Modeling of flow‐induced crystallization in blends of isotactic polypropylene and poly(ethylene‐co‐octene)

Poly(ethylene‐co‐octene) (PEOc) has been shown to provide a high toughening contribution to isotactic polypropylene (iPP). The theoretical modeling of flow‐induced crystallization (FIC) of blends of iPP and PEOc is not much reported in the literature. The aim of the present work is to clarify the FIC of iPP upon addition of PEOc in terms of theoretical modeling. The crystallization of iPP and PEOc blends in flow is simulated by a modified FIC model based on the conformation tensor theory. Two kinds of flow fields, shear flow and elongational flow, are considered in the prediction to analyze the influence of flow field on the crystallization kinetics of the polymer. The simulation results show that the elongation flow is much more effective than shear flow in reducing the dimensionless induction time of polymer crystallization. In addition, the induction time of crystallization in the blends is sensitive to the change of shear rate. In comparison with experimental data, the modified model shows its validity for the prediction of the induction time of crystallization of iPP in the blends. Moreover, the simulated relaxation time for the blends becomes longer with increasing percentage of PEOc in the blends. Copyright © 2012 Society of Chemical Industry     

Recycling of reactive dye using semi‐interpenetrating polymer network from sodium alginate and isopropyl acrylamide

A sequence of semi‐interpenetrating polymer network (semi‐IPN) were synthesized by free radical photo copolymerizing acrylic acid and isopropyl acrylamide (NIPAAm) in aqueous sodium alginate (NaAlg). Their structures (FT‐IR), thermal stability (TG/DTG), morphology (SEM), mechanical properties, reactive blue 4 (RB 4) dye adsorption (624 mg/g) and its dying characteristics, reusability of dye and adsorbent were evaluated. TG thermograms of semi‐IPN in air revealed zero order kinetics for initial step thermal degradation with an activation energy of 68.68 kJ/mol. Dye adsorption showed best fit for Langmuir adsorption isotherm and the kinetics followed pseudo‐second‐order model. The water and dye diffusion kinetics followed non‐Fickian mechanism. The changes in thermodynamic parameters namely Gibbs free energy (ΔG°), entropy (ΔS°) and enthalpy (ΔH°) indicated that the adsorption was spontaneous and exothermic process for RB 4/semi‐IPN system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40968.     

Effects of material parameters on the diffusion and sorption properties of wood‐flour/polypropylene composites

Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. Knowledge of moisture uptake and transport properties would be useful in estimating moisture‐related effects such as fungal attack and loss of mechanical strength. Our objectives were to determine how material parameters and their interactions affect the moisture uptake and transport properties of injection‐molded composites of wood‐flour and polypropylene and to compare two different methods of measuring moisture uptake and transport. A two‐level, full‐factorial design was used to investigate the effects and interactions of wood‐flour content, wood‐flour particle size, coupling agent, and surface removal on moisture uptake and transport of the composites. Sorption and diffusion experiments were performed at 20°C and 65 or 85% relative humidity as well as in water, and diffusion coefficients were determined. The wood‐flour content had the largest influence of all parameters on moisture uptake and transport properties. Many significant interactions between the variables were also found. The interaction between wood‐flour content and surface treatment was often the largest. The diffusion coefficients derived from the diffusion experiments were different from those derived from the sorption experiments, suggesting that different mechanisms occur. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 752–763, 2007     

Eu2+‐doped strontium aluminum silicon nitrides having α‐SiAlON and polytypoid structures

