• Macromolecular Research
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• v.15 no.3
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• pp.244-255
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• 2007

Nucleation is the most sensitive stage in the preparation of highly cross-linked, monodisperse microspheres by dispersion polymerization, since the addition of a small amount of cross-linker results in particle deformation and coagulation. To overcome these problems, $5\;{\mu}m$ poly(methyl methacrylate) seed particles prepared by dispersion polymerization were used in the preparation of mono disperse, cross-linked PMMA particles containing up to 7 wt% divinylbenzene by seeded batch dispersion polymerization. Spherical particles with a narrow size distribution containing up to 8 wt% of EGDMA were prepared by seeded multi-batch dispersion polymerization processes. These particles were identified by scanning electron microscopy and DSC.

• 제어로봇시스템학회:학술대회논문집
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• pp.1000-1003
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• 1996

Nonlinear unified predictive control(UPC) algorithm was applied to the temperature control of a batch polymerization reactor for polymethylmethacrylate(PMMA). Before the polymerization reaction is initiated, the parameters of the process model are determined by the recursive least squares(RLS) method. During the reaction, nonlinearities due to generation of heat of reaction and variation of heat transfer coefficients are predicted through the nonlinear model developed. These nonlinearities are added to the process output from the linear process model. And then, the predicted process output is used to calculate the control output sequence. The performance of nonlinear control algorithm was verified by simulation and compared with that of the linear unified predictive control algorithm. In the experiment of a batch PMMA polymerization, nonlinear unified predictive control was implemented to regulate the temperature of the reactor, and the validity of the nonlinear model was verified through the experimental results. The performance of the nonlinear controller turned out to be superior to that of the linear controller for tracking abrupt changes in setpoint.

• 제어로봇시스템학회:학술대회논문집
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• pp.51-55
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• 1995

An adaptive unified predictive control (UPC) algorithm is applied to a batch polymerization reactor for poly(methyl methancrylate) (PMMA) and the effects of controller parameters are investigated. Computational studies are performed for a batch polymerization system model developed in this study. A transfer function in parametric form is estimated by recursive least squares (RLS) method, and the UPC algorithm is implemented to control the reactor temperature on the basis of this transfer function. The adaptive unified predictive controller shows a better performance than the PID controller for tracking set point changes, especially in the latter part of reaction course when gel effect becomes significant. Various performance can be acquired by selecting adequate values for parameters of the adaptive unified predictive controller; in other words, the optimal set of parameters exists for a given set of reaction conditions and control objective.

• 제어로봇시스템학회:학술대회논문집
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• pp.305-308
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• 1997

The on-line calculation method is developed to obtain the temperature trajectory that brings the reactants to the desired state in batch styrene polymerization reactor. The temperature trajectory is obtained by applying the moments of the polymer concentration to the 2-step calculation method. The computer simulation is also carried out to verify the superiority of the on-line method to the off-line one. When a temperature disturbance of constant size is introduced, the off-line results shows considerable deviation from the target degree of polymerization. The on-line strategy set up a new trajectory to reach the desired state by using the current state of the reactor. Therefore, the on-line strategy deals with the changes of the system more adequately than the off-line strategy.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• pp.1106-1108
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• 1993

This paper deals with an industrial application of a fuzzy feedback combined learning control to an industrial batch free radical polymerization reactor. As a result, the plant has reduced the batch reaction time by 50 minute and stabilized both by 40 percent reduction of the standard deviations of product qualities, such as the total solid content and the graft gum, and by 45 percent reduction of the standard deviation of the batch reaction end time.

• 제어로봇시스템학회:학술대회논문집
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• pp.263-266
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• 1996

A method to determine an optimal temperature trajectory that guarantees polymer products having controlled molecular weight distribution and desired values of molecular weight is presented. The coordinate transformation method and the optimal control theory are applied to a batch PMMA polymerization system to calculate the optimal temperature trajectory. Coordinate transformation method converts the original fixed-end-point, free-end-time problem to a free-end-point, fixed-end-time problem. The idea is that by making the reactor temperature track the optimal temperature trajectory one may be able to produce polymer products having the prespecified physical property in a minimum time. The on-line control experiments with the PID control algorithm have been conducted to establish the validity of the scheme proposed in this study. The experimental results show that prespecified polymer product could be obtained with tracking the calculated optimal temperature trajectory.

