1 polymer composites in insulation system(corrected)

7/28/2019 1 Polymer Composites in Insulation System(Corrected)

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Insulation System in Energy Sector: The

Benefits of Polymer Composites

ABSTRACT

Polymers with Composite materials are used in

various engineering applications due to their ability

to be adapted for a specific application. As a resulta composite could be selected or designed for a high

performance part such as field grading applications

in high voltage technology. In this paper study,

characterize a polymeric system composed of a

polymer filled with nanomaterial. Composites with

different filler weight concentrations are prepared

and their dielectric performance is characterized.

Measurement results and potential applications of

the composite systems are presented.

KEYWORDS: HDPE, Polystyrene, dielectrics

properties, Nanocomposites

INTRODUCTIONThe most important insulation material is air. A

variety of solid, liquid, and gaseous insulators are

used in electrical apparatus. In smaller transformers,

generators, and electric motors, insulation on the wirecoils consists of up to four thin layers of polymer

varnish film. Windings of thicker conductors are

often wrapped with supplemental fiberglass

insulating tape. Windings may also be impregnated

with insulating varnishes to prevent electrical corona

and reduce magnetically induced wire vibration.

Large power transformer windings are still mostly

insulated with paper, wood, varnish, and mineral oil,

although these materials have been used for morethan 100 years, they still provide a good balance ofeconomy and adequate performance. Busbars and

circuit breakers in switchgear may be insulated with

glass-reinforced plastic insulation, treated to have

low flame spread and to prevent tracking of current

across the material.

Expanded Wood Fiber Polystyrene Composites

Processing, Structure, Mechanical Properties

explained [1]. Carbon dioxide in wood-fiberpolystyrene composites Sorption and dispersal

in [2]. Insulation is a resistive material which

opposes the flow of charge in it. Nano

material is a light volume material which is

added with polymerized material to improve

its insulation property, which intern improves

the chemical, mechanical and electrical

properties of the material.In this paper using nano alumina and nano

magnesium oxide as filler material with high density

polyethylene(HDPE) and polystyrene polymers are

studied. The mechanical and electrical tests are

performed on the above samples prepared and are

compared with other conventional polymers.

Cellulose insulation: Cellulose might be using

increased interest ingreen building. Cellulose has thehighest recycled content of any insulation material

and also has less embodied energy than fiberglassand other furnace produced mineral insulations [2].

Currently cellulose insulation has increased again in

use in the United States. Part of the reason for this

growth are studies that have shown results that

suggest that cellulose may actually protect a building

from damage in a fire better than fiberglass becausecellulose is denser than fiberglass and doesn't allow

the oxygen necessary to burn structural members.

Polymers insulation: Polymer are used in various

electrical applications like wire and cable as

insulation and jacketing materials due to their

exclusive combination of properties such as

temperature flexibility excellent insulatingcharacteristics and resistance to moisture absorption.

By blending suitably selected polymers, newmaterials with desirable final properties can be

prepared. Electrical properties of various polymer

blends have been investigated by different

investigator. In paper it has been shown that the

dielectric properties of polymers and blends in

general depend on structure, crystallinity,

morphology and presence of fillers or other additives.

The dielectric constant of the blends is found toincrease with increase in the effectiveness of the

permittivity was found to increase with increase in

concentration of dipoles. The incorporation of polarcomponents into polymer has increased the dielectric

constant and dielectric loss of the blend. The

measurement of dielectric properties as a function of

temperature was used as a way to study the different

polymer blend systems.Polymers are chain like molecules that are made of

the same repetition unit. Aside from few exceptions

polymers consist of molecules with different chain

lengths. Therefore average values are given for the

molecular weight like the number average, the weight

average or the viscosity average molar mass. A

measure for the width of the molecular weight

distribution is the polydispersity index. The targetedmanipulation of the molecular weight distribution of

a polymer by removing short and/or long chain

material is called polymer fractionation.Polymer structure and morphology, classification of

polymers, polymer characterization, polymers asdielectrics in various electrical equipments,

dielectrics in electric field, relaxation, permittivity
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and dielectric loss, filled polymers for HV

applications were studied in this paper.

