bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of culture conditions of acetic acid bacteria on cellulose biosynthesis
Authors: Kamide Kenji , Matsuda Yukiko , Iijima Hideki , Okajima Kunihiko 
Published: April 2007

AbstractAn attempt was made to clarify the effect of culture conditions of an acetic acid bacteria (Acetobacter xylinum) on cellulose biosynthesis using glucose as carbon source in complex medium. Synchronous culture conditions were first realised on cellulose biosynthesis by cooling the system to 4°C for 24 h. Under the synchronous conditions stepwise division of the cell and the stepwise production of cellulose were found. Furthermore, cellulose was proved to be produced when the cell number in the medium was constant.
VIscometric behaviour of Kevlar fibre filled liquid crystalline solutions of ethyl cellulose in m‐cresol
Authors: Suto Shinichi , Hayasaka Shin‐Ichi 
Published: April 2007

AbstractLiquid crystalline solutions of ethyl cellulose in m‐cresol were mixed with Kevlar® fibres, and the viscometric behaviour with respect to temperature of those filled systems was determined with a cone‐plate type viscometer. The viscosity of the systems exhibited a maximum and a minimum at temperatures denoted by Tmax and Tmin' respectively. The effects of fibre on the critical temperatures (Tmax and Tmin) and critical concentrations (Ca and Cb) and on the viscosity enhancement are discussed.Tmax and Tmin decreased with fibre concentration for single‐phase anisotropic solutions, whereas they increased for the biphasic solution. The critical concentrations increased with fibre concentration and Cb was more sensitive to the fibre than Ca. The viscosity enhancement due to the fibre depended on the phase of solution. In the single‐phase (isotropic and anisotropic), the viscosity enhanced with fibre; however, in the biphasic solution, the effect was not simple. The viscosity enhancement for the single‐phase anisotropic solutions with fibre was lower than that for the isotropic solutions.
Biomedical aspects of the direct measurement of the forces between adsorbed polymers and proteins
Authors: Luckham P. F. , Ansarifar M. A. 
Published: April 2007

AbstractThe forces between mica surfaces covered with an adsorbed layer of a wide range of polymers, polyelectrolytes and proteins are described as a function of the separation between the surfaces. For polymers in a good solvent at full coverages, repulsive forces are always observed, essentially due to osmotic forces. The range of the force increases as the molecular weight of the polymer increases. For adsorbed homopolymers a marked hysteresis on decompression (separation) of the surfaces is noted due to the polymer being forced to the surface and requiring many minutes to relax. For graft copolymers no hysteresis is observed and the force, for a given molecular weight polymer, is much longer range. Polyelectrolytes of opposite charge to mica adsorb flat on the surface in low electrolyte concentrations but extend away from the mica surfaces when adsorbed at high electrolyte concentrations giving rise to a ‘steric’ component to the fores. Forces between adsorbed layers of proteins were also measured. For concanavalin A (a lectin) and cytochrome C long‐range forces are dominated by electrostatic and van der Waals forces and are well described by classical colloid science. However, for myelin basic protein a long‐range attraction was noted, due possibly to hydrophobic interactions between the adsorbed protein.
Gelation—A review
Authors: Djabourov Madeleine 
Published: April 2007

AbstractThis paper reviews the modern ideas on the process of gelation which have arisen from the analogy between gelation and percolation. The basic features which are common to all types of gels, colloidal or polymeric systems are first recalled; then after a simplified presentation of the percolation model, a few examples illustrating these concepts are chosen (for chemical gelation, a copolymerisation reaction and for physical gelation, the gelatin sol‐gel transition). In conclusion, electron micrographs of gel networks (gelatin gel and an inorganic gel of thorium phosphate) are shown, which reveal the great diversity and complexity of the structures.
Increase in thermal stability of vinyl polymers through radical copolymerization with N‐cyclohexylmaleimide
Authors: Otsu Takayuki , Matsumoto Akikazu , Kubota Toru 
Published: April 2007

