Centrifugal Mixer Research Articles

Extraction Chromatographic Separation of Rare-Earth Metals in a Cascade of Centrifugal Extractors

Liquid–liquid chromatographic processes, in particular, separation of rare-earth metals, were proposed to be performed in a cascade of centrifugal mixer–settler extractors. Various modes of extraction chromatographic processes of rare-earth metal separation were theoretically analyzed.

Investigation of the size effect of graphene nano-platelets (GnPs) on the anti-corrosion performance of polyurethane/GnP composites.

In this article, polyurethane/graphene nano-platelet (PU/GnP) composites were fabricated via planetary centrifugal mixer (PCM) and cast on polyethylene terephthalate (PET) and copper substrates. Four different grades of GnP are used to investigate the effect of GnP size on the anti-corrosion performance of the composites. Tafel, Nyquist, and Bode plots are used to quantify and compare the anti-corrosion performance of the composites, and these plots are obtained by electrochemical analysis. In addition to the anti-corrosion performance, mechanical properties and morphologies of the composites are analyzed. Various parameters indicating the anti-corrosion performance illustrate that smaller size of GnP in the composites shows higher anti-corrosion performance on copper substrate. The results show that the smaller size of GnP is not only uniformly dispersed within PU, but also offers a high surface area which helps construct an efficient filler pathway that suppresses the diffusion of a corrosive agent into the polymer matrix. Nevertheless, mechanical properties of the composites are partially improved. Essentially, this study demonstrates that the size of GnP plays a central role in determining the anti-corrosion performance of PU/GnP composites.

Influence of Agitation Equipment on Reinforcing Effect and Dispersion State of Cellulose Nano-Fibers in Natural Rubber

There are many rubber products like tires, and reinforcing agents derived from fossil resources such as carbon black (CB) are used for them. However, in recent years, conversion to biomass resources has been demanded due to problems such as depletion of fossil resources. Therefore, we have studied the composite of natural rubber (NR) reinforced with cellulose nano-fibers (CNF), which has attracted attention as a next-generation biomass resource. It is very difficult to uniformly disperse CNF in the conventional kneading process. Therefore, it is preferable to agitate CNF in NR latex. Then, it is necessary to study the optimum agitation equipment of CNF. In this study, the reinforcing effect by CNF was investigated when the agitation equipment was changed. Agitation of NR latex and CNF was carried out by a hand, a homogenizer, a dispersion mixer, and planetary centrifugal mixer. Thereafter, agitated materials were dried and masterbatches were made. Furthermore, the masterbatch and vulcanizing agents were kneaded using an internal mixer. Tensile test and X-ray CT observation of the prepared vulcanized rubber sheets were carried out to evaluate the reinforcing effect and dispersion state of CNF. As a result, the planetary centrifugal mixer was most useful to uniformly disperse CNF.

Microfabrication of biocompatible hydrogels by proton beam writing

Functionalization of biocompatible materials is expected to be widely applied in biomedical engineering and regenerative medicine fields. Hydrogel has been expected as a biocompatible scaffold which support to keep an organ shape during cell multiplying in regenerative medicine. Therefore, it is important to understanding a surface microstructure (minute shape, depth of flute) and a chemical characteristic of the hydrogel affecting the cell culture. Here, we investigate the microfabrication of biocompatible polymeric materials, such as the water-soluble polysaccharide derivatives hydroxypropyl cellulose and carboxymethyl cellulose, by use of proton beam writing (PBW). These polymeric materials were dissolved thoroughly in pure water using a planetary centrifugal mixer, and a sample sheet (1mm thick) was formed on polyethylene terephthalate (PET) film. Crosslinking to form hydrogels was induced using a 3.0MeV focused proton beam from the single-ended accelerator at Takasaki Ion Accelerators for Advanced Radiation Application. The aqueous samples were horizontally irradiated with the proton beam through the PET cover film, and then rinsed with deionized water. Microstructured hydrogels were obtained on the PET film using the PBW technique without toxic crosslinking reagents. Cell adhesion and proliferation on the microfabricated biocompatible hydrogels were investigated. Microfabrication of HPC and CMC by the use of PBW is expected to produce new biocompatible materials that can be applied in biological and medical applications.

