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The performance of two continuous UV/H2O2 photoreactors in series under unsteady-state condition is studied. An input–output dynamic model is constructed to describe the degradation of water-soluble polyvinyl alcohol (PVA) in photoreactors. Identification techniques, AutoRegressive with eXogenous input (ARX) and AutoRegressive Moving Average with eXogenous input (ARMAX), are employed to construct transfer functions. The simulation is carried out for an open-loop operation by applying step changes to the input variables (PVA and H2O2 inlet concentrations and PVA feed flow rate) using the developed model. For effluent total organic carbon (TOC) and H2O2 concentrations as responses, a model predictive control (MPC) scheme is developed to control the photoreactors to maintain desired values of process variables for setpoint and load changes. The closed-loop simulation results show that the multi-input/multi-output (MIMO) MPC produce a good performance for tracking setpoint changes in the TOC and H2O2 concentrates at the photoreactor effluent and it is also able to handle process interactions and constraints. The MPC controller successfully suppresses stochastic disturbances of the inlet PVA concentration.

In this study, the performance of three black-box identification techniques using linear autoregressive with exogenous input (ARX), nonlinear ARX (NARX), and Hammerstein–Wiener (HW) algorithm to model the dynamics of UV/H₂O₂ continuous tubular photochemical reactor for the treatment of poly(vinyl alcohol) (PVA) based on experimental data is investigated. In addition, the inherent nonlinearity of the reaction process is assessed. The reactor dynamics in the NARX model is estimated by wavelet, sigmoid, and tree partition networks along with the assessment of the performance of each model. Although a sigmoid network describes the nature of chemical processes better, the results show that tree partition network-based NARX is the most suitable estimator for the studied process as represented by its highest quality of fit (91.59% for training data set and 88.17% for validation of data set), lowest loss function (mean-squared error, MSE) (0.0004279), model realizability, open-loop stability, model whiteness, and model independence.

Turbulent bed contactors (TBC) are three-phase fluidized beds which form an important class of process equipment used in many applications. In this work, experiments were conducted to investigate b...

This study examines the ab initio emulsion atom transfer radical polymerization (ATRP) initiated by an eco-friendly reducing agent to produce poly(methyl methacrylate) (PMMA) polymer with controlled characteristics in a 2 L stirred batch reactor. The effect of the reaction temperature, surfactant concentration, monomer to water ratio, and stirring speed was thoroughly investigated. The results showed that PMMA coagulation becomes quite severe at a certain temperature threshold. However, the coagulation could be avoided at mild reaction temperature, since the outcomes showed that loading more surfactant to the system under high mixing speed has balanced the polymer mixture and yielded high monomer conversion. The PMMA product was analyzed by gravimetry and GPC measurements and after 5 h of polymerization at a reaction temperature of 50 &deg, C, monomer conversion of 64.1% was obtained, and PMMA polymer samples produced had an average molar mass of 4.5 kg/mol and a polydispersity index of 1.17. The structure of the PMMA polymer was successfully proved by FTIR and nuclear magnetic resonance (NMR) spectroscopy. The results confirm the living feature of MMA AGET ATRP in emulsion medium and recommend further investigation for other types of surfactant.

In this study, we demonstrate a design of a stable bi-layer coating configuration on UHMWPE fibres surface. UHMWPE fibres show abundant promise as load bearing reinforcement in fibre-based composites; however, its inert chemical nature has been a consistent hurdle for developing high performance composites. An efficient and environmentally friendly two-step coating technique has been performed on UHMWPE fibre surface; viz. Physisorption of polydopamine (PDA) followed by the construction of Polyamide 6,6 coating over PDA layer. The coated fibres revealed improved tensile strength in comparison to the pure UHMWPE fibres. Transverse fibre bundle tension (TFBT) test was used to assess the interfacial bonding strength of the coated fibre with an epoxy matrix. The bi-layer coated fibre/epoxy demonstrated an improvement of ∼ 40% in bonding strength compared to the pure UHMWPE/epoxy system. This bi-layer coated UHMWPE fibres could be of immense potential for several applications, including biomedical engineering.

