bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of cellulose with organic liquids and vapors
Authors: Colombo Edward A. , Immergut E. H. 
Published: June 2010

AbstractThe interaction of three organic compounds (benzene, methanol, and N, N′‐dimethylformamide) with cellulose was examined, and an attempt was made to relate the extent of interaction with cellulose structure and the molecular structure of the organic compound. The observed interaction between cellulose and benzene, methanol, and DMF is consistent with the idea that the extent of interaction is a function of size and hydrogen‐bonding ability of the swelling liquid. The surface areas, obtained from the vapor isotherms, indicate that the interaction is in the order benzene < methanol ≈︁ DMF. Heats of adsorption determined for the three vapors on cellulose are in good agreement with literature values obtained from calorimetric heats of wetting and, when compared with heats of hydrogen‐bond formation for model systems, indicate that the interaction must involve hydrogen‐bond formation. The heats of adsorption indicate that in the case of methanol and DMF the hydrogen‐bond formation extends over a wide range of vapor coverage, while for benzene vapor the hydrogen‐bond formation falls off rapidly after completion of a monolayer. Limited swelling measurements indicate that the heat of adsorption may be more important than the size of the swelling liquid molecule in the early stages of swelling, but after all the high‐energy sites in the cellulose (attributed to mechanical strains induced in the fiber on drying or processing) become saturated, the size of the molecule becomes more important in determining the extent of swelling.
Post‐polymerization of methyl methacrylate after electroinitiation at the anode
Authors: Palit Santi R. 
Published: June 2010

AbstractIt has been found that aqueous solutions of methyl methacrylate (MMA) containing sodium acetate when electrolyzed between platinum electrodes in an almost closed large test tube go on yielding the polymer for a long time, extending over a couple of days even after the current is switched off. MMA (ca. 1% v/v) and sodium acetate (0.2–0.6N) give good yield of polymer. In a typical experiment, when a 1% MMA solution in 0.3N sodium acetate is electrolyzed for about 2 hr with a current of about 100 mA, a yield in the range of 5% is obtained; however, if the system is left undisturbed after switching off the current, the almost clear solution grows turbid due to postpolymerization and after 24 hr gives a polymer yield of about 60–70%. The intrinsic viscosity of the polymer samples in benzene ranges from 1.6 to 3.7 Long‐lived free radicals not visible to the naked eye are presumably formed whose nature is yet to be elucidated.
Synthesis and properties of some phosphorus‐aziridinyl compounds
Authors: Bergmann Ernst D. , Goldschmidt Zeev , Migron Joëlith , Dancona Josef 
Published: June 2010

AbstractPhosphorus‐aziridinyl compounds, which may be good crosslinking agents for biological as well as chemical‐technical systems, have been synthesized by the reaction of phosphorus oxychloride (or the corresponding thio‐compound) with diols and diamines and treatment of the resulting products with aziridine.The chemical reactivity of the tetra‐aziridides so obtained, their infrared and their nuclear magnetic resonance spectra have been studied.
Radical and ionic polymerization of vinyl chloride with tert‐butylmagnesium chloride
Authors: Guyot Alain , Mordini Jacques 
Published: June 2010

AbstractThe earlier results concerning the kinetics of polymerization and initiator consumption, molecular weight distribution, and the nature of the chain ends in the polymerization of vinyl chloride initiated by tert‐butylmagnesium chloride (tBuMgCl) in tetrahydrofuran and other solvents are rediscussed in terms of the simultaneous participation of an ionic mechanism and a radical mechanism. The former is operative mainly at the beginning of the process and gives very low molecular weight products. The latter is responsible for the formation of the high polymer. The radicals are generated from the organomagnesium compound giving a tert‐butyl group as a chain end for every macromolecule. New experiments support the radical mechanism: comparison with radical polymerizations in the same conditions of temperature and solvent medium, inhibition by NO, copolymerization with vinylidene chloride. Also the high polymer is not obtained if the ionic mechanism is exalted by introduction of a powerful solvating agent, the dimethoxyethane.
Creep of plasticized poly(vinyl chloride)
Authors: Pedersen H. Leth 
Published: June 2010