ТЕХНОЛОГИЯ ПРОИЗВОДСТВА СУХИХ СПЕЦИАЛИЗИРОВАННЫХ НАПИТКОВ С ИСПОЛЬЗОВАНИЕМ ВЫСОКОЭФФЕКТИВНОГО СМЕСИТЕЛЯ

The technology of dry special-purpose drinks enriched with vitamins, beta-carotene and pectin has been developed. The task is to obtain multicomponent dry mixtures with high percentage ratios. The raw components differ in size, physical and mechanical properties, which characterize a mixing process as stochastic. A centrifugal mixer with cone working rotors is applied to solve the problem of thorough mixing. The peculiar feature of this device is realization of mixing of loose components in thin layers when crossing flows, which have different directions. The special feature of the device design is also mixing in discharged and intersectional layers using direct and reverse recycling under the action of centrifugal and inertial forces. The process intensity is guaranteed by distribution of dry material flows, under the action of structural blades of the instrument, reduction of dead zones due to the presence of new solutions in the device design, namely a special cone based on the rotor and structural blades. The quality of mixing is evaluated with the help of a coefficient of heterogeneity. The homogeneity of distribution is determined in terms of quantity using a variation factor. It is shown that the use of the developed mixer in the production of dry vitamin beverages makes it possible to obtain a powdered concentrate of high quality, solve the problem of lump formation and caking of loose disperse components of raw materials and their uniform distribution throughout the mass of a product. The technology has been tested at the enterprises of Valetek Prodimpex Company with the establishment of regulated quality indicators of the developed products. The nutritional value of a special-purpose product designed for optimization of healthy meals of workers in metallurgical enterprises is determined.

Silver doped titanium dioxide nanoparticles as antimicrobial additives to dental polymers

ObjectiveThe objectives of this in vitro study were to produce a filled resin containing Ag–TiO2 filler particles and to test its antibacterial properties. MethodsAg–TiO2 particles were manufactured using the ball milling method and incorporated into an epoxy resin using a high speed centrifugal mixer. Using UV/vis spectrophotometry investigations were performed to assess how the photocatalytic properties of the Ag–TiO2 particles are affected when encased in resin. Adopting the bacteria colony counting technique, the antibacterial properties of Ag–TiO2 particles and Ag–TiO2 containing resins were assessed using Streptococcus mutans under varying lighting conditions. ResultsAg doping of TiO2 results in a band gap shift towards the visible spectrum enabling Ag–TiO2 to exhibit photocatalytic properties when exposed to visible light. Small quantities of Ag–TiO2 were able to produce a bactericidal effect when in contact with S. mutans under visible light conditions. When incorporated into the bulk of an epoxy resin, the photocatalytic properties of the Ag–TiO2 particles were significantly reduced. However, a potent bactericidal effect was still achieved against S. mutans. SignificanceAg–TiO2 filled resin shows promising antimicrobial properties, which could potentially be used clinically.

Two-step validation process of particle mixing in a centrifugal mixer with vertical axis

Two-step approach of validation is proposed to validate a numerical model, capable of accurate prediction of mixing power characteristics of a centrifugal mixer with vertical axis. Two sets of experiments and two sets of numerical simulations are presented—the first set to determine physical characteristics of the particles comparing the numerical simulations results with experimental data, and the second set to validate predicted behavior of anchor type vertical axis impeller for mixing of same particles. Zeolite particles were used for actual calculations. After determining shear modulus, coefficient of interaction, static friction coefficient, and rolling friction coefficient through optimization process based on numerical simulations with subject function of diameter and angle of repose derived from experiment, using these values in numerical simulation of impeller mixer mixing zeolite particles led to results, which were in good agreement with results of the second set of experiments. The obtained zeolite material parameter values can therefore serve as a solid basis for discrete elements method based numerical simulation of zeolite granular materials.

