Monte Carlo Simulation of Linear Polymer Thermal Depolymerization under Isothermal and Dynamic Modes

Elena V Bystritskaya,Oleg N Karpukhin,Alla V Kutsenova

doi:10.1155/2011/849370

Elena V Bystritskaya, Oleg N Karpukhin + Show 1 more

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https://doi.org/10.1155/2011/849370

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Abstract

Kinetics of linear polymer thermal depolymerization under isothermal and dynamic TGA modes was simulated by the Monte Carlo method. The simulation was carried out on model arrays having the same initial degree of polymerization and different width (polydispersity index, ) at three constant temperatures and five heating rates. Kinetics of the process in both modes is described by the Avrami equation, the exponent in which decreasing as the distribution width increases. Treatment of the model kinetic curves of degradation using the nonlinear regression method by the Avrami equation, under both isothermal and dynamic modes, gives correct activation energy and pre-exponential factor values independently of the initial PDI. Data obtained in the dynamic mode were also treated by two isoconversion methods, widely applied to kinetic analysis of TGA curves (Flynn-Wall-Ozawa method and Kissinger-Akahira-Sunose (KAS) method).

Highlights

Thermogravimetric analysis (TGA) method is widely applied to the investigation of various polymers and polymeric composites
It has been found that the best description is given by the Avrami equation [16], which we used in the following form: y = exp −(k · t)q
The data obtained by stochastic simulation show that the kinetics of thermal polymerization is strictly affected by the sequence distribution width

Summary

Introduction

Thermogravimetric analysis (TGA) method is widely applied to the investigation of various polymers and polymeric composites. This is a simple and reliable method that allows estimation of thermal resistance of various materials and obtaining of information on kinetics and the mechanisms of thermal degradation processes. Different investigators are using about 20 various methods for quantitative treatment of the TGA thermograms for determination of thermal degradation kinetic parameters, the activation energy, first of all. Where α is the conversion determined from the expression α = (m0 − m)/(m0 − m∞); m, m0, and m∞ are current, initial, and final masses of the sample, respectively; β is the heating rate; T is the absolute temperature; R is the gas constant; A and E are the pre-exponential factor and the activation energy of degradation, respectively. The kinetic function f (α) depends on a particular degradation mechanism

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Conclusion