bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fracto‐emission from neat epoxy resin
Authors: Dickinson J. T. , Jensen L. C. , Bhattacharya S. K. 
Published: March 2011

AbstractFracto‐emission is the emission of particles (e.g. electrons, photons, ions, neutral species) due to crack growth in materials. These emissions can be related to a number of fracture related phenomena including microcracking, crack speed of dynamic crack growth, locus of fracture (in filled materials), and potentially the extent of crack branching. Here, we examine the emission of electrons, positive ions, and photons during and following the fracture of a neat epoxy resin subjected to tensile and tensile impact loading in vacuum. Experiments which detect correlations of crack tip position and emission intensity show that the emissions occur during and following fracture. We also illustrate that observed variations of the fracture surface morphology under different loading conditions correlated with characteristics of the photon and charged particle emission. For example, regions of the surface exhibiting the highest degree of surface roughness resulted in more intense emission.
Acceleration mechanisms in curing reactions involving model systems
Authors: Fedtke Manfred 
Published: March 2011

AbstractThe mechanisms involving some of the most common accelerators in the curing reactions of epoxy resins have been investigated by use of model systems. Phenyl glycidyl ether was used as a model compound. The characterization of the reaction products was mainly carried out by High‐Performance‐Liquid‐Chromatography and by preparative methods. Special attention was paid to the oligomerization reactions of the oxirane ring in the presence of tertiary amines. Three different types of oligomers depending on phenyl glycidyl ethers are discussed. The mechanisms of multifunctional accelerators such as imidazoles or phenol‐MANNICH‐base‐compounds are much more difficult. The extraordinary interaction of imidazoles depends on the formation of different oligomers. Furthermore, the cleavage of the imidazole ring was observed. It is possible that the glycidyl ether oligomerization plays an important role in understanding the network structure. Some aspects of the accelerating effect of tertiary amines in the curing of glycidyl ethers with acid anhydrides were likewise discussed. The results obtained using these model reactions may be applied to influence the curing process in commercial epoxy resin systems.
Molecular weight determination by the small‐angle scattering method without using absolute intensities and contrast
Authors: Pleštil Josef 
Published: March 2011

AbstractA procedure for the molecular weight determination from small‐angle data on a relative scale without knowledge of contrast has been suggested. The contrast may be determined from measurements of scattering curves using at least two concentrations of the dispersed compound. With absolute intensities the method yields the value of excess scattering amplitude. The procedure is applied to the recently published scattering data on bovine serum albumin.
High performance liquid chromatography of glycoconjugates
Authors: El Rassi Ziad , Truei Yunghuoy , Horváth Csaba 
Published: March 2011

AbstractStationary phases were prepared for the analytical and micropreparative high performance affinity chromatography of carbohydrates and glycoproteins by covalent attachment of lectins and certain biogenic amines to the surface of microparticulate, macroporous diol‐silica. Columns packed with immobilized concanavalin A or wheat germ agglutinin afforded rapid separation of both glycoproteins and low molecular weight carbohydrates. The combined use of the two lectins in a mixed bed column or in two columns in series by sequential elution with the appropriate haptenic sugars facilitated the separation of mixtures having a broad range of complex carbohydrates. Chromatographic experiments for the study of the interaction of certain biogenic amines with immobilized glycoproteins used as the stationary phase led to the development of siliceous bonded phases with serotonin, tryptamine or phenylpropanolamine ligates. The sorbents thus obtained were mildly hydrophobic and cationic in contact with eluents of pH 8 or less. They were used for the separation of various carbohydrates; in addition they also proved effective for the separation of protein mixtures under conditions similar to those customarily employed in electrostatic or hydrophobic interaction chromatography.
Development of microbiosensors
Authors: Karube Isao 
Published: March 2011

