bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(β‐hydroxyalkanoates): Biorefinery polymers in search of applications
Authors: Marchessault R. H. , Bluhm T. L. , Deslandes Y. , Hamer G. K. , Orts W. J. , Sundararajan P. R. , Taylor M. G. , Bloembergen S. , Holden D. A. 
Published: March 2011

AbstractPoly(β‐hydroxyalkanoates) are nature's high molecular weight thermoplastic polyesters. They occur as storage granules in a variety of bacteria. From a plastics, film, and fibres perspective, the statistically random copolyesters based on β‐hydroxybutyrate (HB) and β‐hydroxyvalerate (HV) repeating units have high potential for commercial exploitation because of their biodegradability. They provide a range of melting points from 180°C down to 80°C and all compositions exhibit high crystallinity due to isodimorphism. The latter is due to the similar crystalline conformations of poly(β‐hydroxybutyrate) (PHB) and poly(β‐hydroxyvalerate) (PHV). The nascent granules of a 21 mole % HV copolyester sample in freeze‐dried bacterial cells were examined by 13C solid‐state NMR. A disorder in the HV ethyl side group was noted but backbone carbons for HB and HV units showed evidence of crystalline order which was confirmed by x‐ray diffraction. In keeping with the isodimorphous properties of this system, electron diffraction of copolyester single crystals for compositions up to 21 mole % HV confirmed a lattice expansion previously observed for bulk crystallized P(HB‐co‐HV). Solution or melt crystallized films showed decreasing rates of crystallization with increasing HV content. Homogeneous blends of PHB with P(HB‐co‐HV) could be formed which showed a single melting peak by differential scanning calorimetry. The potential of P(HB‐co‐HV) as a source of value‐added small molecules is discussed. Depending on the method of degradation (i.e., chemical or pyrolytic) chiral synthons or vinylic small molecules are obtainable in nearly quantitative yields. Because their physical properties resemble those of polyolefins this family of chiral thermoplastics will probably find wide use in biomedical applications where compatibility and absorbability are essential features.
Enzymatic release of drug from polymer matrices: Diffusion and activity of lysozyme within ophtalmic hydrogels
Authors: Cassiani‐Ingoni L. , Subira F. , Bunel C. , Vairon J‐P. , Halary J‐L. 
Published: March 2011

AbstractDiffusional behaviour of lysozyme into a high‐hydrated hydrogel, used as precursor of contact lenses, is reported. The gel is a swollen statistical copolymer of methyl methacrylate and N‐vinyl‐2‐pyrrolidone (≁ 70% water), and the penetration of the enzyme, labeled with 8‐anilinonaphthalene‐1‐sulfonate, was followed by fluorescence microscopy. Mathematical analysis of the profiles led to the diffusion parameters (D ≁ (2–6) · 10−8 cm2 · s−1). It is shown that the enzymatic activity persists when the lysozyme and the cleavable substrate are trapped in the matrix.
Biodegradation of polymeric drug carriers: Kinetic modeling
Authors: Azhari R. , Lotan N. 
Published: March 2011

AbstractAnalytical models ‐ based on kinetic and mechanistic considerations‐ have been developed, for describing the enzymic degradation of polymers. The models were applied to delineate the degradation patterns expected when endo‐ or exo‐ acting enzymes are used, and when the kinetic constant KM varies with the size (i) of the macromolecular substrate. Utilization of these models, in conjunction with experimentally available data, provides the possibility to define the mechanism of enzymic action, and to determine the kinetic constants of the process. Thus, for example, for the degradation of poly‐N‐(2‐hydroxyethyl)‐L‐glutamine (PHEG) by papain, the correlation between KM and i was established.The above models can also be used to provide data that cannot be obtained experimentally (e.g. exact chain length distribution of degradation products), and to determine, with minimum effort, the experimental set up required for obtaining a desired array of products. They are, therefore, most useful tools for the design of enzyme–actuated drug delivery devices.
Past and future impact of electroactive polymers on the electronics sector
Authors: Matthan Jacob , Uusimäki Antti , Torvela Heikki , Leppävuori Seppo 
Published: March 2011

