bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ring shake in some hardwood species: The individual tree approach
Authors: McGinnes E. A. , Chang C. I‐J. , Wu K. Y‐T. 
Published: June 2010

AbstractThe formation of ring shake, a tangential separation of xylem tissue, is being studied in selected red oaks, white oaks, and black walnut. Previous studies have indicated that it is frequently necessary to make detailed analyses throughout one tree in order to evaluate correctly possible stages of development of this defect for the sample under investigation. In the present study, anatomical and chemical analyses both along the shake zone and for a normal zone within a black walnut tree are discussed. Anatomical investigations formed the basis for selection of xylem subdivisions for subsequent chemical analyses. The ring shake was tangentially confined to a single annual increment. This increment was radially subdivided into eight consecutive portions from earlywood through latewood. Each portion was used for determinations of specific gravity, extractives (ether, alcohol, hot water), methoxyl, and certain inorganics. Similar analyses were made on a “control” increment. The possible development of ring shake within the sample tree is presented in terms of resultant chemical and anatomical data.
Monomolecular film properties of cellulose and amylose triacetates at the air‐water interface
Authors: Hittmeier M. , Sandell L. S. , Luner P. 
Published: June 2010

AbstractSurface pressure‐area isotherms of cellulose triacetate and amylose triacetate at the air‐water interface were determined on a vertical and horizontal film balance. Both polymers show anomalous behavior on the vertical balance, including: higher compressibilities than obtained on the horizontal balance, movement of the vertical plate, and atypical hysteresis of the isotherms.The behavior of the cellulose triacetate film is attributed to heterogeneous gelation of the monolayer at low pressures. A mechanism involving the lateral tilting of pyranose units at the interface and subsequent stabilization of the monolayer by van der Waal's interactions accounts for the properties of this film.A helical conformation for amylose triacetate at the air‐water interface is proposed to explain the low compressibility of this monolayer.
Purification of the precursor of bacterial cellulose
Authors: Colvin J. Ross , Leppard Gary G. 
Published: June 2010

AbstractThe precursor(s) of bacterial cellulose can be separated from cultures of Acetobacter xylinum by elution chromatography of lyophilized cells using chloroform, acetone, and 20% methanol in acetone. The last fraction, which contains the compound, may be purified by precipitation of glucose by diethyl ether and phase partition into petroleum ether, both at low temperature. Ability of the purified fraction to form cellulose microfibrils was demonstrated by electron microscopy. The active compound in the fraction was tentatively identified by thin layer chromatography, is very labile and has the properties of a lipid or lipid‐like substance.
The use of adsorbed cellulase in the continuous conversion of cellulose to glucose
Authors: Mandels Mary , Kostick John , Parizek Richard 
Published: June 2010

AbstractCellulose strongly adsorbs cellulase at pH 4.0‐5.0, 25‐50°C, conditions which are optimum for the enzyme action. The adsorbed enzyme is sufficient to digest the cellulose with no replenishment of enzyme even though the liquid phase containing the sugar is continuously removed. As cellulose is digested, the released enzyme is readsorbed on excess or newly added cellulose with retention of activity. Sugars can be separated from the enzyme‐cellulose complex by simple filtration or centrifugation or by retaining the enzyme‐cellulose complex in a column from which the sugar solution is eluted. Adsorbed cellulase has been used to produce syrups containing 5‐14% glucose continuously from stirred reactors containing 10‐20% cellulose, or from cellulose columns.
Structure of slippery Elm Mucilage(Ulmus Fulva)
Authors: Beveridge R. J. , Jones J. K. N. , Lowe R. W. , Szarek W. A. 
Published: June 2010

AbstractThe structure of the mucilage has been investigated using (a) the methylation procedure, (b) by oxidation of the polysaccharide with periodate (the Smith procedure), and (c) by its partial hydrolysis or methanolysis with the formation of sugars and oligosaccharides. It is composed of a main chain of alternating D‐galacturonic acid and L‐rhamnopyranose residues joined by a‐linkages through positions 4 of the galacturonic acid and 2 of the L‐rhamnopyranose. The polysaccharide has side chains, containing one or two residues of 3‐O‐methyl‐D‐galactopyranose or D‐galactopyranose, attached to some L‐rhamnose residues at C‐4 and C‐3, respectively. The synthesis of the disaccharide present at a branching point, namely, O‐(3‐O‐methyl‐β‐D‐galactopyranosyl)‐(1→4)‐L‐rhamnose is described.
The role of additives in the radiation induced copolymerization of monomers to cellulose
Authors: Dilli S. , Garnett J. L. , Martin E. C. , Phuoc D. H. 
Published: June 2010

