Preparation and performance of poly(vinyl butyral) membrane for ultrafiltration

Ultrafiltration membrane was prepared from poly(vinyl butyral). The effects of membrane thickness, polymer concentration, evaporation time, and evaporation temperature, etc., on the performance of the resulting membranes have been studied. Dimethylacetamide was used as a casting solvent. The membrane formed by casting the polymer from a 15 wt % solution and evaporation at 25°C for 30 s had a flux value of 250 cm³ / cm² h (4.8 kg/cm², 26°C) at 92.9% rejection level for dextran sodium sulfate (average mol. wt. 550,000) separation. © 1993 John Wiley & Sons, Inc.     

A polyacrylonitrile-based gelled electrolyte: electrochemical kinetic studies

The bulk and interfacial properties of thin films of a polyacrylonitrile-based (PAN-based) gelled electrolyte, which was tested in conjunction with lithium electrodes, were evaluated at room temperature. The typical composition of the gelled electrolyte (GE) studied was PAN (9.13 wt %); propylene carbonate, or PC (84.87 wt %); and LiBF₄ (6 wt %). A.c. and d.c. measurements were used to determine the bulk conductivity and the interfacial apparent charge-transfer resistance (R _act) of the GE. While the bulk conductivity remains stable at around 10^–3 S cm^–1, the R _act varies initially before reaching a steady value. The steady R _act value obtained from the electrochemical measurements is near 1000 cm². The plating/stripping efficiency of lithium, from potentiostatic and galvanostatic measurements, is 70 to 80%.     

Raman spectroscopic studies of the polyacrylonitrile-zinc complexes in aqueous solutions of zinc chloride and bromide

Raman spectroscopic studies of the dissolution of polyacrylonitrile (PAN) in aqueous zinc halides are reported. The dissociation constants of aqueous PAN-zinc chloride and PAN-zinc bromide containing 60-75% wt/wt and 65-80% wt/wt zinc in aqueous polyacrylonitrile solutions, respectively, have been measured by Raman spectroscopy. Intensity measurements allowed for a quantitative measurement of the amount of free and complexed CN groups to be made, utilising the 2259 and 2290cm^?1 v(CN) stretching Raman bands. The degree of complexation was found to be small in many of the solutions. The effect of the addition of salt on the structure of the v(OH) band at 3000-3800 cm^?1 was studied for the aqueous zinc salts and an aqueous sodium thiocyanate solution. The low wavenumber regions of the Raman spectra, Δv = 100-350cm^?1, for both zinc chloride and zinc bromide solutions of PAN have also been studied.     

Electrochemical co-deposition of ternary Sn–Bi–Cu films for solder bumping applications

This paper reports the co-deposition of Sn–Bi–Cu films using stannic salt bath which has good stability for up to a week. The effect of current density and bath stirring on the film composition and microstructure has been studied. The deposited films are rich in the more noble metal Bi at current densities up to 5 mA cm⁻² but stabilize to about 49 wt. % Bi, 47 wt. % Sn and 4 wt. % Cu at 10 mA cm⁻² and beyond, indicating the effect of limiting current density. There is improvement in the microstructure with stirring or aeration, but the film composition reverts to the Bi rich state, with close to 90 wt. % Bi for deposition at 5 mA cm⁻². This is attributed to the dispersion of Sn²⁺ ions generated at the cathode during the two-step reduction of Sn⁴⁺ ions, due to stirring. The bath is suitable for near eutectic compositions of Sn–Bi with <5 wt. % Cu content.     

Synthesis and study of the chemical stability and strength of zirconium phosphates with the structure of langbeinite with imitators of high-level radioactive waste (HLRW)

Crystalline zirconium phosphates with the langbeinite structure containing macroquantities of elements that imitate high-level radioactive waste (HLRW) (Cs 4.6 wt %, Sr 6.2 wt %, La 10.0 wt %, or U⁴⁺ 11.6 wt %) have been synthesized. To impart finely the dispersed materials with the necessary rheological properties, they have been made more compact with the addition of an 2.4–4.4 wt % aluminophosphate binder. The rate of leaching (logR) of the prepared langbeinite samples in distilled water at room temperature for 100 days decreased to–6.1 (Cs),–5.4 (Sr),–5.5 (La), and–5.6 (U) g/(cm² day) with a noticeable trend toward further reduction, which meets, in practical terms, the requirements for the matrix material used for HLRW management. The samples’ axial compression strengths after leaching tests varied from 600 to 1100 kg/cm².     