AbstractTest rings 0.8 mm thick are loaded about 125 N/cm2 and the creep is measured for 100–200 minutes. The load may be varied from 75–200 N/cm2.Increase of length (δ) is plotted versus log time which gives a linear relation. δ is converted to elongation [ε = (δ × 100)/1o], and the slope of this line α = Δε/(Δ log time) gives further a linear relationship plotted versus temperature or 1000/T, the energy of activation being 5–7 kcal.The creep is measured in the temperature interval 20–100°C where the increase of log α is between 0.01–0.015/°C. We have tested variation of plasticizers content from 30–80 parts per 100 part resin and resins having MW from 75,000–150,000. The MW was determined by means of gel permeation chromatography (Waters Associates).Together with α the elongation after creep of one minute represents another rate parameter, the logarithm of which is linear versus temperature.In the case where log α exceeds 1.8–i.e., an increase of 63% elongation per decade of time–the sample will break after varying times depending upon amount of plasticizer and Mw.The method covers a wide range of creep and new plasticizers and resins may be characterised by the position of the log α/temperature‐line.
Etude de L' ionisation de films insolubles de poly‐peptides
Authors: Caspers J. , Ruysschaert J. M. , Jaffé Et J. 
Published: June 2010

AbstractRecently, evidence has been obtained that the monolayers of a number of synthetic polypeptides are in the α‐helical conformation at the air‐water interface. This hypothesis has been based on measurements of deuterium exchange rates and examination of collapsed films by infrared spectroscopy.In this paper, the influence of the interface is studied with a method of the surface chemistry: the surface potential. The modification of the properties of the ionized groups with the macromolecular conformation was more particulary investigated in the case of poly‐L‐glutamic acid. Orientation of the molecules in the monolayers is imposed by the nature of the interface (air‐water, cyclohexane‐water). The theories of the ionic double layer (Gouy model, Donnan equilibrium) allow to calculate α, the degree of ionization of the film. The results obtained demonstrate that, at the cyclohexane‐water interface, the accessibility to the ionized groups is more difficult than at the air‐water interface. The variation of α with the PH of the substrate is used to calculate an intrinsic dissociation constant K of the monomer of the spread molecules. The values are similar to that obtained in solution.
Measurement of the strength of steric barriers in non‐aqueous polymer dispersions
Authors: Doroszkowski A. , Lambourne R. 
Published: June 2010

AbstractThe forces of repulsion generated in the steric barriers of a series of monodisperse spherical polymer particles, varying in diameter, have been measured using a surface balance. The particles were stabilized using a graft copolymer with a poly(methyl methacrylate) backbone and heptane soluble poly(12 hydroxy stearic acid) side chains. It was established that the particles were supported on a water surface and that the stabilizing polymer was in a heptane phase in the plane of compression. From pressure‐area measurements, a stabilizing barrier thickness of 130 Å (independent of particle size) was found which was in good agreement with the value from viscometry. Compression of the particles at the interface permitted the measurement of the collapse pressure of the steric barrier from which the work done in compressing the barrier was computed. Two theoretical models for the system, one similar to Fischer's treatment of osmotic pressure changes associated with the overlap, or inter‐penetration, of the steric barrier and another based upon Ottewill and Walker's treatment of the free energy of dilution of the steric barrier have been evaluated. Both models are in good agreement with the experimental data.
The viscoelastic properties of poly(phenylene ethers). I. Unsubstituted and methyl or phenyl substituted polymers
Authors: Eisenberg A. , Cayrol B. 
Published: June 2010