AbstractSemiconductor fabrication technology was used for development of ion sensitive field effect transistor (ISFET) and micro‐electrodes which have been utilized as transducers of enzyme‐based microbiosensors. A urea sensor consisted of two ISFETs; one ISFET is urease‐coated ISFET and the other ISFET is reference ISFET. A linear relationship was obtained between the initial rate of voltage change and the logarithm of urea concentration over the range 1.3 to 16.7 mM. ATP and hypoxanthine sensors were also developed utilizing ISFET as a transducer. Furthermore, microelectrodes such as hydrogen peroxide and oxygen sensors were prepared by the silicone fabrication technology. A glucose sensor consisted of a hydrogen peroxide electrode and immobilized glucose oxidase membrane. A linear relationship was observed between the current increase and the concentration of glucose (1–100 mg dl−1). A microoxygen electrode was constructed from Au electrodes, polymer matrix containing alkaline electrolyte and a photocross‐linkable polymer membrane. This electrode was used as a transducer in microglucose sensor. A microglutamic acid sensor is also described.
Ablative photodecomposition and modification of polymer surfaces with the excimer laser radiation
Authors: Lazare S. , Granier V. 
Published: March 2011

AbstractAblative Photodecomposition of organic polymers, discovered by Srinivasan (IBM, USA) in 1982, is the object of intense research. This spontaneous ablation obtained by absorption of the high intensity, pulsed, far‐UV, radiation of the excimer laser allows micro‐ and submicroscopic etching of heat‐sensitive and soft materials (polymers and living tissue). Numerous applications are foreseen in various fields like microelectronics and microsurgery. Applications in basic research are also being developed. For instance, changes of the morphology of the surface by ablation give information on the microstructure in poly(ethylene terephthalate) films. The present status of the mechanism is described.
Ultrasonically controlled polymeric drug delivery
Authors: Kost J. , Leong K. , Langer R. 
Published: March 2011

AbstractThe area of polymeric controlled drug delivery systems has been a field of increasing interest. However, relatively little attention has been given to developing systems in which the rate of delivery can be manipulated externally. We now report that release rates of biologically active substances from a polymeric matrix can be repeatedly modulated from a position external to the environment of use by ultrasonic energy. The ultrasound affects the degradation rate of bioerodible polymers as well as permeation through non‐erodible polymers. The system has been shown to be responsive in vivo. Skin histopathology of the ultrasound treated area didn't reveal any differences between the treated skin and the untreated controls.
Synthesis, characterization and recent developments of liquid crystalline polymers
Authors: Noël C. 
Published: March 2011

AbstractRecent developments of polymer liquid crystals (PLCs) are reviewed. The virial expansion method of Onsager and the lattice model used by Flory to appreciate the most relevant parameters in establishing mesomorphic behavior in polymeric systems are presented. These and other theoretical predictions are confirmed by numerous experiments. Both lyotropic (polymer solutions) and thermotropic (polymer melts) types of PLCs are considered with emphasis placed on the latter. The general properties of mesophases formed by such polymers are surveyed and some chemical structures capable of producing mesophases are classified in relation to their ability to form lyotropic and thermotropic systems. The synthetic routes, the effects of polymer structure on physical properties, and applications of two major classes of lyotropic systems (polypeptides, polyamides) and of a range of potentially important thermotropic polymers are discussed.
Ageing, weathering and stabilisation of polymers
Authors: Scott Gerald 
Published: March 2011

AbstractThe common chemical basis of thermal ageing and weathering are outlined, and the mechanisms of antioxidant action which follow from thermal and photo‐oxidation are discussed. The physical behaviour of antioxidants and stabilisers in polymers is assuming increasing importance as the polymer environment becomes more aggressive, and the rationale for the development of polymer‐bound antioxidants is discussed.
Microscopic FT‐IR analysis of blends from functionalized polyolefins and poly(vinyl chloride) or polystyrene
Authors: Benedetti E. , Galleschi F. , D'Alessio A. , Ruggeri G. , Aglietto M. , Ciardelli F. , Pracella M. 
Published: March 2011

