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991.
Study of polyarylene ether nitrile terminated with phthalonitrile/hybrid Fe3O4 nanospheres composites by orthogonal experiments
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A novel series of composites of polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph) filled with hybrid Fe3O4 nanospheres (h‐Fe3O4) was prepared via in situ composition. Based on the cross‐linking interactions between the phthalonitrile at the end of PEN‐t‐Ph molecular chains and the phthalonitrile on the surface of h‐Fe3O4 particles to form phthalocyanine ring, it was shown that the PEN‐t‐Ph/h‐Fe3O4 system had superior interfacial compatibility and the h‐Fe3O4 particles were locked in the matrix resin. These results had been confirmed by scanning electron microscope analysis. By orthogonal experiments and statistic analysis, the optimal conditions of cure temperature, type of h‐Fe3O4 and content of h‐Fe3O4 had been determined. Meanwhile, the results of range analysis and variance analysis indicated that the cure temperature had great effects on the thermal properties. Thermal studies revealed that the glass transition temperature of PEN‐t‐Ph/h‐Fe3O4 cured at 320°C was 214.7°C, increased by about 40°C compared to the PEN‐t‐Ph/h‐Fe3O4 without heat treatment, and the temperature corresponding to the weight loss of 5 wt % was increased by about 20°C. Mechanical measurements indicated that PEN‐t‐Ph/h‐Fe3O4 cured at 320°C possesses excellent mechanical properties with tensile strength of 93.33 MPa and tensile modulus of 2414.05 MPa, 9.91 MPa, 355.76 MPa higher than pure PEN‐t‐Ph film cured at 320°C, and 13.26 MPa, 397.90 MPa higher than PEN‐t‐Ph/h‐Fe3O4 without heat treatment. Most importantly, the presence of h‐Fe3O4 particles endows PEN‐t‐Ph/h‐Fe3O4 system with good magnetic property. Thus, PEN‐t‐Ph/h‐Fe3O4 cured at 320°C may have potential applications in field of magnetic materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40418. 相似文献
992.
Electrospun polyvinyl alcohol/waterborne polyurethane composite nanofibers involving cellulose nanofibers
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TEMPO‐oxidized cellulose nanofibers (TOCNs) were used as nanofillers in this work. Composite nanofibers of polyvinyl alcohol (PVA)/waterborne polyurethane (WPU) reinforced with TOCNs were produced by electrospinning. The reinforcing capability of TOCNs was investigated by tensile tests. Scanning electron microscopy (SEM), X‐ray diffraction, and thermogravimetry analyses were also carried out in order to characterize the appearance, crystallinity, and reinforcing effect of the cellulose nanofibers. SEM results showed that PVA/WPU/TOCNs composite nanofibers presented a highly homogeneous dispersion of TOCNs. The reinforced composites had about 44% increase in their mechanical properties with addition of only 5 wt % of TOCNs while about 42% decrease in elongation at break. The TOCNs reinforced composite nanofibers were more thermally stable than pure PVA/WPU nanofibers. The development of crystalline structure in the composite fibers was observed by XRD. Since PVA, WPU, and TOCNs are hydrophilic, non‐toxic, and biocompatible, and therefore, these nanocomposite nanofibers could be used for tissue scaffolding, filtration materials, and medical industries as wound dressing materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41051. 相似文献
993.
Selective hydrogenation of nitriles to imines over a multifunctional heterogeneous Pt catalyst
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Jilan Long Biaolin Yin Yingwei Li Lianjie Zhang 《American Institute of Chemical Engineers》2014,60(10):3565-3576
Imines and their derivatives are versatile synthetic intermediates for the industrial preparation of both bulk and fine chemicals and for pharmaceuticals, but preparing these compounds efficiently through direct hydrogenation of nitriles are hindered by overhydrogenation to secondary amines. Here we report a highly efficient multifunctional catalyst system for selective hydrogenation coupling of nitriles to secondary imines using a heterogeneous Pt catalyst that was deposited on a nickel‐based metal‐organic framework (MOF) containing DABCO. The catalyst showed excellent synergy in promoting the hydrogenation of a variety of nitriles, giving significantly improved activity and selectivity (up to >99% yield) even under atmospheric pressure of H2. It is suggested that the Lewis base (DABCO) sites on the Ni‐MOF inhibit further hydrogenation of the imines. The influence of H2 pressure, reactant concentration, stirring speed, and reaction temperature was investigated. The kinetics and mechanism of hydrogenation of benzonitrile (BN) by the Pt/Ni‐MOF catalyst has been studied. The reaction showed a first‐order dependence on both BN concentration and H2 pressure. A kinetic model was proposed based on the mechanism of nitriles hydrogenation and compared with experimental observations. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3565–3576, 2014 相似文献
994.