AbstractA series of poly (phenylene ethers) with methy or phenyl substituents or without substituents have been studied. They are: M2PPO poly (2,6‐dimethyl p‐phenylene oxide), ϕ2PPO poly (2,6‐diphenyl p‐phenylene oxide), MϕPPO poly (2‐methyl, 6‐phenyl p‐phenylene oxide), H2PPO poly (p‐phenylene oxide), and H2PPS poly (p‐phenylene sulfide).Several sub Tg relaxation regions have been found for these polymers which seem to have a common mechanistic origin. The β region which was found for H2PPO (H2PPS), M2PPO, and ϕ2PPO has an activation energy, respectively, of ca. 12, 16, and 23 kcal/mole and is most probably due to hindered oscillatory motions of the backbone phenylene groups. The tan δ peaks at 1 cps occur, respectively, at ca. −110°, −50°, and +80°C. The next lower or γ region was found for MϕPPO and ϕ2PPO with an activation energy of ca. 12 kcal/mole and is probably due to hindered torsional oscillations of the side chain phenyl. A still lower relaxation region (called δ) was also found for the two last compounds. Its activation energy is ca. 4 kcal/mole and is most probably caused by some type of wagging motions of the side chain phenyl.No main chain relaxation was found for MϕPPO. All the relaxations have a very low intensity. The trend in the activation energies for the β region suggests that the barrier is intermolecular. An attempt to correlate the frequencies and activation energies of the β relaxations within the formalism of O'Reilly and Tsang gave good quantitative agreement.
Applications of gel permeation chromatography in the pulping process
Authors: Alexander W. J. , Muller Thomas E. 
Published: June 2010

AbstractThe major changes which occur in the DP distribution of cellulose in wood pulp owing to the refining of unbleached stocks to produce several types of finished pulp have been examined by GPC. Represented in this study are sulfite and sulfate pulping processes and paper and dissolving grade pulps. Factors which influence the definition by GPC of small differences in chain length among high DP pulps were considered. The high DP extremes of ten celluloses were compared by GPC after prefractionation by fractional precipitation. Results classify only small percentages above 3500 DP and then only in the highest average DP pulps examined. The cold alkali‐soluble fractions isolated from a high and low DP sulfite paper pulp and a prehydrolyzed sulfate pulp were compared by GPC and differences have been revealed which were not evident from viscometric DP measurements.
Light scattering by cellulose. V. Anisotropy scattering by wood fibers
Authors: Muggli Reto , Marton R. , Sarko A. 
Published: June 2010

AbstractSolid state light scattering patterns from single wood fibers were recorded using a laser as the light source. The scattering was recorded in the Hv mode; i.e., with the incident light beam vertically polarized, the scattered light was passed through a horizontal analyzer, thus permitting the recording of only the scattering arising from anisotropy fluctuations. The scattering pattern was confined to a narrow line consisting of regularly spaced maxima and minima. The overall scattering envelope could be accounted for by a hollow cylindrical model with helically wound dipoles, while the periodicity in the intensity is a function of fiber diameter and cell wall thickness. Comparison of relative intensities led to the conclusions that cellulose of the wood fiber behaves optically as a biaxial crystal in that the cellulose crystallites are biaxially oriented in an axial‐tangentoplanar fashion in the cell wall.
Plasticizing wood with ammonia‐control of color change
Authors: Schuerch C. , Davidson R. W. 
Published: June 2010

AbstractRecent studies of plasticizing wood with anhydrous ammonia have demonstrated that pronounced changes in the color of wood can occur. These changes are thought to be the result of various oxidation and condensation reactions that are enhanced by ammonia. It was postulated that pretreatment of the wood with sulfur dioxide would effectively block these reactions and thus lead to little, or no, color change in subsequent ammonia treat‐ment. A series of tests were run on maple, birch, red oak, and douglas fir specimens that confirm this hypothesis. Reflectance spectra over the range of visible wave lengths show that both liquid ammonia at −35°C and gaseous ammonia at +25°C darken the wood with more darkening occurring at the higher temperature. Pretreatment with sulfur dioxide followed by gaseous ammonia treatment to a highly plastic state results in only slight changes in color while the reverse procedure (NH3 first followed by SO2) results in considerable color change.
Southern pineprehydrolyzates: Characterization of polysaccharides and lignin fragments
Authors: Sears K. D. , Beelik A. , Casebier R. L. , Engen R. J. , Hamilton J. K. , Hergert H. L. 
Published: June 2010