Nanomaterials: Polymer nanocomposites,

processing of nonocomposites, dispersion ofnanofillers in polymer matrix, influence of nanofillers

on dielectric properties, interface phenomena,electrical degradation treeing, stochastic models of

breakdown, multi stress ageing, Nanodielectrics for

specific HV applications, Computational dielectrics

were also studied.

There are three common methods used to enhance

polymers with nanofillers to producenanocomposites. Melt compounding or processing of

the nanofillers into a polymer is done simultaneously

when the polymer is being processed through an

extruder, injection molded, or other processing

machine. The polymer pellets and filler are pressed

together using shear forces to help with exfoliation

and dispersion [4].

SCOPE OF NANO COMPOSITES:

Polymer nanocomposites are constructed by

dispersing a filler material into nanoparticles thatform flat platelets. These platelets are then distributed

into a polymer matrix creating multiple parallel

layers which force gases to flow through the polymer

in a torturous path forming complex barriers to gases

and water vapor. As more tortuosity is present in a

polymer structure, higher barrier properties will

result.

EXPERIMENTAL WORK:

Latest generation dielectrics

In the recent times there have been excellentdevelopments in the field of dielectric materials with

the intension of reducing the maintenance costs.

The actual comparisons of the dielectric materials of

HDPE and Polystyrene were studied.

Properties of HDPE:

Abrasion Resistant:

The extremely high molecular weight of HDPE

combined with its very low coefficient of friction

provides an excellent abrasion resistant product

preventing gouging, scuffing and scraping.

Exceptional Impact Strength:

HDPE is one of the highest impact resistantthermoplastics available and maintains excellent

machinability and self- lubricating characteristics.Properties are maintained even at extremely low

temperatures.

Chemical Resistant:

HDPE has very good chemical resistance of

corrosives as well as stress cracking resistance (with

the exception of strong oxidizing acids at elevated

temperatures). Certain hydrocarbons cause only a

light surface swelling at moderate temperature.

Water Resistant:

Moisture and water (including saltwater) have no

affect on HDPE. It can be used in fresh and salt water

immersion applications.

HPDE is more rigid and harder than lower densitymaterials. It also has a higher tensile strength fourtimes that of low density polyethylene, and it is three

times better in compressive strength. It also is

accepted by USDA(United States Department of

Agriculture), NSF(National Science Foundation) and

the Canadian Department of Agriculture.Properties of HDPE:

HDPE has little branching, giving it stronger

intermolecular forcesand tensile strength than lower-

density polyethylene. It is also harder and more

opaque and can withstand somewhat highertemperatures (120 C/ 248 F for short periods, 110

C /230 F continuously). High-density polyethylene,

unlike polypropylene, cannot withstand normally-

required autoclaving conditions. The lack of

branching is ensured by an appropriate choice of

catalyst (e.g., Ziegler-Natta catalysts) and reaction

conditions. HDPE contains the chemical elements

carbonand hydrogen.CHEMICAL PROPERTIES:

The longer the main chain, the greater the number of

atoms, and consequently, the greater the molecular

weight. The molecular weight, the molecular weight

distribution and the amount of branching determine

many of the mechanical and chemical properties of

the end product.Thermal properties:

The melting pointof polyethylene is defined as that

temperature at which the plastic transitions to acompletely amorphous state. In HDPE and other

thermoplastic materials, the molecular chains are not

cross-linked and such plastics will melt with the

application of a sufficient amount of heat. With the

application of heat, thermoplastic resins may beshaped, formed, molded or extruded. Thermosetting

resins are composed of chemically cross-linked

molecular chains, which set at the time the plastic is

Fig.1, HDPE Molecular chain
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first formed, these resins will not melt, but rather

disintegrate at a temperature lower than its melting

point, when sufficient heat is added.

Mechanical Properties:

HDPE is a non-linear viscoelastic material with time-

dependent properties[6]. A thermoplastic pipe,serving as composite structure, benefits by its

attribute of stress relaxation. Predictability of

performance of a pipe in service requires knowledge

of the mechanical properties of the HDPE resin and

knowledge of the profile geometry.

