Electrical Insulation Characteristics of Silicone and EPDM Polymeric Blends. I

IEEE Transactions on Dielectrics and Electrical Insulation Vol. 14, No. 5; October 2007

1070-9878/07/$25.00 © 2007 IEEE

1207

Electrical Insulation Characteristics of Silicone and EPDM Polymeric Blends – Part I

R. Raja Prabu

B.S.A Crescent Engineering College Vandalur, Chennai – 600 048

Tamil Nadu, India

S. Usa, K. Udayakumar High voltage division, College of Engineering, Anna University

Gunidy, Chennai – 600 025 Tamil Nadu, India

M. Abdullah Khan and S.S.M. Abdul Majeed B.S.A Crescent Engineering College

Vandalur, Chennai – 600 048 Tamil Nadu, India

ABSTRACT

The typical parts of a polymeric insulator are core, metal end fittings and polymeric housing material. The housing is intended to protect the fibre glass rod from the environment and electrical surface discharges. Since the housing materials are made of organic polymeric material, its insulation characteristics need to be studied. Amongst the many different polymers available, this work focuses on Silicone rubber and Ethylene Propylene Diene Monomer (EPDM). Blends of EPDM and silicone rubber are prepared in a two roll mixing mill. Dicumyl Peroxide is used as vulcanizing agent. The blends consisting of various proportions of component polymers are prepared, compression moulded into sheets, and post cured. The blends are tested for their insulation characteristics as per IEC and ASTM standards. Volume and surface resistivity, dielectric strength, dielectric constant, tan δ, tracking resistance, arc resistance, comparative tracking index, tensile strength, and percentage elongation at break of the blends are studied and discussed. The test results show that the increasing proportion of silicone enhances the electrical insulation properties whereas increasing weight percentage of EPDM improves the mechanical strength of the blends.

Index Terms – Polymeric Insulators, insulation characteristics, tracking resistance, dielectric strength, tensile strength, blend composition.

1 INTRODUCTION

POLYMERIC insulators are being accepted increasingly for use in outdoor applications. The tremendous growth is due to their advantages over the traditional ceramic and glass insulators. It includes lightweight, higher mechanical strength to weight ratio, resistance to vandalism, better performance in the presence of heavy pollution in wet condition, and better withstand voltage than porcelain insulators. However, because polymeric insulators are relatively new, the expected lifetime and their long-term reliability are not known, and therefore are of concern to users. The typical parts/components of a polymeric insulator are core/rod, metal end fittings/rings and polymer housing/ weather sheds. Here, the fibre glass or ceramic rod is employed for mechanical strength and electrical strength under dry conditions. However, fibre glass is a poor insulator

under wet conditions, as it absorbs moisture. To overcome this limitation of intrinsic core, the housing is installed over the core with a suitable, stable interfacial sealant to maintain dielectric strengths. Proper end fittings are provided for connections to pole and conductor. Housing material made of Silicone and EPDM rubber for a polymeric insulator is the focus of this research work. EPDM elastomer possesses good mechanical strength and outstanding resistance to attack by oxygen, ozone and weather [1]. It has excellent dielectric properties even at high temperatures. Silicone elastomers have excellent dielectric properties coupled with high temperature stability [2]. Blending of two polymers is an attractive way to develop a new material with good dielectric characteristics, thermal stability, and resistance towards polluted environment [3]. Polymeric materials cost higher than porcelain materials, with respect to Indian context. Manuscript received on 29 November 2006, in final form 17 May 2007.

