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Dissertation
Mechanistic modeling and model-based studies in spontaneous solution polymerization of alkyl acrylate monomers
Doctor of Philosophy (Ph.D.), Drexel University
Aug 2006
DOI:
https://doi.org/10.17918/etd-1306
Abstract
High-temperature (above 120°C) free-radical polymerization of alkyl acrylate monomers is studied to gain a better quantitative understanding of the governing reaction network behind the observed process measurement dynamics. At higher reaction temperatures, mechanistic models developed based on lowertemperature data fail to quantitatively predict the dynamics of polymer property indices such as monomer conversion and average molecular weights. In recent studies, this failure has been attributed to the occurrence of secondary chain reactions that become increasingly significant with temperature increase. Experimental data obtained from high-temperature batch polymerization of nbutyl acrylate (nBA) in xylene points to the occurrence of short chain branch formation, as opposed to long chain branch formation. This observation substantiates the backbiting (intra-molecular chain transfer) mechanism postulated in earlier studies on alkyl acrylate polymerization. In this study the activation energy is estimated through multivariate data fitting of several measurements. The estimated value of the activation energy of the postulated self-initiation reaction points to actual occurrence of self-initiation. The measurements include monomer conversion, number- and weight-average molecular weights and microstructure quantities (number-average of terminal solvent group, terminal double bond and chain branch per polymer chain). This provides an explanation to the observed spontaneous polymerization in alkyl acrylate polymerization at higher temperatures. A free-radical polymerization mechanistic model for the spontaneous solution high-temperature polymerization of n-butyl acrylate in xylene is developed. This effort involves characterizing polymer solutions, postulating reaction networks, screening the networks by performing global parameter identifiability analyses, reducing the complexity of the developed mechanistic model, estimating unknown kinetic parameters, and validating the model. A method of global parameter identifiability analysis is developed for models that are affine in parameters. The model reduction techniques used in this study include the method of moments modeling method, the tendency modeling method, and the quasi-steady-state assumptions on the concentrations of free radicals. The model is used to (a) develop a model-based optimal control policy for a spontaneously-initiated semi-batch polymerization reactor and (b) design of a multi-rate state observer to estimate polymer-chain microstructure properties from currently-available on-line and off-line measurements.
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Details
- Title
- Mechanistic modeling and model-based studies in spontaneous solution polymerization of alkyl acrylate monomers
- Creators
- Felix Suryaman Rantow - DU
- Contributors
- Masoud Soroush (Advisor) - Drexel University (1970-)Michael Charles Grady (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Chemical (and Biological) Engineering [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 1306; 991014631957804721