Thermal Analysis (thermal + analysis)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Thermal Analysis

  • differential thermal analysis
  • dynamic mechanical thermal analysis
  • mechanical thermal analysis

  • Terms modified by Thermal Analysis

  • thermal analysis data
  • thermal analysis techniques

  • Selected Abstracts

    Unmodified and Modified Surface Sisal Fibers as Reinforcement of Phenolic and Lignophenolic Matrices Composites: Thermal Analyses of Fibers and Composites

    Jane Maria Faulstich de Paiva
    Abstract Summary: The study and development of polymeric composite materials, especially using lignocellulosic fibers, have received increasing attention. This is interesting from the environmental and economical viewpoints as lignocellulosic fibers are obtained from renewable resources. This work aims to contribute to reduce the dependency on materials from nonrenewable sources, by utilizing natural fibers (sisal) as reinforcing agents and lignin (a polyphenolic macromolecule obtained from lignocellulosic materials) to partially substitute phenol in a phenol-formaldehyde resin. Besides, it was intended to evaluate how modifications applied on sisal fibers influence their properties and those of the composites reinforced with them, mainly thermal properties. Sisal fibers were modified by either (i) mercerization (NaOH 10%), (ii) esterification (succinic anhydride), or (iii) ionized air treatment (discharge current of 5 mA). Composites were made by mould compression, of various sisal fibers in combination with either phenol-formaldehyde or lignin-phenol-formaldehyde resins. Sisal fibers and composites were characterized by thermogravimetry (TG) and DSC to establish their thermal stability. Scanning electron microscopy (SEM) was used to investigate the morphology of unmodified and modified surface sisal fibers as well as the fractured composites surface. Dynamic mechanical thermoanalysis (DMTA) was used to examine the influence of temperature on the composite mechanical properties. The results obtained for sisal fiber-reinforced phenolic and lignophenolic composites showed that the use of lignin as a partial substitute of phenol in phenolic resins in applications different from the traditional ones, as for instance in other than adhesives is feasible. Micrograph of the impact fracture surface of phenolic composite reinforced with mercerized sisal fiber (500 X). [source]

    Dependence of magnetoimpedance effect on nanocrystalline structure of Fe-based amorphous ribbons

    I. Z. Rahman
    Abstract This study investigates the magnetoimpedance (MI) behaviour and its dependence on the nanocrystalline structure due to annealing of nominal composition Fe73.5Cu1Nb3Si13.5B9 metallic glass ribbons. Differential Thermal Analyses have shown two distinct stages of primary and secondary crystallisations at ,532 °C and ,703 °C, respectively. XRD, SEM and AFM have shown the evidence of nanocrystallization and surface roughness initiated by changes from glassy to primary crystalline state. Coercivity has decreased near the primary crystallisation temperature and a monotonous increase between the two stages of crystallisation. Beyond the secondary crystallization temperature, the coercivity value remained practically unchanged. Magnetoimpedance ratio (MIR) is found to be sensitive to the annealing temperature. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Nucleation and Crystallization of a Lead Halide Phosphate Glass by Differential Thermal Analysis

    Hongsheng Zhao
    The nucleation and crystallization mechanisms of a lead halide phosphate glass [40P2O5·30PbBr2·30PbF2 (mol%)] were investigated by differential thermal analysis (DTA) and X-ray diffraction analysis. There were two crystalline phases in the crystallized samples: the major phase was PbP2O4, and the minor phase was PbP2O6. The average activation energy for crystallization, E, for two different particle sizes of this glass was determined to be 119 ± 4 kJ/mol by the Kissinger method and 124 ± 4 kJ/mol by the Augis,Bennett method. The Avrami constants were determined to be 1.6 and 2.5 for particle sizes of 203 and 1040 ,m, respectively, by the Ozawa equation, and 1.7 and 2.4 for particle sizes of 203 and 1040 ,m, respectively, by the Augis,Bennett equation. The decrease in the crystallization peak height in the DTA curve with increasing particle size suggested that the particles crystallize primarily by surface crystallization. A nucleation-rate type curve was determined by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, 1/Tp, or the height of the crystallization peak, (,T)p, as a function of nucleation temperature, Tn. The temperature where nucleation can occur for this glass ranges from 360°,450°C and the maximum nucleation rate is at 420°± 10°C. [source]

    Thermal Analysis of Polymers: Fundamentals and Applications

    József Karger-Kocsis
    No abstract is available for this article. [source]

    Improvement of the interfacial compatibility between sugar cane bagasse fibers and polystyrene for composites