AbstractBinary mixtures consisting of ethylene‐propylene copolymer functionalized with diethyl maleate (FEP) and poly(vinyl chloride) or polystyrene have been studied by means of the microscope‐FT‐IR system. Parallel DSC measurements have been carried out on the functionalized ethylene‐propylene copolymer/poly(vinyl chloride) mixtures. Intermolecular interactions involving the carbonyl of the ester groups of the copolymer and the methin hydrogen of poly(vinyl chloride), through hydrogen bonding, have been evidenced in the various microareas of the samples. Intensity of these effects depends on composition in different domains of the blends. An increase of the gauche sequences with respect to the long and short trans sequences of poly‐(vinyl chloride) chains has been detected with increasing the content of FEP. The partial compatibility of FEP/poly (vinyl chloride) blends has been confirmed by DSC measurements.
Interpretation of micromechanical measurements on butyl acrylate, vinyl acetate based systems: Role of interfaces in “polymer‐polymer composites”
Authors: Cavaille J. Y. , Jourdan C. , Perez J. , Guillot J. 
Published: March 2011

AbstractFilms were obtained by coalescence of different types of latex particles; the purpose of this work was to get informations on the geometric arrangement (so called “morphology”) of the different phases and on the role of interfaces. Such informations are difficult to get by direct investigations (weak contrast in Transmission Electron Microscopy, poor information provided by X‐ray measurements on amorphous polymers …) the analysis of experimental data obtained in high resolution mechanical spectrometry appears powerful: it is possible, for instance, to estimate the profile gradient of composition at the interface. Comparison is made between the morphology of the different phases in some films and the correspondent structure of particles.
Influence of the catalyst system on the morphology, structure and conductivity of a new type of polyacetylene
Authors: Theophilou Nicolas , Naarmann Herbert 
Published: March 2011

AbstractDifferent new catalysts based on transition metal compounds of groups IVb, Vb, VIb and VIIIb combined with a reducing agent such as: triethylaluminium and butyllithium in various solvents; toluene and silicone oil, were used for the polymerization of acetylene. By changing the catalyst, cocatalyst, solvent and polymerization conditions, a large variety of polyacetylenes were obtained. The polyacetylenes were characterized by SEM, FTIR and C13 NMR spectroscopies. Some of the new polymers were stretched mechanically and then doped with iodine. Thus highly conducting thick (20μm) and transparent films (0.1 μm) were obtained, with conductivities of 20000 ω−0.cm−1 and 8000 ω−1.cm−1, respectively.After modification of the standard catalyst system (Ti(OC4H9) 4‐Al (C2H5) 3‐silicone oil) by the introduction of some additional reducing agents, conductivities as high as 120000 ω−1.cm−1, after elongation and iodine doping of the polymers, were reached.In this paper we present also a comparative stability study of the new (CH)x films and powders.
Substituent positional variations and the lithographic properties of poly(methylstyrene‐CO‐chloromethylstyrene) resist systems
Authors: Griffiths Llŷr G. , Jones Richard G. , Brambley David R. , Tate Philip Miller 
Published: March 2011

AbstractThe lithographic performances of structurally different copolymers of methylstyrene (ortho‐, meta‐ and para‐isomers) and chloromethylstyrene (meta‐ and para‐isomers) have been assessed. Linear correlations of the data, based on Charlesby's theory of radiation‐induced crosslinking of polymers, demonstrate that sensitivity and contrast are functionally related for this system. Variation of the structure of the chloromethylstyrene component of the copolymers had little effect on the lithographic parameters, but the effect of structural variation of the methylstyrene component was pronounced, the order of increasing sensitivity being ortho < meta < para.
Thermotropic copolyesters of 4‐hydroxybenzoic acid
Authors: Kricheldorf Hans R. , Conradi Arnd , Pakull Ralf , Schwarz Gert 
Published: March 2011