Yellow single crystals of aluminum silicon nitrides containing strontium and europium were prepared by heating starting mixtures of Sr₃N₂, Si₃N₄, AlN, and EuN at 2050°C and 0.85 MPa of N₂ for 8 hours. Single‐crystal X‐ray diffraction revealed that prismatic crystals 20‐100 μm in size were Sr_0.31Al_0.62Si_11.38N₁₆:Eu (trigonal, a=7.7937(2) Å, c=5.6519(2) Å, space group P31c), which are isotypic with Sr‐α‐SiAlON, Sr_m/2Al_m+nSi_12?m?nN_16?nO_n, with m=0.62 and n=0. The Eu²⁺ content was approximately 1 at.% of Sr contained in the framework of corner‐sharing (Al/Si)N₄ tetrahedra with an occupancy of 0.154(2). Block‐shaped crystals with a side length of 50‐300 μm were a new polytypoid of Sr‐α‐SiAlON, Sr_2.97Eu_0.03Al₆Si₂₄N₄₀. Streak lines were observed in the direction of the c* axis in the X‐ray oscillation photographs, indicating stacking faults of the structure. The fundamental X‐ray reflections were indexed with a hexagonal cell (a=7.9489(3) Å, c=14.3941(6) Å). The structure was analyzed with a model of space group P in which one of the six Al/Si sites was statistically split into two sites with occupancies of 0.673(5) and 0.227(5). The atomic arrangements in the layers of the structure were similar to those of Sr‐α‐SiAlON, but the stacking sequences of the layers were different. The peak wavelengths and full widths at half maximum of emission spectra measured for the single crystals of Sr_0.31Al_0.62Si_11.38N₁₆:Eu and Sr_2.97Eu_0.03Al₆Si₂₄N₄₀ were 583 nm and 87 nm, and 584 nm and 91 nm, respectively, under 400 nm wavelength light excitation at room temperature.     

Kinetic and thermodynamic investigation of Arthrospira (Spirulina) platensis fed‐batch cultivation in a tubular photobioreactor using urea as nitrogen source

BACKGROUND: Fed‐batch culture allows the cultivation of Arthrospira platensis using urea as nitrogen source. Tubular photobioreactors substantially increase cell growth, but the successful use of this cheap nitrogen source requires a knowledge of the kinetic and thermodynamic parameters of the process. This work aims at identifying the effect of two independent variables, temperature (T) and urea daily molar flow‐rate (U), on cell growth, biomass composition and thermodynamic parameters involved in this photosynthetic cultivation. RESULTS: The optimal values obtained were T = 32 °C and U = 1.16 mmol L^?1 d^?1, under which the maximum cell concentration was 4186 ± 39 mg L^?1, cell productivity 541 ± 5 mg L^?1 d^?1 and yield of biomass on nitrogen 14.3 ± 0.1 mg mg^?1. Applying an Arrhenius‐type approach, the thermodynamic parameters of growth (ΔH* = 98.2 kJ mol^?1; ΔS* = ? 0.020 kJ mol^?1 K^?1; ΔG* = 104.1 kJ mol^?1) and its thermal inactivation ( kJ mol^?1; kJ mol^?1 K^?1; kJ mol^?1) were estimated. CONCLUSIONS: To maximize cell growth T and U were simultaneously optimized. Biomass lipid content was not influenced by the experimental conditions, while protein content was dependent on both independent variables. Using urea as nitrogen source prevented the inhibitory effect already observed with ammonium salts. Copyright © 2012 Society of Chemical Industry     

Alkoxysilane modification of a Ti‐based catalyst system for ethylene dimerization: A step forward in enhancing productivity and selectivity

Alkoxysilanes were used as novel enhancing agents in the Ti‐based catalyst for the highly selective ethylene dimerization to butene‐1. The dimerization of ethylene was carried out using the homogeneous Ti(OBu)₄/THF/TEA/alkoxysilane catalyst system, where Ti(OBu)₄, THF (tetrahydrofuran), TEA (triethylaluminum), and alkoxysilane were used as catalyst, additive, activator, and modifier, respectively. The nature and concentration of alkoxysilanes on the dimerization rate, catalyst yield, by‐products production, and selectivity to butene‐1 were investigated in detail. It was found that the performance of alkoxysilanes assisted with the class of the Ti‐based catalyst system, developed in this work, has been furthered by high productivity and selectivity with respect to the bare catalyst system. It proved that alkoxysilanes could play an excellent improving role in the selective ethylene dimerization process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44615.     

On the inhomogeneous hydration kinetics and stiffness evolution of HNBR‐MgO reactive elastomer composites

Swellable elastomers are widely used in oilfield industry for sealing and zonal isolation applications. These materials need to sustain a large amount of external load after swelling. A newly developed reactive hydrogenated nitrile butadiene rubber (HNBR) based elastomer composite with magnesium oxide (MgO) as filler can swell and stiffen when exposed to water, which makes it ideal for oil field applications. However, both the filler hydration and the stiffness evolution inside this composite material are observed to be highly inhomogeneous even for samples on the length scale of millimeters. To understand this coupled diffusion‐hydration process is critical for applications of these materials with larger length scales. In this work, the hydration kinetics and stiffness evolution of the HNBR‐MgO composite are quantitatively studied on microscopic level. The extent of MgO hydration along the thickness of the sample are measured at the different stage of swelling. These results are used to determine the diffusion coefficient of water inside the composite. The diffusivity increases orders of magnitude after the filler hydration. In addition, the modulus change is non‐proportional to the degree of filler hydration as demonstrated by instrumented grid indentation on the hydrated composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43420.     