AbstractThe radiation induced grafting of monomers to cellulose using a variety of solvents by the mutual irradiation technique is discussed. The monomers studied were styrene, 15 substituted styrenes, methylmethacrylate, vinyl acetate, and the vinylpyridines. The types of substituents examined included o‐, m‐, and p‐halogen derivatives, also the alkylstyrenes and certain methoxy monomers. The effect of wetting and nonwetting solvents in the grafting reaction was also investigated. A Trommsdorff effect (accelerated grafting) has been observed in certain systems at low doses and dose rates. The effect of oxygen, nitrogen, and vacuum on the Trommsdorff peak is discussed. The role of additives in the grafting of styrene is considered. The additives examined include aromatic and nonaromatic compounds, also typical free radical scavengers such as hydroquinone and thiourea. With certain additives sensitization is observed. A model for the grafting mechanism is proposed involving charge transfer bonded species. The role of energy transfer and free radical processes in the copolymerization reaction is also discussed.
Contributions to the grafting of the cellulose by radical mechanism
Authors: Simionescu Christofor I. , Feldman Dorel , Ciubotariu Martha 
Published: June 2010

AbstractThe grafting of the cellulose with vinyl monomers in the absence of the radical initiators was studied. The nature of the grafting medium and of the promoters was varied. The obtained copolymers have been investigated by chemical and physical‐chemical methods. The mechanism of the grafting was discussed.
Inorganic redox systems in graft polymerization onto cellulosic materials
Authors: Bains Malkiat S. 
Published: June 2010

AbstractA review is attempted of the inorganic redox systems in the context of free radical graft polymerization. Metal ion‐H2O2 redox systems are considered as part of the spectrum of such inorganic and organic reagents used for the purpose. It is emphasized that the chemistry of these latter systems in particular is much like the radiation chemistry of aqueous solutions caused by high energy ionizing radiations. On the other hand, these systems involve low energy and therefore are less damaging to the substrate and relatively more specific. The reactivity of free radicals in these systems varies subtly with the system and the medium. It is observed that only ceric ion method and [Fe(II); Fe(III)] ‐H2O2 system are most successful in grafting onto cellulosic materials. Attention is paid to the features which makes these systems so useful. Concrete results from ESR study are presented which underline the nonspecific nature of various free radical producing systems including radiations.
Researches in the field of the grafting on cellulose with acrylic and methacrylic derivatives
Authors: Simionescu Christofor I. , Oprea Spiridon 
Published: June 2010

AbstractThe grafting on rayon fiber of acrylic and methacrylic monomers was studied through the decomposition of the hydroperoxide and peroxide groups, created in a process of ozonization. The graft copolymers was characterized by chemical analysis, infrared spectroscopy, and thermo‐oxidative decomposition.
Chemical structure of cellulose‐styrene graft copolymers
Authors: Sakurada I. , Ikada Y. , Nishizaki Y. 
Published: June 2010

AbstractAt first polyvinyl alcohol was used as a model for cellulose, and the grafting of styrene and methyl methacrylate was carried out in a heterogeneous system by use of mutual irradiation, preirradiation, and catalytic method. In all cases trichloroethylene or carbon tetrachloride was added to the reaction mixture to shorten the branches. True graft copolymers were isolated by vigorous alternate extraction of unreacted PVAL and homo‐PST (or‐PMMA), and hydroxyl groups in the copolymers were completely acetylated to carry out osmotic measurements. Molecular weights of the separated chains and the mother polymers were also determined by osmometry. It was shown that the graft copolymer has only one mother PVAL molecule and one graft branch regardless of the grafting methods employed. In the case of cellulose, high tenacity rayon was used as a substrate. The reaction product was acetylated, and the extraction of homo‐PST and unreacted cellulose (in the form of triacetate) was carried out with benzene (at 80°C) and CH2 Cl2 ‐MeOH (1:1, at room temp.), respectively. In this case also, it was shown that the graft copolymer molecule consisted of one graft branch and one mother cellulose molecule.
Phase separation in polymer solutions. I. Liquid‐liquid phase separation of PPO poly (2, 6‐dimethyl 1, 4‐phenylene oxide) in binary mixtures with toluene and ternary mixtures with toluene and ethyl alcohol
Authors: Van Emmerik P. T. , Smolders C. A. 
Published: June 2010

