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Weight Fraction (weight + fraction)
Kinds of Weight Fraction Selected AbstractsEnhanced Electrical Switching and Electrochromic Properties of Poly(p-phenylenebenzobisthiazole) Thin Films Embedded with Nano-WO3ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Jiahua Zhu Abstract The electrical switching and electrochromic phenomena of a novel nanocomposite comprising poly(p-phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO3) nanoparticles are investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfonic acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%). The electrical conductivity of 5% WO3/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as-received PBZT and PBZT/CSA thin films. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow an ohmic conduction mechanism. Stable electrical conductivity switching is observed before and after applying a bias on the pristine PBZT and WO3/PBZT nanocomposite thin films. Electrochromic phenomena of both PBZT and WO3/PBZT nanocomposite thin films with high contrast ratio are observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed. [source] In vitro haem solubility of red cell fraction of porcine blood under various treatmentsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2010Tong-Xun Liu Summary An in vitro peptic digestion at gastric pH 2.0 was used to assess the haem solubility of red cell fraction (RCF) of porcine blood derived samples. The in vitro haem solubility of the RCF decreased greatly in the denaturated form of haemoglobin. However, the native haemoglobin was susceptible to be hydrolysed by enzyme mixture of Flavourzyme and Alcalase. The in vitro digestion of the hydrolysates showed that the highest haem solubility was reached at degree of hydrolysis between 8.75% and 12.33%. The in vitro haem solubility was positively correlated with content of the highly soluble peptides with molecular weights ranged from 7.5 kDa to 1 kDa, but negatively with peptides fractions >7.5 kDa and <1 kDa, mostly due to the precipitation of the highly molecular weight fraction (>7.5 kDa) and part of small peptides (<1 kDa) with higher haem/peptide ratio, which was confirmed by gel filtration chromatograms and by the analysis of the precipitate at pH 2.0. [source] Effect of the structure of silane-coupling agent on dynamic mechanical properties of dental resin-nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Irini D. Sideridou Abstract This work was aimed at the study by dynamic mechanical analysis (DMA) of dental composites consisted of a Bis-GMA/TEGDMA (50/50 wt/wt) matrix and silica nanoparticles (Aerosil OX50) as filler, silanized with various silanes. The silanes used were 3-[(1,3(2)-dimethacryloyloxypropyl)-2 (3)-oxycarbonylamido] propyltriethoxy-silane (UDMS), 3-methacryloxypropyl-trimethoxysilane (MPS), octyltrimethoxysilane (OTMS), blends of UDMS/OTMS (50/50 wt/wt), or MPS/OTMS (50/50 wt/wt). The total amount of silane was kept constant at 10% by weight fraction relative to the filler weight. The silanized nanoparticles were mixed with the dimethacrylate matrix (60% filler by weight fraction). The composites were light cured and tested by DMA for the determination of storage modulus (E,), loss modulus (E,), tangent delta (tan ,), and glass transition temperature (Tg). Measurements were performed in samples immediately after curing and samples stored in water at 37°C for 1, 7, 30, or 120 days. OTMS-composite in which OTMS does not form covalent bond with the dimethacrylate matrix showed lower elastic modulus both in dry and wet conditions. The ability of bifunctional UDMS for crosslinking was found not to increase the elastic behavior of the composite, as it was expected, compared with that of MPS-composite, because of the high amount of the silane used. After immersion in water the elastic modulus of OTMS-composite remained constant, while that of the other composites increased after 1 day and then remained constant up to 120 days. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Nonlinear surface electrical resistivity of graphite,polyurethane composite filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Ganesh K. Kannarpady Abstract In this article, we study the surface resistivity of graphite,polyurethane composites using voltage,current characteristics. The evolution of the percolation network of graphite in polyurethane is qualitatively studied using optical micrographs. As expected, the surface resistivity decreases as a function of graphite concentration. In particular, the surface resistivity of the 69% graphite,polyurethane composite is about four orders of magnitude lower than the surface resistivity of the 27% graphite,polyurethane composite. The electrical resistivity of the composite is found to be highly nonlinear with respect to an increasing voltage at a low graphite weight fraction. On the other hand, the nonlinearity is significantly milder