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The model and methodology for estimating diffusion-controlled rate coefficients for the methyl methacrylate (MMA) polymerization system is extended to the vinyl acetate (VAc) case. Comparison of the kinetic behavior and termination rate coefficients ( kt) of both monomers suggests that at low conversions the termination reaction is controlled by the chemical step, whereas at moderate and high conversions it is controlled by the diffusive step which in turn is determined by the segmental diffusion of the long radicals and not by the center of mass diffusion of short radicals. It is found that, for most of the conversion range, diffusion coefficient for VAc is lower than the one for MMA notwithstanding that ktVAc > ktMMA. An explanation of this apparent inconsistency on the base of the model results and in terms of segmental mobility is proposed. [ABSTRACT FROM AUTHOR]

The present work describes a kinetic approach which is able to predict how the internal surface area of polymer particles evolve during suspension copolymerization in the presence of porogen. For such a purpose, the concept of elementary gel structures has been introduced by modeling their surface area through the numerical fractionation technique. Thus, variables such as diluents composition, divinyl monomer concentration, and dilution degree could be assessed in the simulations. The present mathematical model is validated by using different experimental data from literature and a fair agreement is reached. Furthermore, the developed model is also capable of predicting the most significant copolymerization variables, e.g., conversion rate, concentration of species, and average molecular weights. [ABSTRACT FROM AUTHOR]

A kinetic model for the radical homopolymerization of acrylamide in aqueous solution is developed, incorporating propagation and termination rate coefficients as functions of monomer concentration and including the formation and reaction of midchain radicals based on the insights and measured rate coefficients from recent pulsed-laser studies. The model successfully represents the batch conversion profiles measured using an in situ NMR technique between 40 and 70 °C with initial monomer concentrations of 5 to 40 wt%, as well as the associated polymer molar mass distributions. In particular, the model captures the decreased rate that occurs at lowered monomer concentrations as a result of the formation of less-active midchain radicals by backbiting. Previous literature data are also well represented by the model. [ABSTRACT FROM AUTHOR]

In this work, a mathematical model is developed to characterize the batch atom transfer radical suspension polymerization (batch suspension ATRP). For the first time, the morphological and molecular properties of particles, as well as their dynamics in methyl methacrylate ATRP can be simultaneously simulated by solving the model that consists of ATRP kinetic equations, moment equations, a phase equilibrium equation for calculating equilibrium monomer distributions in various phases, and a particle population balance model. The proposed model is verified using the open experimental data. Based on the verified model, two key operating factors including the ratios of monomer to initiator and water to monomer are studied in order to investigate the batch suspension ATRP kinetics. In addition, the model is also used to predict the droplet/particle size distribution. The effects of breakage rate, coalescence rate, and agitation speed on the droplet volume density distribution and the Sauter mean diameter are discussed in details. The simulated results demonstrate that the coupled model can describe the batch suspension ATRP kinetics and its droplet kinetics. [ABSTRACT FROM AUTHOR]

The photopolymerization of acrylated oligomers dispersed in an aqueous medium is successfully demonstrated using a simple continuous photoreactor designed with flexible tubing, which presents straightforward up-scaling and maintenance features. The performance of the continuous photoreactor is assessed by varying the length of the tube exposed to ultraviolet light as well as the flow rate of the aqueous dispersion thr ough the reactor. The insoluble nature of the dispersed particles after in-situ photo-crosslinking is particularly suitable for the estimation of the actual number of polymerized particles from static and dynamic light scattering data. The procedure is discussed in detail. Along with the overall acrylate double bond conversion of the particles determined by infrared spectroscopy, an estimation of the average conversion per polymerized particle is provided as a function of the exposure time to ultraviolet light. The sub-microscopic characterization by peak-force tapping atomic force microscopy of the particles after photopolymerization is also presented. [ABSTRACT FROM AUTHOR]

Profit margin reduction and global competition are pushing latex producers to consider process intensification that relies on the replacement of semicontinuous reactors by continuous ones. The challenges involved and ways in which the challenges can be transformed into opportunities are discussed for: (i) production of branched polymers in CSTRs; (ii) minimization of the grade transition product in the production of a portfolio of pressure sensitive adhesives (PSA) in CSTRs; (iii) synthesis of flocculants by inverse microemulsion polymerization in CSTRs and in tubular and Couette-Taylor reactors; and (iv) production of polyurethane-acrylic PSAs by miniemulsion polymerization in a tubular reactor. [ABSTRACT FROM AUTHOR]