    POLYMER COMPOSITES, Issue 2 2004
    Edgar García-Hernández
    Sugar cane bagasse fibers were modified by surface treatments using either physical or chemical methods in order to improve their adhesion to polystyrene matrices. The surface treatment methods used were alkaline treatment, treatment with silane coupling agents, physical coating with polystyrene and grafting of polystyrene with and without crosslinker. Fiber modifications were monitored by Fourier Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis coupled with Thermogravimetric Analysis (DTA-TGA) and Scanning Electron Microscopy (SEM). On the other hand, the improvement of the adhesion between sugar cane modified fibers and polystyrene was assessed by micromechanical pull-out and by macromechanical Iosipescu tests. It was found, from Interfacial Shear Strength values (IFSS), that substantial improvements in fiber-matrix compatibility were achieved. According to micro- and macromechanical test results, the IFSS increased for all treated fibers as compared to non-treated fibers. Particularly, both the coating the fibers or grafting with polystyrene using crosslinker resulted in substantial adhesion improvement to the polystyrene matrix in comparison with the non-treated fibers and fibers treated by alkaline and silane methods only. Polym. Compos. 25:134,145, 2004. © 2004 Society of Plastics Engineers. [source]

    Supporting mechanism of non-toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalysts

    Pengyuan Qiu
    Abstract Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO3 was substituted by chromium (III) acetate for the preparation of Phillips catalyst on the industrial scale owing to health and environmental considerations. There is still considerable research focusing on the relations between the preparation process and catalyst properties in academics. In this work, the supporting mechanism of chromium (III) acetate on silica has been studied by Thermogravimetry,Differential Thermal Analysis (TG-DTA), and Electron Spin Resonance (ESR), in comparison with that of supporting CrO3 on SiO2. The basic chromium (III) acetate supported on high surface area silica gel decomposed differently from that for bulk basic chromium acetate when decomposition temperature was decreased by 15 °C. The decomposition temperature was 299 °C for Cr3(OH)2(Ac)7/SiO2 catalyst precursor, which would be firstly transferred into CrO3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr2O3, which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr3(OH)2(Ac)7/SiO2, such thermal inductive reduction became more severe. ESR spectra of Cr3(OH)2(Ac)7/SiO2 and CrO3/SiO2 catalyst precursors showed that a small amount of supported Cr5+ can exist stably on silica gel surface at temperatures higher than 200 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Estimation of Flame Retardancy Effect by Thermal Analysis Using Kinetic Parameters Obtained under Non-Isothermal Conditions in Air

    Gabriela Vlase
    Abstract A series of compounds obtained from urea, phosphoric acid and inorganic salts of Zn, Ni and Ca, were tested in respect of their flame-retardancy behavior. The estimation criteria were the kinetic parameters obtained in air, under non-isothermal conditions, on a Perkin-Elmer Diamond device, at heating rates of 5, 10, 12 and 15 deg·min,1. The flame-retardancy effect was assigned to the significant endothermic decomposition at relatively low temperature (150,200°C). The quantitative estimation of the thermal behavior was performed by comparison of the kinetic data obtained by Flyn-Wall-Ozawa, Friedman and NPK (Sempere-Nomen) methods. The kinetic homogeneity and a very good quality of the model are arguments in favour of the NPK method. The Ni containing material exhibited the best flame-retardancy behavior, i.e. higher activation energy and mass loss, respectively a single decomposition step with both physical and chemical processes. The results were validated by fire resistance tests. [source]

    Synthesis, Characterization, and Field-Effect Transistor Performance of Thieno[3,2-b]thieno[2,,3,:4,5]thieno[2,3-d]thiophene Derivatives

    Ying Liu
    Abstract The synthesis, characterization, and field-effect transistor (FET) properties of a new class of thieno[3,2-b]thieno[2,,3,:4,5]thieno[2,3-d]thiophene derivatives are described. The optical spectra of their films show the presence of stronger interactions between molecules in the solid state. Thermal analyses reveal that the three materials are thermally stable and have no phase transitions at low temperature. The crystal structures are determined, and show ,-stacked structures and intermolecular S···S contacts. These organic materials exhibit p-type FET behavior with hole mobilities as high as 0.14,cm2,V,1,s,1 and an on/off current ratio of 106. These results indicate that thieno[3,2-b]thieno [2,,3,:4,5]thieno[2,3-d]thiophene, as a linear ,-conjugated system, is an effective building block for developing high-performance organic semiconductors. [source]

    Effect of molecular structure of hybrid precursors on the performances of novel hybrid zwitterionic membranes

