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Inspired by the partitioned pipe mixer (PPM), a barrier-embedded partitioned pipe mixer (BPPM) is designed and analyzed using a numerical simulation scheme. The BPPM is a static mixer, composed of orthogonally connected rectangular plates with a pair of barriers, which divide, stretch, and fold fluid elements, leading to chaotic mixing via the baker's transformation. The aspect ratio of the plate (α) and the dimensionless height of the barrier (β) are chosen as design parameters to conduct a parameter study on the mixing performance. The flow characteristics and mixing performance are analyzed using the cross-sectional velocity vectors, Poincare section, interface tracking, and the intensity of segregation. The results indicate that several designs of the BPPM significantly enhance the PPM's mixing performance. The best BPPMs are identified with regard to compactness and energy consumption. © 2017 American Institute of Chemical Engineers AIChE J, 64: 717–729, 2018

Applying an electric field is an efficient way to fabricate polymer/clay nanocomposites. It helps to achieve a good dispersion of nanoclays which improves the performance of the polymeric system. In this study, the effect of an alternating current (A.C.) electric field was investigated on clay exfoliation with various combinations of polymer/clay nanocomposites. Three different types of organoclays (Cloisite 10A, 20A, 30B) were introduced in polypropylene (PP) and poly(lactic acid) (PLA) matrices. Their rheological properties showed that the A.C. electric field was effective in enhancing the dispersion of organoclays in both the PP/clay and PLA/clay composites. The efficiency of the A.C. field varied depending on the combination of polymer and clay nanoparticles. In the case of PP, the best combination was PP/C20A followed by PP/C10A and PP/C30B. In contrast, PLA/clay showed an opposite trend. This difference arises from the different affinities between the polymers and the functional groups of the clays. The Hansen solubility parameter was introduced to quantify the affinities between the polymer and clay. The electric field was more effective for polymer/clay combinations that had less difference in the Hansen solubility parameter. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43582.

To compare the rheological characteristics of structurally different hyaluronic acid (HA)-based biomaterials that are presently used for phonosurgery and to investigate their influence on the viscoelastic properties of vocal folds after implantation in an in vivo rabbit model.In vitro and in vivo rheometric investigation.Experimental laboratory, Inha and Seoul National Universities.Viscoelastic shear properties of 3 HA-based biomaterials (Rofilan, Restylane, and Reviderm) were measured with a strain-controlled rheometer. These biomaterials were injected into the deep layers of rabbit vocal folds, and viscoelastic moduli of the injected vocal folds were determined 2 months after the injection. The vocal fold specimens were observed using a light microscope and a transmission electron microscope.All HA-based biomaterials showed similar levels of shear viscosity, which were slightly higher than that of human vocal folds reported in previous studies. Compared with noninjected control vocal folds, there were no significant differences in the magnitudes of both elastic shear modulus (G') and viscous modulus (G") of injected vocal folds among all of the materials. Light microscopic images showed that all materials were observed in the deep layers of vocal folds and electron scanning images revealed that injected HA particles were homogeneously distributed in regions of collagenous fibers.HA-based biomaterials could preserve the viscoelastic properties of the vocal folds, when they were injected into vocal folds in an in vivo rabbit model. However, further studies on the influence of the biomaterials on the viscoelasticity of human vocal folds in ECM surroundings are still needed.

The addition of organically modified layered silicates (organoclay) to highly immiscible polypropylene/polystyrene, PP/PS, blends leads to a significant change in blend morphology and rheology. In this study, the kinetics for morphological development of the blend nanocomposites was studied by two mixing methods (internal batch mixing and continuous mixing), with a focus on the mechanism of dispersion of the silicate layers and its dependence on mixing conditions. Through the use of a twin-screw co-rotating extruder specially modified with sampling ports along its length it was possible to study, for the first time, the kinetics of morphology developed upon mixing. The results show that the evolution of silicate layer dispersion during morphology occurs by and large relatively early in the mixing process and that the most favorable breaking process of the dispersed phase occurs initially due to the breaking up of the initial silicate tactoids into thinner ones and also due to their presence inside it. As a consequence of these sequential processes, the organoclay layers end up at the interface between the PP and the polystyrene phases and stabilize the morphology.