R. Raja Prabu et al.: Electrical Insulation Characteristics of Silicone and EPDM Polymeric Blends – Part I 1208

To access the suitability of the blends for housing material applications and to obtain a complete database, seven formulations of EDPM and silicone are prepared [Table 1] and tested for their electrical insulation characteristics as per IEC and ASTM standards. [Section 2.4] Polymers can be formulated suitably to make them more resistive to damage from the numerous elements in nature such as UV radiation, chemicals, corona, electrical arc discharge activity, and extreme temperature [3]. Standard tests are prescribed by various agencies like IEC, ASTM, and BIS for evaluating the resistance of the material to these polluting elements. Even on well-formulated material, electrical discharges present a significant cause of degradation. A reasonably accurate prediction of the onset of material degradation has defied researches for many years. The present investigation is directed towards the development of new material for housing/weather sheds of a polymeric insulator. Hence, the focus is to prepare blends of EPDM and silicone elastomer and to study systematically the dielectric characteristics and mechanical properties, as per the standard procedures given in section 2.4, so as to use the same for housing material.

2 EXPERIMENTAL 2.1 MATERIALS

The characteristic parameters of the commercial polymers used to prepare the blends are as follows. Silicone rubber is supplied by Japan synthetic rubber company. It is of VMQ type elastomer. EPDM (EP96) is supplied by Japan synthetic rubber company. It contains third monomer as ethylene norbornene (ENB). Dicumyl Peroxide (98 % active) is supplied by MERK, Germany.

2.2. BLEND PREPARATION The blends of EPDM and Silicone containing various proportions of component polymers are prepared in a laboratory model two roll mixing mill at a temperature of 353 K. Vulcanizing agent dicumyl peroxide is mixed during the mill mixing. The compositions of the blend prepared are listed in Table 1. The blend preparation procedure is detailed in appendix-A.

2.3 VULCANIZATION The vulcanization of the blends is carried out in a hydraulically operated press at 443 K for 10 minutes. The vulcanized samples are post cured at 423 K for 2 hours in an air-circulated oven. Test specimens are punched out from the compression-moulded sheets. The various blends prepared (Table 1) are tested for their electrical characteristics like tracking resistance [4], arc resistance, volume resistivity, surface resistivity, dielectric strength, comparative tracking index and tan δ and mechanical characteristics like tensile strength and percentage elongation at break.

Table 1. Composition of silicone and EPDM blends.

Silicone rubber

(in percentage by weight)

EPDM (in percentage

by weight)

Dicumyl Per oxide (in phr)

Blend Notation.

0 100 2.5 A

10 90 2.5 B

30 70 2.5 C

50 50 2.5 D

70 30 2.5 E

90 10 2.5 F

100 0 2.5 G

2.4 CHARACTERIZATION In this section, the test conditions and procedure for the important electrical and mechanical insulation characteristics of a polymeric insulator are described.

2.4.1 TRACKING RESISTANCE Tracking resistance is determined as per IEC-60587. The distance between the top and bottom electrode is adjusted to be equal to 50 mm and 4.5 kV is applied. Ammonium chloride solution of 0.1 % concentration is used as contaminant at a flow rate of 0.6 ml / min, which is controlled by using a peristaltic pump. The conductivity of the contaminant is 2500 μS/cm. The conductivity is measured using Lutron CD 4302. Time to failure due to tracking is arrived at once the arc is noted [5].

2.4.2 VOLUME RESISTIVITY AND SURFACE RESISTIVITY

The volume and surface resistivity of the samples are measured as per ASTM D257 (IEC 60093) Standards. The voltage applied is 500 V (DC) for 60 seconds at room temperature. The diameter and thickness of the specimen are 100 mm and 3 mm respectively. Million meg-Ohm meter is used to measure volume and surface resistivity.

2.4.3 ARC RESISTANCE Arc resistance of the sample is determined as per ASTM D 495 standard at 250 V and 50 Hz. The applied voltage is 12.5 kV and the distance between the electrodes is 6 mm. The thickness of the specimen used is 3 mm. Two electrodes are kept above the specimen, which is placed on the specimen holder. The voltage is applied intermittently and severity is increased in steps, until the failure occurs. An arc is struck in between the electrodes. After some time, the carbon path developed on the surface of the material led to conduction. The arc resistance is measured in terms of time in seconds for failure to take place.