AbstractIt was found that radical polymerization of N‐cyclohexylmaleimide (CHMI) occurred readily under various polymerization conditions, and that the resulting poly(CHMI) had excellent thermal stability; i.e. the onset of decomposition was 362°C and the maximum rate of decomposition was observed at 430°C by thermogravimetric analysis in nitrogen. Subsequently, radical copolymerizations of CHMI with various vinyl monomers were performed, and the monomer reactivity ratios were determined from the copolymer composition curves obtained. It was found that CHMI copolymerized alternatingly with electron‐donating monomers such as styrene and isobutene. It was also discovered that facile copolymerizations proceeded with methyl acrylate and methyl methacrylate as electron‐accepting monomers, and with vinyl acetate and vinyl chloride as non‐conjugated monomers. It was verified that the introduction of the CHMI unit increased the thermal stability of common vinyl polymers.
Liver alcohol dehydrogenase immobilized in nylon tubing: ([Substrate]) kinetic behaviour
Authors: Roig M. G. , Bello J. B. , de Celis C. , Cachaza J. M. , Kennedy J. F. 
Published: April 2007

AbstractThe enzyme alcohol dehydrogenase (ADH) from horse liver (EC 1.1.1.1), cross‐linked through the bifunctional reagent glutaraldehyde, was immobilized in nylon tubing (35 μg/cm2 internal surface). The intrinsic v ([S]) kinetic behaviour of the immobilized ADH, analysed graphically and by non‐linear statistical fitting, was found to fit a polynomial quotient rate equation in [S] of minimum degree 2:2.
Chemical celluloses derived from Pinus radiata wood pulps for nitrocellulose preparation
Authors: Sioumis Anthony A. , Wallis Adrian F. A. , Puri Vinod P. 
Published: April 2007

AbstractThe nitration capabilities of a range of chemical celluloses, including some containing the cellulose‐II polymorph, were examined. The cellulose samples, derived from Pinus radiata wood by bisulphite, prehydrolysis‐kraft or kraft pulping, were compared with a commercial nitration‐grade cellulose and two bleached cotton linters samples. All samples on nitration gave nitrocelluloses (degree of substitution ≈ 2–45) which had satisfactory stabilities and solubilities, with the exception of a P. radiata bisulphite cellulose which had a high pentosan value. The presence of cellulose‐II in the samples was not an impediment to the nitration. High performance size exclusion chromatography of the nitrocelluloses showed that the molecular weight distributions of samples derived from the P. radiata celluloses were generally similar to that derived from a commercial nitration‐grade cellulose.
Morphological and kinetics study of PEO/PVC blends
Authors: Iragorri J. I. , Cesteros L. C. , Katime I. 
Published: April 2007

AbstractThe kinetics of spherulite radial growth and the morphology of the compatible system PEO/PVC have been studied by optical microscopy.The usual spherulite radial growth behaviour has been found for compatible blends with PEO content higher than 70%. For lower composition, distortion of the usual spherulite morphology has been observed; the anomalies have been attributed to partial miscibility of the components.
Reaction kinetics of irradiation‐ prepolymerized methyl methacrylate‐polyurethane interpenetrating polymer networks by FTIR
Authors: Wang Geng‐Chao , Wang Jia‐Xun , Zhang Zhi‐Ping 
Published: April 2007

AbstractThe reaction kinetics of irradiation‐prepolymerized MMA‐PU (polyether) IPNs have been studied by FTIR. The results indicate that the polymerization of each component in the IPN follows its normal distinct reaction mechanism with no mutual interference. Increasing the concentration of TMPTMA (crosslinking agent of PMMA) increased the formation rate of PMMA, while the formation rate of PU networks remained almost the same. Increasing the concentration of TMP (crosslinking agent of PU) increased the formation rate of PU, while the formation rate of PMMA networks decreased. The formation rate of PU was obviously faster than that of PMMA. A theory for the cage effect of the PU network has been proposed.
Characterisation of polymers for semiconductor applications
Authors: Bradley Donal D. C. 
Published: April 2007

AbstractThe proposed use of polymers as active semiconductors in a variety of applications ranging from electronics, through electro‐optics to photonics represents a major extension to the current widespread commercial interest in polymers as electrically passive materials. In this paper the authors highlight some of the features of the class of material, namely the conjugated polymers that are of principal interest in this context, and they discuss the characterisation of these materials and their interesting physical responses.
2D and 3D NMR for polymer characterization
Authors: Mirau Peter A. , Heffner Sharon A. , Koegler Gerhard , Bovey Frank A. 
Published: April 2007