In this contribution, a nonlinear model-based optimizing control for continuous polymerization of acrylic acid in tubular reactors with multiple side injections of monomer is developed. The background of this work is to transfer the production of polymers from semibatch to continuous operations. The configuration of the tubular reactor, which imposes long delays between the inputs and the measurements, and the lack of intermediate measurements as well as the nonlinear reaction kinetics and sharp moving fronts of concentrations when the inflows are changed, make the application of the optimizing control very challenging. In order to simulate the sharp fronts of the reactor system faithfully and fast, the spatial domain of the partial differential equations model of the tubular reactor is discretized by applying the weighted essentially non-oscillatory scheme. We formulate the controller such that it optimizes the productivity of the reactor directly, while the product quality parameters are imposed as constraints. A particle filter is implemented to estimate the states of the reactor system and to initialize the process model. The simulation results show that the controller can increase the product throughput considerably compared to an initial operating point and has a robust performance against the measurement noise. Furthermore, the effect of formulating the quality constraints as hard or soft constraints as well as a changeover scenario between the different grades of a polymer are studied. [ABSTRACT FROM AUTHOR]

In this work, the operation of modular flexible continuous polymerization plants is investigated. For a benchmark problem (six products with an overall yearly demand of 20,000 t, two continuous production lines with modules that can be moved between the lines) that is defined by industrial speciality polymer producers, the optimal campaign planning problem is solved, minimizing the cost of cleaning and waste production. The results are compared to the production of the same portfolio of products in a batch plant. The results show that the changeovers between different products and production parameters lead to a loss of production capacity and additional costs. For long production campaigns (demand satisfaction on a monthly basis), these costs and losses are comparatively small, whereas for short demand satisfaction periods (one week) they are significant. On the other hand, longer demand satisfaction periods require a significant amount of product inventory and hence storage facilities. [ABSTRACT FROM AUTHOR]

A pilot-scale tubular reactor containing static mixers is equipped with several Raman probes in order to perform online monitoring of radical copolymerization of acrylic acid in aqueous solution. This setup allows determination of residence time distribution while polymerization reaction occurs, using sodium nitrate as a tracer. These results prove that the use of convenient static mixers allows obtaining a nearly perfect plug-flow reactor in all explored conditions (reactive and nonreactive medium, between 0.001 and 1 Pa s viscosity). Furthermore, the dynamics of the pilot-scale reactor is characterized. Experimental transient and steady-state values are compared to predictions based both on residence time distribution and model of polymerization kinetics. The applicability of Raman spectroscopy to online monitoring of pilot-scale reactors is demonstrated. [ABSTRACT FROM AUTHOR]

A continuous pilot-scale tubular reactor is designed for the polymerization of acrylic acid in aqueous solution. The reactor is equipped with CSE-X static mixers from Fluitec which strongly increase heat and mass transfer despite laminar flow. A mathematical model of the reactor is proposed assuming that it is a perfect plug-flow reactor and using kinetic and rheological equations previously established using a lab-scale rheo-Raman device. Calculated values of temperature and polymer concentration profile along the reactor as well as outlet average molar masses and viscosity are in good agreement with experimental results. Provided that the outlet viscosity of reaction medium does not exceed 0.5 Pa s, no reactor fouling occurred. On the contrary, fouling is detected after 6 to 8 h running with higher viscosities. This work is the first demonstration of applicability of CSE-X static mixer elements in a continuous polymerization process producing high molar mass water-soluble polymer. In addition, successful scale-up of polymerization reactor is reported up to pilot-scale as well as batch to continuous transposition, only on the basis of lab-scale rheo-Raman data. The interest of rheo-Raman device for the acquisition of primary data is established. [ABSTRACT FROM AUTHOR]

The transfer of a semi-batch emulsion copolymerization to a single feed continuous recipe is investigated herein. A single feed continuous tubular reactor is used in the presented study in accordance with the requirement of minimizing the number of dosing streams. The correlation between operating parameters and the product properties are experimentally presented for the semi-batch as well as for the single feed continuous tubular reactor. It is shown that the transfer from semi-batch to continuous smart-scale tubular reactor needs to be direct as opposed to via a batch reactor. The particle sizes and molecular masses obtained in the tubular reactor are similar to those of the semi-batch process. However, the adjustment of the polymer composition is challenging. Using monomer addition as a means to influence chemical composition is not applicable. Thus, in the tubular reactor the chemical composition of the resulting copolymer depends on the initial monomer composition and reaction temperature. Nevertheless, the mass transfer of the emulsion polymerization damps the copolymer composition distribution (CCD) drift for higher initial monomer contents compared to bulk polymerization. It is shown that transfer of a semi-batch product to a continuous recipe is possible in early stages of process development. [ABSTRACT FROM AUTHOR]

