carbon radiation

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EFFECT OF GAMMA RADIATION 0:"'\ THE ELECTRICAL PROPERTIES OF CARROl" BLACK

LOADED UNVULCANIZED STYRENE-RL1 ADIENE RUBBER FOR APPLICATION TO RADL\TION

DOSIMETRY

M. A. Fadel, H. H. Hassan*, and H. Osman.Physics Department, Faculty of Sciellce, Cairo Un::ersity,

Giza, Egypt and

G. AttiaPilysics Departmel1t, Faculty of Education, Cairo U nivers::y, EI-F ayoum, Egypt

THEARABIANJOURNAL FORSCIENCE AND ENGINEERING I

REPRINT

@Iub/;,hed 1o, the UNIVERSITY OF PETROLEUM AND M'. ERALS. DHAHRAN. SAUDI ARABIAI o . " : t ' ~ by JOHN WILEY & SONS LIMITED, CHICHESTER, NEV\ "'ORK, BRISBANE, TORONTO, SINGAPOREI


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EFFECT OF GAMMA RADIATION ON THE ELECTRICAL PROPERTIES OF CARBON BLACKLOADED UNVlJLCANIZED STYRENE-BUTADIEl""E RUBBER FOR APPLICATION TO RADIATION DOSIMETRY

M. A. Fadel, H. H. Hassan*, and H. Osman.Physics Deparrment, Faculty of Science, Cairo University,

Giza, Egypt and

G.AttiaPhysics Department, Faculty of Education, Cairo University, El-Fayo"Unt,

Egypt

, ~ j J l 4 . 0 ) \ a l I ) ~ ~ , w ~ I j + - 1 j&- 60Co \ . A ~ wi Ml$1 . ; : . t " ' * ' ~ ~ 4 . . 1 ~ i:')J-"i ~ ~ t'.A ~ I (1502 SBR) ~ . ) \ i J : ! . R ~ " J I .l:>U:L. . l = . : J ~ ~ (JyJl ....:.all) JyJI

. (HAF, FEF, SRF & GPF IJJ!}JI. ; : . t ~ \ . . , p f S ' ; ; ' ; ' JyJl..w1I'..iS) JyJl ~ l i ) ~ j J l J.-)\all r.i.) J.I;;-J.o c . ) ~ j el:.:l l J i

4d- ""*, 4",J ~ ~ 41Jt-! .:f...i ~ ) ~ ~ ) -;J'j.&, r ' ~ b . 37-10 Gray .s.u.!.j .;:.J"'*..f.ill ~ \ . . . . ..l:>lb.JJ ~ j J \ J.-)\al\ ...... I.:i ~ ) :ABSTRACT ..

The effect of different doses of 60Co-gamma rays on the electrical properties(resistivity (p) and dielectric constant (E') and loss (E")) of different types of carbonblack (HAF, FEF, GPE, SRF and EPC}-1oaded unvulcanized styrene-butadienerubber has been studied. Th e results showed that remarkable changes in theelectrical properties of some rubber blends have been induced due to irradiationwith gamma doses in the range 0.037-90 kGy. Two empirical formulae have beengiven to calculate for the absorbed gamma dose from measurements of the inducedchanges in the electrical properties of the rubber blends.

0377-9211/86/030271-05$05.00 1986 by the University of Petroleum and M i n e ~ " l ,

The Arahiall Journal J(>r Scie",:e and Er..:;irleerillg. Volume J1. Numher 3 271
http:///reader/full/0377-9211/86/030271-05$05.00http:///reader/full/0377-9211/86/030271-05$05.00


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M. A. Fadel, H. H. Hassan, H. Osman, and G. Auia

EFFECT OF GAMMA RADIATION ON THE ELECTRICAL PROPERTIES OF CARBON BLACKLOADED UNVULCANIZED STYRENE-BUTADIENE RUBBER FOR APPLICATION TO RADIATIOl'l DOSIMETRY

r.-ITRODUCfIONThere is increasing interest in radiation research andmeasurement technology involving high-intensitysources of ionizing radiation, such as massive 60Co_

gamma ray sources. Moreover, special attention hasbeen given to the uses of gamma radiation in the range10-103 Gray for insect control, seed and vegetablesprouting inhibition, vegetable and fruit shelf lifeextension, radiotherapy, etc. Therefore, there is a needfor a dosimeter that can measure simply, directly, andreproducibly doses in this range.

In the present work, the effect of different doses of60Co-gamma rays on the electrical properties(electrical resistivity (p), dielectric constant () and loss( of different types of carbon black-loadedunvulcanized styrene-butadiene rubber have beenstudied.

~ f E T H O DThe rubber used in this work is styrene-butadiene

rubber (SBR-1502), non-staining, with (2,6-di-tertbutyl-4-methylphenol) - (Inol) as stabilizer. Differenttypes of carbon black were used, namely: HighAbrasion Furnace black (HAF). Fast ExtrusionFurnace black (FEF), General Purpose Furnace black

(GPF), Semi-Reinforcing Furnace black (SRF), andEasy Processing Channel black IEPC). The criticalconcentration from each type of carbon black [1 ] wasintroduced in SBR according to the formulationsillustrated in Table 1. This critical concentration waschosen, owing to the great sensiti"ity of the electricalresistivity of the rubber blend to energy transfer [2].

