Morphology and properties of Nafion membranes prepared by solution casting

In this study, dilute Nafion solutions consisting of solvents with various dielectric constants ? and solubility parameters δ, i.e. N,N′-dimethyl acetamide, N,N′-dimethyl formamide, N-methyl formamide, methanol-water mixture (4/1 g/g), ethanol-water mixture (4/1 g/g), and isopropanol-water mixture (4/1 g/g), were freeze dried and the conformations of Nafion molecules in dilute solutions were observed using transmission electron microscope. The membranes were prepared by solution casting from these solutions and evaporating the solvents at temperatures below T_G of Nafion, then annealing the membranes at 150 °C which was ∼50 °C above T_G of Nafion. We show Nafion molecular conformations in dilute solutions are strongly influenced by δ and ? of solvents. And, thus the morphology, water uptake, proton conductivity, and methanol permeability of membranes prepared by solution casting are also influenced by δ and ? of solvents.     

Effect of different compatibilizers on the mechanical and thermal properties of starch/polypropylene blends

Starch was treated with three kinds of compatibilizers (coupling agents or modifying agents), KH‐550, KH‐570, and glycerin monostearate. Blends of polypropylene (PP) and treated starch were prepared by a twin‐screw extruder. The effects of the starch before and after treatments and the kinds and contents of the compatibilizers on the mechanical and thermal properties of the PP/starch blends were investigated in this study. We found that the mechanical properties (tensile strength, impact strength, and elongation at break) of the blends were obviously improved with increasing content of different kinds of compatibilizers. Meanwhile, the most significant improvement in the mechanical properties was obtained in the samples containing just a 1 wt % loading of compatibilizers, and KH‐570 had the best improved effects among the different kinds of compatibilizers. The results of thermogravimetric analysis demonstrate that to some extent, the thermal stability of the PP/starch blends was improved after the addition of compatibilizers. Scanning electron microscopy showed that the dispersion of starch in the PP matrix and adhesion between the starch and PP matrix were obviously improved after the addition of compatibilizers. KH‐570 not only had the best improved effects among the coupling agents but also still acted as a similar plasticizer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43332.     

Effect of plastic fats on thermal stability and mechanical properties of fat- protein gel products

Meat was comminuted with soybean-oil-based plastic fats of differ-ent physical properties and cooked at 2 different rates. Thermal stability of emulsion was inversely related to fat softness and heating rate. Stable emulsions were obtained when prepared with fat containing 30% solids at 16% product fat level, 40% solids at 22% level, and 50% solids at 28% level. Release of fat and water upon heating commenced about 10 C below the softening point of the fat. Compressive force (CF) increased markedly and shear force (SF) increased moderately with increasing hardness of fat Both CF and SF reached a maximum at the 40% fat solids level. Increased total fat tended to reduce mechanical strength. Faster heating resulted in greater mechanical strength of cooked product but caused fat separation in high fat products formulated with soft fats.     

Influence of chain flexibility and crosslink density on mechanical properties of epoxy/amine networks

Blends of a bisphenol A diglycidyl ether prepolymer and an aliphatic diepoxy diluent crosslinked with a cycloaliphatic diamine were studied. These model networks have the characteristic that the crosslink density and the chain flexibility increase with the amount of diluent. These combined effects were studied by observing their mechanical properties. The decreases in the Young's modulus and the ultrasonic modulus were associated with the secondary thermomechanical relaxations that have been recorded and identified. Pre-plastic and plastic behaviors were discussed in terms of flexibility and crosslink density. A linear relationship was established between pre-plastic activation volume and crosslink density at temperatures lower than the activation of molecular chain motions responsible for the sub-T_g relaxations. At 0°C, a temperature above these secondary transitions, the higher the flexibility, the more defect nucleation and propagation increased. The work hardening rate and the upper yield stress decreased as the amount of diluent was increased. Fracture toughness was improved as the amount of diluent was increased. Crack propagation was related to the ability of the networks to deform plastically.     