The European project F3 Factory aims at designing small to medium scale plants consisting of standardized container assemblies for delocalized production of various chemicals. Within the framework of the F3 Factory project, the design of a modular, multiproduct, and continuous plant for manufacturing water-soluble polymers is addressed. Free radical polymerization in aqueous solution is examined through two industrial cases: polymerization of acrylic acid (AA) in the presence of chain transfer agent (CTA) and copolymerization of AA with one comonomer. A methodology for performing the transition from batch recipes to continuous operations is proposed. Offline and inline monitoring of monomer consumption is achieved using Raman spectroscopy combined with chemometrics. A modular pilot plant meeting the requirements of F3 Factory project is designed and demonstrated at INVITE (Bayer, Leverkusen). The two polymerization processes are successively operated in the same pilot plant separated by an intermediate extensive washing. For each process, several polymer grades are produced by modification of reaction conditions (inlet flow of CTA or reactor temperature). Transition dynamics are characterized using inline monitoring. The flexibility of the modular plant is demonstrated. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) is used to study the gas-particle heat transfer in gas-phase olefin polymerizations. Particularly, the effects of particle rotation on the gas-particle heat transfer coefficient and internal particle temperatures are evaluated, showing that particle rotation can exert a significant impact on observed temperature profiles, so that this effect should not be neglected during detailed CFD process simulations. As a consequence, particle rotation can lead to particle cooling and development of spherical gradient symmetry, validating the use of simpler modeling schemes that are based on reaction-diffusion in symmetrical spherical geometry. [ABSTRACT FROM AUTHOR]

As some complexes of transition metal cations in high oxidation state can oxidize tertiary amines under proper conditions into aminoalkyl radicals to initiate polymerization of electron-deficient vinylic monomers, they form mono-centered redox-initiation pairs for preparation of 100% alpha-amino telechelic polymer. Radical emulsion polymerization of methyl methacrylate (MMA) is performed by using water-soluble amines as a reducing agent and FeIII or CuII as an oxidizing agent. Tertiary amines such as 2-( N, N-dialkylamino)ethanol and N, N, N′, N′-tertramethylethylenediamine exhibit a higher initiation activity. Monomer conversion can reach 80% in 8 h and 95% in 16 h, leading to PMMA with an absolute weight-average molecular weight above 1.5 × 106 g mol−1. The alpha-amino terminal functionality is verified by ultraviolet-induced diarylketone-initiated radical bock polymerization by using these PMMA chains as the macro-sensitizer. Such a facile heterogeneous technique results in syndiotactic-rich high- Tg PMMA (rr > 50%, Tg = 124-127 °C). PMMA chains may be oxidized by FeII-O2 complexes to initiate further radical polymerization, leading to PMMA with a long-chain branched architecture. [ABSTRACT FROM AUTHOR]

A novel vanadium-modified (SiO2/MgO/MgCl2)·TiCl x Ziegler-Natta ethylene polymerization catalyst with much better catalytic performance is successfully developed. The catalyst is prepared by co-impregnation of aqueous solution of water-soluble magnesium and vanadium compounds on SiO2, and a supported thin layer of magnesium and vanadium oxides is formed over the surface of SiO2 after high temperature calcination in dry air, followed by further reaction with titanium tetrachloride to synthesize the magnesium dichloride carrier in situ and to support the titanium species simultaneously. By characterization of the catalysts and the polymers and investigation of the polymerization behaviors, it is found that compared with the original (SiO2/MgO/MgCl2)·TiCl x ZN catalyst, the introduction of vanadium species induce improved catalytic performance with 27% higher activity, 48% higher hydrogen response, and 60% higher 1-hexene incorporation ability with better short chain branch distribution. [ABSTRACT FROM AUTHOR]

Analytical solutions for the impact of branching on the polymer molecular architecture in the presence of two catalysts are developed. One catalyst forms only linear chains while the other produces linear as well as branched species. Emphasis is placed on the average molecular weight and polydispersity index of the populations associated with each catalyst rather than the overall quantities. By defining the cross-incorporation number, x, which represents the relative value of the β-hydride elimination and terminal double bond polymerization rate coefficients of each catalyst, we map the effect of branching on the molecular architecture of the polymer in order to understand the underlying kinetics and guide system design. [ABSTRACT FROM AUTHOR]

Batch radical polymerization of 5-40 wt% non-ionized acrylic acid (AA) in aqueous solution has been studied between 35 and 90 °C under variation of initiator concentration and type as well as upon addition of different levels of 2-mercaptoethanol as chain-transfer agent (CTA). Chain-length-dependent termination was taken into account in a model developed to describe the system, as high amounts of CTA have an impact on polymerization kinetics due to reduced chain length. The model also considers the 1,5-hydrogen shift (backbiting) reaction that transforms the secondary propagating radical into a tertiary midchain radical, with the backbiting reaction quantified via 13C NMR. The model developed is the most comprehensive treatment to date of this complex polymerization system and is able to represent monomer conversion profiles and polymer molar mass distributions over a wide range of conditions. [ABSTRACT FROM AUTHOR]

