Mechanical and Morphological Properties of PP/LLPDE/NR Blends—Effects of Polyoctenamer

In this study, impact-modified polypropylene (PP) ternary blends based on PP/natural rubber (NR)/linear low-density polyethylene (LLDPE) with ratios of 72/10/18 and 64/20/16 were produced by a twin-screw extruder with polyoctenamer (TOR) as the compatibilizer. The mechanical properties of the blends were determined on injection-molded specimens in tensile, flexural, and impact testing. The impact strength and elongation at break of the blend increased significantly while the flexural modulus and tensile strength decreased slightly with increasing TOR content. The impact strength improved with the increasing TOR due the increase of interfacial adhesion resulting in finer dispersion of the rubbery minor phase in the PP matrix. The improvement in compatibility with the addition of TOR into PP/NR/LLDPE blends is being supported by both scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA).     

Preparation and properties of SEBS/PP/OMMT nanocomposites

SEBS/PP/OMMT纳米复合材料的制备及性能庞绍龙1,2,王霞1,杨帆2(1.上海应用技术学院材料工程系,上海200235;2.华东师范大学化学系,上海200062)通过对蒙脱土的有机化处理,利用熔融插层的方法制备了苯乙烯-乙烯/丁烯-苯乙烯三嵌段聚合物(SEBS)/聚丙烯(PP)/有机蒙脱土(OMMT)纳米复合材料,对其结构、热性能及力学性能进行了研究。结果表明,少量有机化蒙脱土能够大幅度提高SEBS中聚苯乙烯嵌段的玻璃化转变温度,而对材料的力学性能影响很小。     

Characterization of MgMnxFe2?xO4 as a possible cathode material for electrochemical reduction of NOx

Spinel-type oxides of MgMn _x Fe_2−x O₄, x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, were synthesized as a solid state reaction and characterized with dilatometry and resistivity measurements up to 1000 °C. Results showed a general decrease of the linear expansion and an increase in conductivity as a function of the Mn content. Point electrodes were analyzed from 300 to 600 °C in a pseudo-three-electrode setup in 1% NO, 1% NO₂, and 10% O₂ using cyclic voltammetry. The activities in O₂ were in general very low whereas the activities in NO were slightly higher. The activities in NO₂ were for all materials much higher than the activities in O₂. Even though Mn tends to decrease the activity of the materials, current ratios of I_NOx/I_O2I_{{\rm NO}_{x}}/I_{{\rm O}_2} have relatively high values in both NO and NO₂.     

Investigation of the effect of ZrO2 and ZrO2/Al2O3 additions on the hot-pressing and properties of equimolecular mixtures of α- and β-Si3N4

In this work, hot-pressing of equimolecular mixtures of α- and β-Si₃N₄ was performed with addition of different amounts of sintering additives selected in the ZrO₂–Al₂O₃ system. Phase composition and microstructure of the hot-pressed samples was investigated. Densification behavior, mechanical and thermal properties were studied and explained based on the microstructure and phase composition. The optimum mixture from the ZrO₂–Al₂O₃ system for hot-pressing of silicon nitride to give high density materials was determined. Near fully dense silicon nitride materials were obtained only with the additions of zirconia and alumina. The liquid phase formed in the zirconia and alumina mixtures is important for effective hot-pressing. Based on these results, we conclude that pure zirconia is not an effective sintering additive. Selected mechanical and thermal properties of these materials are also presented. Hot-pressed Si₃N₄ ceramics, using mixtures from of ZrO₂/Al₂O₃ as additives, gave fracture toughness, K_IC, in the range of 3.7–6.2 MPa m^1/2 and Vicker hardness values in the range of 6–12 GPa. These properties compare well with currently available high performance silicon nitride ceramics. We also report on interesting thermal expansion behavior of these materials including negative thermal expansion coefficients for a few compositions.     

Production of middle distillate through hydrocracking of paraffin wax over Pd0.15CsxH2.7?xPW12O40 catalysts: Effect of cesium content and surface acidity

Palladium-exchanged heteropolyacid (Pd_0.15Cs _x H_2.7−x PW₁₂O₄₀) catalysts were prepared by an ion-exchange method with a variation of cesium content (x=2.0, 2.2, 2.5, and 2.7) for use in the production of middle distillate through hydrocracking of paraffin wax. Surface acidity of Pd_0.15Cs _x H_2.7−x PW₁₂O₄₀ catalysts determined by NH₃-TPD experiments showed a volcano-shaped trend with respect to cesium content. Surface acidity of the catalysts played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing surface acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to surface acidity of the catalyst. Among the catalysts tested, Pd_0.15Cs_2.7PW₁₂O₄₀ catalyst with moderate surface acidity showed the best catalytic performance.     