Reversible-addition fragmentation chain transfer (RAFT) polymerization enabled the synthesis of novel, stimuli-responsive, AB and ABA block copolymers. The B block contained oligo(ethylene glycol) methyl ether methacrylate (OEG) and was permanently hydrophilic in the conditions examined. The A block consisted of diethylene glycol methyl ether methacrylate (DEG) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMA). The A block displayed both salt- and temperature-response with lower critical solution temperatures (LCSTs) dependent on the molar content of TMA and the presence of salt. Higher TMA content in the AB diblock copolymers increased the critical micelle temperatures (CMT) in HPLC-grade water due to an increased hydrophilicity of the A block. Upon addition of 0.9 wt% NaCl, the CMTs of poly(OEG-b-DEG95TMA5) decreased from 50 °C to 36 °C due to screening of electrostatic repulsion between the TMA units. ABA triblock copolymers displayed excellent hydrogel properties with salt- and temperature-dependent gel points. TMA incorporation in the A block increased the gel points for all triblock copolymers, and salt-response increased with higher TMA composition in the A block. For example, poly(DEG98TMA2-b-OEG-b-DEG98TMA2) formed a hydrogel at 40 °C in HPLC-grade water and 26 °C in 0.9 wt% NaCl aqueous solution. These salt- and temperature-responsive AB diblock and ABA triblock copolymers find applications as drug delivery vehicles, adhesives, and hydrogels. 相似文献
995.
CO2 Adsorption capacity of activated N‐doping porous carbons prepared from graphite nanofibers/polypyrrole
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In this study, N‐doping porous carbons (NPCs) with a 3D aperiodic hierarchical and layered structure were prepared by the sodium hydride (NaOH) activation of graphite nanofibers (GNFs)/polypyrrole (PPY) composites. The effects of the N groups and structural features on the CO2 adsorption capacity of NPCs were investigated by N2 full isotherms, XRD, SEM, and TEM. The CO2 adsorption capacity was measured by the CO2 isothermal adsorption at 25°C and 1 atm. It was found that GNFs served as a substrate and layered graphitic carbons were formed by the thermal annealing of PPY. The content of N groups and textural properties of NPCs were enhanced with increasing activation temperature, resulting in improved CO2 adsorption capacity. The CO2 adsorption isotherms showed that GPK‐600 exhibited the best CO2 adsorption capacity of 88.8 mg/g when the activation temperature was 600°C. The result indicates that the pore size and its distribution of NPCs lead to feasible contact CO2, and the presence of high N groups on the NPCs could have resulted in further stabilization of the surface effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40517. 相似文献
996.
A strong shear flow was imposed on the melt of polycarbonate (PC) microfibril reinforced high density Polyethylene (HDPE) during a secondary melt flow process, i.e. gas assisted injection molding (GAIM). Classic shish-kebabs and typical transcrystallinity were simultaneously observed in the entire thickness of the GAIM HDPE/PC microfibril composites, which were closely related to the strong shear flow that was further amplified and distributed by incorporated PC microfibrils. Interestingly, some nano-sized ultrafine PC microfibril inclined to absorb extended chain bundles to form shish nuclei on its surface first, which subsequently evolved into hybrid shish-kebab superstructures. It was deemed that the induced formation of hybrid shish-kebab superstructures on nano-sized ultrafine PC microfibril was due to the absorbing of extended chain bundles for hybrid shish nuclei with the strong shear flow serving as the driving force. Importantly, large scale formation of these highly oriented crystalline superstructures can bring significant mechanical reinforcement in GAIM HDPE/PC microfibril composite. For GAIM HDPE/PC microfibril composites, its yield strength is increased by 68% and 66%, compared to the GAIM HDPE parts and the common injection molded (CIM) HDPE/PC composites, respectively; meanwhile, the Young's modulus is enhanced by 253% and 17%, compared to the GAIM HDPE parts and the CIM HDPE/PC composites, respectively. 相似文献
997.
采用沉淀-浸渍法制备了固体超强酸SO2-4/ZrO2催化剂,经FT-IR、XRD对制备的固体超强酸进行表征。以十二烷二酸、异辛醇为原料,采用SO2-4/ZrO2固体酸催化剂合成十二烷二酸二异辛酯。考察了反应温度、反应时间、原料配比、催化剂的质量分数等对合成反应的影响。使用该催化剂合成十二烷二酸二异辛酯的最佳反应条件为:反应温度为130℃,醇酸物质的量比为4∶1,反应时间为5 h,催化剂质量为酸的质量的1.5%,酯化率为98.4%。催化剂不经处理可循环使用,使用5次以后酯化率为95.3%。 相似文献
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