2.4.4 COMPARATIVE TRACKING INDEX (CTI) The comparative tracking index is determined as per IEC 60112. The voltage applied is 500 V. The electrolyte used is 0.1 % of

IEEE Transactions on Dielectrics and Electrical Insulation Vol. 14, No. 5; October 2007 1209

aqueous ammonium chloride. The distance between the electrodes is 4 mm. The thickness of the electrode is 3 mm. Two chisel edged electrode, usually of brass are rested on horizontal test piece 4 mm apart. Drops of specified size of 0.1 % NH4Cl solution are made to fall between the electrodes at 30 seconds interval. The number of drops required to cause failure is found for several voltages and a curve of number of drops to failure against voltage is constructed. The voltage corresponding to 50 drops is noted. The numerical value of this voltage is called C.T.I.

2.4.5 DIELECTRIC STRENGTH Dielectric strength of the blended sample is determined as per IEC-60243-1 (ASTM D 149) standard at 250 V and 50 Hz. The diameter and thickness of the samples are 100mm and 1mm respectively. Test specimen is placed between two electrodes and the voltage is increased at a fixed rate of 2 kV/s, until the dielectric breakdown occurs. The voltage at which dielectric breakdown occurs is read as dielectric breakdown voltage. Dielectric breakdown strength (kV/mm) is calculated from the ratio of dielectric breakdown voltage (kV) to the thickness of the specimen (mm).

2.4.6 DIELECTRIC CONSTANT AND DISSIPATION FACTOR (tan δ)

The measurement of dielectric constant and dissipation factor (tan δ) is carried out as per IEC 60250 standard at 50 Hz. The specimens with 50 mm in diameter and 3 mm in thickness are used.

2.4.7 TENSILE STRENGTH AND PERCENTAGE

ELONGATION AT BREAK The tensile Strength and percentage elongation at break are assessed by ASTM D-412, using universal testing machine. The shape and the size of the test specimen used are also as per ASTM D-412. The tensile testing machine of constant rate of crosshead movement is used.

3 RESULTS AND DISCUSSIONS Table 2 gives the comprehensive experimental results obtained for various blends of silicone rubber and EPDM.

It can be seen that amongst the electrical characteristics, except dissipation factor, all other characteristics that are studied in this work continue to increase as silicone rubber composition is increased in the blend. As expected, the dissipation factor decreases with increasing silicone rubber composition in the blend, as silicone rubber possesses good electrical characteristics against EPDM.

Amongst the mechanical properties, tensile strength of the blend decreases with increasing silicone rubber composition in the blend. Also, higher the value of percentage elongation at break, lower is the mechanical strength of the material and this is also observed when the silicone composition is increased in the blend.

It is quite intuitive to assess the increase in electrical properties against the decrease in tensile strength or the increase in percentage elongation at break in order to identify the optimal composition of silicone rubber and EPDM in the polymeric blend.

The effect of silicone rubber on each and every electrical property, considered in this work and its effect on the tensile strength of the polymer blends is compared. Later, a similar comparison on the effect of silicone composition in the polymer blend on dissipation factor and percentage elongation at break is made.

3.1 TRACKING RESISTANCE The tracking resistance and tensile strength obtained for the blends are plotted against each other as a function of percentage by weight of silicone rubber in the silicone: EPDM polymeric blend and shown in Figure 1.

Table 2. Insulation characteristics of silicone/EPDM polymeric blends.

Electrical Characteristics Mechanical Characteristics

Notation

Tracking Res. (TR)

(minute)

Vol. Res. (VR) Ω-m

Surf. Res. (SR) Ω

Arc Res. (AR)

(s)

Dielec. Str. (DES) kV/mm

CTI (V)

Dielectric Const.