Application of liquid gel polymer electrolyte based on chitosan–NH4NO3 for proton batteries

Liquid gel polymer electrolyte (LGPE) based on chitosan, ammonium nitrate, and acetic acid with a ratio of 1.9 : 0.17 : 96.3 wt % gives the highest conductivity of (1.46 ± 0.07) ´ 10⁻¹ S cm⁻¹ at room temperature. This optimized composition of electrolyte is then used in proton batteries with the configuration of Zn + ZnSO₄·H₂O/LGPE/MnO₂. The open circuit voltage of battery is 1.41 V during 48 h of storage. The battery obtained a discharge capacity of 27.90 mA h⁻¹ upon discharge at 1.0 mA current. The maximum power density for the battery is 3.67 mW cm⁻². © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication and characteristics of graphene oxide/nanocellulose fiber/poly(vinyl alcohol) film

Poly(vinyl alcohol) (PVA), PVA/nanocellulose fiber (CNF), and PVA/CNF/graphene oxide (GO) films were prepared simply by casting stable aqueous mixed solutions. FTIR investigation indicated that hydrogen bonding existed between the interface of GO and PVA‐CNF. Scanning electron microscopy and X‐ray diffraction analysis showed that GO was uniformly dispersed in PVA‐CNF matrix. Introducing CNF into PVA caused a significant improvement in tensile strength, and further incorporating GO into PVA/CNF matrix led to a further increase. The tensile strength of the neat PVA film, PVA/CNF composite, and PVA/CNF/GO film (0.6 wt % GO) was 43, 69, and 80 MPa, respectively. Moreover, when incorporating 8 wt % CNF into PVA matrix, O₂ permeability and water absorption decreased from 13.36 to 11.66 cm³/m²/day and from 164.2% to 98.8%, respectively. Further adding 0.6 wt % GO into PVA/CNF matrix resulted in a further decrease of permeability and water absorption to 3.19 cm³/m²/day and 91.2%, respectively. Furthermore, for all composite samples, the transmittance of visible light was higher than 67% at 800 nm. CNF and GO‐reinforced PVA with high mechanical and barrier properties are potential candidates for packaging industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45345.     

Enhanced breakdown strength and energy storage density in a new BiFeO3-based ternary lead-free relaxor ferroelectric ceramic

A new ternary lead-free relaxor ferroelectric ceramic of (0.67-x)BiFeO₃-0.33(Ba_0.8Sr_0.2)TiO₃-xLa(Mg_2/3Nb_1/3)O₃+y wt.% MnO₂+z wt.% BaCu(B₂O₅) (BF-BST-xLMN+y wt.% MnO₂+z wt.% BCB) was prepared by a solid-state reaction method. The substitution of LMN for BF was believed to induce a typical dielectric relaxation behavior owing to the increased random fields. After co-doping MnO₂ and BCB, a significant decrease in the conductivity and grain size was simultaneously realized, resulting in obviously enhanced dielectric breakdown strength and energy-storage performances at room temperature. A high recoverable energy storage density W˜3.38 J/cm³ and an acceptable energy storage efficiency η˜59% were achieved in the composition with x = 0.06, y = 0.1 and z = 2 under a measuring electric field of 23 kV/mm. In addition, the energy-storage performance is quite stable against both frequency (0.1 Hz–100 Hz) and temperature (30–170 °C), suggesting that BF-BST-xLMN+y wt.% MnO₂+z wt.% BCB lead-free relaxor ferroelectric ceramics might be a promising dielectric material for high-power pulsed capacitors.     

Reformulation of bone china body for the reduction of pyroplastic deformation

This work is aimed to decrease the pyroplastic deformation using sodium feldspar and potassium feldspar in bone china revealing the viscosity and crystalline phase effect. For this, we reformulated the traditional bone china recipe considering the amount and ratio of fluxing agents. In the first group, sodium feldspar (coded as Na-F) and potassium feldspar (coded as K-F) were introduced individually into the body from 20 to 35 wt.%. In the second group, we fixed the feldspar amount to 35 wt.% but changed the Na-F/K-F ratio to 1/3–1/2–1/1–2/1–3/1. Optical dilatometry measurements revealed that K-feldspar reduced the sintering temperature by about 50°C compared to Na-feldspar. Densified 35% K-F and 35% Na-F bodies showed very low pyroplastic index (PI) such as 5.36 × 10^–6 cm⁻¹ (at 1150°C) and 7.46 × 10⁻⁶ cm⁻¹ (at 1200°C), respectively, whereas Na-F/K-F 1/3 sample exhibited the lowest PI (3.58 × 10⁻⁶ cm⁻¹) at very low sintering temperature (at 1150°C). Microstructural analysis showed that the dissolution of residual quartz grains and the homogeneity of the distribution of the crystal phases support decrease in pyroplastic deformation.     