This study presents a photochemical kinetics model to describe the degradation of water-soluble PVA (Polyvinyl Alcohol) polymer in a UV/H2O2 batch reactor. Under the effect of UV light, the photolysis of hydrogen peroxide into hydroxyl radicals can generate a series of polymer scission reactions. For a better understanding and analysis of the UV/H2O2 process in the cracking of the PVA macromolecules, a chemical reaction mechanism of the degradation process and a relevant photochemical kinetics model are developed to describe the disintegration of the polymer chains. Taking into account the probabilistic fragmentation of the polymer, the statistical moment approach is used to model the molar population balance of live and dead polymer chains. The model predicts the PVA molecular weight reduction, the acidity of the solution, and hydrogen peroxide residual. In addition to previously published data collected in this laboratory, a new set of experiments were conducted using a 500 mg/L PVA aqueous for different hydrogen peroxide/PVA ratios for model validation. Measurements of average molecular weights of the polymer, hydrogen peroxide concentrations and pH of the PVA solution were determinant factors in constructing a reliable photochemical model of the UV/H2O2 process. Experimental data showed a decrease in the PVA molecular weight and a buildup of the solution acidity. The experimental data also served to determine the kinetics rate constants of the PVA photochemical degradation and validate the model whose predictions are in good agreement with data. The model can provide a comprehensive understanding of the impact of the design and operational variables.

In advanced oxidation processes (AOPs) operating in continuous mode, the flow rate and the concentration of oxidants such as H2O2 at the mixing point of the influent must be controlled so that the oxidant residuals in the effluent are minimized while the organic degradation is maximized. Designing a controller to regulate the oxidant flow rate and therefore, its concentration at the mixing point of the photoreactor influent, needs the determination of a reliable process dynamic model. In this study, a step testing technique is employed to construct a dynamic model for the degradation of polyvinyl alcohol (PVA) in a UV/H2O2 continuous annular photoreactor. The experimental design consists of preparing three initial PVA concentrations of 60, 280, and 500 mg PVA/L and conducting eight experimental tests for different inlet mass flow rates of H2O2 ranging from 0.336 to 125 mg H2O2/min. The process responses of pH solution and total organic carbon (TOC) are measured versus time for different step changes of H2O2 inlet flow rates. Process dynamic models represented by transfer functions of the continuous UV/H2O2 photoreactor are determined from the collected input-output data using graphical method, identification algorithm, and ARX (AutoRegressive with eXogenous) in Matlab environment. The dynamic models predict the data trend quite well. Variations of the steady state gain demonstrate that the PVA degradation in UV/H2O2 continuous photoreactor is a nonlinear process. Besides, the ARX algorithm generates reliable dynamic discrete models that could be used to develop digital controllers for computer control of the UV/H2O2 photochemical reactor.

Polyvinyl alcohol (PVA), being a dominant contributor of total organic carbon (TOC) in textile wastewater, is not easily degradable by conventional methods of wastewater treatment. This study investigates the degradation of aqueous PVA in a continuous UV/H2O2 photoreactor since the feeding strategy of hydrogen peroxide proves to have considerable effects on the process performance. Response surface methodology involving the Box–Behnken method is adopted for the experimental design to study the effects of operating parameters on the process performance. Experimental analysis shows that the TOC removal varies from 16.11 to 42.70 % along with a reduction of the PVA molecular weights from 56.7 to 95.3 %. The TOC removal is significantly lower than the molecular weight reduction due to the generation of the intermediate products during oxidation. Operating the UV/H2O2 process in a continuous mode facilitates the degradation of highly concentrated polymeric solutions using a relatively small hydrogen peroxide concentration in the feed with a small residence time ranges from 6.13 to 18.4 min.

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.

The performance and effectiveness of sonophotolytic process, aerobic activated sludge (AS) process, and their combination in reduction of total organic carbon (TOC), chemical oxygen demand (COD), and biological oxygen demand (BOD) from a synthetic pharmaceutical wastewater (SPWW) are evaluated. Batch mode experiments are performed to obtain optimal experimental operating conditions of the sonophotolytic process. An ultrasonic power of 140 W, initial pH solution of 2, and air flow rate of 3 L min −1 are found to be optimal operating conditions. The initial optimum molar ratio of H 2 O 2 /TOC was found to be 13.77 for the sonophotolytic process operated in batch mode. In continuous mode, a 90% TOC reduction was obtained in the sonophotolytic process after 180 min retention time, whereas only 67% in an aerobic AS process for retention time of 48 h. However, combined sonophotolytic and aerobic AS processes improved the biodegradability of the SPWW with 98% TOC and 99% COD removal while reducing the retention time in sonophotoreactor and aerobic AS bioreactor to 120 min and 24 h, respectively. Besides, the consumption of H 2 O 2 was reduced significantly in the combined processes.