Dissip. Factor (tan δ)

Tensile Strength

(TS) N/mm2

% Elongation at Break

A 86 8.00 e12 5.65 e13 182 20.00 415 2.244 0.0412 4.257 76

B 95 2.00 e13 1.30 e14 246 24.27 435 2.303 0.0335 2.971 101

C 108 3.00 e13 1.80 e14 308 25.92 452 2.349 0.0239 2.733 130

D 116 4.70 e13 2.60 e14 363 27.56 475 2.678 0.0134 2.332 175

E 123 8.00 e13 5.00 e14 382 31.95 495 2.851 0.0077 1.936 182

F 129 1.30 e14 7.80 e14 427 33.26 505 3.397 0.0029 1.490 260

G 138 6.29 e14 3.10 e15 600 36.08 520 3.973 0.0029

0.500 400


15

20

25

30

35

40

A B C D E F GSilicone:EPDM Blend Composition

Diel

ectr

ic S

tren

gth

(kV/

mm

)

00.5

11.52

2.533.5

44.5

Tens

ile S

tren

gth

(N/m

m2 )

Dielectric Strength Tensile Strength

Figure 1. Effect of blend composition on tracking resistance and tensile strength of polymeric blends.

The tracking time increases with increasing percentage of silicone rubber in the blends whereas the tensile strength decreases with increasing percentage of silicone in the blends. The tracking time for pure silicone rubber is 60 % more than that of pure EPDM. On the other hand, the tensile strength of pure silicone rubber is almost one tenth of the pure EPDM. Here, an attempt is made to study the performance of the given blend (with respect to silicone rubber) at the cross over point. % decrease in tracking resistance by the addition of

50 % EPDM 100138

)116138(×

−=

= 15.9 Similarly, % increase in tensile strength by the addition of

50 % EPDM 1005.0

)5.0332.2(×

−=

= 366.4 The tensile strength increases with increasing percentage of EPDM in the blends and the tracking time decreases with increasing percentage of EPDM rubber in the blends. The reason for the poor tensile strength of the silicone-rich blends is hypothesized due to highly flexible bonding in silicone. Increasing trend in tracking time as the silicone proportion increases could be attributed to the presence of high bond energy of Si-O-Si bonds in silicone. From the above calculations, it is found that the tracking resistance for the 50: 50 blends is reduced by 16 %, whereas, the tensile strength of the blend is improved by 366 %.

3.2 DIELECTRIC STRENGTH The values of dielectric strength obtained for the blends with various compositions of component polymers are

presented in Figure 2 and a comparison is made on the impact of silicone rubber on the tensile strength of the polymer blends.

Figure 2. Effect of blend composition on dielectric strength and tensile strength of polymeric blends.

An increasing trend in dielectric strength is observed as the proportion of silicone rubber is increased in the blends. % decrease in dielectric strength by the addition

of 50 % EPDM 10008.36

)56.2708.36(×

−=

= 23.6 The increasing trend in dielectric strength is because of silicone- oxygen bond, which is stronger than the carbon-carbon bond of organic polymers. Silicones make better electrical insulators and are more resistant to oxidation. Each silicone molecule can sweep out its own space, preventing close contact with its neighbors. Hence, silicones have weak forces of attraction, low surface tension, and low freezing points. These inherent characters make it a choice for remote, coastal, desert regions and highly polluted areas. The main properties are hydrophobic, less weight, UV and ozone stability and better dielectric properties [6, 7]. Figure 2 indicates that 50:50 silicone rubber: EPDM is the best composition where the cross over of both the curves occurs. From the above calculations, it is found that the dielectric strength for the 50: 50 blends is reduced by 24 %. But, the tensile strength of the blend is improved by 366 %.

3.3 VOLUME AND SURFACE RESISTIVITY The effect of silicone rubber composition in the blend on volume resistivity and surface resistivity is presented in Figure 3 and Figure 4 along with its effect on tensile strength. It is clearly observed that increasing proportion of silicone rubber increases both volume resistivity and surface resistivity of the blends. In the case of silicone rubber-rich blends, a significant improvement in the above properties is noted. This may be due to the Si-O-Si bonds present in silicone, which imparts higher electrical resistance [8].

