Preparation and characterization of semi‐interpenetrating network polystyrene/PVDF cation exchange alloy membranes

The polystyrene‐DVB/PVDF alloy particles were prepared by pulverizing the polymerization product of styrene/DVB/PVDF in DMF, and then sulfonated with concentrated sulfuric acid to gain the cation exchange alloy powder, which was directly thermoformed by a hot‐press machine to form the titled cation exchange alloy membranes with the structure of semi‐interpenetrating polymer network. The effects of the polystyrene‐DVB to PVDF mass ratio and the DVB content in the monomers on the physical and electrochemical properties of the prepared alloy membranes were investigated. While the Fourier transform infrared spectroscopy (FTIR) confirms the components of membranes, the scanning electron microscopy (SEM) reveals that the alloy membranes possess a uniform distribution of functional groups, and a more dense structure with the increases of DVB content and PVDF content. The optimal prepared membranes have the area electrical resistance values within 3.0–6.6 Ω·cm², obviously superior to the commercial heterogeneous cation exchange membrane, as well as the moderate water contents of 35–40% and the desirable permselectivity with a transport number more than 0.95. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1220‐1227, 2013     

Optimization‐based design of polymer sheeting dies using generalized Newtonian fluid models

A polymer sheeting die design methodology is presented, which integrates finite element flow simulations, numerical optimization, and design sensitivity analyses to compute die cavity geometries capable of giving a near‐uniform exit velocity. This work extends earlier die design methods to include generalized Newtonian fluid (GNF) models that represent the shear‐thinning behavior of polymer melt. Melt flow computations and design sensitivity analyses are provided using the generalized Hele‐Shaw flow approximation with isothermal power‐law, Carreau‐Yasuda, Cross, Ellis, and Bingham fluid models. The nonlinear equations for die cavity pressure are solved using the Newton‐Raphson iteration method and design sensitivities are derived with the adjoint variable method. The die design method is applied to an industrial coat hanger die, in which a design parameterization is defined that allows for an arbitrary gap height distribution in the manifold of the die. In addition, die performance is assessed and compared for power‐law and Carreau‐Yasuda fluid flow over a range of die operating conditions. Pareto optimal die designs are also considered in this study. POLYM. ENG. SCI., 45:953–965, 2005. © 2005 Society of Plastics Engineers     

Optimal Designs of Multiple Dividing Wall Columns

Since the optimal design of dividing wall columns (DWC) is a highly nonlinear and multivariable problem, an appropriate solving tool is required. In this paper a multi‐objective genetic algorithm with restrictions is considered to design columns with dividing walls. Also, a methodology is proposed for sizing the DWC. The proposed design methodology allows achieving appropriate designs for columns with two dividing walls. As expected, the physical structures that allow the use of one or two dividing walls are not so different from each other and, as a consequence, the difference in the total annual costs for both systems depends mainly on the energy requirements.     

Biological Wastewater Treatment System Design Part II. Effect of Parameter Variations on Optimal Process System Structure and Design

This paper presents a study of the effects of parameter variations on optimal process system structures and designs for biological wastewater treatment systems. Results indicate that optimal system structure and design are sensitive to variations in the rate constants and feed concentration. Some of the process flowsheets deduced are innovative and have surprisingly low total costs. The process system structures and designs developed in this study merit consideration in future planning and design of wastewater treatment systems.     

Electron holography and AFM studies on styrenic block copolymers and a high impact polystyrene

Many of the artifacts of conventional electron microscopy can be avoided if the unstained polymers are studied by electron holography and atomic force microscopy (AFM). Holograms of thin sections (50–70 nm) of organic block copolymers were recorded, and the corresponding phase images were reconstructed. In this way, typical structures such as lamellae and cylinders could be imaged without any staining. In addition, we successfully recorded holograms and performed Lorentz microscopy of an impact‐modified polystyrene (high‐impact polystyrene). The results were compared with the tapping mode AFM phase images. Electron holography and AFM have been demonstrated as suitable tools to image unstained heterogeneous polymers, leading to the understanding of their structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1573–1583, 2005     

A mathematical optimization framework for the design of nanopatterned surfaces

The recent explosion of capabilities to fabricate nanostructured materials to atomic precision has opened many avenues for technological advances but has also posed unique questions regarding the identification of structures that should serve as targets for fabrication. One material class for which identifying such targets is challenging are transition‐metal crystalline surfaces, which enjoy wide application in heterogeneous catalysis. The high combinatorial complexity with which patterns can form on such surfaces calls for a rigorous design approach. In this article, we formalize the identification of the optimal periodic pattern of a metallic surface as an optimization problem, which can be addressed via established algorithms. We conduct extensive computational studies involving an array of crystallographic lattices and structure‐function relationships, validating patterns that were previously known to be promising but also revealing a number of new, nonintuitive designs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3250–3263, 2016     