AbstractPrehydrolyzates obtained by treatment of southern pine chips at 175° with steam and water were examined in parallet studies. Carbohydrates were separated from other solids and fractionated into monosaccharides, low‐molecular weight polysaccharides and highmolecular weight polysaccharides. The latter fractions were selectively subfractionated into series of glucomannans and galactoglucomannans using barium precipitation. The poly‐saccharide fractions were characterized by gel permeation chromatography (gpc), the hemicellulose subfractions by periodate oxidation, vapor pressure osmometry, polarimetry, and end‐group assay. Sugar ratios were determined on hydrolyzates of all fractions. Water prehydrolysis was shown to remove substantially more carbohydrates from the chips than steam prehydrolysis, 9.3% versus 3.3% (O.D. wood basis), and these carbohydrates had higher average molecular weight, contained more mannose per unit glucose and yielded more galactoglucomannans than those removed by steam. One of the galactoglucomannans from water prehydrolyzate had the highest number average molecular weight in this study: 3100 by end‐group assay, 3800 by osmometry; polysaccharides of even higher molecular weight were indicated by gpc prehumps. Several monomeric lignin degradation products were identified in the methyl ethyl ketone soluble fraction of steam prehydrolyzate. Among these were coniferaldehyde, vanillic acid, vanillin, protocatechualdehyde, phydroxybenozic acid and, unexpectedly, a sizeable proportion of dihydroconiferyl alcohol.
Investigation in the field of thermal degradation of grafted celluloses
Authors: Simionescu Cristofor I. , Schneider Ion Adam , Hurduc Natalia 
Published: June 2010

AbstractIn this work we tried to explain the thermal behavior of grafted celluloses. Using the thermogravimetric method with constant heating rate, we came to the following important conclusions concerning the thermal stability and the mechanism destruction: the thermal stability of cellulosic derivatives decreases comparatively with the cellulosic material used; the degradation mechanism is very complex occurring by concurrent reactions depending on the nature of the nature of the initial cellulosic support and the degree of substitution.
Determination of solubility parameters of chlorinated poly(vinyl chloride) by turbidimetry and viscosimetry
Authors: Tillaev R. S. , Khasankhanova M. , Tashmukhamedov S. A. , Usmanov Kh. U. 
Published: June 2010

AbstractThe product of chlorination of poly(vinyl chloride), perchlorovinyl (PerCV), dissolves in most organic solvents, a fact explained by the weakening of intermolecular interaction by irregular disposition of chlorine atoms along the chain. For evaluation of the changes in these forces, solubility parameters were determined by the method of turbidimetry and viscosimetry proposed by Suh, Clark, and Mangarai.For turbidimetry 15 solvents of differing chemical nature and 2 nonsolvents were used: hexane (low solubility parameter) and methanol (high solubility parameter). Values of the intrinsic viscosity and Huggins constants were obtained from viscometric data. Consideration of the results in terms of the Flory‐Huggins theory gave a value of 9.30(cal/cm3)1/2 for the solubility parameter of PerCV.
Specific interactions in solutions of polymers. IV. A calorimetric study of butyl methacrylate oligomers in chloroform
Authors: Máša Z. , Biroš J. , Trekoval J. , Pouchly J. 
Published: June 2010

AbstractSome general features of the concentration dependence of the reduced heat of mixing are derived for a system of nA moles of solvent and nB moles of polymer, provided that the enthalpy change referred to one mole of properly defined structural elements is expressed as a function of the fraction θB = cnB/(nA + cnB) where c denotes the number of structural elements in a polymer molecule. The heat of mixing ΔHM of a polymer with a solvent capable of binding to a macromolecule via specific interactions is analyzed on the basis of the association equilibrium theory. The effective number of binding sites ce, i.e., a value of c for which the curve ΔHM versus θB is symmetric, is defined as an invariant basis for characterization of the asymmetry of the enthalpy curve. Rules enabling conclusions to be drawn about the change of the binding constants with the degree of polymerization and with mutual interaction of the binding sites from an extensive parameter and the asymmetry are derived. Measurements have been carried out on the concentration dependence of the heat of mixing of mixtures of chloroform with butyl isobutyrate and with oligomers of butyl methacrylate (monomer to tetramer) having a butoxyl group on one chain end. In addition ΔHM for the reference mixtures chloroform + n‐heptane, chloroform + n‐hexadecane, tetrachloromethane + n‐heptane, n‐heptane + butyl isobutyrate was determined. A comparison of the enthalpy curves seems to prove that in the region of θB → 1 the binding constants, or enthalpies of dimer are only slightly lower than those for monomer, while those from dimer through tetramer coincide. On the contrary the binding affinity as θA → 1 decreases with increasing degree of polymerization. On the assumption that this decrease is given by a negative interaction between two occupied adjoining sites, the magnitude of this parameter has been estimated.
Cesium sulfate density gradient centrifugation of biological macromolecules in the presence of aprotic polar solvents
Authors: Hahn C. W. 
Published: June 2010

