Degradation kinetics of polymers in solution: Time-dependence of molecular weight distributions. [Quarterly report, January--March 1996]

McCoy, Benjamin J.; Madras, Giridhar

doi:10.2172/382447

Cited by 1 publication

(2 citation statements)

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“…The pyrolysis of PS is a complex problem, and although various models have been proposed through the years, no definite mechanism nor model has been established. Among these, it is worth mentioning some interesting studies: McCoy and Madras [ 26 ] models are based on random-chain, mid-chain and end-chain scission mechanisms, and they solve the MWD as a function of time from a batch reactor population balance equation. Their results illustrate how the MWDs decrease in time while the dispersity increases due to the formation of smaller molecular weight products.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Pyrolysis of Polystyrene Aided by a Nitroxide End-Functionality Improved Process and Modeling of the Full Molecular Weight Distribution

Monroy-Alonso¹,

Ordaz-Quintero²,

Ramírez³

et al. 2021

Polymers

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A significantly improved thermal pyrolysis process for polystyrene (PS) is reported and mathematically modeled, including the description of the time evolution of the full molecular weight distribution of the polymer during its degradation by direct integration of the balance equations without simplifications. The process improves the styrene yield from 28–39%, reached in our previous report, to 58–75% by optimizing the heating ramp during the initial stage of the pyrolysis process. The process was tested at 390 and 420 °C on samples of conventional PS synthesized via free-radical polymerization (FRP) and PS with a nitroxide end-functionality synthesized via nitroxide mediated polymerization (NMP) with three levels of the nitroxide to initiator (N/I) molar ratio: 0.9, 1.1 and 1.3. The NMP-PS produced with N/I = 1.3 generates the highest styrene yield (75.2 ± 6.7%) with respect to the best FRP-PS yield (64.9 ± 1.2%), confirming the trends observed in our previous study. The mathematical model corrects some problems of a previous model that was based on assumptions that led to significant errors in the predictions; this is achieved by solving the full molecular weight distribution (MWD) without assumptions. The model provides further insight into the initial stages of the pyrolysis process which seem to be crucial to determine the chemical paths of the process and the styrene yield, as well as the influences of the initial heating ramp used and the presence of a nitroxide end-functionality in the polymer.

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Section: Introductionmentioning

confidence: 99%

“…As McCoy stated [ 26 ], pyrolysis can be seen as a fragmentation phenomenon and monitoring the evolution of the MWD and its moments in time provides considerable information and allows a sharper interpretation of the kinetics and mechanism of the degradation reactions.…”

Section: Introductionmentioning

confidence: 99%