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Encapsulating powder ingredients into hydrogel with programmable release ability is highly demanded in many fields including food engineering, medical and healthcare fields. However, directly adding water-insoluble powders into pre-gel solution makes the mixture susceptible to clogging problems during processing, thus limiting the loading rate. To address this problem, a new way to encapsulate water-insoluble powder ingredients without addition of any organic solvent named bubble-assisted encapsulation method is developed in this study. The powders were firstly encapsulated in hydrogel bubbles and further dispersed by T-shaped microfluidic flow to form the core/shell-structured powder in hydrogel microcapsules (P/H microcapsules). The obtained P/H microcapsules had an exceptionally high loading rate of water-insoluble powders up to 94.76%. The P/H microcapsules were freeze-dried for long-term storage, and meanwhile, the as-prepared microcapsules were able to swell rapidly to soft state before use. Moreover, with the well-defined core–shell structure, the P/H microcapsules were endowed with dual release capabilities to external stimuli. The bubble-assisted encapsulation method that enables direct dense encapsulation of powder ingredients at a high loading rate appears promising for water-insoluble food or pharmaceutical ingredients delivery.

Dielectric elastomers can generate large voltage-induced deformation and have been widely used as soft actuators. Dielectric elastomer multilayer structures function as bending-type actuators, enhancing their stiffness and ability to resist external loads. Modeling a dielectric elastomer multilayer bending actuator allows analyzing its bending performance, and obtaining the stress and strain distributions in each layer of the actuator. It is of practical importance to develop a simple, yet accurate model. This work develops a model to analyze the electromechanical behavior of the dielectric elastomer multilayer bending actuator with various pre-stretch, material, and structural parameters. We also propose a simplified model for a bilayer slender beam, which is a typical multilayer structure. The simplified model describes the relation between the beam bending curvature and the applied voltage, achieving fast calculation with little accuracy sacrificed. Both the model for the dielectric elastomer multilayer and the simplified model for the bilayer beam agree well with the experiment results, validating the models for practical applications in soft robots, flexible sensors, and smart structures.

Rotor stator interaction (RSI) is an important phenomenon influencing performances in the pump, turbine, and compressor. In this paper, the correlation-based transition model is used to study the RSI phenomenon between a translational cascade of airfoils and a flat plat. A comparison was made between computational results and experimental results. The computational boundary layer velocity is in reasonable agreement with the experimental velocity. The thickness of boundary layer decreases as the RSI frequency increases and it increases as the fluid flows downstream. The spectral plots of velocity fluctuations at leading edge x/c = 2 under RSI partial flow condition f = 20 Hz and f = 30 Hz are dominated by a narrowband component. RSI frequency mainly affects the turbulence intensity in the freestream region. However, it has little influence on the turbulence intensity of boundary layer near the wall. A secondary vortex is induced by the wake–boundary layer interaction and it leads to the formation of a thickened laminar boundary layer. The negative-vorticity wake also facilitates the formation of a thickened boundary layer while the positive-vorticity wake has a similar effect, like a calmed region which makes the boundary layer thinner.

Monodisperse droplets are important in drug screening, and cell-based and biochemical research. However, conventional methods for creating droplets, such as co-flow, T-junction and flow-focusing, have poor monodispersity because of fluctuations in the flow rate. Because step emulsification is based on the principle of Laplace pressure, it is insensitive to the flow rate and yields a constant and high monodispersity. In the present study, we combine electrowetting and step emulsification to reduce the negative influence of flow-rate fluctuations and to prepare highly monodisperse droplets. We demonstrate that the flow rate and voltage applied to the droplets can independently influence the droplet size. This method has great potential in chip-based bioanalysis and cell-based studies where highly monodisperse droplets are needed.

The concept of isothermal chambers filled with GPMs (gradient porous materials) was presented to homogenize the temperature distribution between the center and outer wall of the chambers with disc-shaped cross-section. An analytical heat transfer model was first developed to study the thermal behaviors of the GPMs chamber. Besides, numerical simulation was conducted to obtain the temperature profiles of the chamber with different GPMs. The effects of various gradient parameters on the heat resistance, temperature profiles and filling mass of the chamber were investigated in details. The results indicated that the gradient direction and gradient magnitude have a significant influence on the comprehensive thermal performances of the chamber filled with GPMs. Increasing the porosity gradient of GPMs along radius direction can effectively enhance the heat conduction. Moreover, the optimum gradient magnitude was obtained analytically to further improve the heat conduction of the GPMs chamber.