Benzene hydroisomerization over Pt/MOR/Al2O3 catalysts

Benzene hydroisomerization is among the promising processes converting benzene into methylcyclopentane (MCP), which is an environmentally friendlier, octane boosting component of motor fuels. Benzene hydroisomerization into MCP over the Pt/MOR/Al₂O₃ (MOR = mordenite) catalytic system is reported here. The dependence of the yield of the target product on the acidic properties of the support and platinum precursor ([Pt(NH₃)₄]Cl₂ or H₂PtCl₆) have been investigated in order to optimize the catalyst composition. The acidic properties of the surface have been altered by introducing 30–95 wt % alumina into the support. Catalytic activity has been measured in the hydroisomerization of cyclohexane and a benzene (20 wt %) + n-heptane (80 wt %) mixture in a flow reactor at 250–350°C, 1.5 MPa, H₂: CH = 3: 1, a cyclohexane LHSV of 6 h^?1, a mixed feedstock LHSV of 2 h^?1, a catalyst bed volume of 2 cm³, and catalyst pellet sizes of 0.25–0.75 mm. The most efficient catalyst for cyclohexane and n-heptane isomerization and benzene hydroisomerization is the platinum-containing catalyst (0.3 wt % Pt) whose support consists of 30 wt % MOR and 70 wt % Al2O3. The highest yield of the target products of isomerization in the presence of this catalyst is attained in the temperature range from 280 to 310°C, which is thermodynamically favorable for MCP formation from benzene. This indicates that this catalyst is promising for the hydroisomerization of benzene-containing gasoline fractions. Use of H₂PtCl₆, a readily available chemical, as the platinum precursor is favorable for commercialization of the catalyst and ensures price attractiveness in its industrial-scale manufacturing.     

Cinetique electrochimique du couple cobalt(III)—cobalt(II) en milieu acide phosphorique concentre

The electrochemical behaviour of the cobalt(III)—cobalt(II) couple in 96.5% and 85 wt% H₃PO₄ have been studied at a stationary gold electrode by using chronopotentiometry and triangular voltamperometry. The results have shown that the Co(III)—Co(II) system is reversible and the electrode reaction involves a single electron. The Co(II) ions' diffusion coefficient in the two phosphoric acid solutions was determined as 4.3 × 10⁻⁸ cm².s⁻ in 96.5% wt % H₃PO₄ and 1.2 × 10⁻⁷ cm².s⁻¹ in 85 wt % H₃PO₄. The stabillity of the Co(III) ion in 96.5 wt % H₃PO₄ media was also investigated.     

Spray-drying of ceramics for plasma-spray coating

The spray-drying process of ceramics which are candidate materials for thermal barrier coatings (TBCs), i.e. 3YSZ+0, 2, 4, 6 wt.% Al₂O₃, is discussed in this paper. The two most important properties of spray-dried powders to determine the coating quality are density and particle size. Polyethyleneimine (PEI) acts as both an organic binder and a dispersant giving low viscosity in the suspension. The optimised suspension composition is: ⩾ 33.6 vol.% powder+1.8 wt.% PEI+ethanol, and operational parameters of the spray-dryer: drying temperature 175°C, feeding rate 55 cm³/min, feeding pressure 1.013×10⁴ Pa.     

Phase behavior and density of polysulfone in binary fluid mixtures of tetrahydrofuran and carbon dioxide under high pressure: Miscibility windows

Mixtures of tetrahydrofuran (THF) and carbon dioxide (CO₂) were identified as new solvent systems for polysulfone. The miscibility and density of polysulfone in binary fluid mixtures of THF and CO₂ were investigated from 300 to 425 K at pressures up to 70 MPa. The influence of the CO₂ and polysulfone concentrations was studied, with the concentrations of the other two components kept constant. At a 4.5 wt % polymer concentration, the demixing pressures in a 10 wt % CO₂ and 90 wt % THF mixture increased with temperature (310–425 K) from 15 to 40 MPa. With increasing CO₂ concentration (from ca. 10 to 14 wt %), a significant increase (from 15 to 70 MPa at 310 K) was observed in the demixing pressures. Furthermore, with an increasing amount of CO₂, the nature of the phase boundary shifted from lower critical solution temperature behavior to upper critical solution temperature behavior. The influence of the polymer concentration was studied in the 0–5 wt % range at two CO₂ levels, with solvent compositions of 10 wt % CO₂ and 90 wt % THF and 13 wt % CO₂ and 87 wt % THF. The system with a higher level of CO₂ (13 wt %) showed highly unusual phase behavior: on pressure–composition and temperature–composition diagrams, the system displayed two distinct regions of miscibility. In the system with 10 wt % CO₂, the distinct regions of miscibility that were observed in the system with 13 wt % CO₂ partially overlapped and led to a W‐shape phase boundary. The densities of the polymer solutions were measured from the one‐phase region through the demixing point into the two‐phase region at a constant temperature. No significant change in density was found around the phase boundary; this indicated that the coexisting phases had similar densities, as is often the case with liquid–liquid phase separation in polymer solutions under high pressure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2357–2362, 2002     

