Optimal operation strategies to control the molecular weight distribution of polymer products (2023)

Cited by (24)

  • Methyl methacrylate polymerization in nanoporous confinement

    2011, Polymer

    The effect of nanoconfinement on the rate of isothermal polymerization of methyl methacrylate (MMA) polymerization is investigated using differential scanning calorimetry. Controlled pore glass (CPG) with pore diameters of 13, 50, and 111nm are used for the confinement of the reaction. Both hydrophilic and hydrophobic pore surfaces are studied. The effective reaction rate and the apparent activation energy at low conversions, prior to autoacceleration, are unchanged in hydrophobic pores. On the other hand, in hydrophilic pores, the reaction rate increases by as much as a factor of 8 in the smallest 13nm hydrophilic pores, and the effective activation energy decreases. For both pore surfaces, the time required to reach autoacceleration decreases with decreasing pore size, with the effect much more pronounced in the hydrophilic pores. The results are consistent with a model of nanoconfined free radical polymerization which accounts for suppressed termination due to a decrease in the diffusivity of nanoconfined chains.

  • Measurement and control of polymerization reactors

    2006, Computers and Chemical Engineering

    Citation Excerpt :

    Therefore, it is also possible to implement more sophisticated control strategies during the batch by establishing operating trajectories for initiator addition, monomer addition, and/or reactor temperature to achieve desired polymer properties in minimum time, maximize productivity, or tailor the polymer molecular weight distribution. This is typically accomplished by solving off line an optimization problem using a kinetic model of the process as shown for example in Maschio, Bello, and Scali (1992, 1994), Saenz de Buruaga, Armitage, Leiza, and Asua (1997), Thomas and Kiparissides (1984), and Tyner, Soroush, Grady, Richards, and Congalidis (2001). These essentially open loop trajectories constitute a form of feedforward control and are then implemented as part of the batch sequential logic and recipe management system using ladder logic and binary logic diagrams as shown in Seborg et al. (2004).

    The measurement and control of polymerization reactors is very challenging due to the complexity of the physical mechanisms and polymerization kinetics. In these reactors many important variables, which are related to end-use polymer properties, cannot be measured on-line or can only be measured at low sampling frequencies. Furthermore, end-use polymer properties are related to the entire molecular weight, copolymer composition, sequence length, and branching distributions. This paper surveys the instrumentation technologies, which are of particular interest in polymerization reactors with emphasis on, for example, measurement of viscosity, composition, molecular weight, and particle size. This paper presents a hierarchical approach to the control system design and reviews traditional regulatory techniques as well as advanced control strategies for batch, semibatch, and continuous reactors. These approaches are illustrated by focusing on the control of a commercial multiproduct continuous emulsion polymerization reactor. Finally, the paper captures some of the trends in the polymer industry, which may impact future development in measurement and reactor control.

  • Control of a solution copolymerization reactor using multi-model predictive control

    2003, Chemical Engineering Science

    (Video) Polymer molecular weight and configurations

    Citation Excerpt :

    Temperature control (Chylla & Haase, 1993; Defaye, Reigner, Chabanon, Caralp, & Vidal, 1993; Ni, Debelak, & Hunkeler, 1997). Optimization of initiator addition, monomer addition, and/or reactor temperature to achieve desired polymer properties in minimum time, maximize productivity in batch or a semibatch reactor, or control the polymer molecular weight distribution (Arzamendi & Asua, 1989; Chen & Jeng, 1978; Chen & Huang, 1981; Louie & Soong, 1985a, b; Maschio, Bello, & Scali, 1992, 1994; Ponnuswamy, Shah, & Kiparissides, 1986; Scali, Carib, Bello, & Maschio, 1995; Secchi, Lima, & Pinto, 1990; Soroush & Kravaris, 1993; Thomas & Kiparissides, 1984a, b; Wu, Denton, & Laurence, 1982). Online estimators of polymer properties by using calorimetric techniques, a kinetic model in the form of an extended Kalman filter, or neural network techniques (Dimitratos, Georgakis, El-Aasser, & Klein, 1991; Eliçabe, Özdeger, & Georgakis, 1995; Ellis, Taylor, & Jensen, 1994; Kim & Choi, 1991; McAuley & MacGregor, 1991; Kozub & MacGregor, 1992; Moritz, 1989; Mutha, Cluett, & Penlidis, 1997; Scali et al., 1995; Semino, Manning, & Brambilla, 1995; Zhang, Morris, Martin, & Kiparissides, 1997).