A Rapid Assessment to Disperse Tailored Acetylene Blacks for the Battery Requiring a Few Amount of Conductive Agents

(Introduction) For recent lithium ion batteries(LiB) application, the demands for higher energy, higher power and longer life have been increasing. Therefore all chemical components in the LiB have been improved to meet the demands corresponding to various application. As for acetylene black(AB) it is one of the major conductive agents in the positive electrode. The smaller particle size ABs can make effective conductive paths for higher energy requiring a few amount of conductive agents(1,2. However, these smaller size ABs are difficult to be dispersed due to its high surface area and low interaction with NMP in the slurry. Even though oil absorption number(OAN) which is an evaluation method of aggregate in carbon blacks tends to be used as an index of the interaction with the solvent, the actual interaction with the solvent must be different from this classical evaluated results. Also, effects of dispersants which are often added in order to disperse AB homogeneously in the slurry cannot be evaluated with this index. In this research, we tried to acquire the exact information about actual interaction between the conductive agents and solvents like NMP with pulse NMR method. Then we defined the new index and researched the relationship between the index and practical properties for LiB application. (Experimental & Results) In the pulse NMR method, the relaxation time of NMP molecule which interacts with AB in the slurry is known to be shorter than of the NMP molecule not interacting(3. Therefore, we defined solvent interaction index(WAB) as the formula below. WAB=(Rav-Rb)/(Rb-SAB) Rav: The reciprocal of the relaxation time in the sample Rb: The reciprocal of the relaxation time in the blank(supernatant) SAB: Surface area of AB in the solvent Larger WABmeans higher solvent interaction between AB and NMP At first, four different specific surface areas of AB have been prepared and evaluated each solvent interaction index(WAB) with pulse NMR and the surface characteristics with desorption gas measurement (Fig.1). These results showed smaller particle size AB had lower solvent interaction index and there were associations between WAB and the amount of functional groups on the surface. That is to say, not only larger surface area but also low interaction with NMP(few functional groups) make smaller size AB difficult to be dispersed(4. AB4 was selected as a conductive agent and three different molecular weights of polyvinylpyrrolidone (PVP) , a major effective dispersant was prepared in this experiment. Then, four slurry samples were prepared by using a planetary centrifugal mixer and each solvent interaction index was evaluated with pulse NMR method (Fig.2). According to our results, PVP can improve solvent interaction between AB and NMP also larger molecular weight PVP showed better effect on the solvent interaction than the smaller one. This is because larger molecular weight PVP is thought to absorb the AB surface easier. In addition, slurry which have higher solvent interaction index shows low viscosity. Finally, in order to evaluate the effect of improved WABfor battery performance, we measured rate capability with AB4 and AB4+PVP samples (Fig.3). The mass was set to LCO:AB:PVdF=97.5:1:1.5 in the electrode. 3wt%(vs AB) of PVP was externally added into the electrode. This result showed battery containing AB4+ PVP 3wt% sample have good rate capability. Therefore, this pulse NMR method which can evaluate solvent interaction related to dispersibility is a useful tool to acquire the information for battery performance. In this presentation, further discussions about more detail results and other solvent interactions(Electrolyte etc.) will be presented. (Reference) (1)T. Saito, et al., 81th Electrochemical society of Japan, 2Q04, (2014). (2)Y. Nako, et al., 56th battery discussion, 3D13, (2015). (3) G.P. van der Beek, et al., Langmuir,Vol. 7, No.2 (1991). (4) T. Sonoda, et al., 42st Carbon material society, 1A09, (2015). Figure 1

Application of Response Surface Methodology to Estimate the Design Space of Pharmaceutical Diluents for Dispensing Powdered Formulations.