60

70

80

90

100

110

120

130

140

150

A B C D E F GSilicone : EPDM Blend Composition

Trac

king

Res

ista

nce

(min

ute)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Tens

ile S

tren

gth

(N/m

m2 )

Tracking Resistance Tensile Strength


Figure 3. Effect of blend composition on surface resistivity and tensile strength of polymeric blends.

It is seen in Figures 3 and 4 that the surface resistivity and volume resistivity picks up significantly above 70 weight percentage of silicone rubber in the blend. However, the tensile strength of those blends containing such a high proportion of silicone rubber is significantly dropped.

Figure 4. Effect of blend composition on volume resistivity and tensile strength of polymeric blends.

This clearly shows that a penalty has to be paid in terms of significant reduction in tensile strength if the silicone rubber composition is enhanced beyond 50 weight percentage in the blend in order to obtain a higher volume resistivity and surface resistivity. Hence, this comparison also suggests that 50:50 silicone rubber: EPDM is the optimal blend composition.

3.4 ARC RESISTANCE The effect of blend composition on arc resistance of the samples is presented in Figure 5. The resistance towards electric arc decreases when EPDM proportion is increased in the blend. This may be due to the hydrocarbon nature of EPDM. % decrease in arc resistance by the addition

of 50 % EPDM 100600

)363600(×

−=

= 39.5 From the above calculations, it is found that arc resistance for the 50: 50 blends is reduced by 40 %, whereas, the tensile strength of the blend is improved by 366 %.

Figure 5. Effect of blend composition on arc resistance and tensile strength of polymeric blends.

The cross over point of electrical characteristics i.e. arc resistance and the tensile strength plotted as a function of blend composition confirms that 50:50 (on weight basis) combination of silicone rubber and EPDM possesses better dielectric characteristics as well as good tensile strength than their pure counterparts.

3.5 COMPARATIVE TRACKING INDEX (CTI) The values of CTI obtained for various blends are plotted against the blend composition in Figure 6. The increasing trend in the CTI values with increasing weight percentages of silicones indicate that silicone rich blends could give better performance at polluted environments. This may be due to the chemical inertness of silicone elastomers.

Figure 6. Effect of blend composition on comparative tracking index and tensile strength of polymeric blends

However, from the combined perspective of electrical as well as mechanical characteristics of the polymer blend, a 50:50 blend of silicone rubber and EPDM (on weight basis) is the optimal composition as suggested by the cross over point in Figure 6. % decrease in CTI by the addition

of 50 % EPDM 100520

)475520(×

−=

= 8.7

5.00E+13

5.50E+14

1.05E+15

1.55E+15

2.05E+15

2.55E+15

3.05E+15

3.55E+15


Surf

ace

Res

istiv

ity (O

hm)

00.511.522.533.544.5

Tens

ile S

tren

gth

(N/m

m2 )

Surface Resistivity Tensile Strength

5.00E+12

1.05E+14

2.05E+14

3.05E+14

4.05E+14

5.05E+14

6.05E+14


Volu

me

Res

istiv

ity (O

hm-m

)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Tens

ile S

tren

gth

(N/m

m2 )

Volume Resistivity Tensile Strength

0

100

200

300

400

500

600

700

A B C D E F GSilicone:EP DM Blend Composition

Arc

Res

ista

nce

(S)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Tens

ile S

tren

gth

(N/m

m2 )

Arc Res is tance Tensile S trength

400

420

440

460

480

500

520

540


CTI

(Vol

t)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Tens

ile S

tren

gth

(N/m

m2 )

CTI Tensile Strength


From the above calculation, it is found that CTI for the 50: 50 blends is reduced by 9 % whereas the tensile strength of the blend is improved by 366 %.