The emulsion polymerization of methyl methacrylate (MMA) was carried out in a lab-scale reactor, which was equipped with a pitched blade turbine, four baffles, a U shaped cooling coil, and a temperature controller. Potassium persulfate was used as the initiator and sodium dodecyl sulfate as the surfactant. The effects of impeller speed, mounting baffles, and reaction temperature on the monomer conversion, polymer nano particle size and number, and molecular weight were examined in detail. An increase in the impeller speed up to 250 rpm enhanced the polymer properties but further agitation reduced the conversion, particle size, and molecular weight. The installation of the baffles enhanced the particle size and molecular weight but reduced the conversion and particle number. The use of baffles resulted in a narrower size distribution throughout the polymerization process. While the particle size and molecular weight were reduced with an increase in the reaction temperature, the monomer conversion and particle number were improved. POLYM. ENG. SCI., 55:945–956, 2015. © 2014 Society of Plastics Engineers

Water-soluble polymers contaminating industrial effluents create potential pollution concerns in water resources. In particular, polyvinyl alcohol (PVA), which is quite abundant in wastewater effluents, is toxic and cannot be effectively treated by biological processes. The present study investigates the photo-oxidative degradation of aqueous PVA solutions in a UV/H 2 O 2 photochemical reactor and the effect of hydrogen peroxide feeding strategies on the photoreactor performance. The total organic carbon (TOC) removal and the reduction of polymer molecular weights are determined for different initial polymer and hydrogen peroxide concentrations. By treating an aqueous solution containing 500 mg/L of a 130 kg/mol PVA and H 2 O 2 /PVA mass ratio of 10, the results show that nearly 87% of TOC removal was achieved when the photoreactor was operated for 2 h in stepwise operation (semi-batch). Accordingly, the number average molecular weight of the polymer is reduced to 10.9 kg/mol (91.6%). The oxidation reaction without UV light, however, is much less effective and results in merely 43% TOC removal and 21% reduction of polymer molecular weights. As for the case where the UV reactor was operated with no hydrogen peroxide, almost no PVA polymer degradation is achieved. This study also shows that the feeding strategy of hydrogen peroxide can have a significant impact on the degradation of PVA molecules in the UV/H 2 O 2 process.

The study investigates the hydrodynamic behaviour of non-Newtonian liquids under different operating conditions in a turbulent bed contactor (TBC). Hollow plastic spheres were fluidised in an air stream flowing counter currently to an aqueous solution of carboxy methyl cellulose (CMC) of an apparent viscosity ranging from 5 to 25 mPa s. A set of experiments was carried out to investigate the net pressure drop and minimum fluidisation velocity of the process. The column was operated at different superficial gas velocities, liquid flow rates, CMC solution concentrations and static bed heights. Results show that the net pressure drop is independent of the superficial gas velocity, but it increases steadily with liquid flow rate and static bed height. However, it remains almost invariant with a relatively low CMC concentration (0.2–0.4 wt%), and it augments gradually as the CMC percent exceeds the threshold of 0.4 wt% which corresponds to a more viscous liquid solution. The minimum fluidisation velocity decreases with a CMC concentration lower than 0.5 wt% approximately, but increases as the CMC percent exceeds 0.5 wt%. The study presents a new insight on the behaviour of non-Newtonian solutions in TBC columns.

A computational fluid dynamics (CFD) model was developed to study methyl methacrylate (MMA) solution polymerization in a lab-scale stationary continuous stirred tank reactor (CSTR) equipped with a six bladed 45° pitched impeller. Azobisisobutyronitrile (AIBN) and ethyl acetate were taken as the initiator and solvent, respectively. The CFD modeling approach incorporated an integration of the continuity, momentum, and species transport equations along with a polymerization source term. The latter was a function of thermal and chemical initiations, transfer to monomer and solvent as well as the gel effect. Multiple reference frame (MRF) technique, laminar regime, and isothermal condition were considered in the modeling. To validate the CFD model, the simulation results of conversion in a stationary CSTR of MMA polymerization were compared with the data reported in the literature. The CFD model was then employed to investigate the impacts of the impeller speed, reaction temperature, residence time and inlet monomer (or solvent) concentration on the conversion and homogeneity of reaction mixture inside the reactor. Contours of monomer mass fraction conceptually facilitated to visualize the reaction progress in the reactor.