Scientific approaches for dispensation are important for the quality and efficacy of drug treatments. Therefore, for the dispensation of powdered medicines, we have developed a powder blending method using a planetary centrifugal mixer (PCM) to replace the empirical manual method involving a mortar and pestle. The aim of this study was to optimize the formulation of pharmaceutical diluents for dispensing powdered medicines, using PCM. The diluents, composed of powdered lactose, crystalline lactose, and corn starch were assigned to a {3,2}-Simplex Lattice design. Then, the designed diluents were blended with model powders, such as carbazochrome sodium sulfonate powder, rifampicin capsule contents, and crushed sulfasarazine tablets, at ratios of 1 : 4, 1 : 1, and 4 : 1 using PCM at 800 rpm for 60 s at a 20% filling rate. The mixtures were examined for content uniformity relative standard deviation (RSD) and flowability angle of repose (AOR). Response surface methodology was applied to optimize the formulation with the smallest RSD and AOR, and then the design space of desired diluents was estimated. On the basis of the design space, crystalline lactose, the mixture of lactose powder and crystalline lactose at a ratio of 1 : 4, and the mixture of corn starch and crystalline lactose at a ratio of 1 : 4, were suitable diluents for the powdered formulation, the content of the capsules, and the crushed tablets, respectively. The selected diluents were successfully applied to other model medicines showing a sufficient RSD and AOR. This technique could contribute to the development of scientific approaches for dispensation.

Dry Powder Coating using Planetary Centrifugal Mixer.

Extemporaneous compounding is an important part of pharmacy practice, and should be standardized and sophisticated to ensure the quality of the compounded preparations. Recently, we applied a planetary centrifugal mixer (PCM) to powder blending, which has attracted interest for its small scale and lack of contamination. In this study, we aimed to reveal the feasibility of dry powder coating through ordered mixing of fine particles using PCM. Cohesive lactose powders (Pharmatose450M) were dry coated with magnesium stearate (MgSt) using from 0.1 to 5%(w/w) content. The operational variables tested were operation time (1-30 min), operation speed (400-1000 rpm), vessel size (24-100 mL), and charging rate in the vessel (20-40%). The processed powders were evaluated for their surface morphology, flowability, and wettability. Furthermore, fine ibuprofen particles were coated with various lubricants, and then the dissolution profiles were examined. The crystallinity of ibuprofen was assessed using FT-IR and PXRD. Lactose powders were successfully coated with MgSt using PCM. When the level of MgSt was over 1%, the surface of the lactose powders was thoroughly covered. Angles of repose were 51° and 41° for unprocessed and processed powders with 1% MgSt, respectively. The contact angle of the water drop on the 1% MgSt sample leached to be 132°, changing to a hydrophobic surface. Investigations under various operational conditions revealed that higher improvement was observed upon higher speed and longer time, and a smaller charging rate in the vessel. Vessel size had no impact. Moreover, improved dissolution of ibuprofen coated with both hydrophilic and hydrophobic lubricants was observed owing to good dispersing behavior. Besides, no alteration of crystallinity was detected. PCM is an effective tool for dry powder coating with low impact stress. The presented method will contribute a great deal to making crushed tablets a functional powder.

Mixing of thermolabile additives in the centrifugal force field of a fluidized bed

An analysis is given of the process of mixing and heat treatment of solid and gas phases in a fluidized bed, which is being used successfully in mechanical engineering and chemical, oil refining, mining, power engineering, and other industries, for the purpose of mixing various ingredients of mixed animal feeds, including therapeutic and thermolabile. A centrifugal paddle mixer was developed, which passed state tests and is being used successfully in agricultural production. The uniformity of mixing is 0.95–0.98 (95–98%), which meets the requirement of the Sate Standard GOST for the production of mixed and therapeutic feeds. The mixer is easy to maintain and operates reliably.