Effect of different nanoparticles on thermal,mechanical and dynamic mechanical properties of hydrogenated nitrile butadiene rubber nanocomposites

Organically modified and unmodified montmorillonite clays (Cloisite NA, Cloisite 30B and Cloisite 15A), sepiolite (Pangel B20) and nanosilica (Aerosil 300) were incorporated into hydrogenated nitrile rubber (HNBR) matrix by solution process in order to study the effect of these nanofillers on thermal, mechanical and dynamic mechanical properties of HNBR. It was found that on addition of only 4 phr of nanofiller to neat HNBR, the temperature at which maximum degradation took place (T_max) increased by 4 to 16°C, while the modulus at 100% elongation and the tensile strength were enhanced by almost 40–60% and 100–300% respectively, depending upon nature of the nanofiller. It was further observed that T_max was the highest in the case of nanosilica‐based nanocomposite with 4 phr of filler loading. The increment of storage modulus was highest for sepiolite‐HNBR and Cloisite 30B‐HNBR nanocomposites at 25°C, while the modulus at 100% elongation was found maximum for sepiolite‐HNBR nanocomposite at the same loading. A similar trend was observed in the case of another grade of HNBR having similar ACN content, but different diene level. The results were explained by x‐ray diffraction, transmission electron microscopy, and atomic force microscopy studies. The above results were further explained with the help of thermodynamics. Effect of different filler loadings (2, 4, 6, 8, and 16 phr) on the properties of HNBR nanocomposites was further investigated. Both thermal as well as mechanical properties were found to be highest at 8 phr of filler loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystal structure, thermal flexibility and structural transformations of tin umbite and copper exchanged tin umbite prepared from clear solution

For the first time tin silicate with umbite structure K₂SnSi₃O₉·H₂O (AV-6) has been prepared from clear solution using SnCl₂ as a source of tin. In situ high temperature powder X-ray diffraction study of AV-6 and its copper ion exchanged form K_0.98Cu_0.51SnSi₃O₉·2H₂O (Cu-AV-6) has been performed. Rietveld refinement revealed that the ion exchange with copper alters the initial orthorhombic structure into monoclinic one. In this way the temperature stable framework of AV-6 has been transformed into thermally flexible material that can be contracted at 200 °C and preserved at ambient conditions. At higher temperatures (300–700 °C) the structure gradually amorphisize and at 750 °C it transforms into nanosized cassiterite type solid. We also study the structural reversibility and the influence of the dehydration process on the dimensions of the both structures.     

高温溶液法制备SBR的结构和性能研究

以正丁基锂（n-BuLi）为引发剂、醚类化合物为调节剂、环己烷／正己烷为溶剂,采用阴离子高温聚合工艺合成了溶聚丁二烯／苯乙烯橡胶（SSBR）。通过GPC、NMR分别测试了SSBR的相对分子质量及其分布和微观结构;并对硫化胶性能和门尼粘度进行了测定。考察了调节剂、温度等因素对SSBR的相对分子质量及其分布、共聚物微观结构、序列分布以及动态力学性能和物理机械性能的影响。研究结果表明：所用调节剂是有效的SSBR高温聚合调节剂,可很好地调节SSBR中的乙烯基含量,获得微观结构适中的中高乙烯基丁苯共聚物;n（调节剂）／n（Li）对聚合速率及共聚物的1,2-结构含量有明显的影响,但对共聚物的相对分子质量分布无明显影响;温度对共聚物的转化率及微观结构均有一定的影响。     

Effect of silver content on the microstructure,thermal stability and mechanical properties of CrNx/Ag nanocomposite films

CrN_x/Ag nanocomposite films with varying Ag content were prepared by reactive magnetron sputtering under a constant Ar/N₂ stream. The films were annealed between 500 – 800 °C in the air. The microstructure and elemental composition of films were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The mechanical properties were characterized with respect to nano-hardness and high-temperature tribology. The results reveal that the incorporation and concentration of Ag influence the morphology and microstructure of films. The microstructure of films evolves by annealing, and the films with higher Ag concentration exhibit more severe structure evolution. Annealing at 650 °C results in the sublimation of Ag, and the oxide emerges on the film surface. Annealing at 800 °C reveals that the film with 6.2 at.% Ag exhibits superior structural stability, while the one with 20.2 at.% Ag deteriorates. The hardness of films decreases with the increasing Ag concentration and heating temperature. Films with 12.6 at.% Ag and above possess solid lubrication during the sliding at 350–650 °C. Both the friction coefficient and wear resistance are found dependent on the Ag concentration and sliding temperature.     