The performance of batch and fed-batch photoreactors with that of continuous photoreactor for the treatment of aqueous polyvinyl alcohol (PVA) solutions is compared. Hydrogen peroxide feeding strategies, residence time, and [H2O2]/[PVA] mass ratio are examined for their impacts on the molecular weight distribution (MWD) of PVA and the total organic carbon (TOC) removal. The results prove that a continuous addition of H2O2 during the degradation reaction ensures the utilization of the produced radicals to minimize the oxidant consumption and maximize the TOC removal and the PVA degradation in a short irradiation time. Also, the MWD of PVA is found to be bimodal and shifted towards lower molecular weights with small shoulder peak indicating a progressive disappearance of the higher molecular weight fractions that is in accordance with the random chains scission mechanism. Besides, the hydrogen peroxide feeding strategies are found to have a great effect on the reduction in H2O2 residuals in the effluent.

A computational fluid dynamics (CFD) model was developed for the mixing of water in oil emulsion in a lab-scale mixing tank equipped with a Rushton turbine impeller. Multiple reference frames (MRF) technique, k – ɛ model, and Eulerian–Eulerian approach were employed to model the impeller rotation, turbulence, and multiphase flow, respectively. The droplet size distribution within the mixing tank was estimated by means of the population balance approach, which employs the discrete method to describe coalescence and breakage of water droplets. To validate the CFD model, the cumulative probability size distribution computed using the model was compared with the experimentally determined values reported in the literature. This validated CFD model was then utilized to explore the effects of the impeller speed, oil type, and volume fraction of water on the cumulative probability droplet size distribution, number density, and distribution of local volume fraction of the dispersed phase.

This paper discusses the design of a model-based multivariable nonlinear model predictive control (NMPC) formulation for the control of a multi-zone multi-feed LDPE autoclave reactor. Unscented Kalman filtering (UKF) state estimation was employed for online estimation of the plant states and disturbances. In addition to structural plant-model mismatch and noisy process measurements, the closed-loop performance of the UKF based NMPC scheme was investigated under parametric uncertainty in the kinetic rate constants. The closed-loop NMPC performance was also assessed for polymer grade changes, and for disturbance rejection at both open-loop stable and unstable operating regions.

This paper presents a multivariable nonlinear model predictive control (NMPC) scheme for the regulation of a low-density polyethylene (LDPE) autoclave reactor. A detailed mechanistic process model developed previously was used to describe the dynamics of the LDPE reactor and the properties of the polymer product. Closed-loop simulations are used to demonstrate the disturbance rejection and tracking performance of the NMPC algorithm for control of reactor temperature and weight-averaged molecular weight (WAMW). In addition, the effect of parametric uncertainty in the kinetic rate constants of the LDPE reactor model on closed-loop performance is discussed. The unscented Kalman filtering (UKF) algorithm is employed to estimate plant states and disturbances. All control simulations were performed under conditions of noisy process measurements and structural plant–model mismatch. Where appropriate, the performance of the NMPC algorithm is contrasted with that of linear model predictive control (LMPC). It is shown that for this application the closed-loop performance of the UKF based NMPC scheme is very good and is superior to that of the linear predictive controller.

Thermal polymerization of styrene in a lab-scale CSTR equipped with a pitched blade turbine impeller was simulated using a computational fluid dynamics (CFD) software package. The rotation of the reactor impeller was modeled using the multiple reference frames (MRF) technique. The path lines of the particles, released at the reactor inlet, were also generated to analyze the reaction progress throughout the reactor vessel. The effects of the impeller speed, the input–output stream locations and the residence time were investigated. The simulation showed the formation of a well-mixed region around the impeller and stagnant or slow moving fluids elsewhere in the reactor due to high viscosity of the polymer mass. The monomer conversion computed using the CFD model was in good agreement with that obtained from the CSTR model at low residence time. The input–output locations have a significant impact on the monomer conversion and the system homogeneity in the CSTR.