3.6 DIELECTRIC CONSTANT The comparison of dielectric constant and the tensile strength as a function of blend composition is shown in Figure 7. The blends consisting of higher weight percentages of silicone possess lower values of tan δ and higher values of dielectric constant. The values of dielectric constant and tan δ of silicone- rich blends indicate that Si-O-Si bonds in silicone contribute for the improvement in dielectric properties of the blends.

Figure 7. Effect of blend composition on dielectric constant and tensile strength of polymeric blends.

The dielectric constant is at an optimal value with 50 weight percentage of silicone rubber in the blend. At this blend composition, the tensile strength is reasonably high, although it decreases from the value of pure EPDM. From the data in Table 2, it is seen that the dissipation factor for 50:50 of silicone rubber: EPDM is appreciably lower while possessing significantly higher tensile strength at this blend composition.

3.7 COMPARISON OF ELECTRICAL CHARACTERISTICS AND PERCENTAGE

ELONGATION AT BREAK Similar analyses as described in sections 3.1 to 3.6 can be made by plotting all the electrical characteristics of the blends and the percentage elongation at break as a function of silicone rubber: EPDM composition. The data shown in Table 2 clearly suggests that as the silicone rubber composition increases above 50 weight percentage in the blend, the percentage elongation at break exponentially increases. Hence, it is not advisable to work with more than 50 weight percentage of silicone rubber in the polymer blend. The same is observed with regard to tensile strength also wherein above 50 weight percentage of silicone rubber in the blend, the tensile strength drastically decreases.

The reason for the poor mechanical characteristics of the silicone-rich blends is due to highly flexible bonding in silicone. In order to confirm that the 50:50 silicone rubber: EPDM is indeed the most optimal polymer blend, only the curves of dissipation factor and percentage elongation at break against the blend composition is shown in Figure 8.

0

0.01

0.02

0.03

0.04

0.05


Dis

sipa

tion

Fact

or

050100150200250300350400450

% E

long

atio

n at

Bre

ak

Dissipation Factor % Elongation ta Break

Figure 8. Effect of blend composition on dissipation factor and percentage elongation at break of polymeric blends.

Figure 8 clearly establishes that 50:50 composition of silicone rubber and EPDM is the optimal blend composition to derive the best of electrical and mechanical characteristics of silicone rubber and EPDM blends.

3.8 COST ANALYSIS The raw material cost of silicone rubber (with respect to Indian context) is high. Hence, it becomes necessary to analyze the cost factor, so as to make it economically viable. With respect to Indian context,

1 kg of silicone rubber = INR 575 1 kg of EPDM rubber = INR 275 50 : 50 SIR and EPDM mixture = INR 425 Percentage of saving in the raw Material’s cost

by EPDM addition 100575

)425575(×

−=

=26.0

Thus the addition of EPDM to silicone rubber reduces the cost, by 26 % for the preparation of blends.

3.9 COMPARATIVE PERFORMANCE Table 3 summarizes the various percentage increase /decrease in the insulation characteristics of 50:50 silicone: EPDM blend (with reference to 100 % silicone).

2

2.5

3

3.5

4

4.5

5


Die

lect

ric C

onst

ant

00.511.522.533.544.5

Tens

ile S

tren

gth

(N/m

m2 )

Dielectric Constant Tensile Strength


Table 3. Percentage increase/decrease in the insulation characteristics of 50 : 50 silicone: EPDM blend (with reference to 100 % silicone)

Sl. No. Characteristics

% increase(+)

(or)

% decrease(-)