Structural characterization of the δ-clathrate forms of syndiotactic polystyrene with n-alkanes

The δ-clathrate forms of syndiotactic polystyrene (s-PS) containing a homologous series of guests characterized by an increasing molecular volume (n-alkanes ranging from n-pentane to n-dodecane) have been investigated. The present analysis allows concluding that the volume of the guest plays a crucial role in the choice of the type of δ-clathrate that can be obtained. As a matter of fact, longer n-alkanes, such as n-octane, n-nonane or n-decane, turned out to give rise triclinic δ-clathrates presenting a guest/monomeric-unit ratio of 1/8, while δ-clathrates containing shorter alkanes, like n-hexane or n-heptane, instead, present a monoclinic or a triclinic structure with a guest/monomeric-unit ratio of 1/4. These results confirm the validity of a simple criterion to predict the type of s-PS δ-clathrate with a certain guest on the basis of the experimental d₀₁₀, as described in Macromolecules 2010, 43, 8549-8558. Moreover, our analysis confirms previous solid state ¹³C NMR and Raman spectroscopy data, indicating that shorter n-alkanes molecules, like n-hexane, are hosted in the cavities with an all-trans conformation while longer alkanes, like n-nonane, present bent conformations. The effect of n-alkanes molecules on the crystallization of s-PS amorphous samples has been investigated too.     

Synthesis and characterisation of β-TCP/bioglass/zirconia scaffolds

Tricalcium phosphate scaffolds reinforced with bioglass were characterised morphologically, physically, and mechanically. The scaffolds were fabricated through powder technology and the polymer foaming technique using 80?wt-% of β-TCP and 20?wt-% of phosphate-based bioglass doped with zirconia in various amounts (0, 0.25, 0.5, 0.75, and 1.0?wt-%). The foaming agent was varied (1, 1.5, 2, 2.5, and 3?wt-%) to determine the optimal amount that ensured an interconnected porosity and pore size suitable for increasing osteoconduction and cell attachment. Promising samples for tissue engineering applications showed a pore size ranging from 1.41 to 303?μm, total porosity of 50–53%, compressive strength values between 0.6 and 1?MPa, Young’s modulus from 357 to 574?MPa, and excellent interconnectivity.     

Transformation of the crystal structure in the series of K1 ? xCsxBSi2O6 borosilicate solid solutions

The transformation of the crystal structure by isomorphous K⁺-Cs⁺ substitutions in the non-tetrahedral positions leading to the phase transition has been studied in the series of K_{1 − x} Cs _x BSi₂O₆ solid solutions. The samples have been crystallized from the glass at 850°C for 10 h. According to the data on the crystal structures refined by the Rietveld method, the compositions with 0 ≤ x ≤ 0.35 crystallize in space group I[`4]3dI\bar 43d, structural type KBSi<sub>2</sub>O<sub>6</sub>, and those with 0.37 ≤ x ≤ 1.0, crystallize in Ia[`3]dIa\bar 3d, structural type CsBSi₂O₆. The reversible cubic-cubic phase transition I[`4]3d \rightleftarrows Ia[`3]dI\bar 43d \rightleftarrows Ia\bar 3d occurs in the composition range x = 0.35–0.37.     

Effect of processing conditions on the structural morphology of PP–EP/EVA/organoclay ternary nanocomposites

The effect of processing conditions on the morphology of heterophasic PP–EP/EVA/organoclay ternary nanocomposites was examined. The nanocomposites were prepared in a co-rotating twin screw extruder with different screw configurations and incorporation methods. Three different sizes of EVA granules were used. The results obtained by X-ray scattering (WAXD) and electronic microscopy (TEM) showed an increase in d spacing value of the clay associated with the polar interactions between the vinyl acetate of EVA and the surface of the nanoclays. In addition, some chains of the non-polar copolymer PP–EP may have become intercalated into the clay galleries as a result of polymer diffusion induced by shear stress during melt mixing. An increase in surface area of EVA granules resulted in a more homogenous clay dispersion and intercalation. The morphologic changes resulted in an increase in heat distortion temperature (HDT) and flexural modulus of the ternary nanocomposites.     

