Bhattacharyya, G N

Sen, A K

English

IACS Institutional Repository

THE DIELECTRIC PROPERTIES OF ROSIN-MALEIC ANHYDRIDE RESINA. K . SEN \Ni) G. N. BHATTAOHARYAB e p a k t m ic n t  o k  A r r iA E D  P h y s i c s ,C  \LC 1 -r 'r  A V  NIVE llSIT y  .(Tfeccircri Mat/ 1!>, 1901)ABSTRACT. The dielof'tfic* ])ro|>oi*iies of ronan-iimloir iiuhydndo rosm luivo measured o v (h* the temj)endun; nm e^ uf to 170"C and the fr(‘()ueney janye ol* 1 Ke/s to 500 Ke/s. Within this ram?e of temperalurc' and fre((tieney it* beli.a\'(‘s as Ji polar resin in the anomalous (iisp(>rsion ran e^. Its di(*le(*tric constant V>s tcm]a*nitiire curvt' shows howevt'r a, ]>eculiiir l>ohiviour at hij^ h tempi'rat arcs. At about 150*^ 0 dii^ lcctric (‘oustant values attain a. maximum after gradually rising with temperature in thf^  normal way of ]>olai- resins. Hut above this temporature a sudden, and steep rise in the |K>rinittivity is ol).servod. An att<»in])t lias been made to explain this ])oculiarity on tlio laisie of its estimated rotor dimension and infrared absorption spectrogram.I N T R O D U C T I O NRosin plays an important part in the production of sev era! somi-synthetic resins. It is widely used as a modifier in the production of so-callcd modified synthetic resins, such as rosin modified phenol formaldehyde rosins or alkyds. Another typo of synthetic resin derived from rosin is Ihe rosin-maleic anhydride adduct formed by the metlmd of Dicls-AI<ler reaction known as the diene syn­thesis” . This method of synthesis involves a “ diene” system i.e. a system having conjugated double bonds roatiting with a component having an ethylenit; linkage flanked by carbonyl or carboxyl groups in such a manner that the “ diene” system opens up and the terminal carbons become affixed at the double bond of theethylenic linkage.The chemical structure of rosin or abietic acid shows that it possesses a conjugated system of double i>onds and consequently it reacts with maleic anhy­dride giving an addition compound. In fact, this diene synthesis confirms the presence o f the conjugated double bonds in the structure of the abietic acid mole­cule. It should be noted that this compound is the partial anhydnde of a tribasic acid and heniic its acid value must be reduced and this is usually done by esterification with any polyhydric alcohol like glycerol, mannitol, pentaery-thritol etc.Now X-ray studies on the rosin maleic-anhydride resins and ester gum by Beal and co-workers (1932) have revealed that they show precisely the same55609510 A. K. Sen and 0. N. Bhatlacharyarings which arc associated with raw rosin. Esterification with glycerol or reacting it with maleic anhydride does not change its inherent character.Because of the Jarge size of the esterified rosin-maleic anhydride molecule, its rotation as a whole, when placed in the rapidly alternating electric field, is unlikely. Obviously, if dielectric loss occurs due to orientation it may only be due to contributions from side groups attached to the main molecule. Although rosin has been found to be present in this resin as a constituent unit, its freedom of rotation has boon severely restricted by a pair of (carbon-carbon bonds with the maleic anhydride on the one hand and by its linkage with the pentaerythritol molecule through the esterification of its carboxyl group on the other.From a previous study of the dielectric properties of rosin it has been observed by the authors (Sen and Bhattacharya, 1958b) as well as by Kitchin and Muller (1928) that the dimension of its rotating unit is about 4.6A whicdi is in close agree­ment with the actual dimension of the abietic acid molecule calculated on the basis of its accepted chemical structure. This agreement led the authors to the obvious conclusion that the rotation of the entire abietic acid molecule was res­ponsible for its dielectric behaviour. But< a similar study in the ease of ester gum (Sen and Bhattacharya, J958a) or copal ester (Sen ajul Bhattacharya, 1960) revealed a different story. In both the cases the