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TEM Micrographs (tem + micrograph)
Selected AbstractsSynthesis of CdS Nanoparticles Dispersed Within Poly(urethane acrylate- co -styrene) Films Using an Amphiphilic Urethane Acrylate NonionomerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2006Ju-Young Kim Abstract Summary: CdS nanoparticles dispersed within poly(urethane acrylate- co -styrene) (PUCS) films were prepared using amphiphilic urethane acrylate nonionomer (UAN) precursor chains, which had a poly(propylene oxide)-based hydrophobic segment and a hydrophilic poly(ethylene oxide) segment. CdS nanoparticles were first prepared and dispersed in UAN/styrene mixtures, and then these nano-colloid solutions could be directly converted to CdS/PUCS nanocomposite films via radical bulk polymerization process. Formation of CdS nanoparticles was confirmed by UV absorption spectra, PL emission spectra and TEM images. The size of the CdS nanoparticles was varied from 10.2 to 14.5 nm, in correlation with the increase of amount of cadmium salt in the preparation composition, which was also confirmed by a red shift in the UV and PL emission spectra. In the course of the formation of the CdS nanoparticles within the UAN/styrene mixtures, the PEO segments of UAN are microphase-separated from the hydrophobic segments of UAN and styrene to make a complex with the cadmium cations and stabilize the CdS nanoparticles. This was also confirmed by TEM images and DMA measurements. TEM micrograph of the polyurethane acrylate films containing CdS nanoparticles, prepared using a weight fraction of cadmium acetate of 0.125 wt.-%. [source] Preparation and Characterisation of Pd Nanoclusters in Hyperbranched Aramid Templates to be used in Homogeneous CatalysisMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003Daniela Tabuani Abstract In the present paper the potential use of hyperbranched (HB) aramids as metallic solution stabilisers and carriers for homogeneous catalysis is outlined. Aramids, synthesised either from A2,+,B3 reagents [namely, p -phenylenediamine (PPD) and trimesic acid (TMA)] or from an AB2 monomer [i.e., 5-(4-aminobenzamido)isophtalic acid, named ABZAIA], have been used to stabilise palladium nanoclusters dispersed in two solvent media, namely N,N, -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The influence of the nature of the polymeric support as well as of the solvent medium on both cluster dimensions and stability of the solutions has been investigated. Indeed, the interactions between the polymeric support and the metallic precursor (PdCl2), as revealed by 1H NMR spectroscopy, involve only the amino groups of the HB aramids. Metal nanocluster dimensions and stability are strongly dependent on the polymer used as a stabilizer. Transmission electron microscopy (TEM) analysis has shown that the presence of HB polymer in the solution reduces cluster dimensions and allows the obtaining of stable systems. The low concentration of NH2 end groups in the poly(AB2) system leads to the formation of Pd particles of rather low dimensions with a high tendency to aggregate. All prepared solutions are stable under inert atmosphere for at least a month, with an improved stabilisation when using the poly(A2,+,B3) system for more than five months. A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution. [source] In Situ Polymerisation of Polyamide-6 Nanocompounds from Caprolactam and Layered SilicatesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2009Bernd Rothe Abstract An in situ process for the production of polyamide-6 nanocompounds is investigated as an alternative to melt compounding. During the in situ production, the layered silicates are dispersed in the monomer caprolactam before the polymerisation in a twin screw extruder, leading to an intercalation of the silicates. The production of a polyamide compound containing 0, 2 and 4 wt.-% nanoscale silicates was successful. An improvement of the elastic modulus of approximately 30,60% was reached. The figure shows the TEM micrograph of a nanocompound containing 2 wt.-% nanoclay at a magnification of 30,000×. [source] Organoclay Nanocomposites from Ethylene,Acrylic Acid CopolymersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2006Sara Filippi Abstract Summary: A study of the structure,property relationships for nanocomposites prepared by melt compounding from ethylene,acrylic acid copolymers of varied composition and molecular architecture, and organoclays modified with different ammonium ions has been made by DSC, POM, SEM, TEM, WAXD, and rheological and mechanical tests. Within the series of clays investigated, the best levels of dispersion were displayed by those organically modified with quaternary ammonium ions containing two long alkyl tails. The relevant nanocomposites were shown to possess mixed exfoliated and intercalated