Typical properties of polyethylene :

Advantages of HDPE Electrical Conduit

With its high performance and material

characteristics, electrical insulation provides

necessary security and protection they need against

random construction, harsh and highly pressuredenvironments. Designed to house, protect and cover

sensitive electrical wiring and utility cables in power

distribution systems, HDPE is referred to as asmooth wall electrical conduit. It provides

outstanding performance benefits for any electrical

insulation regardless of voltage or amperage

requirements.

Electrical conduit offers:

High tensile strength to endure heavy

external loads.

Long term strength for increased life and

performance

Lower installation costs

Resistance to corrosive chemicals and

aggressive soils

Moisture proof and watertight when fusion

welded

No biological growth

Low resistance to pulled-in cable

Color coding for easy identificationOther Applications:

Food cutting boards

Corrosion resistant wall coverings

Pipe flanges

Lavatory partitions

Man-hole covers in Chemical Plants

Radiation shielding

Self supporting containers

Prosthetic devices

Properties of

Polystyrene:

It is an aromatic polymer made from the aromaticmonomer styrene, a liquid hydrocarbon that is

commercially manufactured from petroleum by the

chemical industry. Polystyrene is one of the most

widely used kinds ofplastic [5].

Fig.2 HDPE compound

ASTM

testProperty High density

PHYSICAL

D792 Specific gravity 0.941-0.965

D792 Specific volume (in./lb.) 29.4-28.7

D570Water absorption, 24

hours, 1/8 inch thick (%)


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Polystyrene is a thermoplastic substance, which is in

solid (glassy) state at room temperature, but flows if

heated above its glass transition temperature (for

moldingor extrusion), and becomes solid again when

it cools off. Pure solid polystyrene is a colorless, hardplastic with limited flexibility. It can be cast into

molds with fine detail. Polystyrene can betransparentor can be made to take on various colors [1, 3].

Polystyrene can be recycled and has the number 6 as

its recycling symbol. Polystyrene does not

biodegrade and is often abundant as a form of

pollution in the outdoor environment, particularly

along shores and waterways.Chemical Properties:

The chemical makeup of polystyrene is a long chain

hydrocarbon with every other carbon connected to a

phenyl group. Polystyrene's chemical formula is

(C8H8)n, it contains the chemical elements carbon

and hydrogen. Because it is anaromatic hydrocarbon,

it burns with an orange-yellow flame, giving offsoot,as opposed to non-aromatic hydrocarbon polymers

such aspolyethylene, which burn with a light yellow

flame (often with a blue tinge) and no soot. Complete

oxidation of polystyrene produces only carbon

dioxide and water vapor. This addition polymer of

styrene results when vinyl benzene styrene

monomers (which contain double bonds between

carbon atoms) attach to form a polystyrene chain.

Polystyrene is chemically unreactive, is used tocreate products such as containers for chemicals,

solvents and foods. This stability is the result of thetransformation of carbon-carbon double bonds into

less reactive single bonds. Structurally, the

unsaturated alkene monomers have been transformed

into less saturated structures with carbon alkane

backbones. A molecule is considered saturated when

its carbons are bonded to the maximum number ofhydrogen atoms possible. The strong bonds within

the molecule make styrene very stable.Dielectric Strength: It is the ability of the material to

with stand the applied potential difference without

causing the arcing across the insulator. It is very

obvious that more the dielectric strength and have the

value of 500v/mil.

Dielectric Constant: It is an indicative ability of aninsulator to deliver the electrical charge. The

capacitive impedance of the dielectric directly relatedto the dielectric constant and the voltage gradients

induced through the dielectric layer is inversely

proportional to the dielectric constant and has the

value of 2.5 - 2.6.Heat Dissipation: The material that easily dissipates

heat should be selected and specific heat (C) of 1.3 kJ/(kgK).

Porosity: - Porosity causes air entrapment and

absorption of moisture which can cause tracking of

the electrical discharge to the ground. This material

has low porosity.Maximum service temperature: High temperature

often causes the burning of dielectric coverings. This

can be reduced by optimizing the temperature in the

system. Polystyrene hasThermal conductivity (k) of

0.08 W/(mK), Glass transition temperatureof 95 Cand Melting point of 240 C.

Hardness: Surface harness prevents abrasion and of

linear expansion coefficient (a) has 8105 /K,

Elongation at break of 34%.Costs:Each application should be analyzed to

determine the best material for that particular job.