A novel computational fluid dynamics (CFD) model was developed and validated with the experimental data to explore the effect of the agitator type, rotational speed, and the installation of baffles on the methyl methacrylate conversion, particle size and number of particles of poly methyl methacrylate (PMMA) produced in an emulsion polymerization reactor. The originality of this study was to include the reaction kinetics to the population balance through nucleation and growth rates while taking into account the velocity gradients generated by the impeller rotation inside the reactor. The number density achieved by the Rushton impeller was higher than that for the pitched blade impeller. The distribution of polymer volume fraction was more uniform with the pitched blade impeller than that for the Rushton impeller. [ABSTRACT FROM AUTHOR]

The polybutadiene incorporation in waterborne polystyrene nanoparticles by miniemulsion polymerization improves the toughness of the final product. Unfortunately, the polymerization does not proceed to completion, remaining a high level of unreacted monomer. This work addresses the implementation of two post-treatment methods to efficiently remove the residual styrene from polybutadiene/polystyrene latexes with 50% of solid content: i) post-polymerization with redox initiators; and ii) post-polymerization by thermal initiation of styrene at high temperature (≥120 °C). The mechanisms responsible of the effects of both post-treatments on the properties of hybrid materials are here discussed. [ABSTRACT FROM AUTHOR]

The PEGlytation of CTS with poly(poly(ethyleneglycol) methyl ether methacrylate-co-styrene), poly(PEGMA-co-S), via nitroxide-mediated polymerization (NMP) using both grafting to and from approaches has been performed. To conduct the PEGylation of CTS via grafting to, CTS was first functionalized with glycidyl methacrylate (GMA) yielding CTS- g-GMA macromer. Poly(PEGMA-co-S), synthesized via NMP, was then grafted to the CTS- g-GMA. For PEGylation via grafting from, CTS- g-GMA was first converted into a macroalkoxyamine using an SG1-based alkoxyamine. Graft copolymerization of PEGMA-co-S was then performed. The syntheses of CTS- g-GMA-poly(PEGMA-co-S) were confirmed by 1H NMR and TGA. [ABSTRACT FROM AUTHOR]

Hybrid waterborne dispersions provide improved performance in established applications and allow targeting new applications that are out of reach of the conventional homogeneous latexes. They are product-by-process materials that are produced by either emulsion or miniemulsion polymerization and whose characteristics are determined in the reactor. Therefore, it is crucial to produce them by means of an optimal process strategy. This work reviews the fundamental knowledge available as well as the missing parts needed to develop such strategy focusing on particle morphology, which is the most distinctive feature of these materials. [ABSTRACT FROM AUTHOR]

The homogeneous neodymium-based catalyst systems containing neodymium carboxylate, isobutyl aluminum compound and chlorinating agent were successfully developed for the coordination polymerizations of butadiene, isoprene and styrene in our laboratory. The catalyst possessed high catalytic activity to butadiene polymerization in hexane, leading to an obvious decrease in the dosage of catalyst to low level, e.g Nd/Bd (molar ratio) was around 35 ppm. Simultaneously, the catalyst exhibited high stereo-selectivity to butadiene polymerization in hexane and polybutadienes with extremely high cis-1,4 configuration of around 99% could be produced under appropriate reaction conditions. Based on our interesting fundamental research works, the continuous butadiene polymerizations were conducted to produce high cis-1,4 polybutadiene in pilot scale in SINOPEC. The industrial equipments (capacity: 30 000 t/a) for production of neodymium butadiene rubber (Nd-BR) were successfully built in SINOPEC in 2012 and the innovation technology has been achieved from fundamental research to industrial application for large scale production of Nd-BR. The Nd-BR products are now commercially available with the trade names of BR Nd40, BR Nd50, BR Nd60 with ML(1+4) 100 °C of 45 ± 5, 55 ± 5, and 63 ± 5, respectively. The excellent properties of these high cis-1,4 Nd-BR products lead to their especially suitable application in green-tire components. [ABSTRACT FROM AUTHOR]

The polymer industry in China has developed rapidly over the past 30 years, which can be greatly attributed to the active R&D conducted by Chinese scholars in polymer reaction engineering (PRE) and their cultivation of high level talents. The research focus on PRE in China has shifted from the application development to both applied and fundamental research at present. The PRE researchers closely collaborate with the enterprises and the world leading scholars. The research objective has been evolved from optimizing efficiency of polymerization processes to precise control of the structures of polymer chains and primary aggregates. This essay summarizes the history, characteristics, and latest progresses of the PRE research in China, with emphasis on the research activities at Zhejiang University. [ABSTRACT FROM AUTHOR]