Improvement of the mechanical and thermal properties of silica‐filled polychloroprene vulcanizates prepared from latex system

In this work, well‐dispersed silica suspension having excellent storage stability was prepared by using an ultrasonic probe. The obtained silica suspension and curatives were added into the polychloroprene (CR) latex for preparing silica‐filled CR latex compounds having various silica loadings. Then, the silica‐filled CR vulcanizates were prepared via a dipping process. The thermal and mechanical properties of the dipped CR vulcanizates containing silica dispersed by using an ultrasonic probe were compared with those of the dipped CR vulcanizates containing silica dispersed by using a mechanical stirrer. By using thermogravimetric analysis, it could be seen that thermal resistance of the dipped CR films having silica prepared by ultrasonic probe is greater than that prepared by using the mechanical stirrer. This result corresponds well with their tensile strength after aging in the hot‐air oven. In addition, modulus, tensile strength, and tear strength of the vulcanizates prepared from CR latex compounds containing silica prepared by using the ultrasonic probe are obviously greater than those prepared by using the mechanical stirrer, especially at high silica loading. This is because the silica prepared using the ultrasonic probe is uniformly distributed and dispersed throughout the CR matrix, as can be observed in the scanning electron microscope micrographs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of marine sediments on the mechanical properties and thermal stability of proteinic biopolymer

This article focuses on the valorization of marine sediments (MS) in proteinic biopolymer (HE) that will generate HEMS biocomposites. These biocomposites were developed with various percentages of marine sediments (0%, 5%, 15%, and 20%) and characterized. Mechanical properties were examined as a function of the contents of used marine sediments. The flexural and compressive modulus increase with the rise of the MS percentage in the composite. The compressive strength increases while the flexural and tensile strengths decrease. Furthermore, the HEMS composite was characterized using Fourier transform infrared spectroscopy and by using scanning electron microscopy. And the thermal degradation behavior of the composite was investigated by thermogravimetric analysis coupled with differential scanning calorimetry. POLYM. COMPOS., 38:1624–1630, 2017. © 2015 Society of Plastics Engineers     

Structure,thermal stability,electrochemical behaviors,and mechanical properties of organosoluble polyimide with pyrimidine ring in the main chain

A novel organosoluble polyimide (PI) with pyrimidine ring in the main chain was synthesized by chemical and thermal imidization, respectively, from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride and 2,4‐diamino‐6‐chloropyrimidine as raw materials and its molecular structure, solubility, UV–visible absorption characteristic, crystallinity, thermal stability, electrochemical behaviors, and mechanical properties were also studied. It was found that the introduction of pyrimidine ring in the main chain could increase the solubility of PI in polar aprotic solvents at room temperature and 60 °C, respectively, because of its molecular main chain with asymmetric structure and two polar N atoms in pyrimidine ring. Furthermore, PI had strong optical absorption peak intensity, excellent thermal stability, good redox reversibility, especially outstanding mechanical properties, which were conductive to its potential applications in adhesives, polyelectrolyte, separation membrane, and so on. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43680.     

