielectric constant with respect to all the combinations has increased when

compared to the base material i.e. pure HDPE.

Generally, for a better EMI shielding, the shielding material must have low volume

and surface resistivity, high capacitance and dielectric value. All these conditions are

satisfied by composite material with 5% of cenosphere (i.e.; 95:5:10).

Based on our evaluations, we can judge that HDPE with 5% cenosphere content and

10% compatibilizer (i.e., 95:5:10) shows better characteristics as an EMI shielding

material.

The pure HDPE and composite materials were tested for their Electromagnetic

shielding effectiveness in the frequency range of 100 KHz to 1GHz. The results

indicated that electromagnetic shielding effectiveness properties with respect to all the

compositions are nearly the same. The composite material with 5% of cenosphere

(95:5:10)is showing better shielding effectiveness.



6.2 Future Scope:-

HDPE with increased level of ceno addition i.e. more than 15% need to be tried for

improved shielding effectiveness due to EMI.

Filler material other than ceno such as graphite may be tried for improved EMI

performance.

Applicability of these composite materials as shields for the electronic devices like

energy meters.

Study of the mechanical properties of these shielding materials.



CHAPTER-7APPENDIX & BIBLIOGRAPHY



7.1 Appendix A

Tettex instrument:-

Description

This measuring bridge has been developed particularly for testing liquid and solid insulants.

Its design is based on the fact that dielectric tests of insulants requires a broad measurement

range fro the dissipation factor tan δ values for new, pure and clean oil, for example, are

approximately 10^-4, 10^-3 etc.. While tan δ for old, used and dirty oil may amount up to

approximately 5 (500%). The tan δ measurement range of this bridge reaches from 1*10^-5

to 10 *(1000%). The bridge can also be used for normal capacitance measurements in the 9 to

10,000pF range, mainly for type tests of plastic capacitors with accurate tan δ requirements.

The main advantages of this bridge are its simple operation, its high accuracy for

dissipation factor measurements and its high sensitivity and also for its low test voltages. A

simple block diagram of the Tettex AG is given below

Fig 7.1



7.2 Appendix B

ELTEL-ADTR 2K

Automatic Dielectric Constant Tanδ & Resistivity Test Set

Fig 7.2

The ADTR-2K is an automated instrument for measuring the electrical characteristics

of transformer oil, insulating liquids & other insulating material samples. The ADTR-2K

measures Capacitance, Dielectric Constant (Єr), Dielectric Loss, Tan Delta (Dissipation

Factor) Resistance & Resistivity of the test sample. The Tan Delta value gives an indication

of the condition of the oil sample. There are several reasons due to which the Tan Delta value

may be affected such as moisture, dissolving of some of the transformer varnish, insulating

material deteriorating etc. ADTR-2K is especially designed to work with the IEC & ASTM

type oil cell with a 2mm spacing and will apply a stress in the range of 100-1200 volts per

mm as recognised by ASTM and other specifications.



Fig 7.3

The ELTEL automatic Dielectric Constant, tan δ and resistivity test set, (model

ADTR-2k) is an instrument designed to measure three important parameters of a insulation

medium. Once the instrument is installed and test connections are made, test can be carried

out ever disturbing the test set up. Many advanced features and safety checks are built into

this instrument, making it more reliable, simple and safe instrument to operate and maintain.

This instrument is fully automatic and microprocessor controlled, it measures

dielectric constant, tan δ and resistivity of the transformer oil as well as other insulating

media at set voltages and display results.



7.3 BIBLIOGRAPHY

1. Van nostrand and Reinhold, Metal and polymer composites

2. Kubel, E., materials Engineering 102:25 (January 1985).

3. Bradish, F., Conductive Composites for Shielding, Spe composites institute,

(1980).

4. T. Araki, “Electromagnetic Interference and Preventice Measure”, pp.129-143,

Tokyo Denki University, 1984.

5. K. Nakanighi, “Rapidly Developing EMI shielding Materials”, Nikkei New

Materials, No. 51, pp. 74-89, 1988.

6. Kodali, V.P., Engineering Electromagnetic compatibility.

7. Henry W. Ott, “Noise Reduction Techniques in Electronic Systems”, Second

Edition, John Wiley and Sons, 1989.

8. Hand Book of Electrical and Electronic insulating Materials, Shugg.W.Tillar.

9. “Principle of Electromagnetic Compatibility”, 3rd Edition, Bernhard Keiser.

SITES

1. www.google.com

2. www.wickepedia.com

3. www.sciencedirect.com

4. www.freepatents.com

5. www.ieeexplorer.org

6. www.astm.org


http://www.astm.org/

http://www.ieeexplorer.org/

http://www.freepatents.com/

http://www.sciencedirect.com/

http://www.wickepedia.com/

http://www.google.com/

composite characterization of emi shielding

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