    We study the control of a solution copolymerization reactor using a model predictive control algorithm based on multiple piecewise linear models. The control algorithm is a receding horizon scheme with a quasi-infinite horizon objective function which has finite and infinite horizon cost components and uses multiple linear models in its predictions. The finite horizon cost consists of free input variables that direct the system towards a terminal region which contains the desired operating point. The infinite horizon cost has an upper bound and takes the system to the final operating point. Simulation results on an industrial scale methyl methacrylate vinyl acetate solution copolymerization reactor model demonstrate the ability of the algorithm to rapidly transition the process between different operating points.

  • Optimization and non-linear control of a batch emulsion polymerization reactor

    1999, Chemical Engineering Journal

    The optimal temperature policy which minimizes the terminal time in a batch emulsion polymerization reactor of styrene and α-methylstyrene was determined by means of orthogonal collocation techniques combined with a general non-linear programming method. The constraints concern the final latex properties and the thermal limitations of the pilot plant. An experimental validation has been realized. The optimal temperature profile was tracked using a non-linear geometric control technique which is particularly adapted to polymerization reactor control. An extended Kalman filter was used to estimate the non-measured state variables. Experimental results showed excellent agreement with predictions for this complex system. A good temperature tracking was observed and the product quality was well predicted and controlled.

  • Experimental studies on optimal molecular weight distribution control in a batch-free radical polymerization process

    1998, Chemical Engineering Science

    An experimental study on the control of polymer weight chain length distribution is presented for batch-free radical solution polymerization of methyl methacrylate. The weight chain length distribution is calculated using the method of finite molecular weight moments in which the weight fraction of polymers over a number of finite chain length intervals covering the theoretically infinite chain length domain is calculated. Control of a target polymer chain length distribution is achieved by first computing a discrete sequence of reactor temperature setpoints which lead to the best match of a given target weight chain length distribution at a final desired monomer conversion. During the polymerization, an on-line extended Kalman filter is used to incorporate infrequent and delayed off-line molecular weight measurements. The piecewise constant reactor temperature setpoints are taken as the decision variables in a nonlinear programming problem. They are recomputed and updated at each sampling point during the course of polymerization to match the final desired molecular weight distribution. It is demonstrated through simulations and experimentation that it is feasible to control the entire polymer chain length distribution in a batch polymerization process.

  • Thermal characterization of the polymerization of methyl methacrylate

    1996, Chemical Engineering Science

    (Video) MSCI 410 - Molecular Weight by Gel Permeation Chromatography (GPC)

    Two different calorimetric techniques have been used to determine thermokinetic parameters and to asses the thermal stability of bulk methyl methacrylate (MMA) polymerization. The results obtained with both methods are in agreement with those reported in the literature. New correlations based on experimental results have been proposed to describe the influence of diffusion phenomena on the dynamics of the process. A mathematical model based on the experimental results has been developed in order to execute an analysis of the dynamics of the process.

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Copyright © 1995 Published by Elsevier Ltd.


How do you control the molecular weight of a polymer? ›

Control of radical polymerization in order to get a polymer with lower average molecular mass can be done by one of these ways:
  1. Increase the amount of initiator relative to monomer (i.e. double or triple the amount). ...
  2. Use a chain transfer agent such as a thiol or mercaptan (R-S-H).

Why is the molecular weight of polymer controlled? ›

Lower molecular weight will typically flow easier. A High molecular weight increases the impact resistance of the material. The higher degree of entanglement means that in order to rupture, more polymer bonds need to be broken, this means that the polymer can absorb more energy before failing.

