Correlation between heats of depolymerization and activation energies in the degradation of polymers

Kishore, K.; Verneker, V. R. Pai

doi:10.1002/pol.1976.130141211

Cited by 8 publications

(3 citation statements)

References 4 publications

(3 reference statements)

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“…An E of 125 kJ/mole for the oxidative degradation of PS has also been reported by Knight [6]. In an earlier paper [7] it was shown that the E corresponds to the initiation step to form macroradicals. Since the Msal's do not change the E, this suggests that the Msal's do not affect the polymer degradation in the initiation step, but act in the propagation step, as has been proposed previously [1 ].…”

Section: *mentioning

confidence: 74%

Thermochemical and kinetic studies on the effects of cobalt salicylate on the oxidative degradation of polystyrene

Kishore

Nagarajan

1982

Journal of Thermal Analysis

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The effect of cobalt salicylate on the oxidative degradation and ignition of polystyrene has been studied. It was found that cobalt salicylate sensitizes both the degradation and ignition of polystyrene by facilitating electron-transfer processes in the propagation step. From thermochemical and kinetic studies it was found that the cobalt ion, owing to its ability to exist in variable valence states, promotes electron transfer in the propagation step of polymer degradation, increasing the rate of propagation and consequently the overall rate. Using solid-phase thermal ignition theory, an attempt has been made to explain the sensitization of ignition by the cobalt ion.In an earlier paper [1] we have shown that transition metal salicylates (Msal), when added in small quantities, sensitize the polymer ignition process and also the oxidative degradation of the polymer at 400 ~ In the above-mentioned paper [I ] no detailed kinetic analysis was made, and only the average ratedata were presented for comparison purposes. To acquire a deeper knowledge about the mechanism of action of the metal salicylates (Msal), information on the thermochemical and kinetic aspects would be quite useful and rewarding. The present paper aims at fulfilling this task by considering the ignition and degradation of polystyrene (PS) containing cobalt salicylate (Cosal) as an additive. ExperimentalThe preparation of PS, Cosal and PS + Cosal have been described elsewhere [l ]. Thermogravimetric (TG) analyses were performed on a home-made TG assembly, the description of which is given elsewhere [1 ].The differential thermal analysis (DTA) was carried out on an assembly described elsewhere [2]. The area under the endotherm/exotherm in the DTA curve was used to estimate the enthalpy associated with the process. The area measurements under the peaks were calibrated in units of J/degree s-1, using standard substances such as tin, benzoic acid and ammonium nitrate. The calibration constant obtained was 0.1458 _+ 0.0028 J/degree s -1.An assembly similar to the DTA assembly was used for ignition temperature measurements. The heating rate employed was 170~

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Section: *mentioning

confidence: 74%

Thermochemical and kinetic studies on the effects of cobalt salicylate on the oxidative degradation of polystyrene

Kishore

Nagarajan

1982

Journal of Thermal Analysis

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“…5A left). The thermal degradation of pristine Celgard 1 2400, from roughly 290 C, could be ascribed to its depolymerization to, at least partly, monomer [32,33], since the ceiling temperature of PP is close to 300 C, although bond cleavage is not discarded. This thermal degradation of polypropylene based separators does neither affect the Li-ion battery operation nor limit exothermal runaway.…”

Section: Thermogravimetric Analysis (Tga)mentioning

confidence: 99%

Evaluation of polyolefin-based macroporous separators for high temperature Li-ion batteries

Martínez-Cisneros

Antonelli

Levenfeld

et al. 2016

Electrochimica Acta

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Macroporous separators are critical components in liquid electrolyte batteries. Besides preventing physical contact between electrodes, they enable free ionic transport, electronic isolation and thermal shutdown. Nevertheless, separators also increase electrical resistance and takes up limited space inside the battery, affecting ionic conductivity. Widely used in lithium-ion batteries, commercial polyolefinbased separators operate in a limited temperature range, mainly ranging from À20 C to +60 C. The purpose of this contribution is to assess the possibility to use these separators in lithium-ion batteries operating at extended temperatures, i.e. between À20 C and 120 C. For this purpose, four commercially available macroporous separators based on polyethylene and polypropylene, were investigated. To determine the effect of temperature on their performance, they were aged for one week at 120 C. Evolution of their morphology and thermomechanical behavior was investigated using XRD, SEM, DSC, TGA and DMA. The thermal aging impact on the ionic conductivity was also investigated using LP30 1 as reference electrolyte. Thermal aging, i.e. partial clogging of the porosity, was found to have significant effects mainly on mechanical strength, morphology and conductivity.

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“…Heats of depolymerization have been shown to be essentially equivalent to polymer degradation activation energies (191). This led to the conclusion that the initiation step is ratedetermining and requires most of the energy during conversion of polymer to monomer.…”

Section: Thermogravimetrymentioning

confidence: 99%

Thermal analysis

Murphy¹

1978

Anal. Chem.

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Correlation between heats of depolymerization and activation energies in the degradation of polymers

Cited by 8 publications

References 4 publications

Thermochemical and kinetic studies on the effects of cobalt salicylate on the oxidative degradation of polystyrene

Thermochemical and kinetic studies on the effects of cobalt salicylate on the oxidative degradation of polystyrene

Evaluation of polyolefin-based macroporous separators for high temperature Li-ion batteries

Thermal analysis

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