The internal flow of reactor coolant pump (RCP) is much more complex than the flow of a general mixed-flow pump due to high temperature, high pressure, and large flow rate. The pressure pulsation that is induced by rotor-stator interaction (RSI) has significant effects on the performance of pump; therefore, it is necessary to figure out the distribution and propagation characteristics of pressure pulsation in the pump. The study uses CFD method to calculate the behavior of the flow. Results show that the amplitudes of pressure pulsation get the maximum between the rotor and stator, and the dissipation rate of pressure pulsation in impellers passage is larger than that in guide vanes passage. The behavior is associated with the frequency of pressure wave in different regions. The flow rate distribution is influenced by the operating conditions. The study finds that, at nominal flow, the flow rate distribution in guide vanes is relatively uniform and the pressure pulsation amplitude is the smallest. Besides, the vortex shedding or backflow from the impeller blade exit has the same frequency as pressure pulsation but there are phase differences, and it has been confirmed that the absolute value of phase differences reflects the vorticity intensity.

This paper studies the influence of added mass, centrifugal force and hydraulic load on natural frequencies of a Reactor Coolant Pump (RCP) impeller. A series of comparative studies under different conditions were carried out on a modal test bench and a simulation platform. Modal analysis of a full-scale RCP impeller was conducted by simulation, and an improved design of impeller was proposed to prevent hydraulic resonance. These results indicated that hydraulic load increases natural frequencies of the impeller. While the centrifugal force slightly reduces them, but it is negligible. Because the distribution of hydraulic load has an effect to natural frequencies, a solution of cutting inlet edges of blades can be used to increase the natural frequency that may cause hydraulic resonance. In summary, our research shows that both added mass and hydraulic load have a significant influence on natural frequencies of the RCP impeller, and redistributing the hydraulic load can alter natural frequencies of the impeller.

The high concentration of sulfite in preserved fruits wastewater is toxic to microorganisms, which tends to break down the biological treatment system and leads to poor effluent quality. In addition, the pH decreases constantly due to the presence of sulfite during biological treatment, even if it is repeatedly adjusted to neutral. Therefore, to ensure the stable and efficient operation of biological treatment, a novel pretreatment was proposed through transition metal ions catalyzed oxidation coupled with chemical precipitation. The results showed that Fe(III) ion achieved the best catalytic efficacy for the oxidation of sulfite which was attributed to the combination of complexation and free radical reaction. Under the optimal conditions (aeration rate = 0.10 L/min, Fe(III) dosage = 5 mmol/L), the sulfite removal was 80.1%, concomitant with 20.7% of chemical oxygen demand (COD) removal. Further, by calcium oxide precipitation, the sulfite was completely removed, COD decreased by 32.2% as well as BOD5 /COD increased to 0.96, ensuring pH stability and high biodegradability in subsequent biological treatments. These findings demonstrate that this pretreatment process has great potential for sulfite removal and provides an economical and practical approach to the treatment of preserved fruits wastewater. [ABSTRACT FROM AUTHOR]

Distorted inflow caused by the complex structure of the steam generator channel head (SGCH) occurs at the entrance to the reactor coolant pump (RCP) in the AP1000 system, which may generate impeller cracks and result in deterioration of performance and stability. In this paper, to analyze the influence of distorted inflow on flow properties of the RCP, the inflow distortion characteristics are studied by a full three-dimensional steady and unsteady numerical simulation. The simulation model was verified experimentally by testing the RCP with a straight pipe and a channel head at different flow rates. Using this model, the inlet distortion was quantified and the variation law of different distortion was obtained. The results showed that a non-uniform swirling flow under lateral pressure differences was formed when the pump was coupled with a channel head instead of a straight pipe, leading to the destruction of circular symmetry of the inflow field. Further increasing the tube length alone was not effective in improving the inflow field of the RCP, and the inlet swirl effect always existed. As the distorted flow entered the pump with a pair of vortices, the chaotic flow field imposed a non-uniform stress on each blade of the impeller, resulting in the unevenly distributed flow rate of each flow-path of the blade. Then, in the flow channels of the impeller, there were obvious asymmetrical vortex core regions, even in opposite directions, which originally formed in the inflow field of the RCP and raised the risk of blade fatigue failure. Owing to the significant effects of inflow distortion produced by the SGCH, understanding the mechanism of non-uniform inflow characteristic is of great value to the design and optimization of the RCP. Abbreviations: RCP: reactor coolant pump; SG: steam generator; SGCH: steam generator channel head [ABSTRACT FROM AUTHOR]