The comparison between methyl methacrylate (MMA) and styrene (St) RAFT emulsion polymerization using oligo(methacrylic acid41-b-methyl methacrylate8) RAFT agent (oligo(MAA41-b-MMA8) RAFT) as surfactant is investigated in order to gain a better understanding on RAFT emulsion polymerization of MMA. It is found that the colloidal stability during MMA emulsion polymerization is much more sensitive to the initiator concentrations and temperature than that of St polymerization. The coagulum-free latex of highly living PMMA can be achieved only at 80 °C and low initiator concentrations. The final PDI is higher in RAFT emulsion polymerization of MMA than that of St. It is revealed that about 40% acid groups of oligo(MAA41-b-MMA8) RAFT should be buried within the final particles of PMMA, indicating that particle coagulation should occur in the very beginning of the polymerization. The poorer performance of the MMA polymerization could be well explained by the homogeneous nucleation mode of particles combined with relatively slow transporting rate of oligo(MAA41-b-MMA8) RAFT molecules from the partly frozen micelles to the newly-born particles. [ABSTRACT FROM AUTHOR]

Poly(trimethylene terephthalate) (PTT) which combines properties of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), is used in everyday products such as apparel and carpet. DuPont has successfully developed a renewably sourced building block, bio-based 1,3-propanediol (PDO), through industrial bio-technology using glucose as the raw material. This green technology has significantly promoted the commercialization of PTT and its development activities. In DuPont's China R&D center, an industrial polymer technology platform has been established to serve the local China market with PTT manufacturing and application support. This platform explores new industrial applications for and modifications to PTT, such as expansion of the application space into engineering polymers (EP), development of fire retardancy, melt viscosity regulation for PTT fiber spinning and the use of PTT in nanocomposite preparations. [ABSTRACT FROM AUTHOR]

Different values of the kinetic rate constants have been reported for initiator decompositions carried out in microwave and conventional batch reactors. The present work analyzes the confidence regions of kinetic parameters estimated for the thermal decomposition of two initiators, potassium persulfate (KPS) and 2-2′-azobis(2-methylpropionamidine) dihydrochloride (V-50), which confirm the difference between the parameters obtained in microwave and conventional reactors. Moreover, by assuming no changes in kinetics under microwave heating, the temperature and volume of hot spots required to explain the apparent increase of kinetic rate constants are calculated. The results suggest that formation of hot spots may explain the observed effects without the occurrence of additional phenomena. [ABSTRACT FROM AUTHOR]

Novel results on using mixtures of two external electron donors 'phenyltriethoxysilane (donor A)' and 'cyclohexylmethyldimethoxysilane (donor C)' in the synthesis of polypropylene/poly (ethylene- co-propylene) in-reactor blends were presented. Thermal gradient elution fractionation (TGEF) was carried out to separate crystallizable copolymer fractions from the blends. FTIR, DSC, DMTA, and SEM were used to analyze the microstructure of the blends and separated fractions. Although using donor A as pure decreased the catalyst activity and molecular weight, using 'donor A' in combination with donor C had a synergistic effect on the molecular weight of polypropylene homopolymers and the blends. The glass transition temperature ( Tg) of the blend rubbery phase was the lowest in the case of the blend based on pure donor A because of formation of higher sequences of polyethylene and the Tg increased with increasing donor C concentration. PP-PE copolymer concentration and impact strength were found to be higher in the case of the blend based on donor ratio of A/C: 75/25 than other blends. [ABSTRACT FROM AUTHOR]

The synthesis of silicon compounds is mainly achieved by room temperature or high-temperature vulcanization reaction. Several transition-metal organometallic compounds such as platinum complexes can be used as catalysts to accelerate the thermal reaction. Moreover, these compounds are found to be also efficient for the cross-linking of silicone polymer by UV-activated reaction. In particular, cyclopentadienyl platinum complexes are considered as catalysts that can sustain an extremely high photochemical reaction after UV-light excitation. The reactivity of these catalysts (in particular the trimethyl(methylcyclopentadienyl) (IV) complex (Me-Cp)Pt(Me)3) for the photopolymerization of silicon polymer compounds is evaluated and compared with the most common bis(acetylacetonate)platinum (II) catalyst used for the UV-activated hydrosilation reaction. [ABSTRACT FROM AUTHOR]

A concept of a population balance is applied to study evolving structures of propagating linear copolymer chains. As a result, a general numerical toolbox was developed capable to handle various copolymerization mechanisms utilizing two-dimensional distributions as means of system description. The method was applied to free radical copolymerization of styrene-acrylonitrile explaining peculiar bimodality in chain length distribution observed for asymmetrical initial monomer ratios. [ABSTRACT FROM AUTHOR]