AbstractA broad review of the field of applications of electroactive polymers, defined as inherently conductive, charged, piezoelectric and pyroelectric, and systems made electroactive by addition of conductive additives, in the field of electronics and microelectronics. Applications mentioned include the use of polymers for electrodes for rechargeable batteries, electret microphones, hydrophones, vidicons, EMI and ESD protection, and conductor and resistor tracks as thick films on printed circuit boards. Future trends as the development of supermolecular assemblies for parallel processing are also highlighted.
Role of the interface in multicomponent materials
Authors: Ishida Hatsuo , Jang Jyongsik 
Published: March 2011

AbstractStudies of the relationship between interfacial structure and mechanical properties in multicomponent materials are reviewed in this article. The following categories are considered for role of the interface in multicomponent systems: Interpenetrating polymer network(IPN), catalytic effect of silane coupling agent, morphological differences of filler surface, particle‐particle interaction and particle size of the filler. The interfacial role in terms of the reinforcement mechanism of the composite and the behavior in the melt state is also discussed in the multicomponent system.
New trends in commodity polymers
Authors: Brasz A.J.H. 
Published: March 2011

AbstractAfter the recession of the seventies, commodity polymers are today again in a period of stable growth, due to the drastic change in strategy of the polymers producers. Strong cost reduction by debottlenecking, advanced catalyst systems and restructuring improved their position, and diversification in general purpose grades on the one hand and ‘commodity‐plus’ and speciality grades on the other were the key factors for success. Diversification could only be achieved by close cooperation between end‐user, converter, polymer supplier and machine manufacturer and by compounding, blending and grafting. The blends and grafted materials are a new family of materials and are a challenge to all developers in the polymer filed. They create a new future for the commocity polymers.
Compatibility testing in polyamide multicomponent systems by endlinking
Authors: Leumer Gerhard , Rossbach Volker 
Published: March 2011

AbstractHitherto, compatibility in polyamide blends has been characterized by physical and mechanical methods exclusively. The work presented here describes the basis and potential of a chemical method for compatibility testing, transferred from protein chemistry (crosslinking technique). This method can also be applied, with appropriate modification, to synthetic polyamides. The degree of heterogeneity follows from the number of different molecule combinations.
Electron spectroscopic imaging studies on semicrystalline and block‐copolymer systems
Authors: Kunz M. , Möller M. , Heinrich U.‐R. , Cantow H.‐J. 
Published: March 2011

AbstractDiscrimination of elastically and inelastically scattered electrons in transmission electron microscopy (TEM) yields electron micrographs with enhanced and specific contrast. Highly resolved micrographs can be obtained in which the contrast reflects the local concentrations of specific elements. In the present work, Electron Spectroscopic Imaging (ESI) by means of a Zeiss EM 902 TEM is reported for polystyrene‐block‐poly(2‐vinylpyridine) diblock copolymers and for a series of differently crystallized polyethylene samples. Excellent contrast can be achieved without staining. The different techniques allow easy verification of the observed morphology.
Free surface on a viscoelastic liquid in a cylinder with spinning bottom
Authors: Siginer D. A. 
Published: March 2011

AbstractThe shape of the free surface and the flow field of a simple fluid driven by the steadily rotating bottom cap of a cylindrical cup is investigated. A regular domain perturbation in terms of the angular velocity of the bottom cap is used. The velocity field is a superposition of a strong primary, azimuthal field and a weaker secondary meridional field. The effect of the aspect ratio and viscoelasticity of the fluid results in multiple cell structures in the meridional plane. The free surface shape determined at the lowest significant order in the perturbation algorithm, is similarly affected by the same factors. Both the flow field and the interface shape are determined for a wide range of aspect ratios and viscoelastic parameters.
Ultrasonic characterization of polymer viscoelasticity. Application to polystyrene
Authors: Massines F. , Piché L. , Lacabanne C. 
Published: March 2011