The dynamic rheological behavior and phase morphology of Polytrimethylene terephthalate (PTT) and ethylene propylene diene monomer (EPDM) uncompatibilized blends and those compatibilized with maleic anhydride grafted EPM (EPM-g-MA) were investigated. Effects of blend ratio and reactive compatibilization on the morphology and rheological properties of compatibilized and uncompatibilized blends have been analyzed. The viscosity ratio between the polymers was found to be sensitive to frequency which gave an indirect idea about the unstable morphology. The complex viscosity and dynamic modulus increased with increase in compatibilizer addition up to critical micelle concentration. Palierne and Choi-Schowalter models were used to calculate the interfacial tension between the polymers. The interfacial tension decreased with the addition of compatibilizer up to CMC. It was also found that the minimum value of interfacial tension was found at CMC beyond that a levelling off is observed. The rheological properties of both compatibilized and uncompatibilized blends are found to be closely related to their phase morphology. POLYM. ENG. SCI., 50:1945–1955, 2010. © 2010 Society of Plastics Engineers

Key microstructural properties of particulate coatings such as porosity and particle order are established during drying. Therefore, understanding the evolution of particulate distributions during drying is useful for designing coating properties. Here, a 1D model is proposed for the particle distribution through the coating thickness at different drying times and conditions, including Brownian diffusion, sedimentation, and evaporation. Effects of particle concentration on diffusion and sedimentation rates are included. Results are condensed onto a drying regime map which predicts the presence of particle surface accumulation or sediment based on two dimensionless numbers: the Peclet number and the sedimentation number. Cryogenic scanning electron microscopy (cryoSEM) is used to image the transient particulate distributions during the drying of a model system comprised of monodisperse silica particles in water. Particle size and evaporation rates are altered to access various domains of the drying map. There is good agreement between cryoSEM observations and model predictions. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Since biofilms show strong resistance to conventional disinfectants and antimicrobials, control of initial bacterial adhesion is generally accepted as one of the most effective strategies for preventing biofilm formation. Although electrical methods have been widely studied, the specific properties of cathodic, anodic, and block currents that influence the bacterial detachment and inactivation remained largely unclear. This study investigated the specific role of electric currents in the detachment and inactivation of bacteria adhered to an electrode surface. A real-time bacterial adhesion observation and control system was employed that consisted of Pseudomonas aeruginosa PAO1 (PAO1) with green fluorescent protein as the indicator microorganism and a flow cell reactor mounted on a fluorescent microscope. The results suggest that the bacteria that remained on the electrode surface after application of a cathodic current were alive, although the extent of detachment was significant. In contrast, when an anodic current was applied, the bacteria that remained on the surface became inactive with time, although bacterial detachment was not significant. Further, under these conditions, active bacterial motions were observed, which weakened the binding between the electrode surface and bacteria. This phenomenon of bacterial motion on the surface can be used to maximize bacterial detachment by manipulation of the shear rate. These findings specific for each application of a cathodic or anodic electric current could successfully explain the effectiveness of block current application in controlling bacterial adhesion.

In this study, we investigated clay migration and its localization in multiphase blend nanocomposite systems during the evolution of blend morphology to elucidate how a hydrodynamic stress and chemical affinity between the polymer and clay induce them. To observe the morphology evolution, a multilayered blend, alternatively superposed poly(butylenes terephthalate) (PBT) and polystyrene (PS)/clay films or PBT/clay and PS films, was subjected to homogeneous shear flow, 1 s−1. Furthermore, the morphology was observed at different shear rates 1 s−1. When the PBT/(PS/clay) multilayered blend is subjected to flow, the clay dispersed in the PS layer first migrates to the interface depending on the amount of applied strain. The clay at the interface causes the average drop size of blend morphology to become smaller and the blend morphology becomes more stable because of the coalescence suppression effect. As more shear is applied, the clay at the interface moves further into more compatible phase, PBT, although the viscosity of PBT is higher than PS. On the contrary, the clay in the PBT layer does not migrate to the PS phase at any shear rate, which means that its chemical affinity is strong enough to prevent shear-induced migration. The clay increases the viscosity of the PBT phase and results in a different morphology with a droplet, cocontinuous structure. As a result, when the clay is induced to migrate by hydrodynamic stress, it migrates into thermodynamically more stable positions at the interface or in the chemically more compatible phase, depending on the applied strain. Once it is located at a thermodynamically more stable position, it is difficult to push it out only by hydrodynamic stress. The location of clay is significantly affected by the morphology during evolution, which means that the blend morphology can control the droplet form and cocontinuous structure by control of the clay migration kinetics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