morphology. The spacing of the intercalated clay stacks, most of which comprise few silicate layers, was found to be independent of clay loading, in the range of 2,50 phr, and to change with the molecular architecture of the matrix polymer. An indication that the excess surfactant present in some of the clays, and the organic material added in others to expand the interlayer spacing, were expelled from the clay galleries during melt blending and acted as plasticisers for the matrix polymer, was obtained from WAXD and rheological characterisations. TEM micrograph of the nanocomposite of EAA1 with 11 phr of 15A. [source] Preparation and Characterization of Nanostructured TiO2/Epoxy Polymeric FilmsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2006Marco Sangermano Abstract Summary: Titania-containing coatings were prepared by cationic photopolymerization of an epoxy resin either by dispersion of preformed TiO2 nanoparticles or by their in-situ generation through a sol-gel dual-cure process. The kinetics of photopolymerization was evaluated by real-time FT-IR, studying the effect of the TiO2 concentration. The properties of cured films were investigated, showing an increase of hydrophilicity on the surface of the coatings with increasing TiO2 content. TEM analysis demonstrated that it is possible to achieve a significantly better control of the dispersion of the inorganic particles within the organic matrix by in-situ generation of TiO2, thus completely avoiding macroscopic phase separation and obtaining homogeneous, transparent coatings. Bright-field TEM micrograph for TIP20 dual-cured film. [source] Poly(propylene)/Clay Nanocomposites Prepared by Reactive Compounding with an Epoxy Based MasterbatchMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Ling Chen Abstract Summary: Poly(propylene) (PP)/clay nanocomposites have been prepared via a novel reactive compounding approach, in which an epoxy based masterbatch consisting of 20 wt.-% clay was introduced to poly(propylene) with the aid of a maleic anhydride grafted PP (MAPP). The masterbatch was prepared using a recently developed "slurry compounding" technique. After melt compounding, most clay particles have been exfoliated and dispersed into small stacks with several clay layers. WAXD data shows that the dispersion of clay is better at low clay content or high MAPP content. Due to the novelty of the preparation process and complication of the system, the tensile properties of nanocomposites exhibit some unique tendencies with varying the content of MAPP or masterbatch. It is believed that the yield strength and Young's modulus can be dramatically improved after minimizing the excess of unreacted epoxy and optimizing the dispersion of clay. TEM micrograph of PP/clay nanocomposites prepared with epoxy based masterbatch. [source] Surface modification of starch nanocrystals through ring-opening polymerization of ,-caprolactone and investigation of their microstructuresJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Hassan Namazi Abstract Bionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ,-caprolactone (CL). Starch nanoparticle- g -polycaprolactone was synthesized through ring-opening polymerization (ROP) of CL in the presence of Sn(Oct)2 as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X-ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effects of microcompounding process parameters on the properties of ABS/polyamide-6 blends based nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Güralp Özkoç Abstract Melt intercalation method was applied to produce acrylonitrile-butadiene-styrene/polyamide-6 (ABS/PA6) blends based organoclay nanocomposites using a conical twin-screw microcompounder. The blend was compatibilized using a maleated olefinic copolymer. The effects of microcompounding conditions such as screw speed, screw rotation-mode (co- or counter-), and material parameters such as blend composition and clay loading level on the morphology of the blends, dispersibility of nanoparticles, and mechanical properties were investigated. Furthermore, corotating screws were modified to achieve elongational flow which is efficient for obtaining dispersive mixing. The morphology was examined by SEM analysis after preferential extraction of the minor phase. Subsequently, the SEM micrographs were quantitatively analyzed using image analyzer software. The morphology of the blends indicated that processing with counter-rotation at a given screw speed yielded coarser morphology than that of processed with corotation. X-ray diffraction analysis showed that highest level of exfoliation is observed with increasing PA6 content, at 200 rpm of screw speed and in corotation mode. Also, the effects of screw speed, screw rotation mode, and screw modification were discussed in terms of XRD responses of the nanocomposites. The aspect ratio of the clay particles which were measured by performing image analysis on TEM micrographs exhibited a variation with processing conditions and they are in accordance with the modulus of the nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Blending of NR/BR/EPDM by reactive processing for tire sidewall applications.