at higher weight fractions. The reasons behind the nonlinearity are discussed. Very preliminary studies indicate that very low weight fractions of single wall carbon nanotubes (e.g. 2.5%) are sufficient to generate electrical conductivities comparable to much higher loading fractions (, 60% and higher) of the heavier graphite particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Ozonation of complex industrial park wastewater: effects on the change of wastewater characteristicsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009Jen-Mao Fanchiang Abstract BACKGROUND: Ozonation of complex industrial park wastewater was carried out in a semi-batch reactor. The variation of wastewater characteristics was evaluated based on the analysis of 5-day biochemical oxygen demand (BOD5) concentration, BOD5/chemical oxygen demand (COD) ratio, COD fractionation, and dissolved organic carbon (DOC) molecular size distribution before and after ozonation. RESULTS: The experimental results indicated that low efficiency of COD removal with increasing tendency of BOD5 concentration generally appeared after ozonation. Also, the BOD5/COD ratio increased from an initial of 0.27 to a maximum of 0.38. The COD fractionation tests revealed that most of the inert soluble COD was transformed to biodegradable soluble COD at 30 min of reaction time. Additionally, the DOC molecular size distribution tests showed that the fraction larger than 500 kDa was significantly decreased and the fraction smaller than 2 kDa was increased when the reaction time was prolonged to 240 min. CONCLUSION: This study verified that partial oxidation of the complex industrial park wastewater by ozonation could enhance wastewater biodegradability. The biodegradability enhancement was primarily because the inert soluble COD fraction was converted to the biodegradable soluble COD and the high molecular weight fraction of DOC was shifted toward the low molecular weight fraction. Copyright © 2009 Society of Chemical Industry [source] Synthesis of thermosensitive guar-based hydrogels with tunable physico-chemical properties by click chemistryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2010Morgan Tizzotti Abstract Thermosensitive guar-based hydrogels are obtained in water solutions by copper-catalyzed 1,3-dipolar cycloaddition between alkyne-functionalized guars and ,,,-diazido-poly[(ethylene glycol)- co -(propylene glycol)]. Characterization by TGA, HR-MAS 1H NMR, and rheology have shown that hydrogels with tunable physico-chemical properties, such as crosslinking density, viscoelasticity, swelling ratio, and so forth, could be obtained by varying the guar molar mass, the degree of alkyne functionality, the guar/crosslinker weight ratio, and the reaction temperature. Based on swelling measurements, it has been shown that the thermal sensitiveness of guar-based hydrogels is fast, reversible, and intimately related to the weight fraction of the thermosensitive crosslinker in the network. Finally, the monitoring of doxorubicin hydrochloride release has demonstrated the potential of these hydrogels as temperature-dependent drug release devices. The robust, efficient, and orthogonal approach described herein represents a general approach towards the development of well-controlled guar-based hydrogels using ,,,-diazido crosslinkers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2733,2742, 2010 [source] The production of high polymer to surfactant microlatexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2010Raul P. Moraes Abstract Starved-feed microemulsion polymerization of styrene was investigated. The influence of the type (SDS or Dowfax 2A1) and concentration of anionic surfactant on the final particle size of latex made by the polymerization of microemulsions of styrene was studied. In addition, the influence of 1-pentanol and acrylic acid as cosurfactants was examined. Latexes with 20% solids content and polymer to surfactant ratio of 22 were produced, with a particle diameter of 42 nm and very low polydispersity indexes. Smaller particles are produced using SDS than Dowfax 2A1 for the same weight fraction of surfactant; however, similar particle sizes were obtained with the same molar concentrations of SDS and Dowfax 2A1. Further shot additions of monomer increased solids level as high as 40% and polymer to surfactant ratios greater than 40, with particles remaining monodisperse with average diameter smaller than 60 nm. