Preparation and Characterization of Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine/Ammonium Perchlorate Intermolecular Explosives

Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine/ammonium perchlorate/glycidyl azide polymer (RDX/AP/GAP) intermolecular explosives (IMX) with different proportions of RDX to AP were prepared by sol‐gel method, and the structure and performance was characterized by Brunauer‐Emmett‐Teller measurements (BET), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results showed that the specific surface area of RDX/AP/GAP IMX decreased with the addition of AP. The crystals of AP and RDX in RDX/AP/GAP intermolecular explosives were in the range of 20–48 nm and 23–55 nm, respectively. In addition, RDX/AP/GAP intermolecular explosives had the largest heat release at zero balance.     

Role of poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) in the modification of polysulfone membranes for ultrafiltration

In this study polysulfone membranes with antifouling and hydrophilic properties were synthesized using poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (AMPS) as an additive for the first time. Different wt % of AMPS was used to prepare polysulfone membranes by phase inversion method. The role of AMPS on the porosity, pore size distribution, hydrophilicity, and antifouling nature was investigated and analyzed in detail. Characterization techniques like field emission scanning electron microscope, atomic force microscopy, and imageJ software were used to characterize the morphology of prepared membranes. There is positive effect of the additive addition on all the membrane parameters like Pure water flux [101.76 L/(m² h)] (MR0) to 464.06 L/(m² h) (MR4)], hydraulic permeability [0.65 (MR0) to 2.01 (MR4)], equilibrium water content [21.74 (MR0) to 71.45 (MR4)], and porosity [0.024 (MR0) to 0.58 (MR4)]. Response surface methodology was used for the optimization of bovine serum albumin (BSA) flux and rejection. The results of the morphological as well as permeation studies depicted that permeate flux and antifouling nature were increased with the amount of AMPS present in the membrane matrix. The antifouling study of the prepared membranes was undertaken by using BSA solution of 1000 mg/L. Positive results were seen with the increase in amount of AMPS, since, the total membrane resistance has been decreased from 0.95 (MR0) to 0.74 (MR4). Separation of humic acid from aqueous medium was also performed with the best performing membrane (MR4, having the highest amount of AMPS). Separation efficiency of 100% and 94% were obtained using 10 mg/L and 50 mg/L of HA, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45290.     

Fabrication and Evaluation of Polycaprolactone–Poly(hydroxybutyrate) or Poly(3‐Hydroxybutyrate‐co‐3‐Hydroxyvalerate) Dual‐Leached Porous Scaffolds for Bone Tissue Engineering Applications

Polycaprolactone (PCL) blend with poly(hydroxybutyrate) (PHB) or poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) dual‐leached scaffolds are prepared by using the solvent casting and salt–polymer‐leaching technique. The blending of the PHB and PHBV in PCL scaffolds results in decreased porosities of the scaffolds, and the water absorption capacities of the scaffolds also decrease. The compressive modulus of the PCL–PHB and PCL–PHBV dual‐leached scaffolds is greatly increased by the blending of PHB or PHBV matrix. An indirect cytotoxicity evaluation of all scaffolds with mouse fibroblastic cells (L929) and mouse calvaria‐derived preosteoblastic cell (MC3T3‐E1) indicates that all dual‐leached scaffolds are posed as nontoxic to cells. Both PCL–PHB and PCL–PHBV dual‐leached scaffolds are supported by the attachment of MC3T3‐E1 at significantly higher levels to tissue culture polystyrene plate (TCPS) and are able to support the proliferation of MC3T3‐E1 at higher levels to that cells on TCPS and PCL scaffolds. For mineralization, cells cultured on surfaces of PCL–PHB and PCL–PHBV dual‐leached scaffolds show higher mineral deposition than on TCPS and PCL scaffold.

     

Self‐heating properties of styrene‐butadiene rubber

Rubbers, including styrene‐butadiene rubber (SBR), are well known to be susceptible to self‐heating. SBR is used in a wide range of applications and is often produced in the form of a crumb which is then used to form the final product. The crumb may be transported and stored in large quantities. Self‐heating properties of a SBR crumb have been determined using standard oven methods. The results indicate that self‐heating is a real hazard for SBR crumb. The results are generally consistent with recent measurements by Clothier and Prichard (Combust. Flame 2003; 133 :207–210) for rubber tyre crumb. Copyright © 2005 John Wiley & Sons, Ltd.     