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Abstract Cure incompatibility in NR/BR/EPDM blends is a crucial problem, affecting blend properties. In a previous study, it was demonstrated that the mechanical properties of such blends can be significantly improved by utilizing a reactive processing technique, in which a pretreated EPDM is first prepared by incorporating all compounding ingredients in the EPDM and subsequent preheating, prior to crossblending with premasticated NR/BR. In the present article, the pretreated EPDM-moieties are prepared using two different accelerators, N -cyclohexyl-2-benzothiazole sulfenamide (CBS) and 6-nitro MBTS. The latter was synthesized and applied for the purpose of IR characterization. The infrared (IR) spectra of the pretreated, extracted EPDM demonstrate absorption peaks associated with the IR absorption of the functional groups in the accelerator fragments, attached to the EPDM. NR/BR/EPDM (35/35/30) ternary blends are prepared by reactive mixing of the pretreated EPDM with CBS fragments attached with premasticated NR/BR on a two-roll mill. Their blend morphological features are studied using the atomic force microscopy (AFM) and transmission electron microscopy (TEM) microscopic techniques, in comparison with those of blends prepared by a conventional straight mixing method. Both the tapping mode AFM phase images and TEM micrographs clearly show that reactive mixing leads to more homogeneous blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:2547,2554, 2007 [source] AMP-activated protein kinase deficiency exacerbates aging-induced myocardial contractile dysfunctionAGING CELL, Issue 4 2010Subat Turdi Summary Aging is associated with myocardial dysfunction although the underlying mechanism is unclear. AMPK, a key cellular fuel sensor for energy metabolism, is compromised with aging. This study examined the role of AMPK deficiency in aging-associated myocardial dysfunction. Young or old wild-type (WT) and transgenic mice with overexpression of a mutant AMPK ,2 subunit (kinase dead, KD) were used. AMPK , isoform activity, myocardial function and morphology were examined. DCF and JC-1 fluorescence probes were employed to quantify reactive oxygen species (ROS) and mitochondrial membrane potential (,,m), respectively. KD mice displayed significantly reduced ,2 but not ,1 AMPK isoform activity at both ages with a greater effect at old age. Aging itself decreased ,1 isoform activity. Cardiomyocyte contractile function, intracellular Ca2+ handling, and SERCA2a levels were compromised with aging, the effects of which were exacerbated by AMPK deficiency. H&E staining revealed cardiomyocyte hypertrophy with aging, which was more pronounced in KD mice. TEM micrographs displayed severe disruption of mitochondrial ultrastructure characterized by swollen, irregular shape and disrupted cristae in aged KD compared with WT mice. Aging enhanced ROS production and reduced ,,m, the effects of which were accentuated by AMPK deficiency. Immunoblotting data depicted unchanged Akt phosphorylation and a significant decrease in mitochondrial biogenesis cofactor PGC-1, in aged groups. AMPK deficiency but not aging decreased the phosphorylation of ACC and eNOS. Expression of membrane Glut4 and HSP90 was decreased in aged KD mice. Moreover, treatment of the AMPK activator metformin attenuated aging-induced cardiomyocyte contractile defects. Collectively, our data suggest a role for AMPK deficiency in aging-induced cardiac dysfunction possibly through disrupted mitochondrial function and ROS production. [source] Synthesis and characterization of organic/inorganic hybrid star polymers of 2,2,3,4,4,4-hexafluorobutyl methacrylate and octa(aminophenyl)silsesquioxane nano-cage made via atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008H. Hussain Abstract Well-defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano-cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2-bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 °C using CuCl/2,2-bipyridine or N,N,N,,N,,N,-pentamethyldiethylenetriamine as catalyst system. GPC and 1H NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano-cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of , 120,180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (Tg) (when compared with the linear PHFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower Tg than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by ,60 °C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7287,7298, 2008 [source] A Novel