diincnsioas obtained for the rotating units were exactly the same as that of a hydroxyl group. The presence of hydroxyl groups in these resins was also confirmed from their infra-red absorp­tion spectrograms. These evidences tend to suggest that instead of the whole molecule the hydroxyl groups in these resins are probably the rotating units. Hence it is inferred that when molecules of abietic acid (rosin) or copalh; acid (copal) combine (c.g., by esterification with glycerol) to form larger molecules, their rotation as a whole is restricted and only the rotation of smaller groups can occur in the investigated range of frequency. In this (iontext it is therefore of interest to study the dielectric properties of rosin-maleic anhydride adduct in relation to those of rosin and obtain the dimension of its rotating units.E X P E B I M K N I ^ A LThe game experimental procedure as was followed in the case of other resins and the details of which appeared elsewhere (Sen and Bhattacharya, 1958a, 1958b) has been employed. The sample used in this investigation was a pentaerythritol ester of the rosin-maleic anhydride adduct manufactured by the Imperial Chemical Industries Ltd., London, and sold under the trade name of Bedosol —74.The results of measurements of dielectric constant e\ dielectric loss e'' and power factor tan S at different temperatures and frequencies are shown graphically in Figs. 1, 2 and 3. Quite contrary to our expectation, these graphs give clear evidence of the typical polar nature o f this resin. The loss factor-temperature and the power factor-temperature curves showm in Figs. 2 and 3, are the usual absorption curves o f a polar meterial. These curves begin to rise at a compara­tively higher temperature viz, about 100“C for aliuoot all the frequencies except that o f 1 Kc/s. Tho loiss peaks are also more or l«.»ss of the same heights.The Dielectric Properties of Rosin-Maleic, etc 611612 A , K . Hen and O. N. BhattacharyaTEMP., *5r-Fig. 3But the dielectric conRtaut-temx)erature graphs show a peculiar behaviour. It may be noticed from Fig. 1 that the permittivity for all the frequencies begins to rise from about 1 0 0 °C in the usual way and attains a inaximuni at temperatures between 130°C to 150°C. Bui peculiarly enough, after 150"C it is found to makea sudden and steep rise again. Measurements Mere carried out ui^  to 170*^ 0 only as it was apprehended that the resin might polymerize after tliat teniperatur(\ This peculiar behaviour can only be explained on the supposition that at tempera­tures higher than 150 C the resin becomes unstable and more and more dipoles are somehow set free which now increase the orientation polarization and make the permittivity to rise. Hence an estimation of the size of the rotating unit is considered interesting in this case.The Dielectric Properties o f Rosin-Maleic, etc. 5130750  /2 -o-oa-0-04 -lo  ^f  ----^Fig. r>The radius o f the rotating unit \vas estimated from the calculated relaxation time at the temperature of loss maximum con’esponding to a particular Irequency and the melt viscosity at that temperature. The melt viscosity of this resin at514 A . K . Sen and O. N. Bhattacharya(lifforeut temperatures was measured by the same method as reported earlier (Sen and Bhattacharya, 1957) and the results are shown in Table T. Fig. 6 shows the logarithm of viscosity plotted against the reciprocal of absolute temperature and tin? graph is a straight lino. For the sake of comparison the logarithm of resistivity is also plotted against the reciprocal of absolute temperature using the same scale. The conductivity and resistivity data appear in Table II. Once again the sloj)es of both these graphs are found to be the same. Upto the tem­perature of 170°C, however, none of these graphs shows any abnormality to indi­cate any likely polymerization witliin this temperature region.TABLE IViscosity-temperature dataTomiiemturp^ X 103Viscosity log);T“K in poise130 403 2.481 22,970 4.3612135 40S 2.451 11,000 4.0414140 413 2.421 4,900 3.6902145 418 