Inorganic-Organic Hybrid Phosphor Layer for Si Solar Cells

The wavelength conversion layer (WCL) is attracting more attention from many companies because it is expected to increase the conversion efficiency of silicon solar cells by 5% or more. We have attempted to prepare the WCLs using our synthesized nano-phosphor particles. Nano-phosphor particles were prepared by several solution synthesis methods. To achieve high quantum efficiency, it is important to activate luminescent centers as many as possible without generating defects in the host materials. We pay attention to the microreaction (MR)[1], which is one of a solution synthesis method and has advantages that proper pH level and temperature can be maintained during the synthesis. A Bi3+ and Eu3+ co-activated YVO4 red nano-phosphor was synthesized by MR method with in-situ pH monitoring[2]. The surface morphology of the YVO4:Bi3+,Eu3+ nanophosphor sample was observed with a field emission scanning electron microscope, and spherical grains that are less than 50 nm in diameter have been obtained. Figure 1 shows the PL and PLE spectra of the YVO4:Bi3+,Eu3+ nanophosphor. The six sharp PL peaks due to the 4f6-4f6 electron transition of the Eu3+ centers, the broad PLE band as the YVO4 host (250-300 nm) and the charge transfer state of the Bi3+ centers (300-400 nm) were confirmed [3]. The ZnS:Mn and (Zn,Cd):Mn red nanophosphors were synthesized by controlling the condition of the 3-mercaptopropionic acid (3-MPA) in the reaction solution. Figure 2 shows the PLE spectra of the ZnS:Mn, and (Zn,Cd)S:Mn phosphors. The peak of the ZnS:Mn nanophosphor’s emission is 600 nm, and its excitation spectra range is located at less than 380 nm. The high quantum efficiency (QE) of about 50% has been achieved by changing the amount of 3-MPA quantity and by controlling the proper pH level. Meanwhile, we have attempted to control the excitation wavelength by substituting Zn with Cd. The peak emission wavelength of the synthesized (Zn,Cd)S:Mn nano-phosphor is 600 nm, which is the same as the ZnS:Mn. Contrary, the absorption edge of the PL excitation spectra is varied from 380 nm to 420 nm by changing the content ratio of Cd/Zn. The maximum QE of (Zn,Cd)S:Mn of 40% has been achieved under near-UV excitation at 370 nm. Nanophosphor particles, ethylene vinyl acetate (EVA) as a binder resin, and toluene as a solvent were used as the WCL slurry. They were mixed in a closed container by a planetary centrifugal mixer after heating at 90 ºC for 30 minutes. The WCLs were prepared by the doctor blade method using the bar coater (Kodaira YOA-B type). The thickness was 400 μm for all WCL samples. The I-V characteristics were measured using a solar simulator. The I-V curves of the WCL-mounted Si solar cells with and without fluorescent materials. The power generation efficiency was increased by 0.2%, 0.3%, and 0.5% by mounting the YVO4:Bi,Eu, ZnS:Mn, and (Zn,Cd)S:Mn WCLs, respectively under simulated AM 1.5 solar irradiation of 100 mW/cm2. Moreover, the inorganic-organic hybrid WCLs were also investigated. Figure 3 shows the inorganic-organic hybrid WCL with fluorescent materials including (Zn,Cd)S:Mn nanophosphors. The red emission based on the fluorescent materials under the 365 nm UV light was confirmed. The hybrid WCLs have a higher light resistance compared to WCLs containing only organic dye materials. It is considered that the inorganic phosphor absorbs a UV light and convert to visible light, resulting in prevention of the organic dye from UV damage. Figure 4 shows the I-V curves of the Si solar cells that had a WCL with and without fluorescent materials. The power generation efficiency was increased by 2.7% by mounting the (Zn,Cd)S:Mn / Eu complex dye WCL. In the future, the light conversion efficiency is expected to be furthermore improved by optimizing the process parameters of the MR system, and the phosphor dispersion technique into the EVA sheet. [1] 1) ECS transaction, 33, 95 (2011), 2) Jpn. J. Appl. Phys. 51 (2012) 062602 [2] 1) Phosphor Safari, 5 (2013), 2) The 20thIDW, 797 (2013) [3] J. Lumin., 129, 9 (2009) 1067 Figure 1

Mechanical and electrical properties of PANI-based conductive thermosetting composites

Polyaniline (PANI) is one of the most studied intrinsic electrically conductive polymer in recent years. In the present work, PANI-based conductive composites have been prepared using dodecylbenzenesulphonic acid (DBSA) as a dopant and divinylbenzene (DVB) as a cross-linking polymer to enhance the rigidity. In this mixture, DBSA acts as the dopant of PANI as well as the curing agent of DVB, and this means that doping and curing of the composite occur simultaneously. PANI–DBSA mixture has been prepared by physical mixing using centrifugal mixer. The ratio of PANI and DBSA has been kept constant in weight ratio 30:70. Furthermore, DVB content has been varied to prepare the different samples. It has been found that with the increase in DVB content, a good dispersion of PANI–DBSA/DVB solution is achieved. However, significant improvement in the electrical conductivity of the samples is observed with the increase in PANI content. Mechanical flexural test has been performed on the prepared samples using a three-point bending configuration. It has been found that the flexural modulus and brittleness of the prepared samples increase with the increase in the content of DVB in the composite. Morphology of the composite surfaces has been also studied and it has been found that low concentration of DVB results into a poor dispersion and hence agglomeration of PANI–DBSA in composite can be seen clearly in the images.

