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

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 160
Author(s):  
Antonio Monroy-Alonso ◽  
Almendra Ordaz-Quintero ◽  
Jorge C. Ramirez ◽  
Enrique Saldívar-Guerra
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Molar Ratio ◽  
Pyrolysis Process ◽  
Thermal Pyrolysis ◽  
Initial Stage ◽  
The Mathematical Model ◽  
Nitroxide Mediated Polymerization ◽  
Initial Heating

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.

scholarly journals Matrix-graph model of the polymer materials destruction process

2018 ◽  
Vol 80 (3) ◽  
pp. 50-55
Author(s):  
A. A. Khvostov ◽  
S. G. Tikhomirov ◽  
I. A. Khaustov ◽  
A. A. Zhuravlev ◽  
A. V. Karmanov
Keyword(s):  
Mathematical Model ◽  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Graph Model ◽  
Polymer Materials ◽  
Simulation Environment ◽  
Destruction Process ◽  
Molecular Weights ◽  
The Mathematical Model

The paper deals with the problem of mathematical modeling of the process of thermochemical destruction using the theory of graphs. To synthesize a mathematical model, the Markov chain is used. For the formalization of the model a matrix-graph method of coding is used. It is proposed to consider the process of destruction as a random process, under which the state of the system changes, characterized by the proportion of macromolecules in each fraction of the molecular mass distribution. The intensities of transitions from state to state characterize the corresponding rates of destruction processes for each fraction of the molecular weight distribution (MWD). The processes of crosslinking and polymerization in this work have been neglected, and it is accepted that there is a probability of transition from any state with a lower order index (corresponding to fractions with higher molecular weights) to any state with a higher index (corresponding fractions with lower molecular weights). A computational formula is presented for estimating the number of arcs and model parameters from a given number of fractions of the molecular weight distribution of the polymer. An example of coding in a matrix form of a graph model of the process of degradation of polybutadiene in solution for the case of six fractions of the molecular weight distribution is shown. As the simulation environment, the interactive graphical simulation environment of MathWorks Simulink is used. To evaluate the parameters of the mathematical model, experimental studies of the degradation of polybutadiene in solution were carried out. The chromatography of the polybutadiene solution was used as the initial data for the estimation of the MWD polymer. The considered matrix-graph representation of the structure of the mathematical model of the polymer destruction process makes it possible to simplify the compilation of the model and its software implementation in the case of a large number of vertices of the graph describing the process of destruction

Nitroxide-mediated polymerization of methyl methacrylate by 4,4′-dimethoxydiphenyl-based alkoxyamine

RSC Advances ◽  
2016 ◽  
Vol 6 (77) ◽  
pp. 73842-73847 ◽  
Author(s):  
Zhecheng Zhu ◽  
Guorong Shan ◽  
Pengju Pan
Keyword(s):  
Molecular Weight ◽  
Methyl Methacrylate ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Linear Increase ◽  
Narrow Molecular Weight Distribution ◽  
Nitroxide Mediated Polymerization

4,4′-Dimethoxydiphenyl nitroxide-based alkoxyamine was prepared and used to control the polymerization of methyl methacrylate. Linear increase in molecular weight with conversion and narrow molecular weight distribution was up to 65% conversion.

Synthesis and Characterization of Star-Shaped Porphyrin-Cored Poly(L-lactide)

2011 ◽  
Vol 239-242 ◽  
pp. 1703-1706 ◽  
Author(s):  
Xiao Hui Dai ◽  
Wei Liu ◽  
Ya Fei Huang ◽  
Chang Ming Dong
Keyword(s):  
Molecular Weight ◽  
Photodynamic Therapy ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Molar Ratio ◽  
Synthesis And Characterization ◽  
Porphyrin Core

Star-shaped porphyrin-cored poly(L-lactide) (SPPLLA) was synthesized using a tetra-hydroxyethyl terminated porphyrin as a core initiator and 4-(Dimethylamino)pyridine (DMAP) as a catalyst in THF at 50 °C. The molecular weight of as-synthesized polymer were measured by GPC and1HNMR. It was found that the molecular weight of SPPLLA could be adjusted linearly by controlling the molar ratio of L-lactide to porphyrin core initiator, and the molecular weight distribution was reasonably narrow. Furthermore, SPPLLA polymers showed similar UV-vis spectra compared with porphyrin core initiator. Consequently, this will provide potentially porphyrin-cored poly(L-lactide) for photodynamic therapy.

Sign in / Sign up

Export Citation Format

Share Document