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 48,54, 2010 [source] Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006Yan-Xin Liu Abstract Multiwall carbon nanotube (MWNT) was grafted with polyacrylate- g -poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid-treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X-ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880,6887, 2006 [source] Solid polymer electrolytes I, preparation, characterization, and ionic conductivity of gelled polymer electrolytes based on novel crosslinked siloxane/poly(ethylene glycol) polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Ping-Lin Kuo Abstract A series of crosslinked siloxane/poly(ethylene glycol) (Si,PEG) copolymers were synthesized from the reactive methoxy-functional silicone resin (Si resin) and PEGs with different molecular weights via two kinds of crosslinking reactions during an in situ curing stage. One of the crosslinking reactions is the self-condensation between two methoxy groups in the Si resin, and another one is an alkoxy-exchange reaction between the methoxy group in the Si resin and the OH group in PEG. The synthesized crosslinked copolymers were characterized by Fourier transform infrared spectroscopy, DSC, and 13C NMR. The crosslinked copolymers were stable in a moisture-free environment, but the SiOC linkages were hydrolyzed in humid conditions. The gel-like solid polymer electrolytes (SPEs) were prepared by impregnating these crosslinked Si,PEG copolymers in a propylene carbonate (LiClO4/PC) solution. The highest conductivity reached 2.4 × 10,4 S cm,1 at 25 °C and increased to 8.7 × 10,4 S cm,1 at 85 °C. The conductivities of these gel-type SPEs were affected by the content of LiClO4/PC, the molecular weights of PEGs, and the weight fraction of the Si resin. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2051,2059, 2004 [source] Effects of alkali and silane treatment on the mechanical properties of jute-fiber-reinforced recycled polypropylene compositesJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2010Xinxin Wang Jute-fibers-reinforced thermoplastic composites are widely used in the automobile, packaging, and electronic industries because of their various advantages such as low cost, ease of recycling, and biodegradability. However, the applications of these kinds of composites are limited because of their unsatisfactory mechanical properties, which are caused by the poor interfacial compatibility between jute fibers and the thermoplastic matrix. In this work, four methods, including (i) alkali treatment, (ii) alkali and silane treatment, (iii) alkali and (maleic anhydride)-polypropylene (MAPP) treatment, and (iv) alkali, silane, and MAPP treatment (ASMT) were used to treat jute fibers and improve the interfacial adhesion of jute-fiber-reinforced recycled polypropylene composites (JRPCS). The mechanical properties and impact fracture surfaces of the composites were observed, and their fracture mechanism was analyzed. The results showed that ASMT composites possessed the optimum comprehensive mechanical properties. When the weight fraction of jute fibers was 15%, the tensile strength and impact toughness were increased by 46 and 36%, respectively, compared to those of untreated composites. The strongest interfacial adhesion between jute fibers and recycled polypropylene was obtained for ASMT composites. The fracture styles of this kind of composite included fiber breakage, fiber pull-out, and interfacial debonding. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers. [source] Synthesis 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] Crystallization and Ring-Banded Spherulite Morphology of Poly(ethylene oxide)- block -Poly(, -caprolactone) Diblock CopolymerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2004Shichun Jiang Abstract Summary: The crystallization behavior of crystalline-crystalline diblock copolymer containing poly(ethylene oxide) (PEO) and poly(, -caprolactone) (PCL), in which the weight fraction of PCL is 0.815, has been studied via differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). DSC and WAXD indicated that both PEO and PCL blocks crystallize in the block copolymer. POM revealed a ring-banded spherulite morphology for the PEO- b -PCL diblock copolymer. DSC heating curve for the PEO- b -PCL block copolymer. [source] Miscibility and Physical Properties of Poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate)/Poly(ethylene oxide) Binary BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2009Fang Yu Abstract In order to improve some inferior physical properties of bacterial poly(3-hydroxybutyrate -co- 3-hydroxyhexanoate) [P(3HB -co- 3HHx)] by blending with PEO, the miscibility, spherulite morphology, crystallization behavior and mechanical properties of P(3HB -co- 3HHx)/PEO binary biodegradable polymer blends were investigated. A good miscibility between P(3HB -co- 3HHx) with a 3HHx unit content of 11 mol-% and PEO in the amorphous state was found when the PEO weight fraction was 10,wt.-%, while the miscibility decreased dramatically when the PEO weight fraction exceeded 20,wt.-%. Strongly depending on the blend composition, the mechanical properties of P(3HB -co- 3HHx) was found to be significantly improved by blending with PEO with a weight fraction of ,5,17.5,wt.