The effect of surface modifications of carbon black (CB) on its dispersion in polyether polyol and CB/polyurethane (PU) foams and the properties of the CB/PU composite foams was investigated. Pristine CB (p-CB) was oxidized in nitric acid to obtain oxidized CB (o-CB), and then by the esterification reaction between the carboxyl groups of o-CB and the hydroxyl groups of polyether polyol, polyol grafted CB (g-CB) was obtained. Optical microscopy, scanning and transmission electron microscopy observations showed that surface modifications effectively improved the dispersion of CB in polyether polyol and in the final composite foams. Compared with the p-CB/PU foams, the o-CB/PU and g-CB/PU composite foams exhibited improved conductivities, storage moduli, and increased glass transition temperatures. The compressive strengths of the p-CB/PU and o-CB/PU composite foams decreased with the increase of filler contents, but g-CB has no negative effect on the compressive strength even at a filler content as high as 8 phr. Furthermore, the cell sizes for the o-CB/PU and g-CB/PU composite foams were more uniform than those of p-CB/PU foams. [ABSTRACT FROM AUTHOR]

The article presents a study on the synthesis of an oligomeric phosphorous-nitrogen containing intumescent flame retardant (IFR) and its effect on polypropylene (PP). Despite the widespread use of PP, it said that its application in fields requiring high flame retardancy is limited because it is flammable. The intumescent technology has been adopted by the researchers since it is said to be capable of improving flame retardancy in polymers. The study shows that the incorporation of the IFR poly(4,4-diamino diphenyl methane-O-bicycli pentaerythritol phosphate-phosphate) could increase the thermal stability and flame retardancy of PP.

The electric conductive polymer composites, which were made of carbon black particles through dispersing in mixtures of polyacrylonitrile (PAN)/nylon6 (PA6), were prepared in a Haake Thermo-mixer. The morphology, conductivity, thermorheology properties and their relationships were studied. Microphase separations and partial miscibility were confirmed when a small mass of PAN was introduced into PA6/CB composites. A part of CB particles could be attracted by PAN, and transferred to the interface of PA6 and PAN, leading to an increase of electric conductivity. Results also indicated that the introduction of PAN in the PA6/CB composite improved its elastic modulus as well as the thermal stability of its electric conductivity. [ABSTRACT FROM AUTHOR]

The thermal stability and flame retardancy of a new kind of rigid polyurethane (PU) foams/organoclay nanocomposites developed by our research group were investigated by using thermogravimetry analysis (TGA) and cone calorimeter test. Results indicate that compared with pure PU foams, rigid PU foams/organoclay composites show significantly enhanced thermal stability and flame retardancy. The reasons leading to the results were discussed in detail by relating with the morphology of the composites. The discussion suggests that the enhancement degree of thermal stability and flame retardancy of composites compared with that of PU foams coincides well with the sequences of gallery spacing of organoclay in the PU matrix. [ABSTRACT FROM AUTHOR]

Several carbon black (CB)‐filled binary polymer blends were prepared in Haake rheometer. Distribution states of CB and effect of morphology on the electric conductivity of different ternary composites were investigated. Under our experimental condition CB particles located preferentially at the interface between polymethyl methacrylate (PMMA) and polypropylene (PP) in PMMA/PP/CB composites, in high‐density polyethylene (HDPE) phase in PP/HDPE/CB composites, and in Nylon6 (PA6) phase in polystyrene (PS)/PA6/CB, PP/PA6/CB, PMMA/PA6/CB, and polyacrylonitrile (PAN)/PA6/CB composites; the ternary composites in which CB particles locate at the interface of two polymer components have the highest electric conductivity when the mass ratio of the two polymers is near to 1 : 1. The ternary composites in which CB particles located preferentially in one polymer have the highest electric conductivity usually when the amount of the polymer component having CB particles is comparatively less than the amount of the polymer component not having CB particles; if the formulations of PS/PA6/CB, PP/PA6/CB, and PMMA/PA6/CB composites equaled and PA6/CB in them is in dispersed phase, PS/PA6/CB composites have the highest electric conductivity and PP/PA6/CB composites have the lowest electric conductivity; suitable amount of PS or PAN in PA6/CB composites increase the electric conductivity due in the formation of a parallel electrocircuit for electrons to transmit. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [ABSTRACT FROM AUTHOR]

A novel method for preparing rigid polyurethane (PU) foam/organoclay nanocomposites was developed through the direct incorporation of an organoclay into PU foam matrices without the addition of any physical or chemical blowing agent. The resultant foams with an appropriate content of the organoclay had a finer cell structure than the pristine PU foams because the organoclay not only acted as a nucleating agent as expected but also acted as a blowing agent of the PU foams; this could be attributed to the bound water between the interlayers of the organoclay. In addition, the incorporation of the organoclay up to 4 phr resulted in improvements in the tensile and compressive strengths, with the maximum values appearing at 2 phr (110 and 152%, respectively). The significant improvement in the mechanical properties could be attributed to the finer cell structure and the increased internal strength of the materials due to the higher degree of hydrogen bonding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [ABSTRACT FROM AUTHOR]