In this study, polypropylene (PP)/clay nanocomposites containing different concentrations of ethylene-methacrylic acid ionomer (i.e. Surlyn®) were prepared, and the effect of ionomer on clay dispersion was studied via WAXD, rheology, SEM, and TEM. The role of the ionomer in the nanocomposites was compared with that of maleic anhydride grafted PP (PP-g-MA), which has been widely used as a compatibilizer in making PP/clay nanocomposites. With an increase in the concentration of compatibilizer, the position of d001 peak of OMMT shifted toward a lower angle for PP-g-MA system, while the position remained almost unchanged for Surlyn system, in which a larger interlayer spacing (d001) was found with respect to the former. In rheology, the addition of the ionomer led to a gradual increase in both moduli and complex viscosity, and the nonterminal behavior at low frequency was observed in both systems. In addition, the ternary hybrid containing 20 wt % Surlyn achieved the largest enhancement in relative viscosity, which was more than that of the nanocomposite prepared from pure Surlyn or pure PP, presumably indicative of the existence of strong interaction between the components. Finally, SEM and TEM micrographs demonstrated that exfoliated structure was preferred for PP/Surlyn/OMMT hybrids, while intercalated morphology for PP/PP-g-MA/OMMT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4024–4034, 2007

It is well known that poly(propylene)/clay (PP/ clay) nanocomposite forms an exfoliated structure when mixed with maleic anhydride-functionalized polypropylene (MAPP). This can be easily achieved by melt processing, however, the use of functionalized chemicals like MAPP costs a lot preventing its commercial application. Recently, it was reported that the exfoliated structure of PP/clay nanocomposite could be obtained without using any compatibilizer such as MAPP when exposed to the electric field. They could regulate the degree of dispersion and exfoliation by controlling the amount of clay loading, the strength of electric field, the time exposed to the electric field, etc. However, this was accomplished by applying the electric field on a rheometer for a long time. It will be practically attractive if we produce PP/clay nanocomposites via continuous processing like extrusion. A new design concept is required for this purpose. In this study, we present a novel method to continuously produce PP/clay nanocomposites using the electric melt pipe equipped with a twin-screw extruder. Rheology, XRD, and SEM measurements confirm the formation of nanocomposites. Thermal- and dynamic-mechanical analysis also shows the enhancement of the properties. Though, in this study, only a partial intercalation was achieved through continuous processing, it shows a possibility to produce nanocomposites by this approach. As this is a physical process that can be adapted to the conventional extrusion, the approach suggested in this study may be extended to other polymer/clay nanocomposite systems as well.

In this study, we have investigated morphology evolution of polymer blends during extrusion. By choosing two polymers, high density polyethylene (PE) and poly (1,4-butylene terephthalate) (PBT), having a large difference in melting temperature, we could control the viscosity ratio of the blend as well as the morphology. The morphology of the dispersed phase evolved from film to fibril and to droplet structure depending on thermal and deformation history. We could maintain the film or fibril structure in a final product by keeping the dispersed phase deformable and rigid enough to avoid the relaxation that is related with instability originating from the interfacial tension. The anisotropic structures (film and fibril) were found to enhance the rheological properties significantly, but in different manners under shear and extensional flow fields. This study shows that diverse morphology can be obtained by controlling processing conditions, and the rheological properties can be dramatically enhanced by morphology control.

The normal concept is that the critical molecular weight (MC) is about twice as large as the entanglement molecular weight (Me). However, experimental data have shown considerable deviations from MC ≈ 2Me. Furthermore, a determination of MC requires samples with a wide range of molecular weights, including weights lower than MC and higher than MC. In this article, we suggest a simple method for determining MC from the loss moduli of nearly monodisperse linear polymers with M ≫ MC. We consider two characteristic relaxation times, which correspond to the local maximum and minimum of the loss modulus. MC is determined from the intersection of two phenomenological relaxation times as a function of the molecular weight. The method precisely agrees with MC ≈ 2Me, which is not shown by conventional methods. Moreover, our method provides a determination of relaxation time τe, at which chain segments first feel the constraints imposed by the conceptual tube, without the measurement of the tube diameter and the monomeric friction coefficient, which may be determined by complicated procedures with a lot of data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2724–2729, 2004

We suggest a universal plot that superposes linear viscoelastic data of nearly monodisperse polymers on a single curve, regardless of the molecular weight, temperature, and species of polymers. The plotting method is based on the time–temperature superposition and rescaling of viscoelastic functions with terminal behavior. Without any information from molecular theories, the plot supports the fact that the molecular theories of the linear viscoelasticity of monodisperse polymers are independent of the species of polymers. Although an appropriate scaling may show universality by separately extracting the reptational mode and the Rouse mode from the whole set of viscoelastic data, our plotting method shows universality in a unified manner that scales the viscoelastic functions measured over the whole frequency range. We explain the origin of the universality of the plot in terms of molecular theory, the phenomenological spectra of the relaxation time (the BSW and CW spectra), and the principle of time–temperature superposition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2730–2737, 2004