AbstractUltrasonics is presented as a powerful method for the thermomechanical analysis of polymers. An experiment is described where the specific volume of a polymer is measured in simultaneity with the acoustic parameters. The technique allows full control of the thermal history in the temperature range from — 150°C to 300°C, where the material goes from a glasslike to a liquidlike state. Moreover the technique allows measurements to be performed at different pressures, up to 2 kbar. Results obtained on a typical amorphous polymer (polystyrene) are reported and the propagation of sound is discussed in regards to the well defined thermodynamic state for the material. Also, the results discriminate between the thermodynamic and the relaxational aspects of the glass transition.
Viscoelastic study of carbon/epoxy unidirectional composite materials
Authors: Perret Patrice , Chabert Bernard , Gérard Jean‐François 
Published: March 2011

AbstractProperties of interface in unidirectional composite materials can be studied “in situ” by dynamic mechanical measurements: analysis of relaxations and appearance of damage in shearing. This methodology is applied on composite materials based on an epoxy matrix and carbon fibers with different surface treatments (untreated, oxidized and sized). Mechanical spectroscopy displays modifications of epoxy network with the fiber treatment and evidence for an interphase in the case of sized fibers. Dynamic shearing test clearly shows large differences of behavior with the surface treatments.
Influence of the molecular weight on the elongational behaviour of polypropylene and on the fibre orientation factors
Authors: Prost Catherine , Nemoz Guy , Michel Alain 
Published: March 2011

AbstractThis study shows that the elongational behaviour depends upon molecular weight and upon elongational rate. If the molecular weight is low, elongational viscosity reaches rapidly a steady value but, if the molecular weight is high, the viscosity (or the elongational stress) increases continuously with the time. These behaviours may be explained in comparison of the relaxation rate determined by shear rheology as the reciprocal relaxation time with the elongation rate ϵ. If the elongation rate is lower than the relaxation rate the polypropylene chains may relax and the elongational viscosity reaches a steady value with the time. For high fluidity polypropylene the range of elongation rates within of which the elongational viscosity is constant with time is very large. On the contrary, if the elongational rate is higher than relaxation rate the polypropylene chains undergo a continuous deformation and then the elongational viscosity increases with time. The range of elongational rates within of which the stress is constant is narrow for high‐molecular‐weight polypropylene. Furthermore, the elongational behaviour influences the chain orientation in the crystalline and amorphous phases of the fibres. If the polymer chains are quenched in a relaxed state the orientation is lowered as shown with high fluidity polypropylenes. On the contrary, if the chains are cooled in extended state their orientation may subsist during crystallisation and the orientation factors may reach high values as shown with high‐molecular‐weight polypropylene.
Polyamide 11 as a hard elastic fiber
Authors: Dosià;re M. 
Published: March 2011

AbstractFibers of nylon‐11 annealed in contact with formic acid (90%) have the same unit cell as solution grown crystals; the basal planes of the lamellar crystals are parallel to (ool) crystallographic planes. The melting curves and the stress‐strain curves of such annealed fibers are presently reported. The temperature corresponding to the maximum of the melting peak increases with the annealing temperature: an increase of 10°C is observed although the long spacings keep the constant value of 12 nm. Lower elastic modulus but higher strains are obtained with increasing annealing temperatures. Such annealed samples can undergo large extension without occurrence of necking and plastic flow.
Loss of orientation and shrinkability of drawn atactic polystyrene
Authors: D'Amore A. , Nicodemo L. , Nicolais L. , Carfagna C. 
Published: March 2011

AbstractThe loss of orientation is a much more rapid phenomenon than the thermal shrinkage of drawn polystyrene, as shown by birefringence and FTIR measurements. The properties imparted by the orientation can be lost before the complete shrinkage occurs. The implications of this fact are discussed.
Effect of thermal treatment on the micromechanical properties of segmented polyurethanes
Authors: Etienne S. , Perez J. , Darud V. , Pascault J. P. 
Published: March 2011

AbstractThe effects of thermal treatments on segmented polyurethanes were studied by low frequency mechanical spectrometry. Complementary informations on the morphology of microphases and characteristic temperatures were given by other techniques such as DSC and SAXS. We have shown that low temperature treatments affected the morphology of the soft phase. High temperature treatments induced modification of dynamic modulus spectra attributed to the evolution of the microphase separation rate and the degree of crystallinity of some hard domains.
Characterization of the coating layer on glass fibre used as reinforcement in polyepoxyde matrix
Authors: Escoubes Marcelle , Chabert Bernard , Chauchard Jacques , Nemoz Guy 
Published: March 2011