Preparation and surface properties of core‐shell polyacrylate latex containing fluorine and silicon in the shell

The core‐shell polyacrylate latex particles containing fluorine and silicon in the shell were successfully synthesized by a seed emulsion polymerization, using methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, dodecafluoroheptyl methacrylate (DFMA), and γ‐(methacryloxy) propyltrimethoxy silane (KH‐570) as functional monomers. The influence of the amount of fluorine and silicon monomers on the emulsion polymerization process and the surface properties of the latex films were discussed, and the surface free energy of latex films were estimated using two different theoretical models. The emulsion and its films were characterized by particle size distribution (PSD) analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹⁹F‐NMR) spectrometry, contact angle (CA) and X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. The results indicate that the average particle size of the latex particles is about 160 nm and the PSD is narrow, the synthesized latex particles exist with core‐shell structure, and a gradient distribution of fluorine and silicon exist in the latex films. In addition, both the hydrophobicity and thermal stability of the latex films are greatly improved because of the enrichment of fluorine and silicon at the film‐air interface, and the surface free energy is as low as 15.4 mN/m, which is comparable to that of polytetrafluoroethylene (PTFE). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Determination of sorption kinetic parameters using the relaxation‐dependent solubility model in the methanol vapor—Poly(methyl methacrylate) system

The relaxation‐dependent solubility model was applied to simulate the experimentally observed sorption kinetic behavior of the PMMA–vapor MeOH system at 25°C, to obtain the main transport parameters. Application of the model in series of successive sorption kinetic runs covering small concentration intervals revealed certain trends in the concentration dependence of the diffusion coefficient of the system, not detectable by a previous simpler analysis of the data. Following excess free volume fill up, relaxation frequencies exhibit a weak exponential dependence on concentration. The functional dependence of the thermodynamic diffusivity on the concentration, deduced from the aforementioned simulation procedure, was tested and found to reproduce reasonably well the series of sorption kinetic runs covering considerably larger concentration intervals. In addition, this analysis indicates a strong dependence of the relaxation mechanism on the concentration interval. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2278–2288, 2006     

Modeling the effect of fineness and filler in early‐age hydration of tricalcium silicate

Alite (impure C₃S) being the major and most reactive phase in ordinary portland cement has been studied extensively. This paper focuses on the mathematical modeling of new hypothesis developed, densified volumetric growth, applied to the main hydration peak in alite hydration. This hypothesis assumes a time and particle size‐dependent growth rate and densification rate of C–S–H controlled by its internal surface area. To test this hypothesis, a new microstructural modeling platform (Cementitious Reactions Simulator) has been developed. The model was used to calibrate and predict the isothermal calorimetric results from the literature and two sets of original experimental results with alite replaced with different replacement fractions of quartz, fly ash, and slag of different fineness. The model is able to capture and predict the effect of fineness and fillers without the need of varying the parameters for the particular set of simulations. The values of the parameters of simulation reflect the current experimental evidence from the literature and thus provide validation of the hypothesis which suggests that the main hydration period including deceleration period in the alite hydration is induced by the densification and reducing outer growth rate of C–S–H.     

Reaction kinetics of 2‐((2‐aminoethyl) amino) ethanol in aqueous and non‐aqueous solutions using the stopped‐flow technique