AbstractIn the system poly(2, 6‐dimethy1‐1, 4‐phenylene oxide) (PPO)‐toluene three phase separation lines can be detected: the melting point curve, the cloud point curve, and the spinodial. Because crystallization of PPO occurs very slowly, a phase transition will always be initiated by liquid‐liquid phase separation. Depending upon the experimental circumstances two mechanisms are possible, either nucleation and growth (extremely slowly in this system) or the spinodial decomposition mechanism. In the system PPO‐toluene‐ethanol, liquid‐liquid phase separation occurs leading to two bulk liquid fractions. Only in mixtures containing very small concentrations of alcohol can three phase separation curves be detected from which the position of the cloud point curve of the system PPO‐toluene can be confirmed.
Morphology of glassy polymers
Authors: Ali M. S. , Sheldon R. P. 
Published: June 2010

AbstractA study has been made of the annealing process which takes place when glassy polymers are heated at temperatures near their glass transition temperatures. Low‐angle x‐ray diffraction measurements, extending previous work using wide‐angle techniques, infrared, laser‐Raman, and scanning electron microscopical studies reflect no difference between quenched and annealed polymer. Replica electron micrographs do however indicate some structural reorganization. Differential scanning calorimetry and stress‐strain studies in conjunction with density measurements show that changes in all these occur on annealing but that at the present time conclusive evidence of local chain parallization is still awaited.
Creep behavior of polycaproamide fibers in various stages of homogeneous cold drawing
Authors: Kudrna M. , Janáček J. 
Published: June 2010

AbstractCreep of partly oriented polycaproamide fibers in the course of large tensile strain was investigated and the two‐parameter Voigt model was used to describe the resulting creep curves. It follows from the dependence of the constants of the Voigt model on the magnitude of deformation before the onset of the actual creep, that the decisive deformation mechanism consists in the destruction of microscopic regions, accompanied in a later stage by formation of microcracks. No major effect of temperature, within the range from 30 to 60°C, could be observed. The results are compared with the literature data on the nonhomogeneous deformation of less oriented polyamide systems in the same temperature region which exhibit different behavior.
Time‐temperature superposition in ultimate behavior of heterogeneous gels with varying microstructure
Authors: Raab M. , Pelzbauer Z. , Janáček J. , Štol M. 
Published: June 2010

AbstractIf water is present in a volume concentration higher than about 0.5 during the crosslinking copolymerization of poly(2‐hydroxyethyl methacrylate), porous heterogeneous systems are formed. Samples of poly(2‐hydroxyethyl methacrylate) obtained by polymerization in the presence of various concentrations of water and, therefore, exhibiting different heterogeneity, were swollen in water to equilibrium and used to investigate the ultimate behavior. Heterogeneity was characterized by the volume fraction of swollen polymer in the heterogeneous system and morphology was determined by electron and light microscopy. For all samples, the dependence of time to break on tensile stress, and tensile strength and strain at break at various temperatures have been measured. While the rupture stress of homogeneous samples is very temperature sensitive, the effect of temperature is much less pronounced in the case of highly porous samples. This phenomenon has been ascribed to the temperature‐independent coulomb friction which participates in the rupture process of heterogeneous gels.
Precision differential calorimetry and the heat of fusion of polyethylene
Authors: Richardson M. J. 
Published: June 2010