AbstractR glass fibre for the reinforcement of epoxy matrices has been coated with epoxy prepolymer (as film‐former or sizing agent) or γAPS aminosilane (as coupling agent) or a mixture of these two products. The structure of the coating layer and its interaction capabilities with fibre and matrix have been studied by coupled calorimetry‐gravimetry of sorption of different model reactants and by Fourier Transform infra‐red analysis.
Contact angles of water (polar) and methylene iodide (non polar) on glass surfaces treated with aminosilane / mercaptosilane mixtures. Correlation between silane orientation, surface tensions and wetting hysteresis
Authors: Comte Florence , Sage Daniel 
Published: March 2011

AbstractOrganofunctional silanes are generally used to improve bonding between inorganic substrates and organic resins. They are of particular interest when used as adherence promoters between glass and polymeric adhesives: despite their very different properties, these two materials can be assembled. Glass has a high surface tension‐relatively reduced by water adsorption‐ with a marked polar component. The action of the silane is to substitute itself to the low cohesive layer formed by water and to decrease the polar component of the glass surface in order to make it compatible with the adhesive. Polar alkoxy groups react with the glass and a new surface is then formed, mainly by the organofunctional groups of the silane. This new surface must also have a sufficient surface energy to be wetted by the adhesive. It is, therefore, necessary to determine as well as possible the superficial properties, keeping in mind that a good wettability does not always signify a good adhesion, but is just a necessary condition. We have then measured the advancing θm and receding θd contact angles of water and methylene diiodide on a degreased glass surface, treated or not by A1100 (γ ‐aminopropyltriethoxysilane), A189 (mercaptopropyltrimethoxysilane) or a mixture of both. Rinsing the samples with water treatment has also been considered.
Influence of a filler such as silica on network formation of elastomers
Authors: Bomo F. 
Published: March 2011

AbstractThe mineral nature of silica gives it some particular properties. Its surface chemistry is very reactive. The interactions between silica and vulcanization agents such as accelerators are important and disturb the formation of the elastomer network. Following a description of silica surface chemistry we shall study the interactions of this filler with some accelerators and their impact on the cross‐linking density.
Quantitative determination of low strain amplitude dynamic functions of carbon black filled rubber vulcanizates by statistical analysis of the black secondary agglomeration network
Authors: Susteric Zoran 
Published: March 2011

AbstractDeformational breakdown of the secondary agglomeration network, a carbon black aggregate chain association readily formed in rubber matrix and held together by van der Waals forces, is treated statistically. Consistent with observation, the resulting expressions for low strain amplitude dependence of the black filled vulcanizates' dynamic functions, i.e. the storage and loss moduli, provide means for determination of characteristic aggregate chain scission energies. The proposed approach additionally accounts for effects of filler content and temperature, the latter permitting evaluation of van der Waals bond dissociation activation energies, if the black chain scission process is assumed to be thermally activated.
Adhesion mechanisms of grafted polyolefins
Authors: Schultz J. , Lavielle L. 
Published: March 2011

AbstractBy comparing surface properties assessed by wettability measurements with polymer‐metal adhesion strength determined by peeling for different grafted polyolefins (acrylic acid grafted polyethylene, acrylic acid and maleic anhydride grafted poly(ethylene‐vinyl acetate), maleic anhydride grafted polypropylene), a general adhesion mechanism can be proposed. The surface polarity is not the main determining parameter for adhesion.Polyolefin‐aluminium adhesion is obtained through chemical bonding of acid groups grafted in the polymer bulk and basic groups present on the aluminium.
An analysis of the adhesion strength between polyethylene and paper
Authors: Gervason G. , Cheradame H. 
Published: March 2011

AbstractComposites of polyethylene with paper were studied in order to determine the influence of the surface energy of the paper on their cohesive strength. The papers used in this study had the same roughness, but fifferent surface energy owing to treatment with different sizing agents. The surface energies were determined by the contact angle method with various liquids, and the variations of the cohesive strength were followed by the energy of peeling at 180 °C. It was shown that the peeling energy decreases linearly when the reversible energy of adhesion decreases, and becomes negligible when the paper surface energy is approximately equal the surface energy of polyethylene.
Synthesis and phase behavior of liquid crystalline poly(3‐n‐ALKYL‐4‐hydroxybenzoates)
Authors: Stern R. , Ballauff M. , Wegner G. 
Published: March 2011