-%. [source] Metallocene-Catalyzed Gas-Phase Ethylene Copolymerization: Kinetics and Polymer PropertiesMACROMOLECULAR REACTION ENGINEERING, Issue 8 2009Michiel F. Bergstra Abstract The influence of 1-hexene is examined on the kinetics of ethylene copolymerization with a metallocene catalyst in gas phase. A model is derived, which is able to describe a large reaction rate increase due to a small amount of incorporated comonomer. This complexation model describes the measured reaction rates for ethylene and 1-hexene, and the co-monomer incorporation. Polymer properties were analyzed, such as comonomer weight fraction. The density, melting point, and molecular weight of the produced polymer decreased with increase in 1-hexene gas concentration. The in situ 1-hexene sorption is estimated and follows Henry's law, but seems much higher than reported in the literature. [source] Particle size effect on the film-forming process of PS/PBA composite latexesPOLYMER COMPOSITES, Issue 9 2010aziye U In this work, the effect of hard particle size and blend ratio on the film formation behavior of hard polystyrene (PS) and soft poly(n -butyl acrylate) (PBA) latex blends was studied by means of steady-state fluorescence and UV,visible techniques in conjunction with atomic force microscopy. Three different sets of latexes were synthesized: PBA latex (diameter 97 nm), pyrene (P)-labeled large PS (LgPS; diameter 900 nm), and small PS (SmPS; diameter 320 nm). Two different series of latex blends (LgPS/PBA and SmPS/PBA) were prepared with varying blend composition at room temperature separately. Films were then annealed at elevated temperatures above glass transition (Tg) temperature of PS. Fluorescence intensity (IP) from P and photon transmission intensity (Itr) were measured after each annealing step to monitor the stages of film formation. The results showed that a significant change occurred in IP and Itr at a certain critical weight fraction (Rc) of PBA. Below Rc, two distinct film formation stages, which are named as void closure and interdiffusion, were seen. However, at PBA concentrations nearer to or above Rc, no film formation can be achieved. Comparing to the LgPS/PBA, the sintering process of SmPS/PBA particles occurred at much lower temperatures. Film formation stages for R < Rc were modeled, and related activation energies were calculated. Void closure (,H) and interdiffusion (,E) activation energies for SmPS/PBA were also found smaller in comparing with LgPS/PBA series. However, ,H and ,E values were not changed much with the blend composition for both series. POLYM. COMPOS., 31:1637,1652, 2010. © 2009 Society of Plastics Engineers [source] Tensile creep of a long-fiber glass mat thermoplastic composite.POLYMER COMPOSITES, Issue 8 2009This work is part of a larger experimental program aimed at developing a semi-empirical constitutive model for predicting creep in random glass mat thermoplastic (GMT) composites. The tensile creep response of a long-fiber GMT material has been characterized for 3- and 6-mm thick material. Tensile tests showed that the variability within and between plaques are comparable with an overall variability of about 6% and 8% for the 3- and 6-mm thick materials, respectively. The thicker material exhibited slightly higher variability and directional dependence due to greater flow during molding of the plaques. Short-term creep tests consisting of 30 min creep and recovery, respectively, were performed over the stress range between 5 and 60 MPa. Three tests for determining the linear viscoelastic region were considered which showed that the 3- and 6-mm thick GMT are linear viscoelastic up to 20 and 25 MPa respectively. The 6-mm thick GMT consisting of a higher fiber weight fraction was linear over wider stress range. Furthermore, it was found that plastic strains were accumulated during creep, which suggests that a nonlinear viscoelastic,viscoplastic model would be more appropriate for long-term creep at relatively high stresses, which will be presented in our companion paper. The magnitude of the plastic strains developed in the creep tests presented here was lower because a single specimen was loaded at multiple stress level over short durations. Hence, a nonlinear viscoelastic constitutive model has been developed for the two thickness materials. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Transient compositional effects from feeders in a starved flow modular co-rotating twin-screw extruderPOLYMER ENGINEERING & SCIENCE, Issue 11 2002Eung Kyu Kim A process dynamics model of transient output composition variations in a moduar self-wiping twin-screw extruder caused by input disturbances from feeders is developed. The changes of output mass flow rate and weight fraction of additives in the output stream were predicted for various time dependent input modes into a second feeder and other ports part way along the length of the machine. [source] Hydrogen bond-mediated self-assembly and supramolecular structures of diblock copolymer mixturesPOLYMER INTERNATIONAL, Issue 5 2009Shiao-Wei Kuo Abstract