AbstractA procedure is described for the analysis by computer of the output from a differential scanning calorimeter. Enthalpy calibration with a variety of materials confirms that alumina is excellent for this purpose.Both the crystallinity, xT, and the heat of fusion of polyethylene, ΔHT, vary with temperature and it is important that both are measured. The use of a room‐temperature crystallinity with a high‐temperature heat of fusion can be very misleading. Interfacial effects are shown to be negligible in most cases and the heat of fusion of perfectly crystalline polyethylene is given by ΔHT/xT. It is 309 Jg−1 at the melting point.
Morphology of single‐textured polyethylene a new model for polymer in the oriented state
Authors: Point J. J. , Gilliot M. , Dosiere M. , Goffin A. 
Published: June 2010

AbstractSmall‐angle and x‐ray scattering (SAXS) and calorimetric studies support a model, previously proposed, which describes the structure of single‐textured polyethylene samples. These samples consist of distinct parts: some are made of lamellae and the others are without regular structure of the order of a few hundred angstroms. The reversibility and the kinetic of the evolution of SAXS patterns are due to the melting and the recrystallization of a part of the sample. Thermograms of samples annealed at high temperature show two melting peaks. The peak at the lower temperature is due to the melting of the lamellar crystals possessing a large thickness distribution which can be inodified by subsequent annealing. Melting and recrystallization of these lamellae affect the intensity of SAXS patterns. Thermograms of samples annealed at a relativity low temperature (To) present a third melting peak in the neighborhood of To. The thickness of the corresponding lamellae can be calculated from SAXS patterns. Thus lamellae are only a small fraction of the sample, not the whole as it was previously suppossed. The other fraction has no regular structure of the order of 100 Å.
Effect of jet stretching and draw ratio on the supermolecular structure of nylon 6 threads
Authors: Baranov V. G. , Bychkovsky N. I. , Goikhman A. Sh. , Nosov M. P. 
Published: June 2010

AbstractThe peculiarities of the spherulite structure formed in the course of nylon 6 fiber formation have been investigated. The dimensions and shape of the spherulites were determined by small‐angle scattering of polarized light with a simultaneous check by microscopy. Subsequent deformation at room temperature of the threads containing spherulites embedded in the amorphous glass‐like matrix causes the development and relaxation of stresses in the matrix. At this stage of elongation the spherulites themselves are “flattened” owing to the destruction of regions coinciding with the drawing direction. When the elongation exceeds X2.0 spherulite deformation sets in; it ends with the transition spherulite macrofibril. In the cross sections of the deformed samples spherulite‐like scattering and extinction patterns are observed up to sample rupture. This confirms that there is a direct genetic connection between the spherulite and orientational supermolecular order and indicates that the polarizability ellipsoids in the macrofibril exhibit complex distribution.
Electron‐microscopic study of polymer mixtures
Authors: Kazhdan M. V. , Bakeyev N. F. , Berestneva Z. Ya. 
Published: June 2010

AbstractThe effects of several factors on the morphology of films cast from binary polymer mixtures dissolved in a single solvent have been studied by electron microscopy. An elastomer‐elastomer system (isoprene rubber and polyisobutene) was used.The effects of the relative amounts of components, change of the molecular weight of one of the components, the history of the solution, and the rate of evaporation of solvent on the morphology of films prepared from polymer mixtures were studied. It is inferred from the results that these factors affect the kinetics of the phase separation of polymer mixtures.
The effect of small quantities of structural plasticizer additive on the structure and properties of vulcanizates
Authors: Zharikova Z. F. , Reztsova E. V. , Berestneva Z. Ya. , Kargin V. A. 
Published: June 2010

AbstractThe effect of small quantities of an insoluble plasticizing additive (0.01‐5% by weight) on the structure and properties of vulcanizates of different rubbers has been studied. Silicone oil was used as the plasticizer. It has been shown that significant changes in the mechanical properties of vulcanizates are caused by this type of plasticizer. For instance, a polychloroprene vulcanizate specimen without plasticizer broke down after 25,000 cycles (in extension cycling tests) whereas the same specimen with 0.1% silicone did not break down after 360,000 cycles. It has been shown, with the use of electromicroscopic, IR spectroscopic and x‐ray diffraction methods, that the introduction of small quantities of plasticizing additive leads to the formation of more highly ordered supermolecular structures in vulcanizates. A mechanism proposed for the action of small quantities of additives on the mechanical properties of vulcanizates is based on the idea of structural plasticization.
Effect of high‐pressure annealing on the structure of oriented polyethylene
Authors: Zubov Yu. A. , Selikhova V. I. , Konstantinopolskaya M. B. , Sukhov F. F. , Slovokhotova N. A. , Bakeyev N. F. , Kruykov A. V. , Sokolsky V. A. , Belov G. P. 
Published: June 2010