AbstractCopolyesters of 4‐hydroxybenzoic acid were prepared by thermal polycondensation of 4‐acetoxybenzoic acid with various acetylated comonomers, such as 4‐mercaptobenzoic acid, 3‐hydroxybenzoic acid, N‐(4‐carboxyphenyl)4‐hydroxyphthalimide or hydroquinone in combination with 1,12‐dodecane bistrimellitimide. The copolyesters were characterized by elemental analyses, inherent viscosities, 1H‐ or 13C NMR spectroscopy, DSC‐measurements, WAXS‐measurements at temperatures between 25 and 425°C, microscopic observation, thermomechanical and thermogravimetrical analyses. Copolyesters containing 4‐mercaptobenzoic acid or N‐(4‐carboxyphenyl)4‐hydroxyphthalimide possess a reversible first order phase transition which represent a change of modifications and not a melting process. Both classes of copolyesters adopt the same kind of high temperature modification as poly(4‐hydroxybenzoate), namely a pseudo‐hexagonal chain packing. In contrast, copolyesters of 3‐hydroxybenzoic acid or copoly(ester imide)s with aliphatic spacer containing more than 50% 4‐hydroxybenzoic acid form a nematic phase over a broad temperature range. However, in the case of copolyesters derived from 3‐ and 4‐hydroxybenzoic acid the homogeneous nematic melt is thermodynamically unstable and gradually turns into a heterogeneous more or less crystalline material with blocks of 4‐hydroxybenzoate units.
Suspension polymerization of vinyl chloride and the processibility of poly(vinyl chloride)
Authors: Lukáš Rudolf 
Published: March 2011

AbstractThe most important technological procedure in the production of PVC is the suspension polymerization of vinyl chloride, as processibility of the polymer may be influenced to a considerable extent by the choice of polymerization conditions. Structure heterogeneities in PVC powders manifest themselves in plasticized PVC by the occurrence of “fish eye” particles. This review concerns the formation and properties of these particles and discusses the causes of their difficult processibility. Also, the relation between polymerization process and PVC dehydrochlorination is discussed and a new mechanism of its initiation based on the reactivity of cisoid enone structures is proposed. These structures catalyze elimination of hydrogen chloride from regular units of PVC by an interchain enzyme‐like mechanism giving rise to chloroallyl structures.
Structural parameters of the network formed first in in‐situ sequential interpenetrating polymer networks
Authors: Tabka M. T. , Widmaier J. M. , Meyer G. C. 
Published: March 2011

AbstractAs part of a study concerning poly(propylene glycol)‐based polyurethane / poly(methyl methacrylate) interpenetrating polymer networks, polyurethane networks were synthesized at various dilutions of the reaction medium and at different values of the [NCO]/[OH] ratio. The network defects arising in such materials were evaluated by three independent experimental approaches: solvent extraction, swelling behaviour, and compression measurements. It was found that the networks with the least defects are formed at high precursor concentration, with a [NCO] over [OH] excess of about 7%.
On the uniaxial stress‐strain dependence of highly swollen chemically crosslinked networks
Authors: Zrinyi M. , Kilian H.‐G. , Horkay F. 
Published: March 2011

AbstractMany experiments show that the second Mooney‐Rivlin coefficient disappears for highly swollen chemically cross‐linked gels. Hence we are led to a paradox: Highly swollen gels seem to behave phenomenologically like phantom networks. Due to the finite extensibility of network chains, entanglements and excluded volume effects, one should ‐on the contrary‐ expect non‐Gaussian behaviour. On the basis of the phenomenological van der Waals equation of state, we have concluded that the virtual ideality of highly swollen gels is the consequence of a compensation between global interactions and excluded volume effects.
Pressure‐volume‐temperature measurements on polymers and polymer mixtures
Authors: Walsh David J. , Dee Gregory T. , Ougizawa Toshiaki 
Published: March 2011

AbstractWe have measured the PVT properties (density as a function of pressure and temperature) for polymers and polymer mixtures and analyzed these in terms of equations‐of‐state. The Cell Model equation (CM) gives a better description of the PVT properties of the pure polymers than the equation of Flory, Orwoll and Vrij (FOV). For the pure polymers we obtain the hard core pressure and hard core temperature. The hard core pressure depends on the cohesive energy, whereas the hard core temperature depends on the energy divided by the entropy. When we use the pure component parameters to describe mixture phase diagrams the CM equation is more consistent with experimental data. For the mixtures the energy depends on those of the pure components modified by an interaction parameter. The interaction parameter can thus be determined from the hard core pressures and temperatures. For high polymer mixtures the resulting parameter determined from the hard core pressure is unphysically large and negative whereas that from the hard core temperature is unphysically large and positive. Neither value coincides with those required to explain the phase diagrams or those obtained from methods such as heats of mixing of oligomers. We suggest possible reasons for this discrepancy.
Analysis of fracture behaviour of fibre reinforced polypropylene using R‐curve concept
Authors: Grellmann Wolfgang , Seidler Sabine , Nezbedova Eva 
Published: March 2011