AbstractHigh resoluton NMR can be used for polymer characterization both in solution and in the solid state. The power of NMR as a method arises from the observation of individual carbon and proton atoms along the main chain and side chains of polymers. This makes it possible to charaterize in detail the microstructure, the conformation, and the molecular organization in the solid. NMR experiments with more than one frequency dimension (2D and 3D NMR) have revolutionized materials characterization, mainly owing to the increase in resolution and the ability to visualize interactions that were previously obscured by peak overlap. It is possible not only to assign many peaks in the spectra, but also to explore interactions between polymer chains to understand at a molecular level the formation of compatible blends. NMR experiments in two and three dimensions can be combined to determine polymer chain conformation and chain packing. The goal of these studies is to understand the relationship between the polymer properties on a molecular level and the behaviour of bulk materials.
Polymer studies by simultaneous thermal analysis techniques
Authors: Redfern John P. 
Published: April 2007

AbstractSimultaneous thermal analysis techniques (notably TG‐DSC and TG‐DTA) offer many clear advantages over techniques conducted singly. The advantages are enumerated. A more complete thermal profile is provided when a thermal analyser is coupled to some form of gas analyser such as a mass spectrometer or a FTIR analyser.A brief description of the instrumentation is given, with particular reference to the interface in the case of coupled instrumentation since the coupled instruments each need to operate under optimum conditions. Interface design is therefore critical in enabling this and allowing rapid transfer while not degrading the species being transferred.A number of polymer studies, including the thermal behaviour of uncured polyimide resin, polytetrafluoroethylene and polybutadiene, are discussed.
Relationship between gelation and morphology of rubber‐modified epoxy resins
Authors: Pucciariello Rachele , Villani Vincenzo , Bianchi Nadia , Braglia Roberto 
Published: April 2007

AbstractThe addition of both a solid and a liquid rubber to an epoxy resin has been shown to strongly increase the toughness of the material. Moreover, it is well known that toughening depends on the morphology of the system, which, in turn, depends on the cure conditions.In the present work the morphologies of epoxy resins modified with mixtures of solid and liquid rubbers have been studied through transmission electron microscopy. An investigation of the influence of the elastomers and of the gel time on the morphology of the hardened material was carried out. Gel times were evaluated, through rheological measurements, at different cure temperatures.
Low temperature modification of polymers by triazolinediones. 3—blends of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) modified with 1,2,4‐triazoline‐3,5‐diones with polystyrene
Authors: Kuhrau Martin , Stadler Reimund 
Published: April 2007

AbstractPoly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (PPE) reacts with 1,2,4‐triazoline‐3,5‐diones to give poly([oxy‐2,6‐dimethyl‐3‐(1′, 2′,4′‐triazolidine‐3′,5′‐dione)‐1,4‐phenylene]‐co‐poly[oxy‐2,6‐dimethyl‐1,4‐phenylene]). Miscibility of these highly polar PPE copolymer with PS is probed for varying degree of polar substitution and various functional groups in the 4‐position of the heterocycle. The copolymers are miscible with polystyrene up to concentrations of counits of about 10%. For a selected blend system of PS and PPE modified with 4% of 4‐(4‐hydroxy‐3‐nitrophenyl)‐1,2,4‐triazoline‐3,5‐dione the concentration of PS was varied. Glass tion with triazolinediones, miscibility with polystyrene, Gordon‐Taylor equation.
Kinetic model for lonic polymerization initiated by difunctional initiator with monomer transfer
Authors: Feng Jing , Yan Deyue 
Published: April 2007

AbstractThe kinetics of difunctional ionic polymerization with monomer transfer and without assumption of instantaneous initiation is studied theoretically. The set of kinetic differential equations is rigorously solved by way of graphical theory. Expressions for the molecular weight distribution (MWD) function, the number‐ and weight‐average degrees of polymerization, and the distribution of functionality are obtained. A procedure is proposed for calculating the MWD curve and the values of other molecular parameters.
Morphology‐properties relationship in ternary polyamide‐6/ldpe/modified ldpe blends: Part II
Authors: Raval Heta , Singh Y. P. , Mehta M. H. , Devi Surekha 
Published: April 2007