Effect of fillers on thermal and mechanical properties of polyurethane elastomer

The effects of five different types of fillers on the thermal and mechanical properties of hydroxyl-terminated polybutadiene-based polyurethane elastomers were explored to develop a filled polyurethane elastomeric liner for rocket motors with hydroxyl-terminated polybutadiene-based composite propellants. Two type of carbon black, silica, aluminum oxide, and zirconium(III) oxide were used as filler. Based on the improvement in the tensile properties and the erosion resistance achieved in the first part of the study, an ISAF-type carbon black was selected to be used as the main filler in combination with an additional filler. The second part involves the investigation of polyurethane elastomers containing a second filler in various amounts in addition to the ISAF-type carbon black used as the main filler. In addition to the thermal and mechanical properties, the processability of the uncured polyurethane mixtures were also explored by measuring the viscosity in this second part of the study. The studied fillers do not considerbly change the thermal degradation temperatures and the thermal conductivity of the polyurethane elastomers with a filler content up to 16 wt %. The best improvement in the erosion resistance and tensile strength of the polyurethane elastomers with additional fillers is also achieved when filled with the ISAF-type carbon black, whereas the use of zirconium(III) oxide as additional filler provides almost no improvement in these properties. Viscosity of the uncured polyurethane mixtures increases with the increasing filler content and with the decreasing particle size of the filler. Aluminum oxide-filled elastomers seem to be the most suitable compositions having sufficiently high thermal and mechanical properties, together with the processability of uncured mixtures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1057–1065, 1998     

Effect of Ba concentration on phase stability and mechanical and thermal properties of La2Mo2O9

Ba-substituted La₂Mo₂O₉ ((La_1−xBa_x)₂Mo₂O_9−δ, x = 0–0.12) was prepared and the thermal and mechanical properties were evaluated. The thermal expansion coefficients (TECs) were determined from high-temperature X-ray diffraction (XRD) analysis. Phase transition in La₂Mo₂O₉ was suppressed via substitution of Ba for La, as demonstrated by differential scanning calorimetry (DSC) analysis. The mechanical properties, such as the bulk modulus, shear modulus, Young’s modulus, compressibility, and Debye temperature were evaluated from the measured sound velocities. The thermal conductivity was evaluated from the thermal diffusivity, heat capacity, and density in the temperature range from room temperature to 1073 K. The thermal conductivity decreased with increasing Ba content. Theoretical calculations based on the Klemens–Callaway model were performed to analyze the thermal conductivity, and the results suggest that the reduction of the thermal conductivity was mainly attributed to oxygen defects in the anion sublattice of La₂Mo₂O₉.     

硫酸铵溶液对混凝土碳化及力学性能的影响研究

将混凝土标准试块分组放入清水和浓度分别为2.5%和5%的硫酸铵溶液中,浸泡28 d后取出烘干,在实验室进行快速碳化实验、回弹实验和抗压强度实验,分析研究硫酸铵溶液浓度对混凝土碳化及抗压强度的影响规律。制定了2.5%和5%两种浓度硫酸铵溶液环境下混凝土专用测强曲线,误差范围满足规范要求,可供实际工程参考。     

硫酸铵溶液对混凝土碳化及力学性能的影响研究

将混凝土标准试块分组放入清水和浓度分别为2.5%和5%的硫酸铵溶液中,浸泡28 d后取出烘干,在实验室进行快速碳化实验、回弹实验和抗压强度实验,分析研究硫酸铵溶液浓度对混凝土碳化及抗压强度的影响规律。制定了2.5%和5%两种浓度硫酸铵溶液环境下混凝土专用测强曲线,误差范围满足规范要求,可供实际工程参考。     

Removal of metal ions from an acidic leachate solution by nanofiltration membranes

This paper presents the feasibility of the application of two commercial nanofiltration (NF) membranes (Desal5 DK and NF-270) in the removal of metal ions from an acidic leachate solution generated from a contaminated soil using H₂SO₄ as a soil washing agent. The experimental results of soil washing indicated that H₂SO₄ is highly effective in removing metal ions from contaminated soil. Following this process, the treatment of this acidic solution by nanofiltration membranes showed good metal ion rejection (between 62% to 100%) where divalent ions were better rejected than monovalent ions. For characterization purposes, the membrane experiments were conducted using K₂SO₄ solutions at different pHs. Membrane performance criteria were evaluated according to membrane permeability and ionic retention in the tank and permeate, taking into account different operating conditions such as pressures, flow rate and pH. These results demonstrated the effectiveness and feasibility of the application of nanofiltration treatments in the cleaning-up of contaminated water residues generated during soil washing processes.     