Impact Modifier for Nylon 6MACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2002Jing Peng Abstract A new carboxylated styrene-butadiene rubber (CSBR) in ultrafine powder form was used to modify the properties of nylon 6. The nylon 6/CSBR blends possessed higher toughness than nylon 6/maleic anhydride-grafted polyethylene-octene elastomer (POE- g -MAH) system. TEM micrographs revealed the fine dispersion of CSBR particles with a diameter of 150 nm. The effective toughening of nylon 6 with CSBR was attributed to the good interface, fine dispersion, and shear yielding. TEM photograph of undeformed Nylon 6/CSBR (80/20) blend (×40,000). [source] Investigation of oxygen barrier properties of organoclay/HDPE/EVA nanocomposite films prepared using a two-step solution methodPOLYMER COMPOSITES, Issue 6 2009S.M. Reza Dadfar In this article, oxygen barrier properties of nanocomposite films composed of organoclay (OC), high-density polyethylene (HDPE), and ethylene vinyl acetate (EVA) copolymer have been investigated. The nanocomposite films whose EVA forms a dominant fraction were prepared using the solution method. The dispersion of the OC in the HDPE/EVA blend was improved through taking two-step procedure in the preparation of nanocomposite. First, the OC and EVA were dissolved in chloroform. Then, the resulting product, after evaporating most of the solvent, along with HDPE was dissolved in xylene. The obtained nanocomposite films underwent a number of tests in order to examine their barrier properties including X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that OC/HDPE/EVA nanocomposites are intercalated and partially exfoliated. Furthermore, from the TEM micrographs, the organoclay experimental aspect ratio was found. Also, the O2 permeability through the films was evaluated, which showed that adding both OC and HDPE to EVA leads to a remarkable increase in the barrier properties of EVA films. Finally, by using the gas permeation results and existing permeation theories, the organoclay theoretical aspect ratio was predicted. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Melt processing effects on the structure and mechanical properties of PA-6/clay nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2006Nitin K. Borse Polyamide-6 nanocomposites were prepared using two organoclays, Cloisite 30B and Cloisite 15A, and Cloisite Na+, which is unmodified sodium montmorillonite (Na-MMT) clay. Nanocomposites were prepared using two twin-screw extrusion systems: System B employing conventional mixing and residence time conditions, while System A was modified to achieve longer residence time and higher mixing efficiency. The work considers the effects of mixing conditions, residence time, and interactions between the polymer and clay surface on the structure and mechanical properties of polyamide-6 (PA-6)/clay nanocomposites. Furthermore, a comparison was made between experimental data and the predictions of composite models usually employed to predict mechanical properties of nanocomposites. The melt processing of Cloisite 30B in System A produced the highest degrees of exfoliation and the largest enhancement of mechanical properties. The aspect ratios of the filler particles in the nanocomposites were estimated from TEM micrographs and from composite models. Yield stress data were employed to calculate the values of parameter B in Pukanszky's equation, which incorporates the effects of the interfacial interaction, interfacial strength, and specific surface area of the filler particles. POLYM. ENG. SCI. 46:1094,1103, 2006. © 2006 Society of Plastics Engineers [source] Melt processing of PA-66/clay, HDPE/clay and HDPE/PA-66/clay nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 6 2004Mahmood Mehrabzadeh Polyamide 66/clay, high-density polyethylene (HDPE)/clay and HDPE/PA66/clay nanocomposites were prepared, using a twin-screw extruder. The nanocomposites were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), optical microscopy and tensile testing. Effects of processing conditions and clay modifier were evaluated. The results show that exfoliation in the twin-screw extruder is enhanced by the incorporation of mixing and shearing elements and high residence times. Compatibility of the clay modifier with the polymer matrix plays an important role in exfoliation. Clay does not influence the crystal form, melting temperature or crystallinity of PA-66 and HDPE. However, it acts as a nucleation agent, increases marginally the crystallization temperatures, and reduces the crystallite size. Clay in the blend nanocomposites acts as a compatibilizer and changes the morphology of the blend. TEM micrographs suggest the presence of an exfoliated structure in PA-66 and an intercalated structure in HDPE. Polym. Eng. Sci. 44:1152,1161, 2004. © 2004 Society of Plastics Engineers. [source] | ||||||||||