The preparation of the rubber blends [3] and themeasuring techniques for electrical resistivity [4] havebeen previously described. The rubber samples wereshaped at 35C into the form of squares 2.3 x 2.3 cmand about 0.4 cm thick under pressure of 40 kg cm - 2.Good contact was attained by covering both sides ofthe sample with air-drying silver paste type FSPImanufactured by Johnson and Matthey, UK. Thedielectric constant and dielectric loss where measuredusing a Tesla precision capacitance bridge typeBM 400G, working at a fixed frequency of 800 Hz. Thedielectric loss was calculated from the relation, =E'tan b.

A 7.4 TBq-60Co gamma source manufactured byAtomic Energy of Canada Ltd.., presented at theNational Institute of Standards, Dokki, Egypt, wasused for irradiation of the samples. At the irradiationpositions, the dose rate had been calibrated using astandard ionization chamber and found to be 74.45Gy h I . All measurements were carried out at 35C.

Table 1. Composition of SBR Samples Cootaining Different Types and Concentrations of Carbon BlackIngredient, phr* 40 EPC 50 HAF 60 FEF 70 SRF 80 GPFSBR (1502)Stearic acidCarbon black

100240

100250100260

IOO270100280Processing oil

MBTS"10,- 102 102 10,- 102PBNtZinc oxideSulfur :;,-

152:;,- 5,-

152*Parts per hundred pans of rubber b) weigr.L **Dibenthiazyl disulfide. tPhenyl-p-na ph! h yla mine.

272 Th e Arabiall Journalfor Science wul EngineerillY. VO/I,me 11 .";umber 3


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M. A. Fadel, H. H. Hassan, H. Osnum, and G. Attia

RESULTS AND DISCUSSIONBulk d.c. Electric Resistivity

Figure 1 shows the relation between the bulk d.c.electrical resistivity (p) measured at 35"C and theirradiation dose (D in Gray) for three types of carbonblack (60 FEF, 70 SRF, and 80 GPF) loadedun vulcanized SBR s2..-nples. It is clear from the figurethat anomalous beha \;or appeared through the slightincrease in p followed by a sharp decrease to aminimum value at 65kGy for 60 FEF/SBR and 80GPF /SBR, and at 25 kGy for SRF/SBR. The variationof p as a function of D in the dose range 2 kGy-60 kGy was found to be conveniently expressed by the

1410.-- - - - - - - - - - - - - . ~ E 13 ::::;-- 10

T=35"Ca .6Q,=EFjsBR12


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M. A. Fadel, H. H. Hassan, H. Osman, and G. Attia

EPC/SBR sample upon irradiation for doses up to 12kGy. This may be due to th e type of carbon blackwhich has high tendency to form stable structures [6].Further irradiation causes degradation processes inthe host material followed by breakdown in thecarbon black aggregates which may lead to theincrease of p.

Th e linear portion in th e curve in Figure 2 fo t 50HAF/SBR sample was found to fit formula (1) withA 4 x 1Oi3 and B 1.93. I t ma y be presumed that, theaction of gamma rays on unvulcanized rubbercomposites results in scissions in rubber chains.breakdown in the carbon black aggregate structure,formation of conjugated structure and bonds, and thepresence of several functional groups on the surface ofcarbon black, such as hydroxyl, carbonate, and stablefree radical groupings [7, 8J , which may act as centersof linkages between carbon black and rubbers, leadingto a decrease in the c a r b o n ~ c a r b o n interspacing distances. However, the radiation effects phenomena onunvulcanized rubber are very complicated since theshare of each radiation-induced process varied withthe irradiation dose, type. and concentration of carbonblack.Dielectric Constant (E') and Dielectric Loss (")

Figure 3 shows the variation of ' for different typesof carbon black-loaded SBR unvulcanized compositesas a function of irradiation dose. It is clear that, thebehavior of the three samples, namely 60 FEF/SBR, 70SRF/SBR and 80 GPFSBR is approximately the

40.----------------,[=35 C'w 60FEF/SBR,-:~ l> 70SRF/SBR

VJ 30 A. 80GPF/SBR0V t.OEP::;/S8R.ct'-

V rJ...,4J ~20Ci . . )(-)t. A210 10 'OJ 101. 105

DO::=- , D (Gray)Fiyure 3. !'aria/ion o{ Diel",':,-ic COllstalll (IS a FUI/lrion 0/Irradiatioll D"5e/or: . 40 E?CSBR; . 60 FEF,S13R.II...