    Junsheng Liu
    Abstract Three types of novel hybrid zwitterionic membranes were prepared via a coupling reaction between two silane-coupling agents in a nonaqueous system and a subsequent reaction with 1,4-butyrolactone to create ion pairs in the hybrid precursors. FT-IR spectra corroborated the corresponding reactions. The synthesized membranes were characterized by thermal analyses, ion-exchange capacities, streaming potentials, and pure water flux. Thermal analyses exhibited that the degradation temperature of the hybrid precursors decreased with an increase in zwitterionic extent because of the introduction of ion pairs. Ion-exchange capacity measurements revealed that the anion-exchange capacities and cation-exchange capacities were in the range of 0.023,0.05 and 0.32,0.58 mmol g,1, respectively. Streaming potentials displayed that when the membranes coated for one or three times, the isoelectric points were in the pH range of 6.6,7.58 and 6.58,7.7, respectively. The pure water flux showed that it could be affected by the coating times and the ingredients of these zwitterionic membranes. This difference in membrane's characteristics can be ascribed to the effect of molecular structure of the hybrid precursors. Both the Coulombic interactions of ion pairs between the polymer chains and the hydrophilicity of these membranes were proposed to clarify the above phenomena. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    Role of Sulfate in Structural Modifications of Sodium Barium Borosilicate Glasses Developed for Nuclear Waste Immobilization

    Raman K. Mishra
    A sodium barium borosilicate glass matrix with a higher solubility of sulfate has been developed recently at Bhabha Atomic Research Centre for vitrification of sulfate bearing high-level nuclear waste. We report here the studies carried out to understand the influence of sulfate ion on the three-dimensional borosilicate network. Experiments were carried out with sodium barium borosilicate base glass samples loaded with varying amounts of SO42, (0,5 mol%). Phase separation studies on the samples revealed that as much as 3 mol% of SO42, can be loaded within the base glass without any phase separation, however, beyond this limit BaSO4 (barite) crystallizes within the matrix. Thermal analyses of the samples indicated a shift in glass transition temperature from 534° (0 mol% SO42,) to 495°C (3 mol% SO42,) and it remained more or less unaltered afterwards even with high SO42, loading. A similar observation of structure stabilization was obtained from 29Si MAS,NMR studies also, which showed that with 2 mol% of SO42, loading, the Q2:Q3 ratio changed from 59:41 (for samples with 0 mol% SO42, loading) to 62:38 and it remained almost the same afterwards even with higher SO42, loading. 11B MAS NMR patterns of the glass samples, however, remained unchanged with SO42, loading ([BO4]:[BO3]=38:62). Based on 29Si and 11B MAS NMR studies, the authors propose two different ways of interaction of SO42, ions with the borosilicate network: (i) the network modifying action of SO42, ions with -Si,O,Si- linkages, at low SO42, ion concentration (<2 mol%) and (ii) the preferential interaction of SO42, with the Ba2+ ions at high SO42, concentration (>2 mol%). [source]

    Preparation of polyaniline/vermiculite clay nanocomposites by in situ chemical oxidative grafting polymerization

    Zhaobin Tang
    Abstract BACKGROUND: Recently, conducting polymers have attracted much attention, since they have interesting physical properties and many potential applications, such as in conductive coating charge storage. Hence the synthesis of conducting polymer nanocomposites is also an area of increasing research activity. RESULTS: Vermiculites (VMTs) were successfully delaminated using an acid treatment. Polyaniline (PANI)/VMT nanocomposites were prepared by in situ chemical oxidative grafting polymerization. CONCLUSION: The chemical grafting of PANI/VMTs was confirmed by Fourier transform infrared and UV-visible spectroscopy. The percentage of grafted PANI was 142.7 wt% as a mass ratio of the grafting PANI and charged nano-VMTs, investigated using thermogravimetric analysis. In addition, characteristic agglomerate morphology of PANI was observed in the composites using scanning electron microscopy. Thermal analyses indicated that the introduction of VMT nanosheets had a beneficial effect on the thermal stability of PANI. The electrical conductivity of the nanocomposites was 3.9 × 10,3 S cm,1, a value typical for semiconductors. Copyright © 2009 Society of Chemical Industry [source]