AbstractThe effect of annealing at different temperatures and pressures of 3000, 5000, and 7000 kg/cm2 on the structure of oriented films of linear polyethylene has been studied. It has been established that for each of the above pressures there is an optimal temperature of annealing at which the maximum crystallinity of the sample is achieved. The results obtained by wide and small angle x‐ray diffraction, infrared spectroscopy, electron microscopy, and density show that annealing at the optimal temperature leads to extended‐chain crystallites in the sample. Orientation of crystallites remains largely unchanged.
Unperturbed dimensions and viscosity of polyarylates
Authors: Pavlova S. A. , Timofeeva G. I. , Menshov V. M. 
Published: June 2010

AbstractCondensation polymers of phenolphthalein with sebacic acid (PA‐1) and of phenolphthalein with isophthalic acid (PA‐2) covering a wide molecular weight range were prepared and fractionated. Studies of solution viscosity were carried out on the fractions dissolved in tetrahydrofuran and in tetrachloroethane. Mark‐Houwink plots for PA‐1 are markedly nonlinear, and the effect is interpreted in terms of coil permeability. It is concluded that permeability effects are negligible in PA‐2. The molecular weight dependence of the second virial coefficient (determined by the Archibald method) in tetrahydrofuran is abnormal for both polymers. The characteristic unperturbed dimension for PA‐1 calculated by the Flory‐Williams method agrees with deductions from experiment.
Light scattering investigations on moderately concentrated solutions
Authors: Dautzenberg H. 
Published: June 2010

AbstractWe performed light scattering measurements on some polymers (polystyrene, polystyrene/poly(methyl methacrylate) graft copolymer, cellulose derivatives) to contribute to the clarification of the structure of solutions in the region of moderate concentrations. In particular, we investigated the influence of molecular weight, chain structure, and conditions of preparation of the solutions. Since a theory is lacking for the quantitative evaluation of scattering curves in this concentration range, we treated the results by the theories of dilute solutions and tried to draw conclusions about the structure of solutions at higher concentrations. Our results suggest network formation at high concentrations.
On the incompatibility of blocks in an isolated molecule of an A‐B block polymer. II. Application of the perturbation theory and of the Casassa‐Markovitz approximation
Authors: Pouchlý J. , Živný A. , Sikora A. 
Published: June 2010

AbstractBy use of the perturbation theory, the number of contacts between blocks in a molecule of an A–B block polymer is expressed as a function of an excluded volume parameter in the from of a power series. The first two coefficients of this series are evaluated as functions of the relative length of one of the blocks. Introducing an approximate assumption according to Casassa and Markovitz, a closed‐form expression is obtained; its limiting value and first derivative as the excluded volume effect vanishes are in agreement with those given by the exact power series. Similarly to the preceding results obtained with the Flory‐Krigbaum segment cloud model, it turns out that on a change of thermodynamic conditions the number of interblock contacts is lowered only gradually; however the extent of this block segregation is higher than that according to the Flory‐Krigbaum model.
Coil dimensions and hydrodynamic properties of methylmethacrylate random copolymers
Authors: Wunderlich W. 
Published: June 2010

AbstractLight scattering and viscosity measurements have been carried out on random copolymers of methylmethacrylate with methyl, ethyl, and n‐butylacrylate as well as n‐butylmethacrylate in acetone at 20°C. The parent homopolymers have also been included in the measurements. Unperturbed dimensions and excluded volume parameters were evaluated from the experimental data. It has been found that the Flory's hydrodynamic constant Φo in copolymer systems exceeds the value calculated and experimentally determined for binary homopolymer solutions. Also, in a fairly good solvent, the copolymer coil behaves as if it were less expanded than it is in reality. The short range interactions exceed the mean value calculated from homopolymers in combining an α‐substituted monomer with an unsubstituted one. Long range interactions resulting from heterocontacts can be determined quantitatively and related to the incompatibility of the parent homopolymers.