Polymer-Fraction Dependence of Entry Rate Coefficients in Emulsion Polymerization

1992 ◽  
Vol 45 (12) ◽  
pp. 2057 ◽  
Author(s):  
GL Leslie ◽  
DH Napper ◽  
RG Gilbert
Keyword(s):  
Emulsion Polymerization ◽  
Aqueous Phase ◽  
Rate Coefficient ◽  
Monomer Concentration ◽  
Weight Fraction ◽  
Rate Coefficients ◽  
Seeded Emulsion Polymerization ◽  
Entry Rate ◽  
Initiator Efficiency ◽  
Approach To Steady State

Data on the rate of approach to steady state in a series of studies of the seeded emulsion polymerization of styrene yield the dependence of the rate coefficient for entry of free radicals into latex particles as a function of the weight-fraction polymer and hence of monomer concentration in the aqueous phase. The results are in accord with a model for the entry process (i.e., for the initiator efficiency) based on aqueous-phase propagation and termination being the rate-controlling events.

Entry rate coefficients in emulsion polymerization systems

1986 ◽  
Vol 82 (7) ◽  
pp. 2247 ◽  
Author(s):  
Ian A. Penboss ◽  
Robert G. Gilbert ◽  
Donald H. Napper
Keyword(s):  
Emulsion Polymerization ◽  
Rate Coefficients ◽  
Entry Rate

scholarly journals Preparation of Monodisperse Poly(Methyl Methacrylate)/Polystyrene Composite Particles by Seeded Emulsion Polymerization Using a Sequential Flow Process

2021 ◽  
Vol 3 ◽  
Author(s):  
Takaichi Watanabe ◽  
Kengo Karita ◽  
Midori Manabe ◽  
Tsutomu Ono
Keyword(s):  
Methyl Methacrylate ◽  
Emulsion Polymerization ◽  
Aqueous Phase ◽  
Slug Flow ◽  
Particle Diameter ◽  
Monomer Conversion ◽  
Composite Particles ◽  
Seeded Emulsion Polymerization ◽  
Flow Process ◽  
Seed Particles

We develop a sequential flow process for the production of monodisperse poly (methyl methacrylate) (PMMA)/polystyrene (PS) composite particles through a soap-free emulsion polymerization of methyl methacrylate (MMA) using the first water-in-oil (W/O) slug flow and a subsequent seeded emulsion polymerization of styrene (St) using the second W/O slug flow. In this process, monodisperse PMMA seed particles are first formed in the dispersed aqueous phase of the first W/O slug flow. Subsequently, removal of the oil phase from the slug flow is achieved through a porous hydrophobic tubing, resulting in a single flow of the aqueous phase containing the seed particles. The aqueous phase is then mixed with an oil phase containing St monomer to form the second W/O slug flow. Finally, monodisperse PMMA/PS composite particles are obtained by a seeded emulsion polymerization of St using the second W/O slug flow. We compared the reaction performance between the slug flow and the batch processes in terms of particle diameter, monomer conversion, particle size distribution, and the number of particles in the system. We found that internal circulation flow within the slugs can enhance mass transfer efficiency between them during polymerization, which results in monodisperse PMMA/PS composite particles with a large particle diameter and a high monomer conversion in a short reaction time, compared to those prepared using the batch process. We believe that this sequential microflow process can be a versatile strategy to continuously produce monodisperse composite particles or core-shell particles in a short reaction time.

scholarly journals Seeded emulsion polymerization of butadiene. 1. The propagation rate coefficient

1993 ◽  
Vol 26 (2) ◽  
pp. 268-275 ◽  
Author(s):  
Edwin M. Verdurmen ◽  
Erik H. Dohmen ◽  
John M. Verstegen ◽  
Ian A. Maxwell ◽  
Anton L. German ◽  
...  
Keyword(s):  
Emulsion Polymerization ◽  
Rate Coefficient ◽  
Propagation Rate ◽  
Seeded Emulsion Polymerization ◽  
Propagation Rate Coefficient

scholarly journals Crosslinking in Semi-Batch Seeded Emulsion Polymerization: Effect of Linear and Non-Linear Monomer Feeding Rate Profiles on Gel Formation