1 Tensile Strength +366

2 Tracking resistance -16

3 Dielectric strength -24

4 Arc resistance -40

5 Comparative tracking index -9

4 CONCLUSION The present work reveals that, the mechanical properties of silicone rubber can be significantly improved by blending it with EPDM rubber. Also, this addition does not cause much reduction in any of the electrical properties, studied. The addition of EPDM to silicone rubber enhances the mechanical strength of the polymeric blend by 366 % and reduces the raw material cost by 26 %, with a less percentage reduction in electrical characteristics. The blends consisting of 50:50 weight percentage of silicone/EPDM possess balanced electrical and mechanical properties. The experimental values confirm that the EPDM-rich blends possess better mechanical strength properties. The silicone-rich blends show better electrical characteristics and poor mechanical properties due to highly flexible bonding in silicone. The literature [9-11] shows that addition of filler particles enhances the mechanical strength of polymeric insulators and offer better tracking resistance. Hence, it is not wise to enhance the EPDM level beyond 50-weight percentage in the blend to gain mechanical strength at the cost of poor electrical characteristics of the blend. In the subsequent paper by the same authors (part-II), the influence of adding inorganic fillers to this optimal (50:50) blend of silicone rubber and EPDM would be discussed

APPENDIX A PREPARATION OF BLENDS

Passing through the rollers for three minutes softens EPDM rubber initially and then silicone rubber is mixed The mixing of EPDM and silicone rubber is carried out for twelve minutes. Di cumyl peroxide is mixed at the final stage of mixing. The blends of silicone and EPDM containing various proportions of component polymers are prepared in a laboratory model two roll mixing mill at a temperature of 353 K. Dicumyl Peroxide is mixed during the mill mixing as a curing agent to all the blends at 2.5 parts per hundred parts of rubber (phr).

A.1 VULCANIZATION The vulcanization of the blends is carried out in a hydraulically operated press at 443 K for 10 minutes. The vulcanized samples are post cured at 423 K for 2 hours in an air circulated oven. Test specimens are punched out from the compression moulded sheets.

A.2 BLEND COMPOSITION Various compositions of silicone rubber and EPDM blends prepared are given as follows First EPDM rubber is blended with silicone rubber in a complementary mixture of 0, 10, 30, 50, 70, 90, and 100 percent by weight. 2.5 phr of di-cumyl peroxide is added as the curing agent. With the above set of mixtures, it becomes possible to analyze the performance characteristics of silicone rubber alone, EPDM rubber alone and a mixture of silicone and EPDM in various ratios.

ACKNOWLEDGEMENT The authors wish to express their gratitude to the Management of B.S.A Crescent Engineering College, Mr Abdul Qadir A. Rahman Buhari, Correspondent, Dr.V.M. Periasamy, Principal and Dr.T.R. Rangaswamy, Dean (Academic) for their support and encouragement. Special encomiums are due to the faculty, department of High Voltage Engineering, College of Engineering, Guindy, Anna University, Chennai-25. The authors wish to thank All India Council for Technical Education (AICTE), Government of India, for providing funds to carry out the research work.

REFERENCES [1] Y. Kurata, “Evaluation of EPDM rubber for high voltage insulators”,

IEEE. Conf. Electr. Insul. Dielectr. Phenomena (CEIDP), pp. 471-474, 1995.

[2] S. Simmons, M. Shah, J. Mackvich and R.J. Chang “Polymeric Outdoor Insulating Materials, Part-III – Silicone Elastomer Consideration”, IEEE Electr. Insul. Mag., Vol.13, No.5, pp.25-32, 1997.

[3] M.Brown, “Compounding of ethylene propylene polymers for electrical application”, IEEE Electr. Insul. Mag., Vol.10, No.1, pp. 16-22, 1994.

[4] R. S. Gorur, J. Montesinos, L. Varadadesikan, S. Simmons and M. Shah, “A Laboratory Test for Tracking and Erosion Resistance of HV outdoor insulation”, IEEE Trans. Dielectr. Electr. Insul., Vol.4, pp. 767-774, 1997.

[5] L. Centurioni, “A contribution to the study of the tracking phenomenon in solid dielectric materials under moist conditions”, IEEE Trans. Electr. Insul., Vol. 12, pp.147-152, 1977.