An experimental study was conducted to investigate the hydrodynamic characteristics of a turbulent bed contractor (TBC) with non-Newtonian liquids under different operating conditions. Hollow plastic spheres fluidized in an air stream countercurrently with an aqueous solution of carboxy methyl cellulose (CMC) of an apparent viscosity ranging from 5 to 25 mPa s. The first set of experiments confirmed the non-Newtonian behavior of the CMC solutions and experimental data were fit to power law model. The second set of experiments was conducted to analyze the hydrodynamic behavior of CMC solutions in the turbulent bed contractor. The existence of three hydrodynamic stages was characterized and the analysis was confined to the fully fluidized bed regime. The column was operated at different superficial gas velocities, liquid flow rates, static bed heights and CMC solutions concentrations. The study concluded that the liquid holdup rises with solutions of higher CMC content, which are more viscous for different liquid flow rates. But less liquid holdup is observed with higher static bed heights irrespectively of the solution viscosity. This study presents a new insight on the behavior of the non-Newtonian liquids in TBC beds.

The purpose of this work is to evaluate a new tetra-functional peroxide initiator and offer comparisons with a di-functional peroxide commonly used in the production of controlled-rheology polypropylene (CRPP) resins. CRPP resins have been produced by reactive processing in a batch mixer by using various equivalent amounts of a tetra-functional and a conventional di-functional peroxide at two different temperatures. At a lower processing temperature (200°C), the chain length of CRPP decreases with increasing initiator concentration of the di-functional initiator, while in the case of tetra-functional initiator system, the change of chain length is larger than that in the di-functional initiator system. At a higher temperature (230°C), the observation is reversed. The molecular weight reduction increases with initiator concentration level for the tetra-functional initiator, while the di-functional initiator causes larger reduction in the molecular weight without any obvious relation to the initiator concentration level. Rheological measurements show results consistent with those from gel permeation chromatography (GPC). The observations are explained based on the competition between chain scission and chain extension caused by the single and multiple radicals generated from the initiators. No evidence of architectural change in the CRPP molecules such as branching and crosslinking has been observed in both GPC and rheological measurements. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

A UV/H 2 O 2 process and an activated sludge bioreactor were integrated to achieve a cost-effective process of aqueous degradation of phenol. By applying the two-step Haldane approach for the activated sludge bioreactor and a validated kinetic model for the UV/H 2 O 2 process, an integrated model was developed for the phenol degradation in a combined photochemical–biological system. In this study, a kinetic model was employed to study the effects of different parameters in the combined photochemical–biological system, where the optimum conditions in terms of retention time and cost were determined. Three penalized objective functions were developed to find the best operating conditions including the minimization of the retention time, the power consumption, and the total cost. The least retention time for this system was determined to be 99 h and the optimal electrical energy consumption occurred at a photochemical retention time of 15 h with the biological retention time of 92 h. Total cost for different retention times was calculated demonstrating the fact that the incurred cost by the photochemical unit was considerably higher than that of the biological unit; however, the minimum total cost was evaluated to occur at 15.5 h of photochemical retention time and 90 h of biological retention time.

The severe thermodynamic conditions of the high-pressure ethylene polymerization process hinder ethylene from going to full conversion. One remedy to improve the monomer conversion is to make effective use of difunctional peroxides. Multifunctional peroxides can accelerate the polymerization rate, produce branching, and modify the rheological properties of molten polymers. This article proposes a kinetic model based on a postulated reaction mechanism for ethylene polymerization initiated by difunctional initiators in a high-pressure tubular reactor. Three peroxides suitable for ethylene polymerization were compared for their effectiveness. Compared to dioctanoyl peroxide, the two difunctional peroxides considered performed much better for the higher temperature regions of the reactor and gave ethylene conversions nearly twice as high for only half of the initial amount of dioctanoyl. They also generated low-density polyethylene polymer with a broader molecular weight distribution and longer chain branching. These two important polymer characteristics can influence the end-product rheological properties. Injecting fresh ethylene at different points along the reactor improved the conversion and produced more branched polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The article surveys the drying of solids materials and polymer solutions when infrared radiation (IR) is employed as the main heating source. The study reviews the current research trends of IR drying of specific applications. A case study similar to an industrial setting is presented to illustrate a model development and control scheme of an IR drying unit. The design and online implementation of an internal model controller (IMC) is discussed. The study demonstrates the controller capabilities to suppress random variations of the moisture content in the material entering the dryer. Simulation results also showed the success of model predictive control (MPC) multivariable controller ability, while handling process interactions and process constraints, to track setpoint changes in the humidity and temperature of the material exiting the dryer and to reject unmeasured stochastic disturbances in the inlet humidity stream.