    Reactive doping of PAni,CSA and its use in microwave absorbing materials

    R. S. Biscaro
    Abstract Conductive coatings have been studied for static dissipation and as microwave absorbing materials. The doping process of polyaniline (PAni), which makes it conductive, is an important stage that determines the coating performance. For this purpose, polyaniline was doped by reactive processing in a torque rheometer using different molar ratios between PAni and acid (PAni:CSA) at three different temperatures (80, 90, and 100°C). Aqueous solution doping was also used in the ratio of 1:2 of PAni/CSA, with the aim to investigate the influence of different methods of PAni doping on its characteristics and, consequently, on the performance of coatings. Thermal analyses of the processed materials showed that PAni doped by both routes, reactive and solution processing, showed similar behaviors. X-ray diffraction analyses showed a semicrystalline structure for the PAni,CSA doped by reactive processing using high CSA concentrations and temperature. It was also observed that the doping process affects the dispersion of the components into the conductive coatings. Microwave absorption measurements (8,12,GHz) of PU-doped PAni blends showed the dependence of the doping type, the PAni,CSA concentration, and the mixing conditions of the components on the coating performance; it was found up to 99% of attenuation of the incident radiation for some composites in a narrow frequency range. The microwave absorption efficiency of the coating samples prepared by using the reactive doping process indicates the advantage of this methodology over solution doping. Moreover, the reactive process addresses the environmental requirements. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Recycled PCB flour reinforced linear low-density polyethylene composites enhanced by water cross-linking reaction

    Chen-Feng Kuan
    Abstract Recycled printed circuit board (PCB) flour reinforced linear low-density polyethylene (LLDPE) composites were prepared successfully. Water cross-linking technique was adopted to improve the physical characteristics of the composites. Composites were compounded using a twin-screw extruder and treated with a coupling agent (vinyltrimethoxysilane, VTMOS) and a compatibilizer (polyolefin elastomer grafted with melaic acid, POE-g-MA). They were then moisture-cross-linked in hot water. The composite that was cross-linked in water exhibited better mechanical properties than the noncross-linked composite because of strong chemical bonding between the filler and the polyolefin matrix. When the PCB flour content reaches 60 wt% following 4 h of water cross-linking, the tensile strength and the flexural strength are increased by 18.8% (12.8,15.2 MPa) and 13.2% (21.9,24.8 MPa) respectively. Scanning electron microscopy (SEM) images of the fracture surfaces of water cross-linked composites indicated that good interfacial strength existed between the filler and the polyolefin matrix. Thermal analyses of water cross-linked composites indicated that the thermal degradation temperature and the heat deflection temperature (HDT) of the composite increased with the increasing of water cross-linking time. The HDT of the composite rose from 55.8 to 83 °C. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Growth and properties of ferroelectric potassium ferrocyanide trihydrate single crystals

    R. Kanagadurai
    Abstract Single crystals of potassium ferrocyanide trihydrate, K4[Fe(CN)6·3H2O (KFCT), a ferroelectric material with Curie temperature 251K were grown in silica gel at room temperature for the first time by the solubility reduction method. Resorcinol and ethyl alcohol were used for the purpose of gel setting and supernatant liquid respectively. Optical and mechanical properties were studied for the grown crystal. The structure of the grown crystal was confirmed by X-ray diffraction analysis. Fourier Transform Infrared (FTIR) and FT Raman spectral analysis of the crystalline samples reveal that the crystalline sample consist consists of all functional groups. Thermal analysis of the crystalline sample was performed by TGA and DTA methods. The Vicker's micro hardness value was measured for KFCT crystals. The square etch pits with a hopper-like structure is an indicative of 2D nucleation mechanism. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Extraction, purification and characterization of wax from flax (Linum usitatissimum) straw

    Yasantha Athukorala
    Abstract The chemical composition and selected physical parameters of wax extracted from flax straw with supercritical CO2 (SC-CO2) and hexane have been determined. From the GC/MS results, clear variations in composition and component distributions were observed between SC-CO2 - and hexane-extracted samples. The major components of the SC-CO2 and hexane extracts from three flax cultivars were: fatty acids (36,49%), fatty alcohols (20,26%), aldehydes (10,14%), wax esters (5,12%), sterols (7,9%) and alkanes (4,5%). Purification of SC-CO2 -extracted wax with silica gel chromatography yielded 0.4,0.5% (dry matter) and was composed primarily of wax esters (C44, C46 and C48) and alkanes (C27, C29 and C31). UV-Vis scans of the purified wax samples exhibited two main peaks indicating the presence of conjugated dienes and carotenoids or related compounds. Fourier transform infrared results showed prominent peaks at 2918 (-C-H), 2849 (-C-H), 1745 (-C=O), 1462 (-C-H), 1169 (-C-O) and 719,cm,1 (-(CH2)n -), with NorLin wax showing a slightly deviating pattern compared to the other samples. Thermal analysis by differential scanning calorimetry revealed a mean melting point of 55,56,°C and oxidation temperatures of 146,153,°C for purified wax from flax straw processed using different procedures. [source]