This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self-assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self-assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry [source] Preparation and properties of silicone-containing poly(methyl methacrylate) gelsPOLYMER INTERNATIONAL, Issue 11 2005Hamid Javaherian Naghash Abstract Poly(methyl methacrylate) (PMMA) gels with varying amounts of silicone and solvent and constant amounts of crosslinker were prepared by solution free radical crosslinking copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) comonomer systems. They were then studied in benzene at a total monomer concentration of 3.5 mol L,1 and 70 °C. The conversion of monomer, volume swelling ratio, weight fraction and gel point were measured as a function of the reaction time, silicone concentration and benzene content up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in benzene, gel fraction and Fourier-transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by SEM. Based on the obtained results, it was concluded that the FTIR data did not have the capacity to show the presence of the VTES or TEOS moiety in these kinds of copolymers. On the other hand, the variation of weight fraction of gel, Wg, and its equilibrium volume swelling ratio in benzene, qv, exhibited the same behaviour as that of MMA/EGDM copolymers. Also, the dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percent of conversion and gel fraction. Finally, TEOS is not an ideal silicone compound for reaction in the MMA/EGDM copolymerization system, whereas VTES is a suitable silicone comonomer for this system and it has been proved useful. Copyright © 2005 Society of Chemical Industry [source] Hydrophobic surface properties of fluoropolyetherimide blends for pervaporation membranesPOLYMER INTERNATIONAL, Issue 12 2003M Larhrafi Abstract The well-known polyetherimide (ULTEM 1000) is obtained by step-reaction of bisphenol. A diphthalic anhydride (BAPA) with m-phenylene diamine and newly related fluorinated poly etherimides synthesized from BAPA and 2,3-bis(2,2,3,3,4,4,5,5,5-nonafluoropentyl)butan-1,4 diamine (NFD) led to compatible blends over the entire range of composition. Miscible one-phase blends have been suggested by a good correlation of Tgversus NFD monomer unit weight fraction (w) (Fox and Couchman equations) and a regular morphology by scanning electron microscopy. Surface energy of blend films fell from 45.3 to 27.4 mJ m,2 for w , 0.1 corresponding to a NFD molar fraction y , 0.06. Cast-evaporated films from fluorinated copolyetherimides and blends with y < 0.15 were ductile and gave conveniently hydrophobic non-porous membranes that withstood the experimental conditions of pervaporation tests. Copyright © 2003 Society of Chemical Industry [source] Conductivity studies and performance of chitosan based polymer electrolytes in H2/air fuel cellPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2009S. R. Majid Abstract Four chitosan-based electrolyte systems chitosan,H3PO4, chitosan,H3PO4,Al2SiO5, chitosan,H3PO4,NH4NO3 and chitosan,H3PO4,NH4NO3,Al2SiO5 were studied. The highest conducting sample at room temperature in each system have compositions of (in weight fraction) 0.62chitosan,0.38H3PO4, 0.615chitosan,0.377H3PO4,0.008Al2SiO5, 0.56chitosan,0.34H3PO4,0.10 NH4NO3, 0.5572chitosan,0.3383H3PO4,0.0995NH4NO3,0.005Al2SiO5. The conductivity for the samples is (5.36,±,1.32),×,10,5,S,cm,1, (1.12,±,0.18),×,10,4,S,cm,1, (1.16,±,0.35),×,10,4,S,cm,1, and (1.82,±,0.10),×,10,4,S,cm,1, respectively. The open-circuit voltage of the fuel cells utilizing electrolytes with conductivity of the order 10,4,S,cm,1 is ,0.9,V and the current density is greater than 20,mA,cm,2 at room temperature. Results show that the conductivity of the polymer electrolyte membrane influences the current density and performance of the fuel cell. Copyright © 2009 John Wiley & Sons, Ltd. [source] Investigation of proteins and peptides from yeastolate and subsequent impurity testing of drug productBIOTECHNOLOGY PROGRESS, Issue 2 2009Lawrence W. Dick Jr. Abstract Hydrolysates play an important role in modern biological production. These mixtures are mostly undefined and contain a mixture of proteins, peptides, and amino acids along with other non,amino acid-based components. Recently, there has been an interest in defining and sequencing proteins and peptides in these hydrolysates to subsequently develop an assay to ensure removal during product purification. This work investigates an ultrafiltrate of yeastolate to determine whether any protein is present. Size exclusion chromatography indicated a possible high molecular weight component (>10 kDa). This suspected high molecular weight fraction was collected and investigated. It was determined that this fraction consists of nucleic acids; and no protein was detected using sensitive modern techniques including HPLC, mass spectrometry, and SDS-PAGE. Next, five unique, yeast-specific peptides were identified, sequenced, and confirmed. Finally, an impurity assay for any residual yeast specific peptides was developed and the analytical metrics were determined including accuracy, precision, linearity, range, and limits of detection and quantitation. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Effect of chirality on PVP/drug interaction within binary physical mixtures of ibuprofen, ketoprofen, and naproxen: A DSC studyCHIRALITY, Issue 8 2009Ivan T. Ivanov Abstract We report on the thermal behavior of freshly prepared binary drug/polymer physical mixtures that contained ibuprofen, ketoprofen, or naproxen as a drug, and polyvinylpyrrolidone (PVP), hydroxyethylcellulose (HEC), or methylcellulose (MC) as excipient. At 6,10°C/min heating rates the DSC detected a sharp, single endotherm that corresponds to the melting of drug. On heating physical mixtures of PVP and racemic ibuprofen or ketoprofen at lower heating rates, another endotherm was registered in front of the original one. To observe the additional endotherm, specific minimal values of the heating rate and of PVP weight fraction were needed; for ibuprofen and ketoprofen they were 1.5 and 2.0°C/min, and 5 and 15% (w/w), respectively. At greater PVP weight fractions the top temperatures, Tmp, of both peaks were reduced almost linearly indicating strong solid-state interfacial reaction between the drug particles and PVP matrix. The additional endotherm was abolished at greater heating rates (2°C/min for ibuprofen, 3°C/min for ketoprofen), by replacing the racemate with respective S(+)-enantiomer and by replacing PVP with HEC and MC. Hence, the possible inclusion of enantioselective component within the PVP/drug interaction, responsible for the amorphization of physical mixture over storage, is assumed. Chirality, 2009. © 2008 Wiley-Liss, Inc. [source] Relationship between antithrombotic activities of fucans and their structureDRUG DEVELOPMENT RESEARCH, Issue 4 2000Catherine Boisson-Vidal Abstract A low molecular weight fucan fraction extracted from the brown seaweed Ascophyllum nodosum was previously shown to exhibit dose-related venous antithrombotic activity with an ED80 of about 20 mg/kg, 2 h after a single subcutaneous injection HCII (Colliec et al. [1991] Thromb Res 64:143,154; Mauray et al. [1995] Thromb Haemast 74:1280,1285). Its activity was comparable to that of a low molecular weight heparin (Dalteparin®). This fucan fraction is one of several, with a range of different structure parameters, prepared by degradation of the whole native fucan. These low molecular weight fractions were compared using a Wessler stasis thrombosis model in rabbits and by determination of their in vitro and ex vivo anticoagulant activities. Intravenous administrations of these fractions reduced thrombosis in a dose-dependent manner. Partial removal of sulfate groups and/or partial degradation lead to a significant decrease in their anticoagulant and antithrombotic activities. The integrity of the regular pattern of sulphation of the fucoidan is necessary for antithrombotic activity. Drug Dev. Res. 51:216,224, 2000. © 2001 Wiley-Liss, Inc. [source] Fracture behaviour of PC/ABS resin under mixed-mode loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2001Husaini Fracture behaviour of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) under mixed-mode loading conditions was studied for several weight fractions of PC and ABS. Mode I and mixed-mode fracture tests were carried out by using compact,tension,shear specimens. At a certain value of mixed-mode loading ratio KII,/KI, a crack of the shear type will initiates at the initial crack tip. Fracture toughness increases under mixed-mode loading with an increase in the mode II component, whereas it reduces with the appearance of a shear-type fracture. Fracture toughness and the appearance of a shear-type fracture depends on the blending ratio of PC and ABS. The transition to shear-type fracture occurs at lower value of KII,/KI for resins with higher fracture toughness. [source] Modeling the Relaxation Mechanisms of Amorphous Shape Memory PolymersADVANCED MATERIALS, Issue 31 2010Thao. D. Nguyen Abstract In this progress report, we review two common approaches to constitutive modeling of thermally activated shape memory polymers, then focus on a recent thermoviscoelastic model that incorporates the time-dependent effects of structural and stress relaxation mechanisms of amorphous networks. An extension of the model is presented that incorporates the effects of multiple discrete structural and stress relaxation processes to more accurately describe the time-dependent behavior. In addition, a procedure is developed to determine the model parameters from standard thermomechanical experiments. The thermoviscoelastic model was applied to simulate the unconstrained recovery response of a family of (meth)acrylate-based networks with different weight fractions of the crosslinking agent. Results