Effects of density and heat treatment of C/C preforms on microstructure and mechanical properties of C/C–SiC composites

Twill multidirectional carbon-fiber-reinforced carbon and silicon carbide composites (i.e., C/C–SiC) were prepared via chemical vapor infiltration combined with reactive melt infiltration process. The effect of heat treatment (HT) on the microstructure and mechanical properties of C/C–SiC composites obtained by C/C preforms with different densities was thoroughly investigated. The results show that as the bulk density of C/C preforms increases, the thickness of the pyrolytic carbon (PyC) layer increases and open pore size distribution narrows, making the bulk density and residual silicon content of C/C–SiC composites decrease. Moreover, the flexural strength and tensile strength of the C/C–SiC composites were improved, which can be attributed to the increased thickness of the PyC layer. The compressive strength reduces due to the decrease of the ceramic phase content. HT improves the graphitization degree of PyC, which reduces the silicon–carbon reaction rate and thereby the content of the SiC phase. HT induces microcracks and porosity but not obviously affects the mechanical properties of C/C–SiC composites. However, the negative impact of HT can be compensated by the increased density of the C/C preforms.     

Evaluation of adhesion of continuous fiber–epoxy composite/aluminum laminates

Continuous fiber composite/metal laminates (FMLs) offer significant improvements over currently available composite materials for aircraft structures due to their excellent fatigue endurance and low density. Glass fiber–epoxy composite laminae and aluminum foil (GLARE) are commonly used to obtain these hybrid laminates. In this work, FMLs were produced by treating the aluminum foil to promote adhesion bonding by two methods: sulphuric chromic acid etching (SCAE) and chromic acid anodization (CAA). The surface treatments were evaluated by contact angle, roughness and scanning electron microscopy techniques. In order to compare different families of fiber composite/metal laminates, carbon fiber and glass fiber fabrics were used as reinforcements for the hybrid laminates. The adhesion of the hybrid laminates was evaluated by scanning electron microscopy (SEM) and three-point bending test. CAA resulted in better wetting properties. The interlaminar shear strength results for both carbon fiber-epoxy/metal and glass fiber-epoxy metal, were close to the interlaminar shear strength results found in the literature (approx. 40.0 MPa).     

Development of solid base catalyst X/Y/MgO/γ-Al2O3 for optimization of preparation of biodiesel from Jatropha curcas L.seed oil

The preparation and regeneration conditions of the identified catalyst X/Y/MgO/γ-Al₂O₃ with high catalytic activity were studied and optimized. The biodiesel was prepared by transesterification of Jatropha curcas seed oil produced in Guizhou with methanol at its reflux temoerature in the presence of X/Y/MgO/γ-Al₂O₃. The pilot plant tests were carried out in a 100 L reaction vessel. Both average yield and fatty acid methyl esters (FAME) content reached more than 96.50% under the optimum reaction conditions of the pilot plant tests designed withan oil/methanol molar ratio of 1: 10, catalyst concentration of 1.00%, and reaction time of 3 h at reflux temperature. In addition, analysis shows that the quality of biodiesel meets the standard EN 14214. __________ Translated from Modern Chemical Industry, 2007, 27(Suppl. 2): 452–455 [译自: 现代化工]     

Cure kinetics of melamine–formaldehyde resin/clay/cellulose nanocomposites

As a part of improving the properties of surface laminates for wood-based panel products, this study attempted to investigate cure kinetics of the melamine–formaldehyde (MF) resin/clay/cellulose nanocomposites. Three different methods (Ozawa, Kissinger, and isoconversion) of differential scanning calorimetry (DSC) were employed to study cure kinetics of the nanocomposites, using three different heating rates (5, 10 and 20 °C/min). Both Ozawa and Kissinger methods showed that the overall activation energy (E_a) of the nanocomposite at the 0.5 wt% nanoclay level reached a maximum and then decreased thereafter. But, the Ozawa method provided greater E_a values than those of the Kissinger method. The isoconversional method provided the change of activation energy (E_α) values as a function of the degree of conversion (α). The E_α values increased as the degree of conversion increased, while the influence of nanoclay levels followed a similar trend to the overall E_a values from the both Ozawa and Kissinger methods. These results indicated that the exfoliation of layered nanoclay particles into MF resin delayed the cure of MF resin/nanoclay/cellulose nanocomposites.     

Investigation of energy-efficient heat pump assisted heterogeneous azeotropic distillation for separating of acetonitrile/ethyl acetate/n-hexane mixture

The conventional distillation is hard to accomplish the separation of acetonitrile/ethyl acetate/n-hexane mixture. Herein, a heterogeneous azeotropic distillation(HAD) without adding entrainer is proposed to separate ternary mixture. The proposed scheme is optimized via the simulated annealing algorithm and minimum total annual cost(TAC) is used as objective functions. To minimize energy consumption,heat pump is added on the basis of optimal heterogeneous azeotropic distillation and heat integra...     