Basic characterization of polypropene‐block‐poly(methylene‐1,3‐cyclopentane‐co‐propene) synthesized from propene and 1,5‐hexadiene with modified stopped‐flow method

Block copolymerization of propene and 1,5‐hexadiene was carried out by a modified stopped‐flow polymerization method with an MgCl₂‐supported Ziegler catalyst. The resulting polymer, polypropene‐block‐poly(methylene‐1,3‐cyclopentane‐co‐propene) (PP‐b‐(PMCP‐co‐PP)), in which the crystallizable PP part was linked with the non‐crystallizable PMCP‐co‐PP part, was characterized by optical microscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile testing. The block copolymer having a chemical linkage between PP and PMCP‐co‐PP showed properties different from those of homopolymer, random copolymer and blend polymer. © 2001 Society of Chemical Industry     

Comparative investigations of radiation‐grafted proton‐exchange membranes prepared using single‐step and conventional two‐step radiation‐induced grafting methods

Proton‐exchange membranes containing poly(styrene sulfonic acid) grafts hosted in poly(vinylidene fluoride) (PVDF) films were prepared using two radiation‐induced grafting methods: a single‐step grafting method (SSGM) involving grafting of sodium styrene sulfonate onto electron beam (EB)‐irradiated PVDF films and a conventional two‐step grafting method (CTSGM) in which styrene monomer is grafted onto EB‐irradiated PVDF films and subsequently sulfonated. Differential scanning calorimetry, universal mechanical testing and scanning transmission electron microscopy were used to evaluate the thermal, mechanical and structural changes developed in the membranes during the preparation procedures. Physicochemical properties such as water uptake, hydration number and ionic conductivity were studied as functions of ion‐exchange capacity and the results obtained were correlated with the structural changes accompanying each preparation method. Membranes obtained using the SSGM were found to have superior properties compared to their counterparts prepared using the CTSGM suggesting the former method is more effective than the latter for imparting desired functionality and stability properties to the membranes. Copyright © 2010 Society of Chemical Industry     

Synthesis,Characterization, and In Vitro Bioactivity of Sol‐Gel‐Derived Zn,Mg, and Zn‐Mg Co‐Doped Bioactive Glasses

Bioactive glasses in the systems CaO‐SiO₂‐P₂O₅‐ZnO, CaO‐SiO₂‐P₂O₅‐MgO, and CaO‐SiO₂‐P₂O₅‐MgO‐ZnO were prepared and characterized. Bioactive glass powders were produced by the sol‐gel method. The prepared bioactive glass powders were immersed in a simulated body fluid (SBF) for periods of up to 28 days at 310 K to investigate the bioactivity of the produced samples. Inductively coupled plasma (ICP) and ultraviolet (UV) spectroscopic techniques were used to detect changes in the SBF composition. X‐Ray diffraction (XRD) was utilized to recognize and confirm the formation of a hydroxyapatite (HA) layer on the bioactive glass powders. Microstructural characterizations of the bioactive glass samples were investigated by scanning electron microscopy (SEM) techniques. Density, porosity, and surface area values of bioactive glass powders were also determined in order to characterize the textural properties of the samples. The results revealed the growth of an HA layer on the surface of the bioactive glass samples. MgO in the glass sample increases the rate of formation of an HA layer while ZnO in the glass slows it down.     

CFD‐DEM Model for Simulating Solid Exchange in a Dual‐Leg Fluidized Bed

The domain coverage method (DCM) is proposed to establish a computational fluid dynamics‐discrete element method (CFD‐DEM) model based on irregular mesh. The gas field was solved by Fluent software and the DEM model was coupled with Fluent software by user‐defined functions. Gas turbulent viscosity was calculated by the coupled k‐? two‐equation model and the soft‐sphere collision model was used to get particle contact force. The CFD‐DEM model based on irregular mesh was firstly verified to be reasonable by comparing the simulated injected bubble with that simulated by Bokkers et al. The solid exchange behavior was studied numerically in a 2D dual‐leg fluidized bed (DL‐FB). The simulation results were compared with experimental results and proved that the CFD‐DEM model is established successfully based on the efficient DCM. The DEM model is expanded to be used on irregular mesh in fluidized beds with complex geometries.     

Multiscale design of high‐voltage multilayer energy‐storage ceramic capacitors

Multilayer energy‐storage ceramic capacitors (MLESCCs) are studied by multiscale simulation methods. Electric field distribution of a selected area in a MLESCC is simulated at a macroscopic scale to analyze the effect of margin length on the breakdown strength of MLESCC using a finite element method. Phase field model is introduced to analyze the dielectric breakdown mechanism of MLESCC at a mesoscopic scale. The microstructure of selected area is generated through voronoi tessellation random construction routine containing core‐shell‐structured dielectric materials. The effects of margin length, shell permittivity, and shell volume fraction on the breakdown strength of MLESCC are respectively studied. Results indicate that the breakdown strength of MLESCC can be enhanced by adopting larger margin lengths, or by increasing the shell permittivity or volume fraction.     

