Electrical And Properties Of Carbon Black Loaded Nr Sbr Rubber Blends:

Mabrouk Kamel Ramadan Almansy . 

ABSTRACT Rest .1’esis’tan”t_rub~ blends at 50 pbr* fran na1iural .1’Il1>be:l:l om> end 50 pbr from s1iyrene -- bu’llf>die116rubber (Smi - l502) bave been prgpered according 1io 1ihe stendard 1iecbniques. These blends were incurpora1ied wi1ih differentconcentra1iions end 1iypes at carbon black end sUbJected 1io electirical and 1ihermal conduc1iivi1iies measurements~ Forde conduc1iiviiiy , t7” , i1i was found iihaii c-r’ depends on the carbon black concen1iraiiion , F , according to 1ihe6D1pirical formula on the form.In ( d’1?) = In ~o&/crK) I [ 1 + exp ((”1’;- t)~F)] wb$re <%’ is 1ille ini1iial oonduc’liiv.1:liyQf the host rubber material , ~:Il is tbe conc:luciiiviiiy of ’libe extreameLy carbon loaded rubber matirix end F0 is a cri’liical carbon black concentiro’liion arround which Large change of conduc’liivi1o;ywas appeared __within ’lihe concen1ira’liion range OF !The above empirical formula was also found ’lio be in goodagreeman’li with tha1i previously sugges’lied 1)yAmin e1i al (47) !r! Tbe ’liempera’liuredependance of C’for the above rubber blends showed ’libermally aciiiva’lied conduciiion mechanism forlow carbon black coniien’li! For high as well as moderate concentra’liions of carbon black, however, a decreasing inconduc’liivi’liy wi1ih iiempera1iure bas been obtia:i.ned! The.conduc’liion mechanism at such canpos11ies was suggesiied ’lio bedue ”to hopping or ’liunneling mechanisms. The descendingbehaviour at the elec’lirioal conductivi1iies is a”ttribu’liedtio ’lihe thermal expansion of hopping poths due to the higher values at ’lihe ’lihermal expansion coefficien’li of iihe insula’liing rubber, - 3 - The CClIIlpe1ii1ioiofnthe above conduo1i1onmechaniSlllSe,1irele,’t1vel.,yhigh temperatures results in the appearence of m1.nimumconductivity value, This minimumwas found to be dependen’t on ’the carbon black concentration, It is shif’ted towards the bo’th higher values of conductivities andtemperatures as the carbon black oonoentration increases, the dc conductivity of differen1i types of oarbon blaoltloaded lm/SBa blends was found to be dependen1ion bo1ihohemical and physical properties of carbon black used, Six types of carbon black (with 100 phr) were used far 1ihiss’tudy neae13 , :I.SAli’ , IUJI’ , li’1I1II’ , GPJ’. smr and EI?O. Itwas found ’that IS4.’U’, HAP and JIlE’O blaokSwhicl1 have’ 8ma]} plL;Cticlesize endconsequen1;l,yhigh 1iendencyof aggregate forma1i1onsincre.e me.:akedly”the dc conductivity of therubber blend w11i1rlespec”t ”to other ”types of black, Tile ac oonductiv11iymeasurementsfor J’JJBblaok ; leaded Ni/SBRshowa frequency dependence on the form.,().J 0( vP w1’bh0,5 -( n < l this confirms according to JonscharGO)1ihehopping conduc1iionmeohanism’through the carbon filled ~ubber _1ir~”’1i rele:tively higher frequencies approxime1il.1quadra1i1cdependence on 1ihefrequency has been observed whiCha1i’tributed ’to 1iheintar - chain llopp1J:lglIleohanism”J’ina1l3, ’the ’therIaal conduc’tivi1iy, K, or all aboveccmposi1iesa’t dj,ftden1i 1i.pera’tures ~as been measured 1181 ••••’the s1i_4y sta’t6 !low ’techniques. Tbe de~ease of ’theraaal conduc’tivi’tl wi’th ’the fncrease of ’tempera’ture was found to be ’the predomina’tefea’ture of ’the It (T) relatiClD. !l!b:Liss. at1iributed ’to ’the increase of ’the pbQnon- phononin’terac’t1an,whioh is in good &greemen’twith tha’t sl1ggec1iedin ’the previous publications.