How does molecular weight distribution affect polymers? ›

A polymer's molecular weight distribution (MWD) impacts material properties such as processability, mechanical strength, and morphological phase behavior1,2,3,4,5,6. This correlation is general across all polymers and has motivated the development of many synthetic and process techniques.

What are the techniques of molecular weight control? ›

(1) MW can be measured using many different methods including gel permeation chromatography (GPC), osmometry, light scattering, viscometry, cryoscopy, ebulliometry, ultracentrifugation, mass spectrometry, and end-group analysis.

How to control the molecular weight in chain growth polymerization? ›

If chain growth proceeds in a living manner, both the molecular weight and composition of the polymer is controlled by the feed ratio of monomers and monomers to initiator. Furthermore, the molecular weight increases directly with monomer conversion while retaining low polydispersity over the whole conversion range.

Which technique is commonly used to determine the molecular weight of polymer? ›

Gel permeation chromatography (GPC) Gel permeation chromatography is also called size exclusion chromatography. It is widely used method to determine high molecular weight distribution.

How does molecular weight affect polymer solubility? ›

As the molecular weight of the solute increases, the value of Ω decreases, and, as a result the entropic driving forces are diminished for dissolution of polymers. As a consequence, polymer solubility depends strongly on the enthalpic interaction between the polymer and the solvent.

What is molecular weight and why is it important? ›

Molecular weight is a measure of the sum of the atomic weight values of the atoms in a molecule. Molecular weight is used in chemistry to determine stoichiometry in chemical reactions and equations. Molecular weight is commonly abbreviated by M.W. or MW.

What is the effect of molecular weight on polymer adsorption? ›

The type of molecular weight species adsorbed was found to be concentration dependent: the lower the concentration, the higher the molecular weight species adsorbed.

Which technique could be used for molecular weight determinations of proteins? ›

An apparent molecular weight (MW) of a protein can be determined from the migration distance of a protein complexed with a strong cationic detergent sodium dodecyl sulfate (SDS) separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

What technique can be used to separate different molecular weight proteins? ›

Western Blotting

The most common version of Western blotting is known as immunoblotting. In this technique a sample of proteins is first electrophoresed by SDS-PAGE to separate the proteins on the basis of their molecular weights.

Which of the following method is used for the determination of molecular weight? ›

Viscometry is the leading method for determining average molecular weight in industrial applications.

How do we control the speed of polymerisation process? ›

Catalysts – these control the SPEED of the reaction. Monomers or oligomers – these are the building blocks of the reaction, the base material that is transformed into the polymers.

How do you control polymer size? ›

You can use a chain transfer agent. You can add a terminating agent that will stop polymerization prematurely, which will shorten your chain lengths. You can change temperature. If you increase the amount of initiator relative to the amount of monomer, you get smaller chains.

What are the three steps involved in chain growth polymerization? ›

Usually an initiator compound reacts with the monomer to start the reaction, and the mechanism of chain polymerization consists of three phases, called initiation, propagation, and termination.

Which one is the best method for the determination of molecular weight of proteins and polymers ROM the Colligative properties of solution? ›

Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.

What is the most accurate method to determine molecular weight of a given polypeptide? ›

The relative molecular weights of polysaccharides and peptides are usually determined using gel permeation chromatography (GPC) or size exclusion chromatography (SEC). This method provides not only the average molecular weight value but also information on the molecular weight distribution in the polymer sample.

Which method for determination of molecular weight of polymer is convenient and least complicated? ›

The most accurate method for determine absolute molecular mass of a polymer is vapor pressure osmometry (VPO).

Does temperature affect molecular weight of polymers? ›

In a number of cases the molecular size parameters have been found to depend on the solution temperature. When observed, the temperature dependence can change molecular weight values by as much as 50%.

What is molecular weight and how it affects the properties of a polymer? ›

Polymer molecular weight reflects the number of entanglements of polymer chains in solution, thus solution viscosity. It has been found that a low molecular weight solution tends to form beads rather than fibers and a high molecular weight solution helps to form fibers with larger diameters (Huang et al., 2008).