A model-based design of experiments is implemented for the problem of reactivity ratio estimation in terpolymerizations for the first time in the literature. Optimal terpolymerization feed compositions are calculated using a design criterion, based on the Error-in-Variables-Model (EVM) approach. The results show that there are three optimal feed compositions with their locations naturally dependent on the values of the reactivity ratios. However, the interesting observation is that in almost all cases the optimal feed compositions are located close to the corners of the terpolymerization composition triangular plot. In addition, the impact of the reactivity ratio values on the location of the optimal feed compositions is explored and 'practical heuristics' are presented. [ABSTRACT FROM AUTHOR]

Model-based D-optimal design of experiments is applied to the nitroxide-mediated radical polymerization (NMRP) of polystyrene. Recent studies of this system (in terms of both experimental work and model development) have led to the development of a refined (detailed) mechanistic model and a substantially reduced model. Both the fully mechanistic model and the reduced model are validated by comparing model predictions with experimental data. The D-optimal designs (formulated using models of different complexity) are compared to each other, and contrasted with work done previously regarding the Bayesian design of experiments applied to the same system, in addition to comparisons with an anti-correlation criterion. [ABSTRACT FROM AUTHOR]

A mathematical model is developed to simulate the production of bio-based polytrimethylene ether glycol (PO3G) using 1,3-propanediol. The effect of super-acid catalyst is accounted for in the model, as is mass transfer of small species (water, monomer, and propanal) and linear oligomers (dimer to heptamer). This model correctly predicts dynamic trends in concentrations of linear oligomers, but the predicted maxima in these concentrations appear slightly earlier than in the experimental data. Predictions of the degree of polymerization (DP) are improved compared with those from a previous model, where evaporation of linear oligomers was not considered. Additional model improvements, including accounting for the effects of cyclic oligomers, are suggested. [ABSTRACT FROM AUTHOR]

Monte Carlo methods are heuristic algorithms that use probabilities to select an outcome among several possible events in a given process. Monte Carlo methods are useful in polymer reaction engineering because they can predict the molecular architecture of polymers with details that cannot be easily captured by any other modeling technique. One of the advantages of Monte Carlo simulation is that one does not need to solve differential or algebraic equations to predict the microstructures of polymers. This article reviews the literature on steady-state and dynamic Monte Carlo methods in polymer reaction engineering. We hope to convince the readers that playing dice regularly can be a great asset to polymer reactors engineers. [ABSTRACT FROM AUTHOR]

Acrylamide (AAm)/acrylic acid (AAc) copolymer application performance is tied to copolymer properties, which in turn are related to the kinetics of the copolymerization. A systematic study has been conducted to investigate the effect of reaction factors such as total monomer concentration and solution pH on polymerization kinetics and copolymer microstructure. To study the effect of these factors, reliable reactivity ratios were estimated first. The trends in copolymer composition, molecular weight, sequence length distribution, and triad fractions were subsequently examined. Having a better understanding of kinetic profiles is needed in order to manipulate influential factors for tailoring AAm/AAc copolymer properties for the desired application. [ABSTRACT FROM AUTHOR]

A generalized model is presented here for the semicontinuous heterophase polymerization of methyl and hexyl methacrylate, which have very different water solubility. In this polymerization technique, neat monomer is fed at a controlled rate over a monomer-free aqueous solution of surfactant and initiator, to produce nanometer size particles with controlled molar masses, and high polymer/surfactant ratios similar to those used in conventional emulsion polymerization. For the two monomers studied at three different addition rates, model predictions accurately reproduce conversion-versus-time curves, the evolution of particle size, and the number density of particles. The model reveals that the controlling nucleation mechanism shifts from micellar to homogeneous nucleation as the monomer solubility in water increases. [ABSTRACT FROM AUTHOR]

A chemical reaction scheme is proposed here to describe the polyamide 66 (PA 66) solid state polymerization (SSP) with effective kinetic parameters. The main objective of the suggested model is to predict the maximum molecular weight attainable at each SSP isotherm, which is in turn determined by the occurrence of polymer chain degradation coupled to other important side reactions. Accordingly, a number of side reactions have been firstly considered, based on which a comprehensive particle model was constructed to predict PA 66 kinetics, equilibrium, and transport phenomena. The SSP model parameters were estimated with a maximum-likelihood estimator, using data measured under kinetic- and diffusion-controlled process conditions for reaction temperatures in the range of 160-200 °C and reaction times up to 8 h. Calibration models were also developed to allow the determination of PA 66 solution viscosities. [ABSTRACT FROM AUTHOR]