• Elastomers and Composites
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• v.46 no.1
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• pp.60-69
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• 2011

The various types of PBA/PMMA composite latexes were prepared by $2.1\;{\mu}m$ PBA seeded batch and seeded semi-continuous dispersion polymerization. The morphology of the PBA/PMMA composite latexes by seeded batch process was found to be closely dependant on the weight ratios of methanol/water in polymerization medium and of PBA seed/MMA at the second stage. In general, egg, snowman, confetti, peanut-like nonspherical composite latex particles were formed with increasing amount of water and MMA as a result of the occurrence of the phase separation between PBA seed and PMMA. The morphology of the PBA/PMMA composite latexes by seeded semi-continuous process was controlled by the addition time of MMA, especially, spherical shaped core(PBA)/shell(PMMA) composite latex particles were prepared under the monomer-starved condition at the second stage.

• Proceedings of the Korean Fiber Society Conference
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• pp.8-8
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• 1990

A new method for the graft polymerization of acrylonitrile onto starch is presented. Graft polymerization of acrylonitrile onto starch and the subsequent hydrolysis in sodium hydroxide solution to prepare absorbents is well known. This process has been utilized to produce the commercial product, Super Slurper. In a typical batch process, ~5% starch in water mixture is gelatinized at $95^{\circ}C$ under stirring for 1 hour then cooled to room temperature. The graft polymerization itself is carried out for approximately 2 hours at $25~30^{\circ}C$ on the gelatinized starch by eerie ion initiation. In this study, graft polymerization of acrylonitrile onto starch via a reactive extrusion process which is a continuous, efficient process is described. Initial concentration of starch in water is 35% and the reaction temperatures are between $50~80^{\circ}C$. However, the most significant difference in the reactive extrusion process is the short time in which the graft polymerization takes place. Preliminary results on the properties of graft polymerization products obtained from the reactive extrusion process are compared to those obtained from the batch process as well as the absorbency of the hydrolyzed samples. Absorbent material has also been prepared by sequential grafting and saponification in the extruder followed by a 2 hour heat treatment of the extrudate in an air circulated oven at $100^{\circ}C$.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.62-74
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• 2002

The tracking of a reference temperature trajectory in a polymerization batch reactor is a common problem and has critical importance because the quality control of a batch reactor is usually achieved by implementing the trajectory precisely. In this study, only energy balances around a reactor are considered as a design model for control synthesis, and material balances describing concentration variations of involved components are treated as unknown disturbances, of which the effects appear as time-varying parameters in the design model. For the synthesis of a tracking controller, a method combining the input-output linearization of a time-variant system with the parameter estimation is proposed. The parameter estimation method provides parameter estimates such that the estimated outputs asymptotically follow the measured outputs in a specified way. Since other unknown external disturbances or uncertainties can be lumped into existing parameters or considered as another separate parameters, the method is useful in practices exposed to diverse uncertainties and disturbances, and the designed controller becomes robust. And the design procedure and setting of tuning parameters are simple and clear due to the resulted linear design equations. The performances and the effectiveness of the proposed method are demonstrated via simulation studies.

• Macromolecular Research
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• v.16 no.4
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• pp.293-302
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• 2008

In our previous publication, the problem of particle deformation and coagulation at the nucleation stage in the presence of cross-linker was intensely studied by seeded batch dispersion polymerization of methyl methacrylate (MMA). In the present work, highly cross-linked, monodisperse PMMA particles were prepared under various reaction conditions by seeded semi-continuous process. Monodisperse, $6.5{\mu}m$-diameter PMMA particles containing up to 8 wt% of DVB or EGDMA were successfully made by seeded semi-continuous process and multi-semi-continuous addition process, respectively. Therefore, this study shows that seeded semi-continuous process is more effective and efficient to prepare highly cross-linked, monodisperse particles than non-seeded and seeded batch processes.