    Thermal analysis of multi-finger GaInP collector-up heterojunction bipolar transistors with miniature heat-dissipation packaging structures

    Pei-Hsuan Lee
    Abstract We build up a finite element modeling (FEM) approach to analyze the thermal performance of collector-up (C-up) heterojunction bipolar transistor (HBTs) with a heat-dissipation via configuration. Highly compact heat-dissipation packaging structures of GaInP/GaAs C-up HBTs have been designed and evaluated systematically. In this work, we devise the 2-D and 3-D models to simulate the actual devices and to investigate the temperature distribution behavior. Results from 2-D model indicate that the large heat-dissipation via configuration can be further reduced by 29% to meet the requirement of HBT-based small high-power amplifiers (HPAs) for the cellular phones. Furthermore, the demonstrated results show that the maximum temperature within the collector calculated from 3-D model is lower than that from 2-D model. In the 3-D analysis, it is revealed that the configuration can be reduced by 32%. Therefore, thinning the heat-dissipation via constructed underneath the GaInP/GaAs C-up HBT should be helpful for miniaturization of HBT-based HPAs in future mobile communication systems. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Synthesis and characterization of zwitterionic organogels based on Schiff base chemistry

    Nazia Tarannum
    Abstract Poly(sulfobetaine)s and poly(carboxybetaine)s have been extensively studied for their zwitterionic and biocompatible nature. The specific features that make such zwitterionic structures technologically important are their chemical structure, a straight forward synthetic route, high ionic contents with interesting dilute solution, and solid state properties. The objective of this work is to synthesize novel zwitterionic polymers having gel characteristics. Here, p- phenylene diamine/melamine react as nucleophiles with glutaraldehyde to produce poly(schiff base)s. In the subsequent step, the poly(sulfobetaine)s and poly(carboxybetaine)s were produced on treatment with 1,3-propane sultone/,-butyrolactone. Hence, a catalyst free facile approach to novel zwitterionic polymers was obtained. The polymers were characterized by elemental analyses, FTIR, XRD analyses, SEM, pH metric titrations, conductometric titrations, and thermal analyses (TGA/DTA). The polymeric samples carry the gel characteristics, showing lamellar structure with porous network. XRD pattern shows Bragg peaks indicative of superstructures. Thermal analysis indicates the Hoffman elimination of , hydrogen and subsequent release of sulfopropyl/carboxybutyl group. One of the gel polymers shows fluorescence also. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Study on macromolecular lanthanide complexes (V): Synthesis, characterization, and fluorescence properties of lanthanide complexes with the copolymers of styrene and acrylic acid

    Xing Liang
    Abstract In this study, the luminescent macromolecular lanthanide complexes Ln-PSt/AA (Ln = Eu and Tb; St = styrene; AA = acrylic acid) have been synthesized, and an extensive characterization has been carried out by means of elemental analysis, FTIR, thermal analysis, and fluorescence determination. The results showed that the carboxylic groups on the chain of the polymers acted as bidentate ligands coordinated to lanthanide ions; and the coordination degree of COO,/Ln3+ in the macromolecular complexes was closely dependent on both the pH value of the solution and the molar ratio of St to AA in the polymeric ligands. Thermal analysis manifested that these Ln-PSt/AA (Ln = Eu and Tb) complexes had high thermal stability and solvent resistance, and these macromolecular complexes were highly crosslinked. The fluorescence determination indicated that Ln-PSt/AA complexes could emit characteristic fluorescence with comparatively high brightness and good monochromaticity, and the fluorescence intensity changed with increasing lanthanide ions content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Effect of neutron irradiation on the structural, mechanical, and thermal properties of jute fiber

    E. Sinha
    Abstract This article describes the effect of neutron irradiation on jute fiber (Corchorus olitorius). The jute fibers (4.0 tex) were irradiated by fast neutrons with an energy of 4.44 MeV at different fluences ranging from 2 × 109 to 2 × 1013 n/cm2. An important aspect of neutron irradiation is that the fast neutrons can produce dense ionization at deep levels in the materials. Structural analysis of the raw and irradiated fibers were studied by small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. Thermal analysis carried out on the raw and irradiated fibers showed that the thermal stability of the fibers decreased after irradiation. The mechanical properties of the jute fibers were found to decrease after irradiation. The SAXS study showed that the average periodicity transverse to the layer decreased after irradiation, which may have been due to the shrinkage of cellulosic particles constituting the fiber. The residual compressive stress developed in the fiber after irradiation resulted in a decrease in crystallite size as supported by our XRD analysis. Observation with SEM did not indicate any change produced in the surface morphology of the fiber due to irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis, characterization, and electrical properties of diazophenylene bridged Co, Ni, Cu, Ce, and Er phthalocyanine polymers

