Impact behavior of phenolphthalein poly(ether sulfone) ultrahigh molecular weight polyethylene blends

This work presents the structure and impact properties of phenolphthalein poly(ether sulfone) blended with ultrahigh molecular weight polyethylene (PES-C/UHMWPE) at different compositions. The addition of UHMWPE can considerably improve the Charpy and Izod impact strength of the blends. The fracture surface is examined to demonstrate the toughening mechanics related to the modified PES-C resin. (C) 1998 John Wiley & Sons, Inc.

Characterization and catalytic behavior of La2-x(Sr,Th)(x)CuO4+/-lambda in reaction NO+CO

Two mixed oxide systems La2-xSrxCuO4+/-lambda(0.0 less than or equal to x less than or equal to 1.0) and La2+xThxCuO4+/-lambda(0.0 less than or equal to x less than or equal to 0.4) with K2NiF4 structure were prepared by varying re values; Their crystal structures were studied by means of XRD and IR spectra. The average valence of Cu ion at B site, nonstoichiometric oxygen (A) and the chemical composition in the bulk and on the surface of the catalysts were measured by means of chemical analysis and XPS. The catalytic behavior in reaction CO + NO was investigated under the regular change of average valence of Cu ion at B site and nonstoichiometric oxygen (lambda). Meanwhile, the adsorption and activation of the small molecules NO and the mixture of NO + CO over the mixed oxide catalysts were studied by means of MS-TPD. The catalytic mechanism of reaction NO + CO over these oxide catalysts were proposed; and it has been found that, at lower temperatures the activation of NO is the rate determining step and the catalytic activity is related to the lower valent metallic ion and its concentration, while at higher temperatures the adsorption of NO is the rate determining step and the catalytic activity is related to the oxygen vacancy and its concentration.

Studies on water-swellable elastomers .2. Thermal properties and crystalline behavior of amphiphilic graft copolymers with poly(ethylene glycol) side chains

The thermal properties and crystalline structure of the amphiphilic graft copolymers CR-g-PEG600, CR-g-PEG2000, and CR-g-PEG6000 using chloroprene rubber (CR) as the hydrophobic backbone and poly(ethylene glycol) (PEG) with different molecular weights as the hydrophilic side chains were studied by DSC and WAXD. The results showed that a distinct phase-separated structure existed in CR-g-PEGs because of the incompatibility between the backbone segments and the side-chain segments. For all the polymers studied, T-m2, which is the melting point of PEG crystalline domains in CR-g-PEG, decreased compared to that of the corresponding pure PEG and varied little with PEG content. For CR-g-PEG600 and CR-g-PEG2000, T-m1, which is the melting point of the CR crystalline domains, increased with increasing PEG content when the PEG content was not high enough, and at constant PEG content, the longer were the PEG side chains the higher was the T-m1. The crystallite size L-011 of CR in CR-g-PEGs increased compared to that of the pure CR and decreased with increasing PEG content. (C) 1997 John Wiley & Sons, Inc.

The double-melting behavior of poly(ether diphenyl ether ketone)

Poly(ether diphenyl ether ketone) (PEDEK) synthesized by the nucleophilic route has the following chemical structure: [GRAPHICS] At some given temperatures for a given time isothermally crystallized PEDEK sample exhibits two endothermic peaks which are similar to PEEK and PEEKK The melting behavior of PEDEK crystallized from the glassy state is investigated through differential scanning calorimeter (DSC). We consider that the high-melting peak is related to the perfect crystals and the low-melting peak is associated with a few imperfect crystals. (C) 1997 John Wiley & Sons, Inc.

Miscibility and crystallization behavior of thermosetting polyimide thermoplastic polyimide blends

Compatibility, morphology, crystalline structure and mechanical properties of the blends of a thermosetting polyimide with thermoplastic polyimides consisting of dianhydrides of different lengths have been studied by the use of dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) techniques. The results of our research show that the blends change from compatible to semi-compatible when the difference between the length of the dianhydrides of the two components increases. Addition of a thermoplastic polyimide inhibits the crystallization of the thermosetting component. However, this effect decreases with increasing length of the dianhydrides and the distribution of the molecules of the thermoplastic polyimide component changes from interlamellar to interfibrillar. Impact strength and morphology of the fractured surfaces indicate that among the semiinterpenetrating polymer networks (semi-IPN) obtained the toughening effect of the partially compatible one is the best. The results are discussed in terms of charge transfer interaction between imide group and p-phenylene group.