AbstractGrafting of butyl acrylate‐maleic anhydride copolymer on to LDPE was carried out by a solution polymerization technique. All the PA‐6/LDPE/LDPE‐g‐(BuA‐co‐MA) blends were prepared by a two‐step melt mixing technique. The blends were characterized by their morphology, mechanical properties and water absorption. By addition of just 2·4% of the LDPE‐g‐(BuA‐co‐MA), degree of grafting 12%, a remarkable improvement in the impact strength along with a reduction in water absorption of PA‐6 was observed.
Thermal properties of strained thermoplastic polymers
Authors: Möginger Bernhard , Fritz Ulrich 
Published: April 2007

AbstractInjection moulded tensile bars of several amorphous and semi‐crystalline thermoplastic polymers have been deformed uniaxially to a macroscopic strain of 40% so that they showed necked and unnecked regions. From both the necked and unnecked regions of the tensile bars the specific heat and the thermal expansion coefficient were measured. The specific heat of the necked regions decreases about 20% with respect to unstrained samples for semi‐crystalline polymers at temperatures between 40°C and 60°C and for amorphous polymers at temperatures between 50°C and 70°C. The thermal expansion coefficient becomes negative at these temperatures. A smaller negative expansion coefficient is observed even in the unnecked region although nearly no change in specific heat can be observed. There is also an increase in the heat of fusion of the semi‐crystalline specimens of the necked region. Strain rate dependent effects on specific heat and thermal expansion were not observed within the accuracy of thermal analysis.
Kinetics of curing epoxy formulations with diaminodiphenyl ether
Authors: Jagadeesh K. S. , Siddaramaiah  
Published: April 2007

AbstractKinetic parameters for the reaction between tetra‐functional and trifunctional epoxy resins of diaminodiphenyl methane and 4‐aminophenol and diaminodiphenyl ether (DDE) were studied by dynamic DSC. The curing reaction of either the neat resin or the resin formulation is independent of the concentrations of DDE in a specific range and the mechanism follows with two rate constant values. The activation energies for various epoxy systems were determined by the Kissinger and Ozawa equations and are in good agreement even for other kinetic parameters.
Blends of sulphonated polystyrene and polystyrene: Morphology and deformation modes
Authors: Hara M. , Bellinger M. , Sauer J. A. 
Published: April 2007

AbstractBlends of sulphonated polystyrene, neutralized with metal ions, have been prepared in various proportions with polystyrene homopolymer. Morphology, microstructure, and deformation modes of strained, cast thin films have been examined by transmission electron microscopy. Variables studied include blend composition and ion content. In blends of low ionomer concentration, the ionomer component phase‐separates and takes the form of small dispersed particles. With the increase of ion content, the average particle size increases and, as crazes develop in the matrix, particles elongate and fibrillate. These ionic crosslinked particles adhere well to the matrix, share in carrying the applied stress and reinforce the matrix polymer. Implications of these results for mechanical performance of bulk samples are discussed.
Crystallization behaviour of isotactic polypropylene/linear low density polyethylene blends
Authors: Long Yu , Stachurski Z. H. , Shanks R. A. 
Published: April 2007

AbstractCrystallization behaviour of isotactic polypropylene/linear low density polyethylene (iPP/LLDPE) blends has been investigated by optical microscopy and DSC. Crystallization of iPP depends upon blend composition and thermal history. When blended with LLDPE, the crystallization temperature of iPP, Tc, decreased slightly. Crystallinity did not change in the range 0‐80wt% LLDPE; there were only slight changes in the crystalline structure, but LLDPE seemed to resist forming the β type of spherulites. Below 80 wt% of LLDPE, iPP was a continuous phase. The iPP spherulite growth rate was almost constant; however, overall crystallization decreased due to decreasing primary nuclei density.
DSC investigation of the physical ageing and deageing of wool
Authors: Huson Michael G. 
Published: April 2007

AbstractWool can be deaged both thermally and aqueously, resulting in disruption of the network of secondary bonds. The ensuing increase in mobility of the macromolecular chains manifests itself as a decrease in the glass transition temperature; hence this property can be used to monitor the ageing/deageing process. The extent and stability of the network that forms on ageing is a function of the temperature and time of formation. If samples are allowed to age for two consecutive periods of time at different temperatures then two independent networks are formed, each with its own characteristic glass transition temperature. The moisture content, thermal history and scan rate must be carefully controlled during any thermal analysis. It has also been shown that deageing can be used to facilitate the temporary setting of wool.
Effects of frequency, molecular weight and thermal oxidation on the dynamic mechanical response of poly (ethylene oxide)
Authors: Bigger S. W. , Scheirs J. , Delatycki O. , Billingham N. C. 
Published: April 2007