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 596
Author(s):  
Chang Liu ◽  
Amit K. Tripathi ◽  
Wei Gao ◽  
John G. Tsavalas
Keyword(s):  
Emulsion Polymerization ◽  
Feed Rate ◽  
Monomer Concentration ◽  
Butyl Methacrylate ◽  
Gel Formation ◽  
Seeded Emulsion Polymerization ◽  
Linear Profile ◽  
Gel Fraction ◽  
Non Linear ◽  
Monomer Feed

Waterborne latex is often called a product-of-process. Here, the effect of semi-batch monomer feed rate on the kinetics and gel formation in seeded emulsion polymerization was investigated for the copolymerization of n-butyl methacrylate (n-BMA) and ethylene glycol dimethacrylate (EGDMA). Strikingly, the gel fraction was observed to be significantly influenced by monomer feed rate, even while most of the experiments were performed under so-called starve-fed conditions. More flooded conditions from faster monomer feed rates, including seeded batch reactions, counterintuitively resulted in significantly higher gel fraction. Chain transfer to polymer was intentionally suppressed here via monomer selection so as to focus mechanistic insights to relate only to the influence of a divinyl monomer, as opposed to being clouded by contributions to topology from long chain branching. Simulations revealed that the dominant influence on this phenomenon was the sensitivity of primary intramolecular cyclization to the instantaneous unreacted monomer concentration, which is directly impacted by monomer feed rate. The rate constant for cyclization for these conditions was determined to be first order and 4000 s−1, approximately 4 times that typically observed for backbiting in acrylates. This concept has been explored previously for bulk and solution polymerizations, but not for emulsified reaction environments and especially for the very low mole fraction divinyl monomer. In addition, while gel fraction could be dramatically manipulated by variations in linear monomer feed rates, it could be markedly enhanced by leveraging non-linear feed profiles built from combination sequences of flooded and starved conditions. For a 2 h total feed time, a fully linear profile resulted in 30% gel while a corresponding non-linear profile with an early fast-feed segment resulted in 80% gel.

scholarly journals Mathematical Modeling of the Production of Elastomers by Emulsion Polymerization in Trains of Continuous Reactors

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1508
Author(s):  
Enrique Saldívar-Guerra ◽  
Ramiro Infante-Martínez ◽  
José María Islas-Manzur
Keyword(s):  
Emulsion Polymerization ◽  
Rate Coefficient ◽  
Mechanistic Model ◽  
A Priori ◽  
Particle Diameter ◽  
Styrene Butadiene Rubber ◽  
Copolymer Composition ◽  
Butadiene Rubber ◽  
Entry Rate ◽  
Monomer Composition

A mechanistic model is proposed to describe the emulsion polymerization processes for the production of styrene–butadiene rubber (SBR) and acrylonitrile–butadiene rubber (NBR) elastomers in trains of continuous stirred tank reactors (CSTRs). A single model was used to describe both processes by choosing the proper physicochemical parameters of each system. Most of these parameters were taken from literature sources or estimated a priori; only one parameter (the entry rate coefficient) was used as an adjustable value to reproduce the kinetics (mainly conversion), and another parameter (the transfer to polymer rate coefficient) was used to fit the molecular weight distribution (MWD) experimental values from plant data. A 0-1-2 model for the number of particles and for the moments of the MWD was used to represent with more fidelity the compartmentalization effects. The model was based on approaches used in previous emulsion polymerization models published in the literature, with the premise of reaching a compromise between the level of detail, complexity, and practical value. The model outputs along the reactor train included conversion, remaining monomer composition, instantaneous and accumulated copolymer composition, the number of latex particles and particle diameter, polymerization rate, the average number of radicals per particle, average molecular weights, and the number of branches per chain.

Kinetics and Mechanism of Emulsion Polymerization

1976 ◽  
Vol 49 (3) ◽  
pp. 536-609 ◽  
Author(s):  
J. Ugelstad ◽  
F. K. Hansen
Keyword(s):  
Emulsion Polymerization ◽  
Aqueous Phase ◽  
Relative Effectiveness ◽  
Monomer Concentration ◽  
Particle Formation ◽  
Degree Of Conversion ◽  
Particle Volume ◽  
Vast Number ◽  
Kinetics Of ◽  
Experimental And Theoretical Studies