2.392 2,340 3.3692150 423 2.364 1,200 3.0792155 428 2.336 635 2.8028160 433 2.300 355 2.5602165 438 2.283 210 2 3222170 443 2.257 120 2.0792175 448 2.232 60 1.7782TABLE IID.C. conductivity or resistivity-temperature data'I'cmporaturoX 10»Conductivity Resistivity K  PlogPt^ O T°K in mho cm'i. in ohm cm.120 393 2.645 0.1042 X 10-o» 9.696 x 1013 13.9821130 403 2.481 0.5970 X 10-01 ] .075 x 1013 13.2240140 413 2.421 0.2935 X 10-12 3.407 x 1012 12.5324160 423 2.364 0.1067 X 10-11 9.369 X 1011 11.9717160 433 2.309 0.3339 X 10-11 2.894 X 1011 11.4614170 443 2.267 0.1036 X 10-10 9.654 X 1010 10.9847The Dielectric Properties of Rosin-Muleic, etc. 516The results of calculation of the radius of the rotating units are sho^ An iJi Table I I I .TABLE I I ICalculated lelaxation time and radius of the rotatorFrequency in kc/s Loss maximum temperature tin in ' ( 'Relaxat iofx lime T in sec.at Ilfuliiirt of tho rotator in A5 120 2.80 X lO'*® 4 .00 (extra- polattMl)1 .4510 131 1 .30 X 10^^^ 4.30 1 .4550 142 2.70 X 10-*> 3.00 1 .40100 147 1 .39 X 10*0 3.27 1 .51From these results we find again that the same valu(‘ ol the dinu'iision of the hydroxyl group is obtained here ior the radius ol tlu‘ rotator in this resin. A\e shouhl examine therefore if there is any jiossibility for this resin of (‘outaining hydroxyl groups as probable rotating units. As in the production ot this lesiii pentaerythritol is employed it is not unlikely for souu‘ ot the four liydroxyl gioups o f the pentoerythritol molecule to remain unesterified in the same way as soim  ^hydroxyl grou])s of glyi^erol were found to remai]i unesterified in ester gum (Sen and Bhattac'harya, 195Sa) and copal ester (Seji and Bliattacharya, 1900). Moreover this possil)ility may also provide an explanation for the observed pheno­menon of abnormal rise in pcuniiittivity above 150'0. For some of thest hydioxyl fCroiips may form hydrogen bonds amongst themselves at ordinary temperatures and these may be disturbed only at temperatures above 150“C. O o n se c p io n tly>10 A . K . Sen and 0 . N . Bhattacharyaup to 150'^ C only the free hydroxyl groups can contribute towards polarisation there being no contribution from the bonded hydroxyl groups. But at tempera­tures above 150^0 these hydrogen bonds may break and the released hydroxyl groups may contribute further towards polarization thereby increasing the dielec- t ric. constant. Or, in the alternative there may be condensation-polymerisation above 150°C and the released water vapour may contribute towards increased dielectric constant.The infrared absorption spectra of this resin was obtained in the manner indi­cated previously (Hen and Bhattacharya, 1960) and the spectrogram shown in Fig. 7. In  this figure no absorj>tion peak 0 (;curs at the wave length region of 2.93/^  corresponding to the bonded hydroxyl group but the peak duo to the free hydroxyl group occurs at about 2.7S//. The second explanation for increased values of dielectric constant above 150°C seems therefore reasonable. The free hydroxyl groups may be the unesterified hydroxyl groui)S of the pentaerythritol molecule as stated earlier. As chances of rotation of the entire resin molecule are remote, only side groups attached to the main molecule or segments of it are capable of orientation. Therefore hydroxyl groups attached to the molecule seem to bo the probable rotating units.R E F E R E N C E SBeal, Anderson and Long, 1932, Tnd. E n g . C h cm .f 24, 106S.Kitchin, I). W. an<l Muller, H., 1928, P h fs .  R e x . , 32, 979.»Sen, A. K. and Bhattacharya, G. N., 1957, 7. A su o c . A y p .  P h y s ir ls ts , 4, 72. Son, A. K. and G. N., 1958a, I n d . J , Phy^i., 32, 49.Son, A. K. anti Bhattacharya, G. N., 1958b, I n d . J . P h ya ., 32. 49.Son, A. IC. and Bhattacharya, G. N., 1960, I n d .  J .  P hys.^  34, 461.

The Dielectric Properties of Rosin-Maleic Anhydride Resin

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The Dielectric Properties of Rosin-Maleic Anhydride Resin

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