AbstractThe technique of dynamic mechanical thermal analysis (DMTA), operated in the dual cantilever mode, was used to characterize the effects of frequency, crystallinity, molecular weight (MW) and the extent of thermal oxidation on the dynamic mechanical response of poly(ethylene oxide) (PEO). The glass transition temperature (Tg) of PEO (MW = 9 × 105 Dalton) was found to be −44°C. For PEO (MW = 1 × 105 Dalton) the Tg is −39°C and this value increases by 2–9°C for every decade increase in the measuring frequency. Two minor, second‐order transitions of PEO are also discernible at −33 and 32°C. An inverse dependence of Tg on molecular weight was found in the molecular weight range studied and this is contrary to the Fox‐Flory theory. It was also found that a partially crystalline sample is obtained despite very rapid quenching of PEO from the melt into liquid nitrogen. Thermal oxidation of PEO before processing leads to an increase in the amplitude of the loss tangent peak. This reflects the effect of oxidation products in restricting polymer crystallization and the subsequent increase in the amorphous fraction of the polymer. The position of the Tg peak in PEO remains reasonably fixed with progressive ageing and this was attributed to crosslinking having occurred in addition to chain scission during thermal oxidation.
Staining techniques for detecting localized oxidation in high density polyethylene powders and films
Authors: Scheirs J. , Delatycki O. , Bigger S. W. , Billingham N. C. 
Published: April 2007

AbstractStaining techniques, which reveal the heterogeneous nature of polymer oxidation, are reviewed. A sensitive staining technique is described which identifies the location and distribution of partially oxidized areas within the morphological structure of high density polyethylene (HDPE) powders and films. Gaseous sulfur dioxide (SO2) reacts specifically with the hydroperoxide groups in oxidized HDPE, producing macromolecular sulfates. Subsequent heating leads to the elimination of sulfuric acid and the formation of conjugated sequences along the polymer chains. Such conjugated regions can be readily identified using ultraviolet microscopy. The staining of oxidized polymers with gaseous reagents avoids problems, like extraction of oligomeric material, which are encountered when using conventional solvent‐based methods, e.g. 2,4‐dinitrophenylhydrazine staining.
Synthesis and study of thermal and electrical behaviour of some polyaromatic amines
Authors: Rawat B. , Kansara S. S. , Rama H. S. 
Published: April 2007

AbstractSamples of polyaromatic amines were synthesised by chemical and electrochemical methods, using different amounts of electrolytes for the purpose of doping the polymer. These polymers were found to show electrical conductivity in the range 10−12–10−6 S/cm. A study of conductivity at various temperatures indicates the semiconducting behaviour of these polymers. Thermal analysis shows that these polymers have high thermal stability.
Synthesis and evaluation of paramagnetic particulates as contrast agents for magnetic resonance imaging (MRI)
Authors: Braybrook Julian H. , Hall Laurance D. 
Published: April 2007

AbstractFormulations based on novel particulate ion‐exchange resins, containing a wide range of paramagnetic transition and rare‐earth metals bound to their surfaces, have been synthesised as potential contrast agents for the magnetic resonance imaging (MRI) of the gastro‐intestinal (GI) tract of man. They have been evaluated in terms of their effects upon the spin‐lattice (R1) and spin‐spin (R2) relaxation rates of the protons of water. Careful selection of the polymer, spacer‐arm, ligand and paramagnetic ion provides a means for subtle molecular tailoring.Further potential applications have been highlighted based on the observed properties of such formulations.
Morphology of high surface area polypyrrole structures
Authors: Atchison Shaun N. , Burford Robert R. , Darragh Terrence A. , Tongtam Tantong 
Published: April 2007

AbstractIn this study pyrrole was electropolymerized into polymers having three types of morphology. In the first case, convoluted tubes and dendrites were deposited on filled polymeric and roughened electrodes. Secondly, free‐standing fractals were formed, radiating from central anodes. In some instances the polymers were grown across filter papers located at the base of the anode and at the surface of the solvent. In the third instance, high surface area fibrillar forms were obtained by in‐situ polymerization within coated, γ‐alumina isoporous membrane hosts, followed by leaching in alkali. In all cases the morphology of these products is described by optical and scanning electron microscopy.