Miniemulsions, consisting of submicron droplets of very hydrophobic lauryl methacrylate or 4- tert-butyl styrene, are successfully polymerized using water-soluble sodium persulfate. Monitoring the calorimetric profile as well as the droplet and particle size distribution with conversion manifests a process of monomer redistribution, droplet disappearance, and narrowing of the particle size distribution. The observed reaction characteristics could be modeled adequately, using thermodynamic principles. The results of the work presented do not only have predicting value, but also enfeeble the idea of a one-to-one translation of monomer droplets into polymer particles in miniemulsion polymerization. [ABSTRACT FROM AUTHOR]

Microwave irradiation has been an interesting alternative for heating systems of several chemical reactions. In this work, a comparative study between microwave reactions and conventional heating is evaluated. The effects of temperature, power, and polyol type on the synthesis of poly(urea-urethane) by step polymerization in miniemulsion are evaluated and the final polymer is analyzed by Fourier transform infrared spectroscopy, gel permeation chromatography, contact angle, and nanoparticles size and size distribution are characterized by dynamic light scattering. Polymerization under microwave irradiation have a higher reaction rate showing advantages of using microwaves in this miniemulsion step polymerization processes. In addition, microwave irradiation also affects particle size, the solubility of the polyurethane, and the urea/urethane ratio. [ABSTRACT FROM AUTHOR]

A comprehensive mathematical model was developed based on a detailed kinetic mechanism to predict the dynamic evolution of monomer conversion and molecular weight averages. The predictive capabilities of the mathematical model are demonstrated by a direct comparison of model predictions with literature and new experimental data on monomer conversion as well as number and weight average molecular-weight of PLLA. The effects of monomer to initiator molar ratio and polymerization temperature on the polymerization rate and average molecular weight properties of polylactide were experimentally determined and compared with model predictions. For this reason, high molecular weight polylactides were synthesized in melt via the ring-opening polymerization of L, L-lactide, in the presence of stannous octoate. [ABSTRACT FROM AUTHOR]

The bulk free radical copolymerization of n-butyl methacrylate (BMA) and D-limonene is carried out at 80 °C using benzoyl peroxide (BPO) as initiator. Low conversion experiments are conducted to estimate the copolymer reactivity ratios while full conversion runs are performed to verify the estimates and to achieve high monomer conversions. Reactivity ratios of r1 = 6.0957 and r2 = 0.0459 (1 = BMA, 2 = D-limonene) are obtained using a nonlinear, error-in-variables method with the RREVM computer program. Full conversions and reasonably high molecular weights are achieved at high BMA feed concentrations. Achieving high conversion is limited by a degradative chain transfer mechanism due to the D-limonene. [ABSTRACT FROM AUTHOR]

Controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP) is often conducted in solution processes and stopped at medium monomer conversions to yield well controlled polymer samples. A great challenge lies in running bulk CRP up to high conversions but still retaining system livingness and molecular weight control. In this work, we demonstrate the achievement of good living and well controlled high-conversion bulk ATRP by means of design and optimizing polymerization thermal histories. The initiator-for-continuesactivator- regeneration (ICAR) ATRP of methyl methacrylate (MMA) is used as a model system. Employing step functions in temperature, MMA conversions are pushed up to 98% and the PMMA samples possess polydispersities <1.3. Chain extension experiments confirm good livingness of synthesized polymers collected at high conversions. [ABSTRACT FROM AUTHOR]

The kinetics of ethylene polymerization and the growth of polymer nanofibrils for the rac-Et(indenyl)2 ZrCl2/MAO catalyst supported on flat-surface silica and nonporous silica nanoparticles are presented. The polymerization rate per mol of Zr is highest for the flatsilica supported catalyst due to maximum exposure of catalyst sites to cocatalyst and monomer. The SEM and AFM analysis show that large clusters of oxidized form of MAO are present at the surface, while nano-silica supported catalyst show less of such effects. The polyethylene grows as nanofibrils of 30-50nm in diameter from the silica surface. No particle fragmentation is observed with nano-silica supported catalyst where polymer nanofibrils grow only from the external surface. Polymer properties are little affected by the support type. [ABSTRACT FROM AUTHOR]

Reversible addition fragmentation chain transfer (RAFT) ab initio emulsion polymerization of styrene using poly(acrylic acid)-b-polystyrene trithiocarbonate (AA x-b-St y macroRAFT) as both mediator and surfactant was investigated with systematically changed y from 0 to 7 and x from 15 to 30. A well-controlled polymerization in terms of little coagulum, well predicted molecular weight and low polydispersity (PDI) (≈1.2) could only be achieved by using the macroRAFTs of hydrophile-lipophile balance (HLB) values between 13 and 20. The final latex particle size could be tuned from 80 to 172 nm in diameter simply by changing x and y values while the molecular weight was targeted the same (30 K). [ABSTRACT FROM AUTHOR]