An overview of a systematic investigation of a tetrafunctional peroxide initiator's behaviour is presented. The study focuses on three main areas of research: kinetic experiments, polymer characterization and modelling efforts. The kinetic investigation compared the behaviour of the tetrafunctional initiator (JWEB50) to that of a monofunctional counterpart (TBEC) for a variety of monomers. Although higher rates of polymerization were generated with JWEB50 for all monomers investigated, switching from a mono- to a tetrafunctional initiator actually decreased the polymer molecular weight for methyl methacrylate. While chromatographic characterization methods were able to detect branching in polystyrene samples produced with JWEB50, this was not the case for poly(methyl methacrylate). However, evidence of branching was clearly observed for both polystyrene and PMMA when rheological methods were employed. In order to explain the experimental results, a mathematical model was developed. Through its use, the concentration and chain length of various polymer structures (i.e., linear, star or coupled stars) was found to depend upon monomer type and reaction conditions.

A mathematical model for free radical polymerizations initiated by tetrafunctional initiators is described in detail with comparisons to experimental results. Reactions involving the fate/efficiency of functional groups are properly accounted for, while in the past, kinetic models for difunctional initiators found in the literature have ignored this. Free volume theory is used to describe the diffusion-controlled regime. Based on model predictions, multi-radical concentrations were estimated to be several orders of magnitude smaller than mono-radical concentrations. Through various case studies, the model was able to demonstrate that the concentration and chain length of various polymer structures (i.e., linear, star or coupled stars) depend upon monomer type and reaction conditions. The model was found to be useful in explaining experimentally observed differences in the behaviour of a tetrafunctional initiator with styrene compared to methyl methacrylate (MMA). In both cases, higher reaction rates could be obtained when switching from a mono- to a tetrafunctional initiator; however, the influence on molecular weight was found to vary between the two systems. Work with styrene showed similar trends as with difunctional initiators, where the tetrafunctional initiator maintained similar molecular weights compared to a monofunctional initiator. Yet, for MMA, replacing the monofunctional initiator with its tetrafunctional counterpart decreased the molecular weight.

In this work, the optimal control policies of radiant temperature versus dryer length are determined for the continuous, steady-state operation of infrared dryers. The optimal control objective is to minimize the product humidity subject to a mathematical model of infrared dryers as well as a set of process inequality constraints. A robust optimal control method based on genetic algorithms is applied. Multiple air injections are also considered. The optimal results show considerable reduction in product humidity. Comparisons with corresponding base cases (using maximum possible uniform radiant temperatures) indicate improvements greater than 50% with the application of optimal control policies.

This investigation examines the use of a tetrafunctional peroxide initiator in the bulk free radical homopolymerization of butyl acrylate and vinyl acetate. Rate of polymerization, molecular weights and in certain cases, gel fraction data were collected for selective experiments and compared to the results obtained with a monofunctional counterpart. In order to avoid the formation of insoluble gel material, further experiments were completed with varying concentrations of a chain transfer agent. Experimental results showed that when used at identical concentrations, the tetrafunctional initiator produced a faster rate in the polymerization of both butyl acrylate and vinyl acetate compared to the monofunctional initiator. Without the use of a chain transfer agent, runs with butyl acrylate produced significant amounts of gel material isolated by Soxhlet extraction. For a particular reaction time, the tetrafunctional initiator produced higher levels of gel compared to its monofunctional counterpart. When a chain transfer agent was used, the molecular weights were determined by its concentration and in turn, initiator functionality did not have an impact. In the polymerization of vinyl acetate, similar observations were made and no discernable difference could be seen between the molecular weight results of samples produced with either initiator.