The cost is dependent on the selection of the

dielectric properties in the material.

Fig.3 Polystyrene

Properties

Density 1.05 g/cm3

Density of EPS 16640 kg/m3

Dielectric constant 2.42.7

Electrical conductivity (s) 1016S/m

Thermal conductivity (k) 0.08 W/(mK)

Elongation at break 34%

Notch test 25 kJ/m2

Glass transition temperature 95 C

Melting point 240 C

Vicat B 90 C

Linear expansion coefficient

(a)

8105/K

Specific heat (c) 1.3 kJ/(kgK)

Water absorption (ASTM) 0.030.1

Decomposition X years, still decaying

Table 2 properties of Polystyrene

Substance

Dielectric

Constant

(relative to

air)

Dielectric

Strength

(V/mil)

Loss

Tangent

Max

Temp

(F)

Polystyrene 2.5 - 2.6 500

0.0001 @

100 MHz

0.00033 @

3 GHz

240 C

High Density

Polyethylene

(HDPE),

Molded

1.0 - 5.0 475 - 38100.0000400 -

0.00100

158 -

248

Table 3. Typical property comparison of HDPE and
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Flow chart of Nanocomposites

Synthesis procedure carried:

Weighing granules in preferred quantity

Blend the granules with nano composites in

a blending machine

Put the blended granules in a hot press

(Thermoset) at the temperature of 1600 C,

around 10-15 minutes

Samples are ready for testing

Injection Molding:

In injection molding, polymer granules are

-compressed by a ram or a screw

-heated until molten

-injected into a cold, split mould under

pressure

The molded polymer is cooled below Temperature-The mould opens and the product is ejected

This process gives high precision moldingsbecause the polymer cools under pressure

Cycle time is typically between 1 5minutesCompression Molding:

This method is well suited to forming of

Thermo set casings for appliances

Thermoplastic car bumpers

Since a thermo set can be removed when hot,

cycle times can be as low as:

10 seconds for small components

10 minutes for large thick walled moldings

Both thermoplastics and thermo sets can beformed by compression mould

The polymer or mixture of resin and hardener is

heated and compressed between dies.Finished Samples:

HDPE with nano alumina

HDPE with nano magnesium oxide

Polystyrene with nano alumina

Polystyrene with nano magnesium oxideTESTS CONDUCTED

After designing the samples, it has to undergo the

following tests for comparison of electrical and

mechanical properties.

Break down voltage (BDV) test

Tan (delta)

Tensile test (mechanical strength)

Breakdown: The break down strength of pure

polymer is much greater than of adding

nanocomposites. In our project we tested breakdown

strength of polymer material by using Auto

Transformer, Which is rated of 0-25KVA. The

breakdown voltage of an Insulator is the minimumvoltage that causes a portion of an insulator to

become electricallyconductive.

Dielectric constant and loss factor: The information

obtained from the measurement of tan and complex

permittivity is an indication of the quality of the

insulating material.

If the tan varies and changes abruptly with the

application of high voltage, it shows inception of

internal partial discharge.

The effect to frequency on the dielectric

properties can be studied and the band of

frequencies where dispersion occurs i.e., where

that permittivity reduces with rise in frequencycan be obtained.

Tensile strength: Tensile strength is indicated by the

maxima of a stress-strain curve and, in general,

indicates when necking will occur. As it is anintensive property, its value does not depend on the

size of the test specimen. It is, however, dependent

on the preparation of the specimen and the

temperature of the test environment and material. The

standard way to measure tensile strength is to use a

small bar with uniform width (apart from at the edges

where the thickness increases) and to 'pull' at each

end until the bar fails. In the process, other

mechanical properties may be obtained. Other testingmethods also exist, such as the plane straincompression test.

Fi ure.4 :Flow chart ofNanocom osites

Fig.5 Samples of HDPE and Polystyrene Figure : Samples prepared at CPRI, Bengaluru
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Results and discussion:

Break down voltage of different Samples:

Variation of BDV with respect to HDPE with nano

composites Mgo and alumina, and PS with nano

composites Mgo and alumina.X-axis is the different

samples and Y-axis is the values of BDV.