Systematic controllability analysis for chemical processes

Modern chemical industrial processes are becoming more and more integrated and consist of multiple interconnected nonlinear process units. These strong interactions profoundly complicate a system's inherent properties and further alter the plant‐wide process dynamics. This may lead to a poor control performance and cause plant‐wide operability problems. To ensure entire processes run robustly and safely, with considerable profitability, it is crucial to recognize the inherent characteristics that can jeopardize controllability and process behavior at the early design stage. With a focus on inherently safer designs, from a plant‐wide perspective, a systematic method for chemical processes controllability analysis is addressed in this study. In the proposed framework, based on open‐loop stability/instability and minimum/nonminimum‐phase behavior, the entire operating zone of the process can be categorized into distinct subregions with different inherent properties. Variations in the inherent characteristics of a plant‐wide process with the operation and design conditions, over the feasible operation region, can be probed and analyzed. An attempt of this framework is made to illustrate how to clarify the roots of the poor controllability that arise in the design and operation of a large scale chemical process, and the results can provide guidance for both deciding the optimal operation conditions and selecting the most suitable control structure. Singularity theory is also applied in the framework to improve the computational efficiency. The framework is illustrated with two case studies. One involves a reactor‐external heat exchanger network and the other a more complex plant‐wide process, comprising a reactor, an extractor, and a distillation column. © 2012 American Institute of Chemical Engineers AIChE J, 58: 3096–3109, 2012     

Die Flotation — ein geeignetes Verfahren zur Aufbereitung öl- und fetthaltiger Abwässer

Flotation — a Useful Procedure for Treatment of Oil and Fat Containing Waste Water Waste water of the oil and fat manufacturing industry is characterized by a high content of by petrolether extractable compounds (fats and oils), protein and similar compounds. A considerable part of the contained oil is submitted in emulsified form and cannot be removed by mechanical treatment (gravity separator). Therefore an extensive precleaning is necessary before emission into an outfall ditch, passing in circuit of single streams or introducing into a biological cleaning stage. For this purpose physical/chemical processes are used, whereat in connection with a flocculation chamber the sedimentation — but preferred the flotation — comes into question. Different technical designs and constructive measures which are to con sider for optimal cleaning efficiency are described. Proposals for the design of plants are given too.     

Characterization and strain‐energy‐function‐based modeling of the thermomechanical response of shape‐memory polymers

Shape‐memory polymers (SMPs) are an emerging class of active polymers that can be used on a wide range of reconfigurable structures and actuation devices. In this study, an epoxy‐based SMP was synthesized, and its thermomechanical behaviors were comprehensively characterized. The stress–strain behavior of the SMP was determined to be nonlinear, finite deformation in all regions. Strain‐energy‐based models were used to capture the complicated stress–strain behavior and shape‐recovery response of the SMP. Among various strain energy functions, the stretch‐based Ogden model provided the best fit to the experimental observations. Compared to the sophisticated models developed for SMPs, the strain‐energy‐based model was found to be reliable and much easier to use for practical SMP designs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41861.     

Migration of a representative additive from standard and from high-impact polystyrene into test fat HB 307

The migration of the antioxidant n-octadecyl-3-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionate from standard polystyrene and selected high-impact polystyrenes into the test fat HB 307 was investigated by means of radiotracer techniques, especially its dependence on contact time and temperature. Characteristic differences between the migration properties of the additive in standard polystyrene on the one hand and those in the high-impact types on the other hand were found which obviously are caused by the different physical structures of these plastics. In the high impact types below 70°C the predominant migration process was found to be diffusion from the disperse rubber phase near the contact surface, whereas above this temperature the additive molecules are preferably diffusing through the polystyrene matrix. Simple rules are given by which the procedure for calculating migration values — which we developed earlier for polyolefins — can be used to predict the migration of additives from high-impact polystyrene into fat.     

Study of the thermoformability of ethylene‐vinyl alcohol copolymer based barrier blends of interest in food packaging applications

The thermoforming capacity of a number of blends of an ethylene‐vinyl alcohol copolymer (EVOH‐32, with 32 mol % ethylene) with amorphous polyamide (aPA) and/or Nylon‐containing ionomer with interest in multilayer food packaging structures have been studied. These blends were vacuum‐thermoformed between 100 and 150°C onto male molds of different shapes and areal draw ratios. It was found that EVOH/aPA extruded blends did not improve the inherently poor formability of EVOH alone. In contrast, significant improvements in thermoformability were achieved by blending EVOH with a compatibilized‐ionomer. Optimum forming capacity was achieved in a ternary blend by addition of a compatibilized‐ionomer to EVOH/aPA blends in the range of 140–150°C. Analysis of wall thickness data obtained in the thermoformed parts showed that wall thickness was significantly affected by the ionomer and amorphous polyamide content in the blend. The ternary blend showed a lower thickness reduction in the critical areas, as well as a higher uniformity in the part. A finite element analysis was used to evaluate the wall thickness distribution and the modeling results were compared with the thermoforming experiments. The simulations were performed for the vacuum‐forming process employing a nonlinear elastic material model. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 96: 3851–3855, 2004     