Three different surface modifiers, octadecyl trimethyl ammonium (ODTMA), octadecyl primary ammonium (ODPA), and decanediamine (DDA) were used to modify Na&bond; montmorillonite (MMT), and the resultant organoclays were coded as ODTMA‐MMT, ODPA‐MMT, DDA‐MMT, respectively. Rigid PU foams/organoclay composites were prepared by directly using organoclay as the blowing agent without the addition of water. Investigation shows that the morphology of the nanocomposites is greatly dependent on the surface modifiers of clay used in the composites. In detail, DDA‐MMT is partially exfoliated in the PU matrix with the smallest cell size, while two others are intercalated in the PU matrices with smaller cell sizes. The sequence of their cell sizes is pristine PU foams > rigid PU foams/ODTMA‐MMT > rigid PU foams/ODPA‐MMT > rigid PU foams/DDA‐MMT, and the average cell size of rigid PU foams/DDA‐MMT composites decreases evidently from 0.30 to 0.07 mm. Moreover, all rigid PU foams/organoclay composites show remarkable enhanced compressive and tensile strengths as well as dynamic properties than those of PU foams, and the enhancement degree coincides well with the relative extent of internal hydrogen bonding of materials and gallery spacing of organoclay. For example, in the case of rigid PU foams/DDA‐MMT composite, 214% increase in compressive strength and 148% increase in tensile strength compared with those of pure PU foams were observed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [ABSTRACT FROM AUTHOR]

The article reports on the use of a Lewis acid catalyst to increase the compatibility of popystyrene (PS) and polyolefin elastomer (POE) blends. According to the authors, the catalyst was used to initiate the Friedel-Crafts alkylation reaction for the formation of PS-graft-POE copolymer. The authors also analyze the rheological behaviors of the blends under different temperatures.

Polystyrene (PS)/nylon6 (PA6)/carbon black (CB) composites were prepared in Haake rheometer. The factors influencing the electric conductivity of PS/PA6/CB composites were investigated. Results showed that CB particles only distribute in PA6 phase because of the strong polarity of PA6. The CB content in PA6 phase and the morphology of PA6/CB phase affect the electric conductivity of PS/PA6/CB composites. No matter the PA6/CB phase is continuous or dispersed, the electric conductivity of PS/PA6/CB composites increases with the increase of CB content in the PA6 phase; higher continuous degree of PA6/CB phase leads to higher electric conductivity. A new term, statistical average critical distance (SACD), was defined to explain the electric mechanism of PS/PA6/CB composites, which is a function of CB content in PA6. The SACD of PS/PA6/CB composites, in which CB content is 23 wt % in PA6, was quantitatively counted, which is about 54 nm. Keeping the CB content in composites at 5.67 wt %, the optimum mass ratio of PS/PA6 for the composites having the highest electric conductivity is 80 : 20, resulting from the competitive result of the earlier two factors (that is the CB content in PA6 phase and the morphology of PA6/CB phase). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1042–1047, 2007 [ABSTRACT FROM AUTHOR]

The cocross-linking of polyvinyl chloride (PVC) and low density polyethylene (LDPE) was studied by THF extraction, FTIR, and Dynamic rheological analysis. It is found that dicumyl peroxide (DCP) could neither induce the cross-linking of PVC itself nor cause PVC chains to cocross-link with LDPE. Butadiene rubber (BR), as a solid phase dispersant (SPD) can not give a hand to the cocross-linking. However, NBR, both as a compatibilizer and SPD, can induce PVC to be crosslinked or cocross-linked with LDPE initiated by DCP. The composite cross-linking agent that consists of DCP, triallyl isocyanurate (TAIC), and magnesium oxide (MgO) is easy to induce PVC to cross-link itself or cocross-link with LDPE. [ABSTRACT FROM AUTHOR]

Synergistic effect between multi-walled carbon nanotubes (MWNTs) and clay on improving the flame retardancy of acrylonitrile-butadiene-styrene (ABS) resin was studied. Flammability properties measured by a cone calorimeter revealed that incorporation of clay and MWNTs into ABS resin significantly reduced the peak heat release rate (PHRR) and slowed down the whole combustion process compared to the individually filled system based on clay or MWNTs. The flame retardancy of the ABS/clay/MWNTs nanocomposites was strongly affected by the formation of a network structure. Linear viscoelastic properties of the ABS nanocomposites showed that the coexistence of clay and MWNTs can enhance the network structure which can hinder the movement of polymer chains and improve flame retardancy. From transmission electron microscope analysis, MWNTs were shortened after combustion and there was no significant change in their diameters. For chars of ABS/clay/MWNTs nanocomposites, some MWNTs ran across between clay layers, indicating a strong interaction existed between clay and MWNTs. The existence of clay enhanced the graphitization degree of MWNTs during combustion. Clay can assist the elimination of dislocations and defects and the rearrangement of crystallites. Al2O3, one of the components of clay, acts as the catalyst of graphitization. [ABSTRACT FROM AUTHOR]