Conclude that the BDV of HDPE+nano Mgo is much

lower than that of PS+nano Mgo.Loss angle of various samples:

Variation of tan with respect to HDPE with nano


composites Mgo and alumina. X-axis is the different

samples and Y-axis is the values of tan.

Concluding that the tan of HDPE+nano Mgo is

much higher than that of PS+nano MgoTensile strength of various samples:

Variation of tensile strength of HDPE with nano


composites Mgo and alumina. X-axis for differentsamples and Y-axis is the values of tensile strength.

Concluding that the tensile strength of HDPE+nano

Mgo is much lower than that of PS+nano Mgo.

Applications:

HDPE:

Resistant to corrosion and chemical

attack

Light weight

Chemical resistant piping systems

Fuel tanks for vehicles

Laundry detergent bottles

Polystyrene:

The most important properties of PS are :

Excellent thermal performance

High compressive strength

Out standing impact absorption

Low weight

Imperviousness to moisture

100% recyclable

Conclusion:

From the above tabulation it is clear that the

properties vary with addition of nano filler materials.

In case of loss angle (tan delta) the value ofHDPE+2g alumina (0.605) is less than pure samples

of HDPE as well as Polystyrene, so adding Nano

alumina reduces the loss angle in insulating material.

The break down voltage of nano material, the

electrical strength is reduced. The break downvoltage of pure HDPE (10.021KV) is much more

than any other nano components added material. By

this test shows adding nano material reduces the

break down voltage of insulation system.

The Resistivity of the material depends on the area of

the material. As there is addition of filler material, the

resistivity gradually decreases. For pure insulatingmaterial the value of the resistivity is high (HDPE

2.336E14 m and PS 6.365E13 m). In capacitance

test, the value of pure HDPE (629.71F) is higher

than nano fillers added material. Normally if any

impurity is added

to an insulation system it conducts faster than purematerial. Pure material has good insulating property

than nano added material. The major advantage ofadding nano material is to provide mechanical

strength. This is proved by conducting the tensile

tests on the samples. Usually the tensile strength of

the pure material is low (For Pure polystyrene

7.305Mpa, Pure HDPE 8.165mpa) when compared

with the nano composite materials. Tensile property

of the insulating material is increased by adding
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the nano fillers. While manufacturing the pure

insulating material (HDPE and PS) voids are created,

this leads to treeing effect and break down of

insulation with less span of time (ageing). So Nano

fillers bonds tightly, hence there is a less chances oftreeing effect. This will increase the life span as well.

Nano filler added material having less break downvoltage, capacitance and resistivity value. But there is

an improvement in tan delta and mechanical strength.

Break down strength can be improved by increasing

the thickness of insulating material.

References1. Doroudiani S, Kortschot MT (2004). "Expanded Wood

Fiber Polystyrene Composites: Processing-Structure-

Mechanical Properties Relationships". Journal of

Thermoplastic Composite Materials 17: 1330.doi:10.1177/0892705704035405.

2. Doroudiani, Saeed; Chaffey, Charles E.; Kortschot,Mark T. (2002). "Sorption and diffusion of carbondioxide in wood-fiber/polystyrene composites". Journal

of Polymer Science Part B: Polymer Physics 40: 723.

doi:10.1002/polb.10129.3. Mihai, M.; Huneault, M. A.; Favis, B. D. (2007).

"Foaming of Polystyrene/ Thermoplastic StarchBlends". Journal of Cellular Plastics 43: 215.

doi:10.1177/0021955X07076532.

4. E. Tuncer, I. Sauers, D. R. James, A. R. Ellis, M. P.

Paranthaman, A. Goyal, and K. L. More, Dielectric

properties of various nanocomposites materials,325704 .

5. Digital Object Identifier, February 2008 , Liang, G.D.

Tjong, S.C.

City Univ. of Hong Kong, Hong Kong, Electrical

properties of percolative polystyrene/carbon nanofibercomposites

6. Lester H. Gabriel, Ph.D., P.E. reference chapter 1

History and Physical Chemistry of HDPE
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1 polymer composites in insulation system(corrected)

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