Modeling flow and cell formation in foam sheet extrusion of polystyrene with CO2 and co-blowing agents. Part I: Material model

In foam extrusion, process parameters, material properties, and the blowing agent have an influence on the resulting foam properties. For safety and environmental reasons, carbon dioxide (CO₂) has gained importance as a physical blowing agent for the production of low-density polystyrene foam sheets. The sole use of CO₂ often leads to corrugation, open cell structures, or surface defects on the foam sheet. As an alternative, blowing agent mixtures based on CO₂ and organic solvents such as ethanol, acetone, or ethyl acetate can be used, changing solubility and flow behavior of the gas-loaded melt. Modeling of the foaming process in the extrusion die could help to reduce experimental effort and accelerate the development of novel blowing agent mixtures. A model approach to describe the melt behavior of polystyrene loaded with various blowing agent mixtures in the extrusion die is developed. Part I of the article describes the modeling of material properties, that is, rheological behavior by a Carreau-WLF approach with shift factors for temperature, pressure, and blowing agent effects on the glass transition temperature. Solubility behavior is modeled by a combined Henry solubility coefficient approach, showing good agreement with experimental data. Based on the material model, a process model is developed in Part II of this work.     

On the optimum temperature progression for irreversible non-catalytic gas—solid reactions

Non-catalytic gas—solid reactions are examined, where both pore diffusion and chemical kinetics may affect the overall rate. At low temperatures the system is chemically controlled, whereas at high temperatures the reacted shell sinters, which causes the reaction to slow down appreciably.The system is represented by an appropriate mathematical model and it is shown that in this instance an optimal temperature progression would offer little advantage over operating at a constant optimal temperature throughout the reaction.A physical explanation is suggested for this behavior.     

Plasticization effects on bubble growth during polymer foaming

During polymer foaming with physical blowing agents, plasticization affects the melt viscosity, gas diffusivity in the melt, and the gas–melt interfacial tension. In this paper, we propose a model for plasticization during bubble growth, and estimate its effects under typical foaming conditions. The theoretical model incorporates well‐established mixture theories into a recent model for diffusion‐induced bubble growth. These include the free‐volume theories for the viscosity and diffusivity in polymer‐blowing agent mixtures and the density gradient theory for the interfacial tension. The viscoelasticity of the melt is represented by an Oldroyd‐B constitutive equation. We study the radial growth of a single bubble in an infinite expanse of melt, using parameter values based on experiments on polystyrene–CO₂ systems. Our results show that even at relatively low gas concentrations, plasticization increases the blowing‐agent diffusivity markedly and thus boosts the rate of bubble growth. In contrast, the reduction in melt viscosity and interfacial tension has little effect on bubble growth. Though not intended as quantitative guidelines for process design, these results are expected to apply qualitatively to typical foaming conditions and common polymer‐blowing agent combinations. POLYM. ENG. SCI., 46:97–107, 2006. © 2005 Society of Plastics Engineers     

A comparison of the thermoformability of a PPE/PP blend with thermoformable ABS. Part I: Small deformation methods

Different factors important in ascertaining the thermoformability of polymeric materials are identified and defined. These include resistance to sag, ease of flow, mold replication, deep draw capability, sensitivity to thermoforming temperature and speed, uniformity of thickness distribution, and post‐forming shrinkage and dimensional stability. Methods to study these properties can be classified into small deformation and large deformation methods. The small deformation methods, which are the subject of this paper, include dynamic temperature sweep tests, dynamic frequency sweep tests, stress relaxation time, and creep recovery tests. These tests were used to compare the thermoformabilities of a blend of polyphenylene ether (PPE) and polypropylene (PP) and thermoformable acrylonitrile butadiene styrene (ABS) resin. The dynamic temperature and frequency tests showed that the PPE/PP blend generally has a better viscoelastic balance than ABS implying a better balance between resistance to sag and ease of flow. Creep recovery tests suggested that the PPE/PP blend may offer better mold replication during thermoforming. Studies based on the stress relaxation time showed a lower residual stress build‐up in thermoformed PPE/PP blend than ABS implying better dimensional stability and a higher in‐service temperature window for the thermoformed PPE/PP blend than ABS. POLYM. ENG. SCI., 45:1369–1376, 2005. © 2005 Society of Plastics Engineers     