    Cemil Alkan
    Abstract In this research, diazophenylene bridged metal-phthalocyanine (Pc) polymers were produced from diazonium salt of 1,4-diaminophenylene and presynthesized 1,8,15,22-tetraamino metal-Pcs. 1,8,15,22-Tetraamino metal-Pc complexes of Co, Ni, Cu, Ce, and Er were obtained by reducing 1,8,15,22-tetranitro metal-Pc complexes synthesized from 3-nitrophthalic anhydride, urea, metal salt, and ammonium molybdate catalyst. Complexes and polymers were characterized by Fourier transform infrared (FTIR), ultraviolet,visible (UV,vis), and X-ray powder diffraction spectroscopes. X-ray analysis of the polymers showed that there were short-range orientations in the polymers. Thermal analysis of the complexes and the polymers were done by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10°C min,1 under nitrogen atmosphere. Ash analysis was performed to determine the metal content of the polymers. Viscosimetry and ebullioscopy measurements of the soluble part of the polymers were done for molecular weight analysis of the soluble part in tetrahydrofuran (THF) at 25°C. Four-probe conductivity measurements on isothermal conditions revealed that the polymer samples showed 104 fold increases in their electrical conductivities when doped with iodine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Thermal analysis of merino wool fibres without internal lipids

    M. Martí
    Abstract Merino wool is made up of cuticle and cortical cells held together by the cell membrane complex (CMC), which contains a small amount of internal lipids (IWL) (1.5% by mass). IWL have been extracted from wool on account of their considerable dermatological interest owing to their proportion of ceramides. IWL have been extracted by different methods and solvents, methanol and acetone at laboratory and pilot plant levels. Thermal analysis of these extracted wool fibers is presented using thermogravimetry (TG) and differential scanning calorimetry (DSC). TG provides a measurement of the weight loss of the sample as a function of time and temperature. DSC gives information about possible structure modification of extracted wool fibers. Thermoporometry was applied to evaluate the pore size distribution of extracted wool fibers. The results showed that the extraction process increased the pore size distribution and the cumulated pore volume, which is consistent with some changes in the extracted wool CMC. Extracted fiber becomes more hydrophilic and absorbs a large amount of water. We can conclude that the lipid extraction of wool produced no relevant changes in the crystalline fraction when extracted with acetone. However, part of the amorphous keratin material was extracted with methanol, the rest of the crystalline material becoming more stable. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 545,551, 2007 [source]

    Thermal analysis of polymer,water interactions and their relation to gas hydrate inhibition

    Manika Varma-Nair
    Abstract Gas hydrates formed in oil production pipelines are crystalline solids where hydrocarbon gas molecules such as methane, propane, and their mixtures are trapped in a cagelike structure by hydrogen-bonded water molecules to form undesirable plugs. Methanol and glycol are currently used to prevent these plugs via thermodynamic inhibition. Small amounts of water-soluble polymers may provide an alternate approach for preventing gas hydrates. In this study, we expand the fundamental understanding of water,polymer systems with differential scanning calorimetry. Nonfreezable bound water was used to quantify polymer,water interactions and relate them to the chemical structure for a series of polymers, including acrylamides, cyclic lactams, and n -vinyl amides. For good interactions, the water structure needs to be stabilized through hydrophobic interactions. An increased hydrophobicity of the pendant group also appears to favor polymer performance as a gas hydrate inhibitor. Good inhibitors, such as poly(diethyl acrylamide) and poly(N -vinyl caprolactam), also show higher heat capacities, which indicate higher hydrophobicity, than poor performers such as polyzwitterions, in which hydrophilicity dominated. The phase behavior and thermodynamic properties of dilute polymer solutions were also evaluated through measurements of the heat of demixing and lower critical solution temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2642,2653, 2007 [source]

    Rheological and Thermal Properties of Polylactide/Silicate Nanocomposites Films

    Jasim Ahmed
    ABSTRACT:, Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 °C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G,) of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (Tg) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the,Tg of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. [source]

    Age Determination of Ballpoint Pen Ink by Thermal Desorption and Gas Chromatography,Mass Spectrometry,

