Reliable method for determining the complete kinetic and thermodynamic information for thermal degradation of polymers in a multi-step process
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Proposed approach enables a reliable determination of kinetic and thermodynamic behaviors for thermal degradation of polymers. As a model polymer, poly(ethylene oxide) with average molecular weight Mv ~ 100.000 (PEO100) was used. Two-component continuous distribution kinetics best describes PEO100 thermal degradation, involving two main reactions with different values of reaction orders. Procedure enables the check of existence of true or real enthalpy–entropy compensation (EEC). It was established that in the case of random scission reaction step, the artificial EEC emerges. For second reaction step which involves β-scission reaction step (“slow” step), true (real) EEC emerges. It was found that this reaction step is responsible for occurrence of successive micro-phase transitions. These transitions are associated with significant reduction of PEO100 crystallinity through a hinder effect on polymer chains. It was concluded that these transitions are cyclic and reversible, related to the change of mechanical properties of the polymer.
KeywordsMulti-step thermal degradation Carnot cycle model Enthalpy–entropy compensation Micro-fragmentation (kernel) distribution Micro-phase transitions
The author would like to thank for the financial support of Ministry of Education, Science, and Technological Development of the Republic of Serbia under the Project 172015.
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Conflict of interest
The author declares that there is no conflict of interest.
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