AbstractA series of 3‐n‐alkyl substituted poly(4‐hydroxybenzoates) were prepared by melt‐polycondensation of the corresponding monomers. The length of the alkyl side chains was varied in the range of 3 to 18 carbon atoms. The average degree of polymerisation (DP) was determined by 1H NMR end‐group analysis. The thermal behavior of the polymers was studied by differential scanning calorimetry (DSC) and polarising microscopy (PM). Structural investigations of oriented and not oriented samples were performed by means of wide angle X‐ray scattering (WAXS). The density of the polymers was measured by gradient column technique.
The effect of torsional vibrations superimposed on a creep loaded adhesive joint on its final tensile properties
Authors: Katz Dov , Bron Samuel 
Published: March 2011

AbstractAluminum ‐ epoxy single lap joints were subjected at different temperatures to torsional vibrations at constant amplitude superimposed on a creep load. This combination of dynamic and static stresses was chosen in order to simulate to a certain extent the real service conditions of an ordinary bonded joint. The shear strength of these joints was checked in tension at room temperature after their removal from the special device in which the superimposed stresses were applied. It was found that the shear strength of the joint is very dependent on its thermo‐mechanical history. DSC analyses and SEM micrographs of the failure surface were used in an attempt to find some correlation between the mechanical properties and the microstructure of the adhesive.
Advances in inherently conducting polymers
Authors: Aldissi Mahmoud 
Published: March 2011

AbstractIn this review, the various sub‐classes of material and the motivations to study them is given as well as some of their properties and the various proposed applications. First, an introduction to the general area of conducting polymers is given. The various important efforts in materials synthesis and the motivations and goals for these efforts are outlined, particularly, those geared toward making materials with desirable properties such as high conductivities, high molecular and supramolecular order, solution‐ and/or melt‐processability, and some application areas. The morphology plays an important role in determining conductivity and mechanical properties of the materials. Therefore, a brief description to that effect is given. Second, the distinct sub‐classes of material developed here include oriented polyacetylene polymerized in a liquid crystal medium, polyheterocyclic systems synthesized electrochemically, copolymers, and first water‐soluble, liquid crystalline conducting polymers based on polyheterocycles. Third, the various possible applications are mentioned briefly with a focus on electrochemistry, electro‐optical properties, junctions, and shielding against electromagnetic interferences (EMI) in the radio frequency (RF) and microwave (MW) regions.
Electron‐beam and x‐ray resists for microlithography
Authors: Eranian A. , Bernard F. , Dubois J. C. 
Published: March 2011

AbstractFirstly, general considerations about microlithography and resists were presented, leading to the conclusion that positive resists seemed to be more suitable than negative resists to provide high resolution in electron‐beam lithography and in X‐ray lithography. Therefore, parameters affecting the sensitivity of positive resists to such types of radiation were outlined. Among these positive resists, poly (fluoroalkyl methacrylates) were shown to be interesting candidates, due to their enhanced radiation absorption. Thus, poly(1‐, 1‐ dimethyl 2, 2, 3, 3‐tetrafluoropropyl methacrylate) (called FBP resist) was synthesized and physico‐chemically characterized. The lithographic performances of such a resist were evaluated both upon electron‐beam and X‐ray exposures. Its dry‐etch resistance was also studied. Furthermore, fabrication of Field‐Effect Transistors using this resist was demonstrated.
Electrochemical polymerization of substituted thiophenes
Authors: Havinga E. E. , van Horssen L. W. 
Published: March 2011

AbstractThe electrochemical polymerization of 3‐(n‐butyl)thiophene and of several 3‐ or 3,4‐ substituted α, α'‐terthienyls is described and the properties of the conducting polymers are discussed. A solution in acetonitrile of the terthienyl substituted by a potassium propylsulfonate group is polymerizable as such, and the polymer is the first proven example of a self‐doped conducting polymer. This polymer dissolves readily in water and remains partially self‐doped in solution.