SYNTHESIS, CHARACTERIZATION AND CATALYTIC BEHAVIOR OF LA2-XSRXCOO4+/-LAMBDA (X=0-2) IN COMPLETE OXIDATION

A series of mixed oxides La2-xSrxCoO4+/-lambda (x=0-2) with varying x values was synthesized. The crystal structure of this series of mixed oxides was studied by using XRD. The result showed that when x=0.25-1.5 the mixed oxides possessing K2NiF4 structure are formed. The valences of the transition metal Co and the relation between +/-lambda content and x value by using chemical analysis method have been measured, too. The redox property of this series of mixed oxides and different kinds of oxygen species were studied by IR, TPD, TPR, XPS and SEM methods. The catalytic activity in the complete oxidation of CO and CH4 was investigated and the relationships between the activity, composition and structure of the mixed oxides have been elucidated.

PHASE-TRANSFER CHEMISTRY OF HETEROPOLYANIONS .1. RESEARCH ON SOLVATION BEHAVIOR OF SUBSTITUTED KEGGIN AND DAWSON ANIONS IN THE NONPOLAR-SOLVENTS

The heteropolyanions of the Keggin structure ZW(11)O(39)M(H2O)(n-)(Z = Si, Ge, P; M = Ni2+, Cu2+, Cr3+, Co2+, n = 4 similar to 6) and Dawson structure P(2)W(17)O(61)M(H2O)(n-)(M = Ni2+, Cu2+, Cr3+, Co2+, n = 7, 8) have been transferred into the non-polar

CATALYTIC BEHAVIOR OF METAL-IONS LOCATED AT DIFFERENT SITES OF HETEROPOLYCOMPOUNDS

It was discovered experimentally that heteropolymolybdophosphoric acids (HPA) with Keggin and Dawson structure are inactive for H2O2-decomposition, while their salts (Fe3+, Cu2+, Co2+ and Mn2+) all possess more activity. It could be concluded that the act

EFFECT OF LANTHANIDE IONS ON THE PHASE-BEHAVIOR OF DIPALMITOYLPHOSPHATIDYLCHOLINE MULTILAMELLAR LIPOSOMES

The effect of lanthanide ions (Ln(3+)) and their coordination compounds of diethylenetriamine pentaacetic acid (DTPA) on the phase behavior of dipalmitoylphosphatidycholine (DPPC) multilamellar liposomes has been studied by differential scanning calorimet

AN INFRARED SPECTROSCOPIC CHARACTERIZATION OF THE SOLID SOLID BEHAVIOR OF DODECYLAMMONIUM CHLORIDE

The infrared spectra of the bilayer system dodecylammonium chloride has been studied as a function of temperature. Unusual splitting of some vibrational modes helps us to characterize the structure of different solid states. This study provided the evidence for the occurrence of an order-disorder phase transition whose onset occurs at 327 K and its completion ends at 339 K. In the low temperature phase below 327 K, the virgin crystals form a well-ordered phase with all-transhydrocarbon chains. In the intermediate state between 327 and 339 K, the data demonstrate the introduction of intramolecular as well as intermolecular disorder. The coexistence of solid and liquid-crystal-like states is shown by the persistence of factor group splittings together with the existence of defect bands in the wide intermediate temperature range. In the high temperature phase over 339 K the crystals convert to a liquid-crystal-like system with extensive motional and conformational disorder, but still show characteristics in their infrared spectra which indicate the presence of ordered segments in the hexagonal solid phase.

ELECTROCHEMICAL STUDY OF ISOPOLY AND HETEROPOLY OXOMETALLATE FILM MODIFIED MICROELECTRODES .5. PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF A 2/18-MOLYBDODIPHOSPHATE ANION MONOLAYER MODIFIED ELECTRODE