Mixtures for Vertebroplasty: the Flowability of Their Components and a New Production Technology Using a Centrifugal Mixer

Mixtures for Vertebroplasty: the Flowability of Their Components and a New Production Technology Using a Centrifugal Mixer

Blending powdered antineoplastic medicine in disposable ointment container

On dispensing powdered antineoplastic medicines, it is important to prevent cross-contamination and environmental exposure. Recently, we developed a method for blending powdered medicine in a disposable ointment container using a planetary centrifugal mixer. The disposable container prevents cross-contamination. In addition, environmental exposure associated with washing the apparatus does not arise because no blending blade is used. In this study, we aimed to confirm the uniformity of the mixture and weight loss of medicine in the blending procedure. We blended colored lactose powder with Leukerin(®) or Mablin(®) powders using the new method and the ordinary pestle and mortar method. Then, the blending state was monitored using image analysis. Blending variables, such as the blending ratio (1:9-9:1), container size (35-125 mL), and charging rate (20-50%) in the container were also investigated under the operational conditions of 500 rpm and 50 s. At a 20% charging rate in a 35 mL container, the blending precision of the mixtures was not influenced by the blending ratio, and was less than 6.08%, indicating homogeneity. With an increase in the charging rate, however, the blending precision decreased. The possible amount of both mixtures rose to about 17 g with a 20% charging rate in a 125 mL container. Furthermore, weight loss of medicines with this method was smaller than that with the pestle and mortar method, suggesting that this method is safer for pharmacists. In conclusion, we have established a precise and safe method for blending powdered medicines in pharmacies.

A Novel Blending Method for Dispensing Powdered Medicine

We introduced the application of a planetary centrifugal mixer to dispensing powdered medicines to prevent from individual variation in the skills of pharmacists with a manual blending. The blending performance of the mixer was explored in terms of four operational variables, namely, operation speed (400-1000 rpm), operation time (10-60 s), charging rate in vessel (20-50%), and size of vessel (35, 58, 125, 550 mL), using colored lactose and crystalline lactose as the principle model medicine and diluent, respectively. The blending degree was assessed by image analysis, so the extent of uniformity was expressed as the relative standard deviation of the color difference signal Cb value of YCrCb color space. Application of the mixer to blending three commercial medicines with diluents was carried out. Sufficient blending was achieved at 10 s using a 20% charging rate and 35 mL vessel irrespective of operation speed. As the charging rate was increased, a higher operation speed was needed to obtain uniform blending. A larger sized vessel also required a higher operation speed. Uniform blending was achieved in all of the mixtures of colored lactose and crystalline lactose at the weight ratio of 1 : 9-9 : 1. In the application studies using Adona®, Anginal® and Neophylline® powder, the blending performance of the mixer was equivalent to that of the manual blending method, showing relative standard deviations of 2.2-3.3% and 1.8-3.8%, respectively. These results revealed that the planetary centrifugal mixer was suitable for blending powdered medicine.

Reception of Two and Three-phase Combined Dispersive Systems with the Use of Centrifugal Mixer

The article presents the theory of the formation of disperse combined systems, the greatest attention is paid to the three-phase system consisting of fine particles, gas and liquid. The authors suggest the equation describing the impact of different energies on combined particulate system. Possible conversion processes of surface energy into thermal, mechanical and chemical energy were shown. Also presents the results obtained by various dispersed systems with liquid additives and without them on the continuos mixer of centrifugal type. The study of using of volumetric ratio phases revealed major technological methods that enable to purposefully influence the ratio of different phases in order to obtain materials with the desired properties. The addition of a small amount of a liquid mixture of 4% with a viscosity of 50Pa sec reduces the coefficient of inhomogeneity and to reduce the segregation of the mixture obtained in the dusty area and, consequently, to increase the quality of the final product (uniformity of a three-phase system).