Preparation of micrometer-sized α-Al2O3 platelets by thermal decomposition of AACH

Micrometer-sized α-Al₂O₃ platelets with hexagonal shape were prepared by thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) using AlF₃ as an additive. The precursor and the calcined product were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. The α-Al₂O₃ platelets with the size of 2-3 μm were obtained by calcining AACH at 1200 °C with 5 wt.% AlF₃. The morphology modification is attributed to the various growth rates along different crystal orientations due to the adsorption and uneven distribution of AlF₃. A step growth mode is responsible for the formation of the platelets.     

Development of improved PPARβ/δ inhibitors

GSK0660 (1) is the first peroxisome proliferator-activated receptor (PPAR) β/δ-selective inhibitory ligand described in the literature. Based on its structure, we designed and synthesized a series of modified compounds to establish preliminary structure-activity relationships. Most beneficial for increased binding affinity towards the PPARβ/δ ligand binding domain was the replacement of the 4'-aminophenyl substituent by medium-length n-alkyl chains, such as n-butyl or iso-pentyl. These compounds show activity down to the one-digit nanomolar range, thus possessing up to a tenfold higher binding affinity compared with GSK0660. Additionally, the subtype-specific inhibition of PPARβ/δ was confirmed in a cell-based assay making these compounds invaluable tools for the further exploration of the functions of PPARβ/δ.     

Synthesis of poly(maleic acid alkylamide-co-α-olefin-co-styrene) and their effect on flow ability of oils

To improve the flow ability of crude oil with high content of aromatic asphaltenes, new comb-type copolymers of poly(maleic anhydride-co-α-olefin-co-styrene) (MASCs) with different ratios of maleic anhydride (MA) to styrene were designed and synthesized. ¹H NMR and FTIR spectra were used to characterize the chemical structure of the copolymers. The effect of copolymers on the flow ability of model waxy oil and crude oil were studied by rheological method and polarizing light microscopy. Upon the addition of MASCs, the yield stresses of oils were decreased by 1 to 3 orders of magnitude, and the morphology of paraffin crystals were reduced and changed from plates to needles.     

Promotional effect of Ca on the Pd/Ce–Zr/Al2O3 catalyst for low-temperature catalytic combustion of methane

Promotional effect of Ca on the catalytic property of Pd/Ce–Zr/Al₂O₃ catalyst towards methane combustion is examined. The surface properties and the oxidation/reduction behavior of these catalysts are investigated by BET, TEM, XPS, TPR, TPO and TPSR techniques. Activity tests in methane combustion show that addition of Ca to Pd/Ce–Zr/Al₂O₃ can promote remarkably its low-temperature activity. The thermal stability of the Pd/Ce–Zr/Al₂O₃ catalyst to the exposure at high temperature is also enhanced by Ca loading. XPS and TEM results show that the addition of Ca to Pd/Ce–Zr/Al₂O₃ catalyst generates well-dispersed PdO particles on support. H₂–TPR, O₂–TPO and CH₄/O₂–TPSR experiments show that the addition of Ca improves the reduction/reoxidation properties and thermal stability of the active PdO species, which increases the catalytic activity and thermal stability of the Pd/Ce–Zr/Al₂O₃ catalyst.     

Pd-Fe/α-Al2O3/cordierite monolithic catalysts for the synthesis of dimethyl oxalate: effects of calcination and structure

Cordierite monoliths coated with Pd-Fe/α-Al₂O₃ catalysts were prepared at various calcination temperatures and characterized by thermogravimetry, temperature-programmed reduction, transmission electron microscopy, diffuse reflectance infrared Fourier transformation spectroscopy and X-ray diffraction. The performance of the catalytic monoliths for the synthesis of dimethyl oxalate (DMO) through a CO coupling reaction was evaluated. Monolithic catalysts with calcination temperatures ranging from 473 K to 673 K exhibited excellent dispersion of Pd, good CO adsorption properties, and excellent performance for the coupling reaction. The optimized monolithic catalyst exhibited a much higher Pd efficiency (denoted as DMO (g)·Pd (g)^-1·h^-1) (733 h^-1) than that of the granular catalyst (60.2 h^-1), which can be attributed to its honeycomb structure and the large pore sizes in the α-Al₂O₃ washcoat which was accompanied with an even distribution of the active component in the coating layer along the monoliths channels.