The need to re‐evaluate laminate design criteria

The aerospace industry uses carbon‐fiber epoxy laminates for structures to reduce weight and increase payload. The “standard” design criterion for strength is that proposed by Tsai‐Wu. For stiffness, which is generally more critical than strength, classical laminated plate theory (LPT) is used. The normal lay‐ups considered for commercial aircraft are made up from 0°, 90° and ± 45° orientations. Angle ply laminates, [± ϕ]_ns, with ϕ fixed to some angle such as 20°, are not normally used (although this type of structure is employed with great success in the pressure vessel industry). According to the Tsai‐Wu criterion, such a structure should be extremely weak, which probably accounts for the absence of simple angle ply structures in aerospace designs. However if short and wide samples (aspect. ratio 0.5 or less) are tested, higher values are obtained for modulus and much higher values for strength than the long narrow samples used to develop the Tsai‐Wu criterion. The short and wide sample test results are in agreement with results from tests on tubes. These observations show that there is an “edge softening” effect: long narrow samples have a relatively large amount of this soft edge. Since design software normally uses Tsai‐Wu and LPT, large errors in strength and significant errors in stiffness are possible at this stage, and better lay‐up designs may be totally missed. The experimental work leading to these conclusions is described and innovative designs are discussed.     

Modeling,Simulation and Optimized Design of a Microreactor for a Two‐Step Reaction

A two‐step microreactor for the investigation of glucose oxidation is presented. A model is created to pre‐judge the changes in concentrations of the reactants in the straight channels of the microreactor. The structure of the rapid mixing‐reaction units of the microreactor was optimized, and the optimal parameters were found to be p = 1:3, r = 1:1, and w_s = 60 μm. The model and the optimization method can facilitate the design of microreactors.     

Relative viscosity models and their application to capillary flow data of highly filled hard‐metal carbide powder compounds

The rheological behavior of highly filled polymer systems used in powder injection molding (PIM) technology strongly influences the final properties of the products. In this study, the capillary flow data of multi‐component polymer binders—based on polyethylene, paraffin, ethylene‐based copolymers, and polyethylene glycol—compounded with three various hard‐metal carbide powders were employed. The rheology of such highly filled (up to 50 vol%) multiphase systems is necessarily a complex phenomenon characterized by strain dependent, non‐Newtonian properties complicated by flow instabilities and yield. Over 15 mathematical models proposed for highly filled systems were tested, some of them calculating the maximum filler loading. Due to the complex structure of the filler (irregular shape, particle size distribution) and a multi‐component character of the binder, the applicability of these models varied with the powder‐binder systems studied. However, the particular values of maximum loadings are in good accordance with the predictions based on powder characteristics. Simple modification of Frankel‐Acrivos model to the systems containing unimodal hard‐metal carbide powders with particles of an irregular shape and broad particle size distribution gave precise agreement between experimental data and model prediction. POLYM. COMPOS., 26:29–36, 2005. © 2004 Society of Plastics Engineers.     

Grafted syndiotactic polystyrene synthesized via melting graft copolymerization used as a compatibilizer for immiscible syndiotactic polystyrene/polyadimide 66 blends

A new grafted syndiotactic polystyrene (g‐sPS), to be used as a compatibilizer for syndiotactic polystyrene (sPS)/polyadimide 66 blends, was prepared by the melting graft copolymerization of sPS and monomers composed of itaconic acid and dibutyl maleate with dicumyl peroxide as an initiator. The resulting g‐sPS possessed a side‐chain structure identified by IR spectra, and the results of mechanical testing show that a good impact strength and tensile strength were obtained for g‐sPS at a 7.16‐phr addition of monomer with a 3:1 proportion of dibutyl maleate and itaconic acid. Differential scanning calorimetry and scanning electron microscopy analysis indicated that the g‐sPS maintained a high glass‐transition temperature and a crystalline structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1659–1666, 2005     

Distributed economic model predictive control for operational safety of nonlinear processes

Achieving operational safety of chemical processes while operating them in an economically‐optimal manner is a matter of great importance. Our recent work integrated process safety with process control by incorporating safety‐based constraints within model predictive control (MPC) design; however, the safety‐based MPC was developed with a centralized architecture, with the result that computation time limitations within a sampling period may reduce the effectiveness of such a controller design for promoting process safety. To address this potential practical limitation of the safety‐based control design, in this work, we propose the integration of a distributed model predictive control architecture with Lyapunov‐based economic model predictive control (LEMPC) formulated with safety‐based constraints. We consider both iterative and sequential distributed control architectures, and the partitioning of inputs between the various optimization problems in the distributed structure based on their impact on process operational safety. Moreover, sufficient conditions that ensure feasibility and closed‐loop stability of the iterative and sequential safety distributed LEMPC designs are given. A comparison between the proposed safety distributed EMPC controllers and the safety centralized EMPC is demonstrated via a chemical process example. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3404–3418, 2017