Observed pseudo‐first‐order rate constants (k_o) for the reaction between CO₂ and 2‐((2‐aminoethyl) amino) ethanol (AEEA) were measured using the stopped‐flow technique in an aqueous system at 298, 303, 308 and 313 K, and in non‐aqueous systems of methanol and ethanol at 293, 298, 303 and 308 K. Alkanolamine concentrations ranged from 9.93 to 80.29 mol m^?3 for the aqueous system, 29.99–88.3 mol m^?3 for methanol and 44.17–99.28 mol m^?3 for ethanol. Experimentally obtained rate constants were correlated with two mechanisms. For both the aqueous‐ and non‐aqueous‐AEEA systems, the zwitterion mechanism with a fast deprotonation step correlated the data well as assessed by the reported statistical analysis. As expected, the reaction rate of CO₂ in the aqueous‐AEEA system was found to be much faster than in methanol or ethanol. Compared to other promising amines and diamines studied using the stopped‐flow apparatus, the pseudo‐first‐order reaction rate constants were found to obey the following order: PZ (cyclic‐diamine) > EDA (diamine) > AEEA (diamine) > 3‐AP (primary amine) > MEA (primary amine) > EEA (primary amine) > MO (cyclic‐amine). The reaction rate constant of CO₂ in aqueous‐AEEA was double that in aqueous‐MEA, and the difference increased with an increase in concentration. All reaction orders were practically unity. With a higher capacity for carbon dioxide and a higher reaction rate, AEEA could have been a good substitute to MEA if not for its high thermal degradation. AEEA kinetic behaviour is still of interest as a degradation product of MEA. © 2012 Canadian Society for Chemical Engineering     

A Quasi‐Steady State Shell and Shrinking Core Approach to the Drying of Porous Particles and an Example of Parameter Identification

A quasi‐steady state shell and shrinking core approach which recognizes heat and mass transfer resistances in both the gas and particle phases for drying of a porous particle is proposed. A mean field model (constant properties) using this approach was embedded in a spreadsheet combined with a genetic algorithm for parameter identification to provide an easy means of characterizing the drying process from drying data. In drying, assuming a mean field, four major parameters are typically unknown: two related to the process (heat and mass transfer coefficients) and two which incorporate porous particle properties (shell thermal conductivity and vapour diffusivity). It is shown how these four parameters may be determined from experimental drying data. The model was applied to data for spouted bed drying of rice. For the particular case studied, external heat transfer was found to be the controlling mode, although resistance to moisture diffusion within the particle is important. The approach presented admits of future refinements to improve its scope and utility.     

Formula and process optimization of controlled‐release microcapsules prepared using a coordination assembly and the response surface methodology

A model chlorpyrifos microcapsule was prepared using coordination assembly between Fe³⁺ and tannic acid (TA). The influence of independent variables such as the dropping rate of TA (X₁) and Fe³⁺ (X₃), the concentration of TA (X₂) and Fe³⁺ (X₄), and the reaction temperature (X₅) on the encapsulation efficiency (R₁) and release characteristics (R₂) of the microcapsule had been investigated, based on a central composite design with five factors and five levels. The results showed that the main factors influencing R₁ and R₂ were X₄ and X₂, then the interaction between X₂ and X₄, followed by X₅ and X₃. The optimal formula mainly based on higher R₁ and lower R₂ were determined and then tested. The optimized conditions led to an encapsulation efficiency and cumulative release proportion of 97.12% ± 0.72% and 40.07% ± 0.53%, along with the average relative errors of predicted values being 1.78% and ?1.60%, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42865.     

Effect of surface modification on the interface quality between hemp and linear medium‐density polyethylene

In this work, hemp fibers (mercerized or not) were modified by a coupling agent (maleated polyethylene) to evaluate the level of interfacial improvement related to wettability or adhesion in LMDPE composites. To do so, different analyses in the solid (thermogravimetric analysis, dynamic mechanical analysis, and scanning electron microscopy) and melt (rheology) states were combined. From the results obtained, it can be shown that mercerization mostly controls the level of wettability (physical contact) of the fibers, while the addition of a coupling agent mostly controls interfacial adhesion (chemical interactions). These conclusions were obtained based on shifts in transition temperatures (T_g and T_α), as well as maxima in van Gurp–Palmen plots. Overall, the best properties were obtained when mercerization was combined with coupling agent addition under optimized processing conditions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43802.     