High-impact polystyrene (HIPS) was prepared by the bulk or low-solvent polymerization of styrene in the presence of dissolved rubber and characterized to measure the dispersed particle size of the rubber phase. Before preparation, the prepolymerization time was established by measuring the evolution of particle size distribution of the dispersed phase as a function of reaction time. The measurement technique by laser light scattering was found to be efficient enough not only to lead to the right prepolymerization time but also to predict rubber-phase particle size distribution. Polymerization experiments were then conducted to investigate the effect of solvent contents on the particle size distribution of the rubber phase, in which ethylbenzene was introduced as a solvent at levels of 0, 3, 10, and 15%. As the solvent content increased, the size of rubber-phase particles initially increased, reaching a maximum, and then decreased. It is speculated that a decrease in the molecular weight of the matrix, a decrease in the viscosity ratio between polybutadiene to polystyrene phases, and a change in rubber morphology all contributed to the change in the rubber particle size of HIPS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3672–3679, 2003

A novel approach to fabricate poly(propylene)/clay nanocomposites under an electric field without adding any compatibilizer was proposed. The electrically activated poly(propylene)/clay nanocompsites show enhanced rheological properties with the disapearance of the characteristic peak in X-ray diffraction. Transmission electron microscopy was used to confirm the microstructural changes of the nancomposites. Electric field was found to facilitate destruction of the layer-stacking and separation of the silicate layers.

The effect of graft ratio on the dynamic moduli of ABS (Acrylonitrile-Butadiene-Styrene Copolymer) has been investigated. Unlike previous papers, the storage modulus at low frequency shows both minimum and maximum as graft ratio increases, and the rubber particles do not agglomerate significantly at high graft ratios. The dependence of the rheological properties on the graft ratio is quite complicated. This arises from its morphological change that leads to different interactions between the rubbery phase and the matrix phase. The minimum has been reported previously, and is explained in terms of rubber dispersion. However, the maximum at high graft ratio has never been reported. The origin of maximum seems to come from the repulsive forces between the long graft chains of neighboring rubber particles. Analogy between our experimental results and simulation results has been discussed to deduce the mechanism of maximum storage modulus at high graft ratio.

The homogeneous polycarbonate/poly(acrylonitrile-butadiene-styrene) (PC/ABS) nanocomposite thin films were prepared by a facile solvent casting method using phenylene modified-mesoporous silica materials as additives and dichloromethane as a solvent. The physicochemical analyses using small-angle X-ray scattering, nitrogen adsorption–desorption, solid-state 13C and 29Si nuclear magnetic resonance, and scanning electron microscope were investigated to provide clear physical and chemical properties for modified-mesoporous materials and nanocomposite films. Tensile tests were performed at room temperature according to ASTM D638. Rheological properties were also analyzed to observe any variance of solid–liquid property. As a compatibilizer and a reinforcing filler, mesoporous (organo-)silicas showed enhanced features in rheological and mechanical properties. The sound absorption coefficient was measured by the impedance tube up to 6400 Hz according to ISO 10534-2. It was found that the PC/ABS nanocomposites containing mesoporous materials can be used as a sound-proofing support material depending on fabrication process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45777.

We numerically investigated the dynamics of short double-stranded DNA molecules moving through a deep-shallow alternating nanofilter, by utilizing Brownian dynamics simulation. We propose a novel mechanism for high-throughput DNA separation with a high electric field, which was originally predicted by Laachi et al. [Phys. Rev. Lett. 2007, 98, 098106]. In this work, we show that DNA molecules deterministically move along different electrophoretic streamlines according to their length, owing to geometric constraint at the exit of the shallow region. Consequently, it is more probable that long DNA molecules pass over a deep well region without significant lateral migration toward the bottom of the deep well, which is in contrast to the long dwelling time for short DNA molecules. We investigated the dynamics of DNA passage through a nanofilter facilitating electrophoretic field kinematics. The statistical distribution of the DNA molecules according to their size clearly corroborates our assumption. On the other hand, it was also found that the tapering angle between the shallow and deep regions significantly affects the DNA separation performance. The current results show that the nonuniform field effect combined with geometric constraint plays a key role in nanofilter-based DNA separation. We expect that our results will be helpful in designing and operating nanofluidics-based DNA separation devices and in understanding the polymer dynamics in confined geometries.