Effect of conductive polyaniline in thermoplastic natural rubber blends on the mechanical,thermal stability,and electrical conductivity properties

This research was conducted to fabricate thermoplastic natural rubber/polyaniline (TPNR/PANI) blends via melt blending method using an internal mixer and followed by compression molding. The effects of PANI contents between 1 and 5 wt % PANI in the TPNR blends on the mechanical properties, thermal stability, electrical conductivity (impedance), and morphology observation were investigated. The TPNR/3 wt % PANI sample exhibited the highest tensile strength (3.7 MPa), elongation at break (583%), flexural strength (1.8 MPa), flexural modulus (37.0 MPa), and impact strength (7.1 kJ m⁻²). From the aspect of thermal properties, it was found that with the addition of PANI, the thermal stability of the TPNR/PANI increased. Comparing to nonconductive TPNR sample, the incorporation of PANI promoted the electrical conductivity characteristic to PANI-filled TPNR blends which showing a magnitude order of 10⁻⁹ S cm⁻¹. Scanning electron microscopy micrograph revealed the good distribution of PANI at the optimum content (3 wt % PANI) in the TPNR blends and the good interaction between TPNR and PANI. It can be concluded that the TPNR blends incorporated with a low loading of PANI could be a newly good conductive material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47527.     

ZrB2-based solid solution ceramics and their mechanical and thermal properties

Zirconium diboride ceramics as one of the main members of ultrahigh-temperature ceramics are capable of being used as structural components at ultrahigh temperatures. Entropy adjusting is a newly developed approach to improving the properties of ceramics. In this work, a series of ZrB₂-based solid solution ceramics with different mixing entropies, formulated (Zr_xTi_yNb_yTa_y)B₂ (x = .25, .85, .925, .9625, 1; x + 3y = 1), were prepared by adjusting the content of other diborides. Diboride solid solution powders were synthesized by boro/carbothermal reduction process and then densified by spark plasma sintering. The results show that the formation of a single-phase solid solution is independent of the mixing entropy in (Zr_xTi_yNb_yTa_y)B₂ system. The addition of other diborides into ZrB₂ is beneficial to reduce the particle size of the synthesized powder and promote the densification process. The dense sintered samples with higher mixing entropy have finer grain size, higher hardness, and modulus. The (Zr_0.25Ti_0.25Nb_0.25Ta_0.25)B₂ ceramic has the highest hardness of 31 GPa and a modulus of 682 GPa. Severe lattice distortion in samples with higher mixing entropy will result in increased phonon scattering and lower thermal conductivity.     

Effect of SiC nanowires on the mechanical properties and thermal conductivity of 3D-SiCf/SiC composites prepared via precursor infiltration pyrolysis

In this study, SiC nanowires (SiC_NWS) were grown in situ on the surface of PyC interface through chemical vapor infiltration (CVI) to improve the mechanical characteristics and thermal conductivity of three-dimensional SiC_f/SiC composites fabricated via precursor infiltration pyrolysis (PIP). The effect of SiC_NWS on the properties of the obtained composites was investigated by comparing them with conventional SiC_f/PyC/SiC composites. After the deposition of SiC_NWS, the flexural strength of the SiC_f/SiC composites was found to increase by 46 %, and the thermal conductivity showed an obvious increase at 25?1000 °C. The energy release of the composites in the damage evolution process was analysed by acoustic emission. The results indicated that the damage evolution process was delayed owing to the decrease in porosity, the crack deflection and bridging of the SiC_NWS. Furthermore, the excellent thermal conductivity was attributed to the thermally conductive pathways formed by the SiC_NWS in the dense structure.     

Effect of the thermal history of polymers on their dynamic mechanical properties

A torsion pendulum was used to compare quenched and annealed specimens of representative polymers with respect to their dynamic mechanical properties. Among amorphous polymers, the effects of thermal history appear to be both moderate and similar for different polymers. For some crystalline polymers, the effects of thermal history are again moderate. However, the effects are very great in one of the crystalline polymers selected, presumably because it is easily supercooled below its melting point.