The synthesis of monoliths by reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene and divinylbenzene (DVB) at high-crosslinker content is studied using the recently reported multifunctional polymer molecule approach. The agreement between model predictions, incorporating diffusion-control, and experimental data from CSIRO is good for all cases analyzed. This includes examples with high-crosslinker concentrations, which cause deviation from some of the simplifying assumptions imposed in the model. [ABSTRACT FROM AUTHOR]

The predictions of four different models of crosslinking copolymerization,Kinetic Monte Carlo (KMC), statistic/kinetic Flory/Tobita (FT) model, and two kinetic approaches based on population balance equations (PBE) (solved with generating functions (GF) and numerical fractionation (MRNF), respectively), were compared. The approaches underlying more restrictive assumptions but asking for less computational effort, FT and MRNF, lead to very satisfactory predictions in terms of average properties (sol and gel fractions, degrees of polymerizations, crosslinking densities). On the other hand, fully detailed models (KMC) as well as more computationally demanding numerical solutions of the detailed PBE (GF) become necessary when the chain length distributions are required. [ABSTRACT FROM AUTHOR]

Characterization of branched and crosslinked polystyrene (PS) samples, synthesized via nitroxide-mediated radical polymerization (NMRP) in the presence of a small amount of divinylbenzene (DVB), is presented. Results are compared with crosslinked PS samples synthesized through regular free radical polymerization (FRP). Characterization results of PS samples (before the gelation point) using size exclusion chromatography (SEC) and of crosslinked PS samples with thermo-mechanical analysis are discussed. Both techniques are used in an attempt to quantify the homogeneity of the polymer network. Characterization via thermo-mechanical analysis shows that no significant differences are detected between networks synthesized through NMRP and FRP. In fact, replicated results indicate that networks synthesized via NMRP might in fact be as heterogeneous as networks synthesized through FRP; this is not as expected! [ABSTRACT FROM AUTHOR]

The chemical incorporation of an unsaturated alkyd into an acrylic polymer created via miniemulsion polymerisation was studied. The variation of the number ratio of polymer particles to initial droplets with conversion, and changes in individual monomer conversions with increasing alkyd levels were the main quantities used to study the effect of increasing alkyd quantity in the hybrid system. Homogeneous nucleation was more significant in systems rich in the more hydrophilic methyl methacrylate (MMA). Changes in particle morphology with monomer conversion, as well as limited monomer conversion were observed. The results emphasize the importance of proper pairing of the miscibility between the specific acrylics and alkyds used in these hybrid polymers. [ABSTRACT FROM AUTHOR]

The modeling of hydrolytic caprolactam polymerization is reviewed and a state-of-the-art mathematical model is proposed. The model includes the basic reactions of reversible ring-opening, polyaddition, and polycondensation as well as the reversible formation/hydrolysis and polyaddition of cyclic oligomers. For the first time, a method is proposed to implement stabilization with acids of any functionality so that their impact on the molecular weight distribution can be analyzed. A comparison of the model predictions with experimental data taken from the literature reveals excellent agreement. As shown in this work, the proposed model for the synthesis of polyamide 6 can be used to dynamically compute the complete molecular weight distribution. Therefore, it gives access to desired product designs for this industrially important polymer. The method presented for modeling multichain hydrolysis may also be of interest for other polycondensation systems that result in star-shaped polymers. [ABSTRACT FROM AUTHOR]

Blends of poly(styrene)/poly(methyl methacrylate) (PS/PMMA) are produced in situ during suspension polymerizations of styrene performed in the presence of PMMA. The effects caused by the in situ incorporation of PMMA on the kinetic behavior of the reaction and on the molar mass distributions (MMD) and particle size distributions (PSD) of the obtained PS/PMMA polymer particles are evaluated. It is shown that the PMMA content can lead to significant changes of the initial viscosity of the reaction medium, also leading to significant changes of styrene conversions during the reaction course. Besides, addition of PMMA can cause an increase of the average molar masses and average particles sizes of the obtained polymer beads, also leading to broadening of the MMD and PSD of the final resin. [ABSTRACT FROM AUTHOR]

The copolymerization kinetics of hydroxyethyl methacrylate (HEMA) with either ethylene glycol dimethacrylate (EGDMA) or diethylene glycol dimethacrylate (DEGDMA) in the presence of RAFT controllers is studied using a mathematical model recently developed in our group. The model is based on the concept of multifunctional polymer molecules. The cases of conventional and controlled homopolymerizations of HEMA as well as the RAFT copolymerization of HEMA/EGDMA and HEMA/DEGDMA are addressed and are in good agreement with available experimental data. The bulk/solution version of the model is used as first approximation of the behavior of a RAFT dispersion copolymerization of HEMA/EGDMA carried out in supercritical carbon dioxide. [ABSTRACT FROM AUTHOR]