[6] V. Shah, Handbook of Plastics Testing Technology, second edition, John Wiley & Sons, New York, pp. 114-117, 1998.

[7] John S. Dick, Rubber Technology Compounding and Testing for Performance”, Hanser publishers, Munich, pp. 190-193 and pp. 235-237, 2001.

[8] J. E. Davis and D.E.W. Rees, “Silicone Rubbers – Their Present Place in Electrical Insulation”, Proc. IEE, Vol.112, pp. 1607-1613, 1965.

[9] R.S. Gorur, E.A. Cherney, and R. Hackam, "The AC and DC Performance of Polymeric Insulating Materials under Accelerated Aging in a Fog Chamber", IEEE Trans. Power Delivery, Vol. 3, pp.1892-1902, 1988.

[10] L.H. Meyer, S.H. Jayaram, and E.A. Cherney, "Thermal Characteristics of RTV and Hot Pressed Silicone rubber filled with ATH and Silica under Laser Heating", IEEE Conf. Elect. Insul. Dielect. Phenomena (CEIDP), Albuquerque, USA, pp.383-386, 2003.

[11] L.H. Meyer, E.A. Cherney and S.H. Jayaram, "The Role of Inorganic Fillers in Silicone Rubber for Outdoor Insulation - Alumina Trihydrate or Silica", IEEE Electr. Insul. Mag., Vol. 20, No. 4, pp.13-21, 2004.


Dr. R. Raja Prabu (M’05) was born in 1967. He received the B.E. and M.E. degrees in electrical engineering and power system engineering respectively in 1988 and 1990, respectively. He received the Ph.D. degree in high voltage engineering from Anna University. Currently he is working as Professor in E.E.E department of Crescent Engineering College, Chennai. All India Council for Technical Education, India, sponsored his research

work. He is a member of CIGRE, I.E (I) and I.S.T.E. His research interests include outdoor insulation, digital protection, high voltage engineering and nanodielectrics. Dr. S. Usa received the B.E, M.E., and Ph.D., degrees in electrical engineering from the College of Engineering, Anna University in 1986, 1989 and 1995, respectively. From 1992 to 2000, she worked as Lecturer and since 2000 as Assistant Professor at the College of Engineering, Anna University. Her research interests include electromagnetic field computation and high voltage engineering. She is a member of IEE, UK.

Dr. K. Udayakumar (SM’80) received the B.E., M.E., and Ph.D., degrees from the College of Anna University in 1972, 1974 and 1987, respectively. He started his career as Lecturer in Anna University and subsequently promoted as Assistant Professor and currently he is a Professor, in the Department of Electrical and Electronics Engineering, Anna University. He guided a number of Ph.D. students and has several publications in journals. He served as Director of various centers of the University. His

research interest is in high voltage engineering. Dr. Udayakumar was the Chair of the Madras Chapter of IEEE.

Dr. M. Abdullah Khan (M’78) was born in 1940. He obtained the B.E. degree in electrical engineering, the M.E. degree in high voltage engineering and the Ph.D. degree in power system engineering, respectively in 1961, 1968 and 1974. He guided several Ph.D. and M.E. students. Currently he is working as a Professor in the Dept. of EEE, Crescent Engineering College. He is a member

of ISTE (India). He published several papers in journals and conferences. Previously, he was the Dean and Director of Anna University. He has teaching and research experience of more than 40 years.

Dr. S.S.M. Abdul Majeed received the M.Sc degree in industrial chemistry from Bharathidasan University, India and the Ph.D. degree in polymer science and technology from Anna University, India, in 2002. He has been with Crescent Engineering College, Chennai, India, since 1988 and currently he is serving as Assistant Professor in the Department of Polymer Technology. His research interest includes the development and characterization of polymeric insulators, polymer blends, biodegradable plastics and composites.

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Electrical Insulation Characteristics of Silicone and EPDM Polymeric Blends. I