Magnetic‐induced coil‐globule transition for polyelectrolytes

The effects of an applied magnetic field on the system composed of polyelectrolytes (PEs) and magnetic nanoparticles oppositely charged are studied by means of Monte Carlo method within the framework of “single‐site bond fluctuation model.” For a certain concentration of chains, the coil‐globule transition can be induced by the applied magnetic field. The mean‐square end‐to‐end distance and gyration radius as well as the shape factor of PE chains are used to characterize the conformational transitions. The statistical analysis of the system energy demonstrates this significant physical process. The role of entropy‐energy balance is well‐understood for different chain lengths, and a typical phase‐transition anomaly concerned with specific heat curve is observed. Under a certain magnetic field, the PE chains will regularly collapse due to the enough adsorption of magnetic particles. The magnetic particles exhibit peculiar spatial distribution at high magnetic fields: the string‐like arrangement along the magnetic field and the square lattice‐like arrangement perpendicular to the magnetic field. The applied magnetic field has a great influence on the length of string‐like structures formed by nanoparticles. This investigation may cast light on the collapse of PEs and provide a promising method for producing new nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Quasi‐static and dynamic nanoindentation of particle‐reinforced soft composites

The mechanical properties of ferromagnetic particle‐reinforced silicone–rubber matrix composites are examined with quasi‐static and dynamic nanoindentation measurements using Berkovich and flat punch indenters, respectively. Quasi‐static nanoindentation is performed to examine primary factors such as the loading and holding time, particle volume fraction, and indentation depth for these particle‐reinforced soft composites (PRSCs). The Einstein–Guth–Smallwood equation based on macroscopically mechanical property testing is utilized to describe the relationship between elastic modulus and particle content of PRSCs in quasi‐static tests. A good agreement between the nanoindentation and simulation prediction is obtained. To characterize the storage modulus and loss factors of PRSCs, the dynamic nanoindentation is then conducted over the force frequency range of 0–45 Hz to show that the dynamic properties are dominated by the particle content and the force frequency, and independent of indentation depth and oscillation amplitude. It is indicated that the nanoindentation is a versatile methodology to assess mechanical properties of microsized particulate soft composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44559.     

Kinetic Parameters of PBX Based on Cis‐1,3,4,6‐tetranitroocta‐hydroimidazo‐[4,5‐d] imidazole Obtained by Isoconversional Methods using Different Thermal Analysis Techniques

The thermal decomposition kinetics of the interesting polycyclic nitramine cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole (BCHMX) and its polymer bonded explosive (PBX) based on polyurethane matrix, have been investigated using different thermal analysis techniques and methods. The used polyurethane matrix is based on hydroxyl‐terminated polybutadiene (HTPB) cured by hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used nonisothermally, whereas the vacuum stability test (VST) was used isothermally. Kinetic parameters were determined by using isoconversional (model‐free) methods. Furthermore, the Advanced Kinetics and Technology Solution (AKTS) software was used to determine the kinetic parameters of the studied samples in order to provide a comparison. It was found that the decomposition temperature of BCHMX/HTPB is lower than that of pure BCHMX. All the applied techniques as well as computational results showed that BCHMX/HTPB has a lower activation energy than pure BCHMX. The different methods used, Kissinger, Ozawa, Flynn, and Wall (OFW) and Kissinger‐Akahira‐Sunose (KAS) methods presented activation energies in the same range of the AKTS software results. Also the results proved that VST technique could be a useful tool to present results suitable for calculation of the kinetic parameters of explosives.     

Modeling gas‐particle two‐phase flows with complex and moving boundaries using DEM‐CFD with an immersed boundary method

An immersed boundary method (IBM) has been developed and incorporated into the coupled discrete element method and computational fluid dynamics (DEM‐CFD) approach to model particulate systems consisting of a compressible gas and solid particles with complex and/or moving boundaries. The IBM is used to deal with the interaction between gas and complex and moving boundaries by using simple rectangular grids to discretize the fluid field. The developed method has been applied to simulate some typical powder handling processes (e.g., gas fluidization with an immersed tube, segregation in a vertically vibrated bed, and pneumatic conveying). Good agreement is achieved between the present simulation results and the experimental ones reported in the literature. It has been demonstrated that the capacity of DEM‐CFD is enhanced with the incorporation of IBM, which can be used to simulate a wide range of problems that could not be handled with the conventional DEM‐CFD method. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1075–1087, 2013     

Significantly enhanced energy‐storage density in the strontium barium niobate‐based/titanate‐based glass‐ceramics

Two‐step crystallization process was employed to improve microstructure and energy‐storage density of the strontium barium niobate‐based/titanate‐based glass‐ceramics. By using two‐step crystallization process, the optimum nucleation temperature was obtained to improve dielectric breakdown strength. Compared to the breakdown strength by one‐step crystallization process, the breakdown strength by two‐step crystallization process is increased about 1.89 times with the optimum nucleation temperature. Energy‐storage density of 7.73 ± 0.26 J/cm³ is significantly improved by two‐step crystallization process and is about 2.9 times of 2.63 ± 0.17 J/cm³ by one‐step crystallization process. This result is attributed to the homogeneous nucleation improving the microstructures of glass‐ceramics. Identification and quantification of crystalline phases by using Rietveld refinement reveals the difference of dielectric constants for one‐step and two‐step crystallization processes.     

