A study on the thermal degradation of rubber in dilute solutions

Sarfare, P. S.; Bhatnagar, Hari L.

doi:10.1002/app.1963.070070619

J of Applied Polymer Sci

1963

DOI: 10.1002/app.1963.070070619

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A study on the thermal degradation of rubber in dilute solutions

P. S. Sarfare

Hari L. Bhatnagar

Abstract: The kinetics of low‐temperature (60–100°C.) thermal degradation of deproteinized and deresinified petroleum ether soluble fraction of natural rubber in two chemically inert solvents, cyclohexane and trans‐decalin, have been studied. The changes in Mw, A2, and (r2)1/2 at various stages of degradation have been obtained from the lightscattering data. The rate constants and the energy of activation for chain scission have been calculated from the observed variation in Mu. The scission has been found to be random … Show more

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1985

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Cited by 10 publications

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The influence of the relative molecular weight of natural rubber on its thermo‐oxidative stability

Hrivíková¹,

Blažková²,

Lapčík³

1980

J of Applied Polymer Sci

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SynopsisThe influence of relative molecular weight on rubber thermo-oxidation in air a t 130 f l 0 C has been studied by means of infrared spectroscopy. The carbonyl group formation in single fractions of natural rubber has been measured. It was found that the development of kinetic curves AAc=o = f ( t ) corresponds for both fractionated and unfractionated extracted samples. Kinetic curves of natural rubber formation are characterized by an induction period T . Its magnitude is a function of molecular weight up to the value [v] = 0.2 m3/kg, and then stays invariant to changes in [v]. In the range of low values of the internal viscosity up to 0.2 m3/kg, the dependence TC=O = f [ v ] has an exponential character as a consequence of the statistical character of chains breaking down during the degradation. It has been proved that the reciprocal value dependence of the mean viscosity molecular weight of unfractionated acetone-extracted natural rubber on the length of induction period is linear. The change in double-bond amount during the oxidation is not reflected in the induction period determined by infrared spectroscopy.

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The influence of the relative molecular weight of natural rubber on its thermo‐oxidative stability

Hrivíková¹,

Blažková²,

Lapčík³

1980

J of Applied Polymer Sci

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Effect of resin components on the degradation of guayule rubber

Bhowmick

Rampalli

McIntyre

1985

J of Applied Polymer Sci

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SynopsisAll natural rubbers are likely to contain some long chain fatty acids or their esters. The individual effect of the four CIS fatty acids (stearic, oleic, linoleic, and linolenic acid) present in the guayule resin on the degradation of guayule rubber has been investigated concurrently by stress-relaxation of radiation cured rubber networks and by gel permeation chromatography studies on the raw rubber in the temperature zone 70-125°C. CIS unsaturated fatty acids enhance the degradation of rubber several fold. The rate of degradation follows the order: rubber < rubber + stearic acid < rubber + oleic acid < rubber + linoleic acid < rubber + linolenic acid. The thermal degradation is slower than the thermooxidative. The rate of degradation monotonically increased with the number of conjugated double bonds and is first order with respect to acid concentration. The activation energy for the chain scission for both thermal and thermooxidative degradation has been found to be 95 & 10 kJ/mol. The mechanism of degradation of guayule rubber in the presence of fatty acids is discussed.

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Degradation of polytetramethylene oxide. I. Thermally‐induced

Davis

Golden

1965

Makromol. Chem.

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The thermal degradation of polytetramel hylene oxide has been examined in detail. The polymer contained weak links which led to facile chain scission on heating (50 to 150'C.). The activation energy of this degradation process in xylene solution is 13.3 kcal. Imol. The. available evidence indicates that the weak links are hydroperoxide groups formed in the presence of air. These groups could be destroyed by heating in vacuum, the resultant degree of degradation of the polynier depending on the number of hydroperoxide groups present.Measurements of the intrinsic viscosity of polytetramethylene oxide, freed from weak links, showed that the polymer underwent random chain scission a t elevated temperatures according to the equation:The exponent, a, of the KUHN-HOUWINK equation was thus determined to be 0.75 for the polymer in benzene a t 20°C. Analysis of the molecular weight changes occurring during degradation at various temperatures showed that the chain scission process obeyed first order kinetics and could be expressed by the rate equation: k = 1.98 . 1017e-49,700/RT This result is compared with activation energies obtained by thermogravimetry in air and vacuum. ZUSAMMENFASSUNG:Es wurde der thermische Abbau von Polytetrarnethylenoxid untersucht. Das Polymerc enthielt schwache Bindungen, die beim Erwarmen auf 50 bis 150°C leicht spalteten. I n Xylol betrug die Aktivierungsenergie dieses Abbauvorganges 13,3 KcallMol. Wie nachgewiesen wurde, sind die schwachen Bindungen Hydroperoxidgruppen, die sich in Gegenwart der Luft bildeten. Diese Gruppen konnten beim Erhitzen im Vakuum zerstort werden; der sich einstellende Abbaugrad des Polymeren hangt voii der Zahl der vorhandenen Hydroperoxidgruppen ab. Messungen der Intrinsic-Viskositat des von schwachen Bindungen befreiten Polytetramethylenoxids zeigten eine regellose Kettenspaltung bei erhohten Temperaturen, die nach der Gleichung verlief : log [q] = -cc.log (t + to) + c *) Presented a t the 148 th American Chemical Society Meeting, Chicago, Illinois, September, 1964. Degradation of Polytetramethylene Oxide. I. Der Exponent a der KuHN-HouwINK-Gleichung wurde fur das Polymere in benzolischer Losung und bei 20 "C zu 0,75 bestimmt. Die Analyse der Molekulargewichtsanderungen wahrend des Abbaus bei verschiedenen Temperaturen ergab, daO die Kinetik der Kettenspaltung erster Ordnung war und dureh folgende Gesehwindigkeitsgleichung erfaRt wurde: 1~ = 1,98.1017 e--49700/RT Dieses Ergebnis wurde mit den Aktivierungsenergien der in Luft und unter Vakuum durchgefiihrten thermogravimetrischen Analyse verglichen.

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A study on the thermal degradation of rubber in dilute solutions

Cited by 10 publications

References 13 publications

The influence of the relative molecular weight of natural rubber on its thermo‐oxidative stability

The influence of the relative molecular weight of natural rubber on its thermo‐oxidative stability

Effect of resin components on the degradation of guayule rubber

Degradation of polytetramethylene oxide. I. Thermally‐induced

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