Assessing the effect of molecular weight on the kinetics of backbone scission reactions in polyethylene using Reactive Molecular Dynamics

Smith, Kenneth D.; Bruns, M.; Stoliarov, Stanislav I.; Nyden, Marc R.; Ezekoye, Ofodike A.; Westmoreland, Phillip R.

doi:10.1016/j.polymer.2011.04.035

Cited by 27 publications

(35 citation statements)

References 34 publications

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“…The equations of motion were solved using velocity-Verlet integration with a constant time step of 0.1 fs. The time step was chosen based on preliminary simulations and considerations presented in similar studies (Stoliarov et al 2003;Smith et al 2011;Knyazev 2007). This value is also recommended for high-temperature (*2500 K) simulations by the authors of the used ReaxFF parameterisation.…”

Section: Molecular Dynamics Set-upmentioning

confidence: 99%

“…Average reaction rate constants were determined for the depolymerisation reactions, considering separately each combination of molecular weight, initial conformation and temperature (Smith et al 2011):…”

Section: Post-processingmentioning

confidence: 99%

“…We considered a range of models to capture the possible effects of molecular weight and initial conformation, and a range of temperatures to determine the kinetics of the dominant reactions. We adopted the approach from a study on the chain fragmentation of polyethylene (Smith et al 2011). However, we used the ReaxFF reactive force field instead of the switching-function based approach, which was made possible by the availability of a ReaxFF parameterisation for general hydrocarbon and carbohydrate compounds (Chenoweth et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

Paajanen

Vaari

2017

Cellulose

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The kinetics and products of cellulose pyrolysis can be studied using large-scale molecular dynamics simulations at high temperatures, where the reaction rates are high enough to make the simulation times practical. We carried out molecular dynamics simulations employing the ReaxFF reactive force field to study the initial step of the thermal decomposition process. We gathered statistics of simulated reactive events at temperatures ranging from 1400 to 2200 K, considering cellulose molecules with different molecular weights and initial conformations. Our simulations suggest that, in gas-phase conditions at these high temperatures, the decomposition occurs primarily through random cleavage of the b(1 ? 4)-glycosidic bonds, for which we obtained an activation energy of (171 ± 2) kJ mol -1 and a frequency factor of 1:07 AE 0:12 ð ÞÂ10 15 s -1 . We did not observe dependency of the kinetic parameters on the molecular weight or initial conformation. Some of the decomposition reactions involved the release of low-molecular-weight products. Excluding radicals, the most commonly observed species were glycolaldehyde, water, formaldehyde and formic acid. Many of our observations are supported by the existing experimental and theoretical knowledge. We did not, however, observe the formation of levoglucosan, which is the dominant product in conventional pyrolysis experiments at much lower temperatures. This is understandable, since the high temperatures can force the dominance of radical reactions over pericyclic reactions. Nevertheless, our results support further use of ReaxFF-based molecular dynamics simulations in the study of cellulose pyrolysis.

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Section: Molecular Dynamics Set-upmentioning

confidence: 99%

Section: Post-processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

Paajanen

Vaari

2017

Cellulose

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“…Smith et al [23] pointed out that small molecules less than 100 repeat units in kinetic models of thermal decomposition of polymers may result in significant errors. Accordingly, linear PE chains with monomers -[-CH 2 -CH 2 -] n -were modelled with a chain length of 100, which is demonstrated by the number of ethylene monomers n in a single chain.…”

Section: Molecular Structuresmentioning

confidence: 99%

Thermal decomposition behaviour of polyethylene in oxygen-free and low oxygen content circumstances by reactive molecular dynamic simulation

Liao

Meng

Huang

2018

Molecular Simulation

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In the present study, the thermal decomposition characteristics of polyethylene (PE) in oxygen-free and low oxygen content circumstances were examined by molecular dynamic (MD) simulations at atomic scale using reactive force field (ReaxFF). Temporal evolutions of species were captured reasonably during the processes of thermal decomposition. The effects of oxygen content, temperature and heating rate were also analysed. In addition, the kinetic properties were predicted with reliable parameters. The results show good agreements with the available ones, which illustrate that the species with two carbon atoms are the vast majority of final products. Higher oxygen content and temperature promote the generation of small molecules with carbon atom number less than or equal to 10. In the presence of oxygen, greater activation energy span and reaction order are calculated with lower adjust R 2 , which indicates complex reactions according to kinetic analysis. The initial decomposition temperature of PE is proportional to the heating rate owing to heat transfer lag.

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“…[14]. In this paper, n-alkanes of varying length were simulated until a first scission was observed.…”

Section: Scission Ratementioning

confidence: 99%

Pyrolysis and Devolatilization of High-Density Polyethylene

Bruns¹,

Ezekoye²

2011

Fire Safety Science - Proceedings of the 10th International Sym

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A simple model for combined pyrolysis and devolatilization of high-density polyethylene (HDPE) is developed and studied. The model parameters are estimated from available literature data, and the resulting predictions are compared with a single thermogravimetric experiment. It is found that the bubble loss model makes a better prediction than a critical carbon number loss model. As expected, the bubble loss model is seen to lose validity when the sample becomes predominantly composed of volatile species.

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Assessing the effect of molecular weight on the kinetics of backbone scission reactions in polyethylene using Reactive Molecular Dynamics

Cited by 27 publications

References 34 publications

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

Thermal decomposition behaviour of polyethylene in oxygen-free and low oxygen content circumstances by reactive molecular dynamic simulation

Pyrolysis and Devolatilization of High-Density Polyethylene

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