Preparation of poly(DL‐lactide‐co‐glycolide) nanoparticles without surfactant

The preparation of poly(DL ‐lactide‐co‐glycolide) (PLGA) nanoparticles was performed by a dialysis method without surfactant or emulsifiers. The size of the PLGA nanoparticles prepared from dimethylacetamide (DMAc) as an initial solvent was smaller than that from acetone. The sizes of the PLGA nanoparticles from DMAc and acetone were 200.4 ± 133.0 and 642.3 ± 131.1 nm, respectively. The effects of the initial solvent selected to dissolve the copolymer and the lactide:glycolide ratio were investigated. The PLGA nanoparticles were spherical as revealed by the results of scanning electron microscopy and transmission electron microscopy observations. From these results it was shown that PLGA nanoparticles could be formed by the dialysis method without surfactant. The drug‐loading contents and efficiency were also dependent on the lactide:glycolide ratio and initial feeding amount of the drug. A higher lactide ratio resulted in higher drug loading and higher loading efficiency. However, a higher initial feeding amount of the drug resulted in higher drug loading and lower loading efficiency. Clonazepam was released for at least 2 days and the release rate was slower with a higher lactide:glycolide ratio and a larger amount of drug‐loading nanoparticles than that with a lower lactide:glycolide ratio and a smaller amount of drug‐loading nanoparticles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2228–2236, 2001     

Energy‐Efficiency Evaluation of Gas Sweetening Based on Yield‐Energy‐Selectivity Indicators

The high‐sulfur gas sweetening process is energy consuming. To analyze its energy efficiency effectively, and look for ways to improve this process, a novel energy‐efficiency evaluation method based on the yield‐energy‐selectivity and efficiency coefficient methods was proposed. First, the yield, energy, and selectivity are selected as evaluation indicators to establish the yield‐energy‐selectivity evaluation model. Then, the coefficient and score of each indicator were determined by using the analytical hierarchy process and efficacy coefficient method, respectively. Finally, the proposed energy‐efficiency evaluation method was applied to the actual high‐sulfur gas sweetening process. The evaluation results were in good agreement with those obtained by actual experiences.     

Microencapsulated melamine phosphate via the sol–gel method and its application in halogen‐free and intumescent flame‐retarding acrylonitrile‐butadiene‐styrene copolymer

In this paper, a facile method is introduced to modify melamine phosphate (MP) via the sol–gel process. The aim was simultaneously to increase the water resistance of MP and improve the dispersion and compatibility of MP in acrylonitrile‐butadiene‐styrene copolymer (ABS). In addition, the incorporation of SiO₂ particles into the MP/dipentaerythritol (DPER) system can further ameliorate the char‐forming ability and enhance the flame retardant properties of polymer composites. The chemical structure and surface morphology of SiO₂@MP were confirmed and observed by Fourier transform infrared (FTIR) spectroscopy, SEM and TEM, respectively. The results demonstrate that ABS/SiO₂@MP/DPER (3/1) at a loading of 30 phr reaches 31.2% limiting oxygen index and achieves a UL‐94 V‐0 rating. Moreover, FTIR spectra indicate that the main char‐forming process of the SiO₂@MP/DPER system occurs at 365–420 °C. A potential condensed flame retardant mechanism of SiO₂@MP and DPER in ABS composites is proposed via the systematic analysis of char residue after combustion by FTIR spectroscopy, SEM and X‐ray photoelectron spectroscopy. © 2015 Society of Chemical Industry     

Calculation methods of heat produced by a lithium‐ion battery under charging‐discharging condition

Lithium‐ion batteries generate considerable amounts of heat under the condition of charging‐discharging cycles. This paper presents quantitative measurements and simulations of heat release. A thermal condition monitoring system was built to obtain the temperature of a lithium‐ion battery under electrical heating conditions. The results have been validated using two independent simulation methods and show that the heat generated by the battery increases with the decrease of the discharge resistance. In addition, although the total amounts of heat release are larger under lower discharge resistance, the rate of heat release is relatively small. Two methods were reported namely analogy method and data‐fitting in order to determine the heat generated by the lithium‐ion battery. The results are crucial findings for risk assessment and management.