What are the factors affecting polymer solubility? ›

Solubility is affected by 4 factors – temperature, pressure, polarity, and molecular size.

What does molecular weight depend on? ›

The weight average molecular weight depends not only on the number of molecules present, but also on the weight of each molecule.

Why is it important to know the molecular weight of a protein? ›

Protein molecular weight is a key parameter to confirm, as the primary structure is the most foundational level of protein structure. Developing a robust understanding of the unmodified protein molecular weight can assist in initial assessments of the biomolecule's functionality.

What is effective molecular weight? ›

It is just the sum of the mole fractions of each gas, multiplied by the molar mass of that substance. For example, the average molar mass of dry air whose composition by volume is 78% of nitrogen, 21% of oxygen, and 1% of argon is m = (0.21 x 32) + (0.78 x 28) + (0.01 x 20) = 28.

What is molecular weight and distribution of polymers? ›

Polymer molecular weight is defined as a distribution rather than a specific number because polymerization occurs in such a way to produce different chain lengths. Weight average molecular weight (MW) and number average molecular weight (MN) are two ways we can characterize the polymer molecular weight.

What is the relation between molecular weight and density of polymer? ›

The relation between molecular weight and density is dismissal when the molecular weight is high this is mean it have high density. yes, high molecular weight means high density and vice versa. polymers with high molecular weight have high density and vice versa.so,the relation is direct.

What effect does high pressure have on the molecular weight of the polymer product produced? ›

Most polymerization reactions proceed at a faster rate under high pressure. Higher molecular weights are obtained at higher pressures.

Which factor determines the molecular mass of polymer? ›

The molecular masses of polymers are determined by osmotic pressure method and not by measuring other colligative properties.

What method determines protein molecular weight? ›

Abstract. An apparent molecular weight (MW) of a protein can be determined from the migration distance of a protein complexed with a strong cationic detergent sodium dodecyl sulfate (SDS) separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

What are three factors that can affect the properties of polymers? ›

The processing conditions which can affect the properties of the polymer include the temperature and pressure used during the polymerization, the solvent in which the polymer is polymerized, the types of monomer units used, the concentration of monomers in the reaction, the reagent which is used to initiate the ...

What controls the properties of polymers? ›

Polymer properties are strongly linked to the molecular weight and the molecular weight distribution. As an example, Figure 1 shows the effect on molecular weight on physical properties. A polymer such as polystyrene is stiff and brittle at room temperature with a degree of polymerization of 1,000.

What are controlled polymerisation techniques? ›

Broadly speaking, there are three fundamental CRP techniques: Atom Transfer Radical Polymerization (ATRP) using AB* inimers (compounds containing initiator fragment B* and vinyl group A in one molecule; Reversible Addition/Fragmentation Chain Transfer Polymerization (RAFT) of transmers; and Nitroxide-mediated ...

What method improves the strength of polymer? ›

The use of superplasticizers in combination with other methods of modifying concrete with polymers, in particular, impregnating hardened concrete with polymeric materials, can increase the compressive strength up to 70 MPa and more.

What is the process of determining molecular weight? ›

Sample Molecular Weight Calculation

Using the periodic table of the elements to find atomic weights, we find that hydrogen has an atomic weight of 1, and oxygen's is 16. In order to calculate the molecular weight of one water molecule, we add the contributions from each atom; that is, 2(1) + 1(16) = 18 grams/mole.

Why is it important to know the molecular weight of proteins? ›

Protein molecular weight is a key parameter to confirm, as the primary structure is the most foundational level of protein structure. Developing a robust understanding of the unmodified protein molecular weight can assist in initial assessments of the biomolecule's functionality.

What determines molecular weight? ›

molecular weight, also called molecular mass, mass of a molecule of a substance, based on 12 as the atomic weight of carbon-12. It is calculated in practice by summing the atomic weights of the atoms making up the substance's molecular formula.


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