AbstractExperimental results for investigation of dynamical crack resistance curves in the instrumented Charpy impact test on polypropylene (PP)/glass fibre composites are presented. For this purpose the multiple specimen R‐curve method, stop‐block technique is used. With the aid of J‐integral versus stable crack growth (δa) curves the influence of a special coupler system on crack toughness as resistance against stable crack growth is discussed. It is shown that it is possible to quantify different energy dissipative processes with the new fracture mechanical material value J × T7 (T7 ‐ tearing modulus). The problems of determining physical crack initiation values for short fibre composites are discussed. The physical material background for using the ‘plastic hinge’ model to describe the deformation behaviour of PP/glass fibre composites is shown, using the example of selected crack opening displacement (σ) versus δa curves.
The effect of crosslinking of polyolefins on the crack growth rate during three‐point bending
Authors: Chodék Ivan 
Published: March 2011

AbstractThe effect of crosslinking on the stress ‐ strain curves and on the crack growth rate was investigated in three point experiments for notched samples of polyethylene, polypropylene, blends of PE and polypropylene, and PE filled with silica. The crosslinking was found to affect positively the tear resistance of multiphase materials. The stress ‐ strain curves as recorded during experiments for uncrosslinked samples show maxima which are entirely a result of the notch growth. The dependence is almost linear if the curves are recalculated with respect to the change of the sample cross‐section during the experiment. The same curve for crosslinked materials indicates a significant portion of plastic deformation. The rate of the crack growth of crosslinked samples is approx. by one order of magnitude lower than that of uncrosslinked materials.
Coupling of the phase and relaxation transitions in polymer mixtures
Authors: Shibanov Y U. D. , Godovsky Y U. K. 
Published: March 2011

AbstractThe coupling and the competition of two phase transitions (demixing and crystallization) and the coupling of both demixing and vitrification are investigated during phase transformations under far‐from‐equilibrium conditions. The coupling leads to formation of the different non‐equilibrium morphologies and to kinetic pecularities of phase transformations.
Regularities of adhesive failure in particulate filled polymers
Authors: Berlin A. A. , Zhuk A. V. , Knunjantz N. N. , Oshmjan V. G. , Topolkaraev V. A. 
Published: March 2011

AbstractThe effect of adhesion between matrix and filler on mechanical properties of composites is analyzed. It is shown, that the loss of adhesion (extension of exfoliated surface) leads to a marked reduction of uniaxial tension modulus. Regularities of interphase crack growth were found and dependences of initial (critical) and final angles of exfoliation upon mechanical and scale factors were obtained.
Development of ceramic‐matrix composites — A challenge to chemistry
Authors: Ziegler G. 
Published: March 2011

AbstractIn this contribution the state‐of‐the‐art of ceramic‐matrix composites is briefly summarized. A critical review of the different types of ceramic composites is given, particularly emphasizing the challenge to chemistry. As example two important problem areas, which may only be solved by contributions from chemistry, are discussed: some low‐ temperature processing techniques for ceramic composites which avoid damage of fibres by thermal or mechanical loading and/or by chemical reactions as well as the optimization and control of interfaces.
Lattice model theory of chain stiffening and relaxation properties of macromolecules in the nematic LC state
Authors: Gotlib Yuliy , Medvedev Grigoriy , Fridrikh Sergey 
Published: March 2011

AbstractThe relaxation properties of polymer chains In the nematic LC‐state or in the external quadrupole field may depend both on the variation of the conformation in the ordered state and on the activation barrier of the molecular (or external) field. This barrier should be surmounted during reorientation of chain elements. The lattice model theory of chain stiffening of macromolecules in the LC‐state is proposed. The calculation and comparison of the longitudinal and transversal relaxation spectra for the continuous and discrete rotameric mechanism of the mobility are performed. For the simplest model of a heterogeneous polymer chain the possibility of the more complex relaxational behavior i.e. the existence of two longitudinal and two transversal relaxation spectra was shown.