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) samples produced by the bulk homopolymerization of styrene and methyl methacrylate with a tetrafunctional peroxide initiator (JWEB50) are characterized in detail by various solution and rheological methods. For comparison purposes, “linear” PS and PMMA samples were produced under similar conditions with a monofunctional initiator (TBEC). The four sample types were characterized by size exclusion chromatography (SEC) setups to determine molecular weight, radius of gyration, and intrinsic viscosity distributions. Contraction factors were calculated and indicated evidence of branching for polystyrene produced with JWEB50 while no such effects were observed with PMMA. The rheological behavior of the samples was subsequently investigated by performing oscillatory shear and creep experiments. Compared to the “linear” material, samples produced with JWEB50 exhibited a reduction in zero-shear viscosity that was attributed to long-chain branching. Retardation spectra were calculated based on creep data and converted to dynamic compliances that were then combined with the oscillatory data. This provided master curves spanning a much wider frequency range than could be obtained experimentally. Examination of various viscoelastic functions showed evidence of long-chain branching for both polystyrene and poly(methyl methacrylate) samples produced with JWEB50. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1340–1355, 2007

An investigation into the effect of initiator functionality on the free radical polymerization of various monomer systems including styrene, methyl methacrylate (MMA), styrene–MMA and α‐methyl styrene–MMA with a tetrafunctional peroxide initiator (JWEB50) was completed. The performance of the tetrafunctional initiator was compared to a monofunctional counterpart (TBEC). Kinetic results showed that regardless of the monomer system studied, JWEB50 produced a faster rate of polymerization compared to TBEC at an equivalent concentration. Molecular weights, radii of gyration and intrinsic viscosities were obtained from two size exclusion chromatography setups: one equipped with a multi‐angle laser light scattering detector and the other with low‐angle laser light scattering and viscosity detectors. For the homopolymerization of styrene, JWEB50 produced polymer molecular weights similar to TBEC at the same concentration, while experiments with MMA indicated that JWEB50 produced molecular weights closer to those...

For product quality purposes, the drying of some delicate materials is not easily feasible without the realization of a tight, well-designed controller. This study presents the results of a model predictive control for the drying of a thin fiber sheet moving through an electric infrared dryer, whose process dynamics are described by a minimum realization, previously developed. The simulation results indicate that the MPC multivariable controller is able to handle process interactions and produced good performance for tracking set point changes in the humidity and temperature of the material exiting the dryer and also for rejecting measured stochastic disturbances in the inlet humidity stream.

This study examined the use of a new tetrafunctional peroxide initiator in the bulk free-radical polymerization of methyl methacrylate. The objective was to investigate the effect of using a multifunctional initiator through an examination of the rates of polymerization and the polymer properties. The molecular weights and radii of gyration were obtained with a size exclusion chromatograph equipped with an online multi-angle laser light scattering detector. The performance of the tetrafunctional initiator was compared to that of a monofunctional counterpart [tert-butylperoxy 2-ethylhexyl carbonate (TBEC)]. The results showed that the new tetrafunctional peroxide initiator produced a faster rate of polymerization than TBEC at an equivalent concentration but also generated a polymer of a lower molecular weight. This trend was the opposite of what was observed in a previous study with styrene. When TBEC was used at a concentration four times that of the new tetrafunctional peroxide initiator, both produced equal rates of polymerization and similar molecular weights. The degree of branching was also investigated with radius-of-gyration plots. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5647–5661, 2004

Bulk, free-radical polymerization of styrene was carried out in the presence of a new tetrafunctional initiator (JWEB50, ATOFINA Chemicals, Inc.). The objective was to investigate the effect of initiator functionality on the free radical polymerization process. Size exclusion chromatography (SEC) with an on-line-multi-angle laser light scattering (MALLS) detector was used to measure molecular weight (MW), molecular weight distribution (MWD), and radius of gyration (Rg) of polystyrene. These results were compared to those with a monofunctional initiator, LupTBEC, also from ATOFINA. At equivalent molar concentrations, initiation with JWEB50 and LupTBEC produced polystyrene with similar MWs and MWDs. However, the rate of polymerization was faster with JWEB50. When LupTBEC was four times the molar concentration of JWEB50, equal rates of polymerization were achieved for both initiators. The MWDs were again similar, but the MWs were higher for the tetrafunctional initiation. Degree of branching and gelation were also investigated. A mixture of branched and linear polymer was produced by JWEB50, while no insoluble gel was formed.