    Jürgen H. Bügler Ph.D.
    Abstract:, Two main approaches can be used for determining the age of an ink: indirect dating and direct dating. Indirect dating is based on the chemical analysis of an ink followed by comparison with known samples in a reference collection. The collection should contain information about the inks including the market introduction dates. This approach may allow for an anachronism to be detected. The second concept is based on measuring ink components that change with age. The analysis of solvents in ballpoint inks may be a useful parameter for determining the age of ink on paper. In a previous study, the authors demonstrated that thermal desorption of ink directly from paper, followed by chemical analysis using gas chromatography,mass spectrometry (GC,MS), is a promising procedure for characterizing ink-binder resins and solvents. Preliminary tests showed that monitoring the evaporation of ink solvent from ink on paper is not a suitable method for ink dating. Thermal analysis of ink on paper in two steps revealed that fresh ink releases a relative amount of solvent at a certain low temperature in a defined period of time, which decreases as the ink ages. As a consequence, this relative amount of solvent released at a certain low temperature, and its decrease with time, can be used to estimate ink age. This age-dependent parameter was studied in 85 different inks ranging in age from 1 week to 1.5 years. It was found that some inks showed a significant decrease of this parameter up to an age of several months, and that the aging process can be monitored within this period. For other inks, however, the age-dependent parameter decreases relatively fast, e.g., within a few days, to a constant level, which can be too fast for casework. Based on these results, a general procedure for assessing the age of ballpoint pen inks on paper was developed. [source]

    Thermal analysis of frozen solutions: Multiple glass transitions in amorphous systems

    Gregory A. Sacha
    Abstract Frozen aqueous solutions of sucrose exhibit two "glass transition-like" thermal events below the melting endotherm of ice when examined by DSC, but the physical basis of these events has been a source of some disagreement. In this study, a series of sugars, including sucrose, lactose, trehalose, maltose, fructose, galactose, fucose, mannose, and glucose were studied by modulated DSC and freeze-dry microscopy in order to better understand whether sucrose is unique in any way with respect to this behavior, as well as to explore the physical basis, and the pharmaceutical significance of these multiple transitions. Double transitions were found to be a common feature of all sugars examined. The results are consistent with both thermal events being glass transitions in that (1) both events have second-order characteristics that appear in the reversing signals, (2) annealing experiments reveal that enthalpy recovery is associated with each transition, and (3) Lissajous plots indicate that no detectable latent heat of melting is associated with either transition. The data in this study are consistent with the idea that the lower temperature transition arises from a metastable glassy mixture containing more water than that in the maximally freeze-concentrated solute. Freeze-dry microscopy observations show that for all of the sugars examined, it is the higher temperature transition that is associated with structural collapse during freeze-drying. There is no apparent pharmaceutical significance associated with the lower-temperature transition. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3397,3405, 2009 [source]

    Effect of polymer size and cosolutes on phase separation of poly(vinylpyrrolidone) (PVP) and dextran in frozen solutions

    Ken-ichi Izutsu
    Abstract The aim of this study was to elucidate the effect of the molecular weight of polymers on their miscibility in frozen solutions to model the physical properties of freeze-dried pharmaceutical formulations. Thermal analysis of frozen solutions containing poly(vinylpyrrolidone) (PVP) and dextran of various molecular weights was performed at polymer concentrations below the binodal curve at room temperature. Frozen solutions containing PVP 29,000 and dextran 10,200 showed two thermal transitions (glass transition temperature of maximally freeze-concentrated solution: Tg,) representing two freeze-concentrated amorphous phases, each containing predominantly one of the polymers. A combination of smaller polymers (PVP 10,000 and dextran 1,060) was freeze-concentrated into an amorphous mixture phase across a wide range of concentration ratios. Combinations of intermediate size polymers separated into two freeze-concentrated phases only at certain concentration ratios. Addition of NaCl prevented the phase separation of PVP and dextran in the aqueous and frozen solutions. Higher concentrations of NaCl were required to retain the miscibility of larger polymer combinations in the freeze-concentrate. The molecular weights of the component polymers, polymer concentration ratio, and cosolute composition are the important factors that determine component miscibility in frozen solutions. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:709,717, 2005 [source]

    Synthesis and properties of nitrogen-linked poly(2,7-carbazole)s as hole-transport material for organic light emitting diodes