In this paper a carbon fibre (CF) microelectrode modified with the 2:18-molybdodiphosphate anion by simple adsorption is described and its electrochemical behaviour is reported. The 2:18-molybdodiphosphate anion (alpha-P2Mo18O626-), which is a Dawson structure, undergoes five successive multielectron reductions in acidic solution. The first three redox waves correspond to the two-electron process, and the last two waves are four-electron and six-electron processes respectively. On the basis of the experimental results it is shown that the electrode process of alpha-P2Mo18O626- on the CF electrode in acidic solution is simultaneously controlled by the diffusion and adsorption of alpha-P2Mo18O626- anions. When the concentration of the alpha-P2Mo18O626- in the solution is reduced, the electrode process mainly exhibits non-diffusion-controlled behaviour, and the diffusion-limited process takes over as the concentration of alpha-P2Mo18O626- becomes higher. The CF electrode modified with a thin film of alpha-P2Mo18O626- exhibits very good stability and redox behaviour in aqueous acidic solution. The alpha-P2Mo18O626- is reduced to heteropoly blue, with an accompanying protonation process. The addition of more than six electrons to the alpha-P2Mo18O626- anion in an aqueous solution does not result in its decomposition. The result obtained is not the same as that reported previously.

ELECTROCHEMICAL-BEHAVIOR OF N-METHYL-N'-HEXADECYLVIOLOGEN MONOLAYERS ON SILVER ELECTRODES - EFFECTS OF COUNTERIONS

N-Methyl-N'-hexadecylviologen (C16MV) has been the subject of several electrochemical and spectroelectrochemical studies which characterized the species present in various redox states for C16MV monolayers on silver electrode surfaces. Both self-assembled monolayers (SA) and Langmuir-Blodgett (LB) transferred systems have been studied. These indicated inconsistencies regarding the presence or absence of splitting of the first reduction peak in its cyclic voltammogram (CV). The present study demonstrates the important influence of the specific anionic species present in the supporting electrolyte. Splitting may or may not take place, depending on the size and relative strength of the adsorption of specific anions contributed by the supporting electrolyte. Small, strongly adsorbing anions such as iodide produced peak splitting in the CV of C16MV monolayers; bulky but weakly adsorbing anions such as perchlorate may disrupt the ordered structure of monolayers but produce no splitting. Ancillary data provided by surface enhanced Raman spectroscopy (SERS) was consistent with the electrochemical measurements.

DYNAMIC SCALING AND FRACTAL BEHAVIOR OF SPINODAL PHASE-SEPARATION IN POLYMER MIXTURES OF POLY(METHYL METHACRYLATE) WITH POLY(STYRENE-CO-ACRYLONITRILE)

Dynamic scaling and fractal behaviour of spinodal phase separation is studied in a binary polymer mixture of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). In the later stages of spinodal phase separation, a simple dynamic scaling law was found for the scattering function S(q,t):S(q,t) approximately q(m)-3S approximately (q/q(m)). The possibility of using fractal theory to describe the complex morphology of spinodal phase separation is discussed. In phase separation, morphology exhibits strong self-similarity. The two-dimensional image obtained by optical microscopy can be analysed within the framework of fractal concepts. The results give a fractal dimension of 1.64. This implies that the fractal structure may be the reason for the dynamic scaling behaviour of the structure function.

CHARACTERIZATION OF GAMMA-IRRADIATED CRYSTALLINE POLYMER .3. THERMAL-BEHAVIOR OF GAMMA-IRRADIATED POLYAMIDE-1010

Thermal behaviour of gamma-irradiated plain PA1010 and PA1010 containing different amounts of difunctional cross-linking agent BMI was investigated. In DSC endo- and exotherm, it was found that during irradiation, the presence of BMI markedly changes the melting and crystallisation characteristics of PA1010. A supposition that the network of BMI-containing specimens is rather loose in structure was proposed to explain the discrepancy in thermal behaviour between these two kinds of specimens. The supposition was further ascertained by the less brittleness in mechanical property of specimens containing BMI. Besides, the complexity of the thermal behaviour of gamma-irradiated PA1010 was discussed and attributed mainly to the increase in sigma-e, the fold surface free energy of chain fold crystals.

FRACTAL BEHAVIOR OF SPINODAL DECOMPOSITION IN POLYMER BLENDS

Fractal behaviour of ramified domains in the late stage of spinodal phase separation in a binary polymer blend of poly(vinyl acetate) with poly(methyl methacrylate) was investigated by optical microscopic method. In the late stage of the spinodal decomposition, the fractal dimension D is about 1.64. It implies that some anomalous properties of irregular structure probably may be explained by fractal concepts.