Predicting the thermodynamic properties and dielectric behavior of electrolyte solutions using the SAFT‐VR+DE equation of state

We extend the SAFT‐VR+DE equation of state to describe 19 aqueous electrolyte solutions with both a fully dissociated and a partially dissociated model. The approach is found to predict thermodynamic properties such as the osmotic coefficient, water activity coefficient, and solution density, across different salt concentrations at room temperature and pressure in good agreement with experiment using only one or two fitted parameters. At higher temperatures and pressures, without any additional fitting, the theory is found to be in qualitative agreement with experimental mean ionic activities and osmotic coefficients. The behavior of the dielectric constant as a function of salt concentration is also reported for the first time using a statistical associating fluid theory (SAFT)‐based equation of state. At high salt concentrations, the stronger electrostatic interactions between the ionic species due to the dielectric decrement, is captured through the inclusion of ion association. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3053–3072, 2015     

Fabrication and characterization of polymer composites surface coated Fe3O4/MWCNTs hybrid buckypaper as a novel microwave‐absorbing structure

A naval hybrid buckypaper was fabricated by vacuum filtration method with monodispersion solution of Fe₃O₄ decorated Multiwalled carbon nanotubes (MWCNTs). The morphology, element composition and phase structure of hybrid buckypaper were characterized by field‐emission scanning electron microscope, energy dispersive spectrometer, and X‐ray diffraction. The microwave absorption and complex electromagnetic properties of the composites surface coated MWCNTs buckypaper (or Fe₃O₄/MWCNTs hybrid buckypaper) have been investigated in the frequency range of 8–18 GHz. The results indicate that the microwave absorption properties of composite structure have been evidently improved due to the Fe₃O₄/MWCNTs hybrid buckypaper' high magnetic loss and suitable dielectric loss properties. The reflection loss of composite surface coated Fe₃O₄/MWCNTs hybrid buckypaper (with a matching thickness d = 0.1 mm) is below ?10 dB in the frequency range of 13–18 GHz, and the minimum value is ?15.3 dB at 15.7 GHz. Thus, Fe₃O₄/MWCNTs hybrid buckypaper can become a promising candidate for electromagnetic‐wave‐absorption materials with strong‐absorption, thin‐thickness and light‐weight characteristics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41974.     

Enhanced photoluminescence property and mechanism of Eu3+‐doped tellurite glasses by the silver and gold nanoparticles

In this work, the silver or gold nanoparticle single‐existing and co‐existing tellurite glasses doped with Eu³⁺ were prepared, and the influence of gold or silver nanoparticles on the photoluminescence of tellurite glasses doped with Eu³⁺ were investigated. The photoluminescence of tellurite glasses doped with Eu³⁺ was enhanced by the surface plasmon absorption of gold or silver nanoparticles, and the maximum luminescence enhancement factors caused by the silver and gold nanoparticles are 4.8 and 3.5 factors, respectively. The differentiation of luminescence enhancement mechanisms caused by the gold or silver nanoparticles was demonstrated. The enhanced luminescence mechanism of the Au nanoparticle single‐existing tellurite glasses doped with Eu³⁺ was from the increasing of radiative decays rate caused by the Au nanoparticles. The excitation field enhancement caused by the Ag nanoparticles was responsible for the luminescence enhancement of the Ag single‐existing tellurite glasses doped with Eu³⁺. About 4.2‐factor luminescence enhancement was observed in the Ag and Au nanoparticle co‐existing tellurite glasses doped with Eu³⁺, which is attributed to the increasing of radiative decays rate and excitation field enhancement caused by the Au and Ag nanoparticles.     

Study on the modification of epoxy resin by a phosphorus‐ and silica‐containing hybrid

A novel phosphorus‐ and silica‐containing hybrid (DPS) was synthesized by the reaction between diethyl phosphate (DEP) and polyhedral oligomeric siloxanes (POS) formed by hydrolysis condensation of 3‐glycidoxypropyltrimethoxysilane (GPTMS). The novel phosphorus‐ and silica‐containing hybrid was characterized by the flourier transform infrared spectroscope (FT‐IR), silicon nuclear magnetic resonance, and gel permeation chromatography (GPC). Then, the determination of the activation of the reaction between epoxy resin and phosphorus‐, and silica‐containing hybrids was studied by differential scanning calorimeter (DSC). In the presence of catalyst, the activation energies of the curing reaction were 63.3 and 66.7 kJ/mol calculated by Kissinger model and Ozawa model respectively. The thermal and flame retardant properties of the cured epoxy modified by DPS were determined by differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), and limited oxygen index (LOI). The results revealed that those properties were improved in comparison with unmodified epoxy resin. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of the cured epoxy resin modified by DPS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011