    Tsuyoshi Michinobu
    Abstract A novel class of carbazole polymers, nitrogen-linked poly(2,7-carbazole)s, was synthesized by polycondensation between two bifunctional monomers using the palladium-catalyzed amination reaction. The polymers were characterized by 1H NMR, Infrared, Gel permeation chromatography, and MALDI-TOF MS and it was revealed that the combination of the monomer structures is important for producing high molecular weight polymers. Thermal analysis indicated a good thermal stability with high glass transition temperatures, e.g., 138 °C for the higher molecular weight polymer P2. To pursue the application possibilities of these polymers, their optical properties and energy levels were investigated by UV-Vis absorption and fluorescence spectra as well as their electrochemical characteristics. Although the blue light emission was indeed observed for all polymers in solution, the quantum yields were very low and the solid films were not fluorescent. On the other hand, the HOMO levels of the polymers estimated from the onset potentials for the first oxidation in the solid thin films were relatively high in the range of ,5.12 to ,5.20 eV. Therefore, light emitting diodes employing these polymers as a hole-transport layer and iridium(III) complex as a triplet emitter were fabricated. The device of the nitrogen-linked poly(2,7-carbazole) P3 with p,p,-biphenyl spacer, which has a higher HOMO level and a higher molecular weight, showed a much better performance than the device of P2 with m -phenylene spacer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3880,3891, 2009 [source]

    Synthesis and MALDI-TOF analysis of dendritic-linear block copolymers of lactides: Influence of architecture on stereocomplexation

    Alexandre Richez
    Abstract Formation of a stereocomplex from polylactide copolymers can be tuned by changing the size and the chain topology of the second block in the copolymer. In particular, the use of a dendritic instead of linear architecture is expected to destabilize the cocrystallisation of polylactide blocks. With this idea in mind, dendritic-linear block copolymers were synthesized by ring-opening polymerization (ROP) of lactides using benzyl alcohol dendrons of generation 1,3 as macroinitiators and stannous octoate as catalyst. Polymers with controlled and narrow molar mass distribution were obtained. The MALDI-TOF mass spectra of these dendritic-linear block copolymers show well-resolved signals. Remarkably, 10% or less of odd-membered polymers are present, indicating that ester-exchange reactions which occur classically parallel to the polymerization process, were in these conditions, very limited. Thermal analysis of polyenantiomers of generation 1,3 and the corresponding blends were examined. The blend of a pair of enantiomeric dendritic-linear block copolymers exhibit a higher melting temperature than each copolymer, characteristic for the formation of a stereocomplex. Melting temperatures are strongly dependent on the dendron generation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6782,6789, 2006 [source]

    Fe3+ Ions Acting as Probes and Agents in Aggregation Processes and Solid-State Reactions in AlO(OH)/Al2O3 Matrices

    Reinhard Stößer
    The fate of doped iron species during various mechanically and thermally initiated redox reactions and aggregation processes in crystalline and amorphous AlO(OH) or Al2O3 matrices was investigated. The amorphization of the matrix was performed by chemical (i.e., via sol,gel processes) or mechanochemical treatment (high-energy ball milling). Thermal analysis, coupled with mass spectrometry (TA-MS), Mössbauer spectroscopy, and electron spin resonance (ESR), was used. The TA under various gas atmospheres allowed preparing samples under a controlled temperature regime, together with a controlled gas influence. Both the effect of mechanical activation and the influence of the iron doping could be followed macroscopically via the down-shift of the peak temperature of the corundum formation. The ESR data characterize the Fe3+ ions and their interaction with the magnetic surrounding based on the fine structure parameters. The Mössbauer data allowed the characterization of the Fe(0), Fe2+, and Fe3+ species, together with providing information about their coordinative surrounding. Both methods provided general complementary spectroscopical information. Unexpectedly, (FeOx)n and (FexAl1,x)2O3 aggregates could also be detected in the range of low Fe concentrations. It was demonstrated that even in the low-level doped systems [(FexAl1,x)2O3 with x,0.01], all the essential spectroscopic phenomena occur. At higher Fe concentrations, they were discovered to be caused by magnetic and spin exchange interactions as well as by solid-state reactions during and after the mechanical activation. [source]

    Synthesis, Densification, and Phase Evolution Studies of Al2O3,Al2TiO5,TiO2 Nanocomposites and Measurement of Their Electrical Properties

    Vikas Somani
    Alumina,aluminum titanate,titania (Al2O3,Al2TiO5,TiO2) nanocomposites were synthesized using alkoxide precursor solutions. Thermal analysis provided information on phase evolution from the as-synthesized gel with an increase in temperature. Calcination at 700°C led to the formation of an Al2O3,TiO2 nanocomposite, while at a higher temperature (1300°C) an Al2O3,Al2TiO5,TiO2 nanocomposite was formed. The nanocomposites were uniaxially compacted and sintered in a pressureless environment in air to study the densification behavior, grain growth, and phase evolution. The effects of nanosize particles on the crystal structure and densification of the nanocomposite have been discussed. The sintered nanocomposite structures were also characterized for dielectric properties. [source]