Solid‐state microcellular high temperature vulcanized (HTV) silicone rubber foam with carbon dioxide

A series of microcellular high temperature vulcanized (HTV) silicone rubber foams were prepared using CO₂ as a physical blowing agent. Rheological properties, gas diffusive behavior, and foaming parameters of silicone rubber were investigated. The results show that saturation pressure has a significant effect on the diffusivity of CO₂ in HTV silicone rubber matrix. The gas concentration and diffusivity increase from 2.45 wt % to 3.24 wt %, and from 1.62 × 10^?5 cm²/s to 7.83 × 10^?5 cm²/s as the saturation pressure increases from 2 MPa to 5 MPa, respectively. The value of the gas diffusivity in HTV silicone rubber is almost 1000 times higher than that of the gas diffusivity in polyetherimide (PEI) matrix. Additionally, microcellular HTV silicone rubber foams with the smallest cell diameter of 9.8 μm and cell density exceeding 10⁸ cells/cm³ are achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44807.     

Analysis of proton exchange membrane fuel cell polarization losses at elevated temperature 120 °C and reduced relative humidity

Polarization losses of proton exchange membrane (PEM) fuel cells at 120 °C and reduced relative humidity (RH) were analyzed. Reduced RH affects membrane and electrode ionic resistance, catalytic activity and oxygen transport. For a cell made of Nafion^® 112 membrane and electrodes that have 35 wt.% Nafion^® and 0.3 mg/cm² platinum supported on carbon, membrane resistance at 20%RH was 0.407 Ω cm² and electrode resistance 0.203 Ω cm², significantly higher than 0.092 and 0.041 Ω cm² at 100%RH, respectively. In the kinetically controlled region, 20%RH resulted in 96 mV more cathode activation loss than 100%RH. Compared to 100%, 20%RH also produced significant oxygen transport loss across the ionomer film in the electrode, 105 mV at 600 mA/cm². The significant increase in polarization losses at elevated temperature and reduced RH indicates the extreme importance of designing electrodes for high temperature PEM fuel cells since membrane development has always taken most emphasis.     

Partially Sulfonated Poly(vinylidene fluoride) Induced Enhancements of Properties and DMFC Performance of Nafion Electrolyte Membrane

Partially sulfonated poly(vinylidene fluoride) (SPVdF) has been prepared by incorporation of sulfonic acid groups within poly(vinylidene fluoride), using chlorosulfonic acid as the sulfonating agent. The degree of sulfonation (DS) has been varied by modulating the duration of the sulfonation reaction. Blending of SPVdF (having DS = 36.78%) with Nafion at a constituent wt.% ratio of SPVdF:Nafion = 70:30 has resulted in the fabrication of polymer electrolyte membrane with superior properties compared to pristine Nafion‐117 membrane. This particular blend composition exhibited a proton conductivity value of 3.6 × 10⁻² S cm⁻¹ (i.e. ∼12.5% increase over Nafion‐117), a methanol permeability value of 6.81 × 10⁻⁷ cm² s⁻¹ at 6M methanol concentration (i.e. ∼99.31% decrease from Nafion‐117) and a corresponding membrane selectivity value of 5.29 × 10⁴ Ss cm⁻³ (i.e. an increase of approximately two‐orders of magnitude over Nafion‐117) at 20 °C. In addition, this blend composition has also exhibited (a) better heat stability at temperatures as high as 160 °C by virtue of it possessing higher glass transition temperature, (b) higher storage modulus, (c) higher stress relaxation at high angular frequency and (d) superior DMFC performance at high methanol feed concentration in presence of humidified, as well as, non‐humidified air as the catholyte, compared to Nafion‐117 membrane.     