showed significant improvement in predicting the temperature-dependent strain recovery response. [source] Rapid and accurate quantitative phase analysis using a fast detectorJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2004A. F. Gualtieri The accuracy of the weight fractions calculated with the Rietveld method for various polycrystalline systems using data collected for very short times (5,45,min) with an RTMS (real-time multiple strip) detector was verified. The weight estimates were compared with those obtained using the same conventional Bragg,Brentano geometry, a gas proportional detector and a 13,h data acquisition. The analysed samples were monophasic and polyphasic mixtures with different degrees of complexity: the standard corundum NIST 676; a sample (labelled 1g) provided as a standard sample for the IUCr CPD Quantitative Phase Analysis Round Robin; a natural pyroclastic rock from Riano (Rome, Italy) containing zeolitic minerals and a glass phase; and a hydraulic lime. The results of the refinements show estimated weights consistent with both those obtained with a gas proportional detector and with the nominal values, indicating a very good accuracy. Only when variable slits are used, the accuracy of the estimated weights slightly decreases. The outcome of this work is a very important step forward towards fast and accurate QPA for production control and quality management, obtained by combining the use of a rapid detector and existing user-friendly software. [source] Polymerization of methyl methacrylate in the presence of a nonpolar hydrocarbon solvent.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Abstract This article presents the ternary phase diagram for methyl methacrylate (MMA), poly(methyl methacrylate) (PMMA), and n -hexane system at 70°C. It was constructed by both theoretical calculations and online laser light scattering (LLS) technique. In situ polymerization of MMA in a nonpolar nonsolvent carried out in a LLS cell provides a new means for the accurate detection of the cloud points of highly viscous polymer mixtures, with polymer weight fractions over 0.6. The ternary phase diagram measured in this study can be used to design the reaction conditions for the precipitation and/or dispersion polymerization in a nonpolar nonsolvent medium where polymerization kinetics as well as polymer particle morphologies are strongly affected by thermodynamic phase separation phenomena. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Nonlinear surface electrical resistivity of graphite,polyurethane composite filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Ganesh K. Kannarpady Abstract In this article, we study the surface resistivity of graphite,polyurethane composites using voltage,current characteristics. The evolution of the percolation network of graphite in polyurethane is qualitatively studied using optical micrographs. As expected, the surface resistivity decreases as a function of graphite concentration. In particular, the surface resistivity of the 69% graphite,polyurethane composite is about four orders of magnitude lower than the surface resistivity of the 27% graphite,polyurethane composite. The electrical resistivity of the composite is found to be highly nonlinear with respect to an increasing voltage at a low graphite weight fraction. On the other hand, the nonlinearity is significantly milder at higher weight fractions. The reasons behind the nonlinearity are discussed. Very preliminary studies indicate that very low weight fractions of single wall carbon nanotubes (e.g. 2.5%) are sufficient to generate electrical conductivities comparable to much higher loading fractions (, 60% and higher) of the heavier graphite particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] A bi-order kinetic model for poly(methyl methacrylate) decomposition in HNO3 using microwave irradiationAICHE JOURNAL, Issue 8 2009Chun-Chih Lin Abstract In this study, a novel bi-order model combined with zero- and first-order kinetics was proposed for the decomposition of PMMA (MW = 120,000 g/mol) in concentrated HNO3 by microwave irradiation. To develop and validate this model, Fourier Transform Infrared spectroscopy, scanning electron microscopy, fractional-life method, the gravimetric analysis and Newton's method were utilized. Rate constants, activation energies, the pre-exponential factors and the weight fractions (,) via main-chain scission for the decomposition at 423,453 K were derived from this model. The zero-order reaction was observed dominant at 423,443 K, while the first-order reaction dominated at 453 K and 473 K. The digestion efficiency increased as HNO3 was increased to >3 mL at 423 K,443 K. At 473 K, the digestion was almost 100% when HNO3 volume was >3 mL. The estimated , values increased with HNO3 volume at 423 and 443 K, but varied insignificantly at 453 and 473 K. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] | ||||||||||||||||||||||||||||