We numerically investigated the dynamics of short double-stranded DNA molecules moving through a deep-shallow alternating nanofilter, by utilizing Brownian dynamics simulation. We propose a novel mechanism for high-throughput DNA separation with a high electric field, which was originally predicted by Laachi et al. [Phys. Rev. Lett. 2007, 98, 098106]. In this work, we show that DNA molecules deterministically move along different electrophoretic streamlines according to their length, owing to geometric constraint at the exit of the shallow region. Consequently, it is more probable that long DNA molecules pass over a deep well region without significant lateral migration toward the bottom of the deep well, which is in contrast to the long dwelling time for short DNA molecules. We investigated the dynamics of DNA passage through a nanofilter facilitating electrophoretic field kinematics. The statistical distribution of the DNA molecules according to their size clearly corroborates our assumption. On the other hand, it was also found that the tapering angle between the shallow and deep regions significantly affects the DNA separation performance. The current results show that the nonuniform field effect combined with geometric constraint plays a key role in nanofilter-based DNA separation. We expect that our results will be helpful in designing and operating nanofluidics-based DNA separation devices and in understanding the polymer dynamics in confined geometries.

We have developed a numerical algorithm based on 2D/3D finite element method for solving non-Newtonian fluid flow with the moving free surface encountered in polymer processing. The power law model is considered as a rheological constitutive equation. The standard Galerkin finite element formulation/penalty formulation are applied to discrctize the governing equations, the volume-of-fluid (VOF) scheme is used to track the moving free surface, and the donor-acceptor model introduced by Hirt and Nichols is modified and implemented on FEM. We applied the numerical scheme to simulate fountain flow and viscous buckling problems. For fountain flow, the numerical prediction of this study is in good agreement with the experimental results of other investigators. For viscous buckling, both 2D and 3D numerical simulations show that the shear thinning effect retards buckling. As this algorithm is very effective in treating moving free surface problems and requires less memory than previous algorithms, it may help solve challenging problems in polymer processing such as transient visroelastic flow simulations with moving free surfaces.

The weldline morphology of modified-poly(phenylene-oxide)/polyamide-6 blends has been investigated. A distinct contacting layer consisting of fine spherical particles was observed from the V-notch at the surface to the center of the molded part for the low viscosity ratio blend. In contrast, such small particles were not found and a slight deformation was observed near the part's surface for the high viscosity ratio blend. The weldline morphology was found to be dominated by the deformation, the breakup, and the relaxation of the dispersed modified-poly(phenylene oxide) phase. The effect of injection conditions on the weldline morphology has also been investigated. The morphology of the meldline was quite complicated. Distorted multi-layered structures were observed. It was found that those structures arise from the subsequent flow after merging of the two flow fronts. Weldlines and meldlines have been studied separately, and their formation mechanisms were found to be basically similar.

The effect of injection molding conditions and reactive compatibilization on the morphology of maleic anhydryde-modified poly(phenylene oxide)/polyamide-6 blends was investigated. The injection flow rate primarily influenced the position of the subskin layer, and the injection temperature affected the aspect ratio of the dispersed phase. A reduction of the size of the dispersed phase occured during the converging flow in the barrel-to-sprue zone. The reactive compatibilization reduced the flow induced deformation, the coalescence and the breakup of particles and improved the dispersion of the minor phase.

The morphology of injection molded poly(phenylene oxide)/polyamide-6 blends was investigated. A distinct skin layer, subskin layer, and core region were found across the part thickness, and the morphology of the skin layer was clearly observed. The shape and size of the dispersed phase depended on the position across the part thickness and the viscosity ratio of the component polymers. For low viscosity ratios, small and large particles coexisted in the subskin layer, implying that both coalescence and breakup of the dispersed phase occurred in that layer. For high viscosity ratios, an intermediate zone, in which little deformation of the dispersed phase occurred, was found between the skin layer and the subskin layer. These findings are expected to help foster understanding of the mechanism of morphology evolution during the filling and cooling stages of the injection molding process.

The Partial Frame Process (PFP) is a kind of gas-assisted injection molding, in which the void core is generated by imposing low pressure air into the molded part just after the resin is completely filled, after which the void grows as it compensates the volume shrinkage of resin. It resembles a secondary gas penetration step of gas-assisted injection molding, but has more advantages, such as its simplicity, design flexibility, ease of control, and cheap utilities. In this study, modeling of the void growth in PFP was carried out. By comparing the results with the experimental data, basic assumptions have been justified and the mechanism of the void growth could be explained in terms of the process parameters such as mold temperature, melt temperature, and the channel size. An experimental approach was also taken. As there are many factors affecting the process, the method of design of experiments was adopted, and the effects of the process parameters on the void growth length and the mechanism of the void growth were investigated. The results are expected to help in mold design and the determination of the operating conditions, as well as our understanding of this new process.