Abstract The course of emulsion polymerization may be considered as involving three intervals: Interval I, where particle formation takes place. The end of this interval is not dependent upon the degree of conversion, but on the total amount of polymer formed. With usual recipes, it ends at about 1-5% conversion. Interval II lasts from the end of Interval I until monomer disappears as a separate phase. In this interval, the particle number is usually found to be constant, the particle volume increases proportional to conversion, the monomer concentration in the particles is approximately constant, and therefore the termination is also constant within the particles. Interval III starts when the monomer disappears as a separate phase. The transition from Intervals II to III is determined by the degree of conversion and differs for different monomers. In cases where the solubility of monomer in the water phase is low, the monomer present in the aqueous phase may usually be neglected compared to the monomer present in the polymer particles. This will usually hold with most monomers at ordinary conditions, where the amount of polymer per unit of water is relatively high, and when the concentration of monomer in the particles is much higher than in the aqueous phase. In this case, the particle volume during Interval III will decrease slightly due to the contraction by polymerization. The concentration of monomer in the particles generally decreases during Interval III, which leads to an increased viscosity within the particles and thereby also to a decrease in the value of the termination constant. The present paper deals chiefly with the kinetics of emulsion polymerization in the three intervals and the application of kinetics to the study of the mechanism. Several review articles on emulsion polymerization have recently appeared in the literature. The reason for presenting a new review article is that a vast number of papers on emulsion polymerization have recently been published, which have broadened the theoretical and experimental knowledge of the process. Several experimental and theoretical studies on the mechanisms of particle formation have appeared. New theories for particle formation outside the micelles have appeared. Also the relative effectiveness of micelles and particles in capturing radicals from the aqueous phase has been discussed in several papers.

scholarly journals Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad Akbar Ali ◽  
M. Balaganesh ◽  
Faisal A. Al-Odail ◽  
K. C. Lin
Keyword(s):  
Water Molecule ◽  
Energy Surface ◽  
Rate Coefficient ◽  
Water Concentration ◽  
State Theory ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Experimental And Theoretical Studies ◽  
Effective Reaction ◽  
Effective Reaction Rate

AbstractThe rate coefficients for OH + CH3OH and OH + CH3OH (+ X) (X = NH3, H2O) reactions were calculated using microcanonical, and canonical variational transition state theory (CVT) between 200 and 400 K based on potential energy surface constructed using CCSD(T)//M06-2X/6-311++G(3df,3pd). The results show that OH + CH3OH is dominated by the hydrogen atoms abstraction from CH3 position in both free and ammonia/water catalyzed ones. This result is in consistent with previous experimental and theoretical studies. The calculated rate coefficient for the OH + CH3OH (8.8 × 10−13 cm3 molecule−1 s−1), for OH + CH3OH (+ NH3) [1.9 × 10−21 cm3 molecule−1 s−1] and for OH + CH3OH (+ H2O) [8.1 × 10−16 cm3 molecule−1 s−1] at 300 K. The rate coefficient is at least 8 order magnitude [for OH + CH3OH(+ NH3) reaction] and 3 orders magnitude [OH + CH3OH (+ H2O)] are smaller than free OH + CH3OH reaction. Our calculations predict that the catalytic effect of single ammonia and water molecule on OH + CH3OH reaction has no effect under tropospheric conditions because the dominated ammonia and water-assisted reaction depends on ammonia and water concentration, respectively. As a result, the total effective reaction rate coefficients are smaller. The current study provides a comprehensive example of how basic and neutral catalysts effect the most important atmospheric prototype alcohol reactions.

Rapid relaxation NMR measurements to predict rate coefficients in ionic liquid mixtures. An examination of reaction outcome changes in a homologous series of ionic liquids

2021 ◽  
Author(s):  
Daniel C Morris ◽  
Stuart W Prescott ◽  
Jason B Harper
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Homologous Series ◽  
Rate Coefficient ◽  
Liquid Mixtures ◽  
Solvent Mixture ◽  
Rate Coefficients ◽  
Substitution Process

A series of ionic liquids based on the 1-alkyl-3-methylimidazolium cations were examined as components of the solvent mixture for a bimolecular substitution process. The effects on both the rate coefficient...

Colloidal templating: seeded emulsion polymerization of a soluble shell with a controlled alkyne surface density

Soft Matter ◽  
2012 ◽  
Vol 8 (20) ◽  
pp. 5493 ◽  
Author(s):  
Ryan D. Roeder ◽  
Parul Rungta ◽  
Volodymyr Tsyalkovskyy ◽  
Yurii Bandera ◽  
Stephen H. Foulger
Keyword(s):  
Emulsion Polymerization ◽  
Surface Density ◽  
Seeded Emulsion Polymerization ◽  
Colloidal Templating
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