Preparation of a high-performance Pt–Pd/C-electrocatalyst-coated membrane for ORR in PEM fuel cells via a combined process of impregnation and seeding: Effect of electrocatalyst loading on carbon support

The influence of the electrocatalyst loading (2.0–40.7 wt.%) on a carbon support on its suitability as a cathode for proton-exchange membrane (PEM) fuel cells was evaluated at a constant membrane electrocatalyst loading of 0.15 mg/cm². The results clearly demonstrate that different electrocatalyst loadings on a carbon support in the investigated range significantly affect not only the electrocatalyst activity but also the performance in H₂/O₂ fuel cells. Increasing the electrocatalyst loading on a carbon support led to an increase in the particle size of electrocatalyst and the pore size of the membrane electrode assembly (MEA) but a decrease in the particle size distribution and MEA thickness. The maximum oxygen-reduction reaction (ORR) activity and cell performance (745 mA/cm² and 520 mW/cm² at 0.6 V) were obtained at an electrocatalyst loading of 24.1 wt.% on a carbon support.     

An interpolymer anionic composite reverse osmosis membrane derived from poly(vinyl alcohol) and poly(styrene sulfonic acid)

An interpolymer anionic composite membrane for reverse osmosis was prepared from poly(vinyl alcohol) and poly(styrene sulfonic acid). The effects of composition of a casting solution, heat-curing periods, and casting thickness on the reverse osmosis performance of resulted membranes have been examined. A mixture of water and ethyl alcohol (12/7, wt %) was found to be a proper solvent for casting an interpolymer membrane on the supporter. The composite membrane was formed by casting the polymer solution in ultrathin film on a microporous polypropylene supporter, evaporating the solvent, and heat-curing at 120°C for a proper period. the optimum composition of a casting solution was as follows: wt % of poly(vinyl alcohol)/poly(styrene sulfonic acid)/solvent was 3/2/95. The membrane heat-cured at 120°C for 2 h has a good performance for reverse osmosis, viz., water flux of 9.1–28.4 L/m².h at salt rejection level of 88.1–93.4% under applied pressure of 80 kg/cm² with 0.5% NaCl aqueous solution. The formation mechanism of a water-insoluble membrane was discussed.     

Plasticized chitosan-PVA blend polymer electrolyte based proton battery

This paper focused on the transport studies of PVA-chitosan blended electrolyte system and application in proton batteries. The electrolytes were prepared by the solution cast technique. In this work, 36 wt.% PVA and 24 wt.% chitosan blend doped with 40 wt.% NH₄NO₃ exhibited the highest room temperature conductivity. The conductivity value obtained was 2.07 × 10⁻⁵ S cm⁻¹. EC was then added in various quantities to the 60 wt.% [60 wt.% PVA-40 wt.% chitosan]-40 wt.% NH₄NO₃ composition in order to enhance the conductivity of the sample. The highest conductivity obtained was 1.60 × 10⁻³ S cm⁻¹ for the sample containing 70 wt.% EC. The Rice and Roth model was applied to analyze the conductivity enhancement. The highest conducting sample in the plasticized system was used to fabricate several batteries with configuration Zn//MnO₂. The open circuit potential (OCP) of the fabricated batteries was between 1.6 and 1.7 V.     

Studies on binary and ternary blends of polypropylene with SEBS,PS, and HDPE. I. Melt rheological behavior

Studies are reported on melt rheological behavior of some binary and ternary blends of polypropylene (PP) with one or two of the following polymers: styrene–b-ethylene butylene–b-styrene triblock copolymer (SEBS), polystyrene (PS), and high-density polyethylene (HDPE). Blend composition of the binary blends PP/X or ternary blends PP/X/Y were so chosen that the former represent addition of 10 wt % X to PP while the latter represent 10 wt % addition of X or Y to the PP/Y or PP/X blend of constant composition 90:10 by weight, X/Y being SEBS, PS, or HDPE. Measurements were made on a capillary rheometer using both temperature elevation and constant temperature methods to study the behaviors prior to flow and in the flow region. Flow behavior, measured at a constant temperature (200°C) and varying shear stress (from 1.0 to 5.0 × 10⁶ dyn/cm²) to evaluate melt viscosity and melt elasticity parameters, is discussed for its dependence on the nature of the blend. Extrudate distortion, studied as a function of shear stress to evaluate the critical shear stress for the onset of extrudate distortion, showed differences in the tendency for extrudate distortion or melt fracture of these different blends. Also discussed is the effect of melt viscosity and melt elasticity on extrudate distortion behavior at the critical condition, which showed a unique critical value of the ratio (melt elasticity parameter)^1/2 (melt viscosity) for all these blends. Blend morphologies before and after the flow through the capillary are investigated through scanning electron microscopy, and their correlations with rheological parameters of the melt are discussed.