80 GPF SB R and L - 'I SRF,SBR al]5 C274 The Arabian )""l 'I laij()r Sci"/l', . ; : ~ . d Enginl'ering. Volul1le I i . Ilium!>!'/' -'

same. This may be attributed to the role of carbonblack in the three types of rubber which is of the sameorigin (Furnace black) and has nearly similar physicalproperties (large particle size and low tendency toform aggregations). On the other hand, the samplewhich contains channel black (40 EPC/SBR) showedgradual increase in E' upon irradiation in the doserange 0.037-11 kGy. This variation was found to becon\eniently expressed by the formula:

D= Q exp(bE') (2)where a 1.77 x 10 - 20 and b= 2.06.

The increase in ' values may be due to theformation of dipole groups or segments which areformed through breakage of chemical bonds duringirradiation. Moreover, the sulfur atoms in theunvulcanized composites may combine at random asheterocyclic groups along the main chain [9,10lThese groups have relatively high moments per oneatom of combined sulfur which increases the value or

The dielectric loss (E") for the samples 60 FEF/SBR,70 SRFISBR, an d 80 GPFISBR has been measuredbefore and after successive exposures to 60Co gammadoses in the range 0.037-90 kGy. Figure 4 illustratesthe variation of E" as a function of D for the abovesamples. Th e results for E" confirm the measuredresisti vity data for these samples.

Th e Elf data for the two samples 50 HAF/SBR and40 EPC!SBR were ou t of range of our measuringequipment.

I 5 w tI.lI ]lI]0 A.-..l I 0V0:'-u4J-..l4JCi

0 5 -10

DOSE, D (Gray)h,/lIle 4, I aria[ion (({ DieleClric Luss 11 ]5 ' C as a FUI/Clionol/rr(ldill1iOIl Df]se jur : . 60 FEF;SBR 6.70 SRF SBR IIml

A.8(1 GPFSBR

60FEFISBR70SRFISBR80GPFISBR

----41------.
http:///reader/full/FEF,S13R.IIhttp:///reader/full/FEF,S13R.II


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" .

CONCLUSION It may be concluded that the induced irradiation

changes in both p and are rather dependent on thetype of carbon black. These remarkable changes canbe used as a direct, easy, inexpensive, nontoxic, andsensitive method for evaluation of the irradiation dose.Only measurement of either p or for the sample afterirradiation is necessary to evaluate the dose. applyingthe two suggested empirical formulae. However, some work still has to be done to renderthe method applicable, such as, effect of she If and ther-

. mal oxidatJve ageing of the samples before and afterirradiation on the detector renderet, application of thestyrenc:rbutadiene rubber filled with other types ofcarbon black, and study of the effect of gamma rays onvulcanized rubber. This work is already done by ourlaboratory and will be presented in the First Egyptian- British Seminar on Radiation Physics which will beheld in Cairo, Egypt 24-27 November 1985.

ACKNOWLEDGMENTThe authors are most grateful to the authorities ofTransport and Engineering (Rubber Manufac

turing) Co. (TRENCO), Alexandria, Egypt. for supplying the materials and providing facilities.

M. A. Fadel, H. H. Hassan, H. Osman, and G. Atria

REFERENCES[1] E. M. Abdel-Bary, M. Ac:::Un and H. H. Hassan,

'Factors Affecting Electrical Conductivity of CarbonB1ack-Loaded Rubber. II. Effect of Concentration andType of Carbon Black on Electrical Conductivity ofSBR', Journal of Polymer Science, Polymer ChemistryEdition, 17 (1979), p. 2163.

[2] E. M. Abdel-Bary, M. Awin and H. H. Hassan,'Electrical Conductivity 0 ( HAF Carbon BlackLoaded SBR During Vulc:.wization', Gummi AsbestsKunststojJe,34 (11) (1981), p. 728.[3] E. M. Abdel-Bary, M. Amin an d H. H. Hassan, 'Effectof Polyvinylchloride on th e Properties of RubberVulcanizates', Europeall Poly-mer Journal, 10 (1974), p.699[4] E. M. Abdel-Bary, M. Amin and H. H. Hassan,

'Factors Affecting Electrical Conductivity of CarbonBlack-Loaded Rubber. I. E.5'ect of Milling Conditionsand Thermal-Oxidative Aging on ElectricalConductivity of HAF Caroon Black-Loaded Styrene- Butadiene Rubber' , Jot.T71al of Polymer Science,Polymer Chemistry Edition. 15 (1977), p. 197.

[5] H. R. Anderson Jr., Rubber Chemistry and Techllology,Vol. 34, 1961, p. 228.

[6] R. H. Norman, COIlductme Rubbers and Plastics.London: Applied Science Piublishers, 1970.[7] V. A. Garten and D. E. ""'eiss, Review of Pure alldApplied Chemistry, 1 (19571- p. 69.[8] M. H. Studebaker, Rubber Chemistry and Techllology,

Vol. 30, 1957, p. 1400.[9] G. L. Link, 'Dielectric Pr.operties of Polymers', inPolymer Science, Ed. A. D_ Jenkins. North Holland,1972.[10] B. Tareev, Physics of Dielectric Materials. Moscow:Mir Publishers, 1975 (in English).

Paper Received 13 October 1984; Revised 21 July 1985

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The Arabian ]ournaljor Science ulld EI1';;'leerillg, Volume II , Number; 275


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