Modeling the Process of Flow of a Non-Newtonian Liquid in a Centrifugal Birotary Mixer

An analysis of the physical and mathematical models of the flow process of an anomalously viscous liquid along the surface of a conical birotary mixer is presented. A system of integral parameters of the operation of the mixer that makes it possible to determine the equivalent diameter of drops of the dispersed phase in any stage of a birotary mixer is obtained. Experimental verification of theoretical studies confirmed the goodness-of-fit of the engineering technique used to calculate this type of centrifugal mixer.

Preparation of porous bioceramics using reverse thermo-responsive hydrogels in combination with rhBMP-2 carriers: In vitro and in vivo evaluation

Porous biphasic calcium phosphates (BCP) were fabricated using reverse thermo-responsive hydrogels with hydroxyapatite (HAp) and β-tricalcium (β-TCP) powder and planetary centrifugal mixer. This hydrogel mixture slurry will shrink and compress the HAp powder during the sintering process. The porous bioceramics are expected to have good mechanical properties after sintering at 1200°C. Reverse thermo-responsive hydrogels of poly[(N-isopropylacrylamide)-co-(methacrylic acid)] p(NiPAAm–MAA) were synthesized by free-radical cross-linking copolymerization, and their chemical properties were evaluated by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and electrospray-ionization mass spectrometry. The lower critical solution temperature (LCST) of the hydrogel was determined using turbidity measurements. A thermogravimetric analysis was used to examine the thermal properties. The porous bioceramic properties were analyzed by X-ray diffraction, scanning electron microscopy, bulk density, compressive strength testing and cytotoxicity. The compressive strength and average porosity of the porous bioceramics were examined at approximately 6.8MPa and 66% under 10wt% p(NiPAAm–MAA)=99:1 condition. The ratio of HAp/β-TCP can adjust two different compositional behaviors during the 1200°C sintering process without resulting in cell toxicity. The (rhBMP-2)-HAp-PLGA carriers were fabricated as in our previous study of the double emulsion and drop-coating technique. Results of animal study included histological micrographs of the 1-mm defect in the femurs, with the rhBMP-2 carrier group, the bioceramic spacer group and the bioceramic spacer with rhBMP-2 carriers group showing better callus formation around the femur defect site than the control group. The optimal dual effects of the bone growth factors from osteoconductive bioceramics and osteoinductive rhBMP-2 carriers produced better bone formation.

PREPARATION AND PROPERTIES OF STYRENE-BUTADIENE RUBBER/CLAY NANOCOMPOSITES BY USING LIQUID RUBBER/CLAY MASTER BATCHES

ABSTRACT Rubber/clay nanocomposites (RCNs) have many applications because of their improved properties. The dispersion of clay in a rubber matrix, which plays an important role in the properties of RCNs, is a challenge. In this article, a solvent-free approach to produce the styrene butadiene rubber (SBR)/clay nanocomposites by using liquid rubber/clay master batches was introduced. The liquid/rubber master batches were first prepared using a high-speed centrifugal mixer and then compounded with neat SBR using conventional rubber compounding equipment. Compared with the composites prepared by melt mixing, this approach resulted in a better dispersion of the clay in the rubber matrix and improvements in tensile strength (4.98 MPa at 10 phr clay loading) and elongation at break (>1000% at 10 phr clay loading). The improved dispersion was confirmed by X-ray diffraction. The effect of clay loading on the tensile properties, dynamic mechanical properties, and the Payne effect was also investigated. The increase in clay loading resulted in a steady increase in the tensile properties up to a loading of 15 phr. The reinforcement in the RCN modulus using clay was compared with five models, including the Guth and Halpin-Tsai equations. This solvent-free approach offers benefits in dispersion of clay for industrial applications of rubber nanocomposites.