AbstractThe use of equilibrium centrifugation in concentrated aqueous solutions of cesium salts, for the analysis and the separation of biological macromolecules, is restricted because nonspecific interactions may lead to the aggregation and the precipitation (salting out) of a given macrospecies, or to associations and coprecipitation between different species.On the assumption that these phenomena might be compensated for under certain conditions of preferential solvation, attempts were made to achieve pseudoideal conditions, by adding polar aprotic solvents to analytical and preparative cesium sulfate density‐gradient centrifugation of diverse preparations of desoxyribonucleic acid (DNA), ribonucleic acid (RNA), polysaccharides as extracted from biological material, and homopolynucleotides as synthesized by enzymatic methods.The results of these experiments have shown that, thus modified, the technique makes it possible to reduce, if not avert, the precipitation of certain nucleic acids and polynucleotides, as well as the association between certain macromolecular species [4].These advantages allow separations to be achieved which are impossible in conventional aqueous density gradients. In addition, the new technique permits the detection of macromolecular polysaccharides which normally would escape from detection, or which even would give rise to misinterpretation.The purpose of this article is not so much to present new specific biological results, but rather to demonstrate that profiles obtained by the classical technique may be treacherously misleading, and that the new technique should, or at least may, be used in parallel to obtain complementary information.
The photochemical reactions of the peroxide radicals in polytetrafluorethylene
Authors: Milinchuk V. K. , Klinshpont E. R. 
Published: June 2010

AbstractThe kinetics and mechanism of the photochemical reactions of the peroxide radicals have been investigated in polytetrafluorethylene by electron paramagnetic resonance. Under irradiation by UV light, with λ < 300 nm, the peroxide radicals ˜CF2 CF(O2)CF2∼ and ∼CF2 CF2 O2 are dissociated and the end fluoralkyl radicals ∼CF2 CF2 are produced. The activation effective energy of the photodissociation of the peroxide radicals is equal to approximately 1‐2 kcal/mole. Quantum yield of the dissociation of peroxide radicals is equal to about 1. In the presence of oxygen the photorecombination of the peroxide radicals takes place. The photorecombination of the peroxide radicals bring about a reversal of the reactions of the dissociation of the end peroxide radicals and the addition of oxygen to the end fluoralkyl radical. Due to a dependence upon the initial concentration of peroxide radicals, the quantity of molecules of CF2 O produced varies from 25 to 45 per one vanished radical. The rate of the photorecombination of the peroxide radical is in linear dependence on light intensity and in the interval 150‐500 torr does not depend upon oxygen pressure.
The photodegradation of poly(vinyl chloride) films. III. The effect of peroxide additives
Authors: Gibb W. H. , MacCallum J. R. 
Published: June 2010

AbstractThe photodecomposition of films of poly(vinyl chloride) containing benzoyl peroxide and two aliphatic peroxides is investigated. It is proposed that the aromatic peroxide decomposed as a result of absorption of the irradiation, thus speeding up the early stages of the reaction but resulting in a lower final conversion. The aliphatic peroxides broke down as a result of energy transfer from polyenes and contributed to the propagation of the removal of HC1 with an increase in conversion. Films containing acenaphthene were ultimately more stable than the reference but decomposed faster in the early stages. It is suggested that energy transfer plays an important part in the mechanism.
The study of the inhibiting activity of poly (2‐methyl‐5‐ethynylpyridine) during initiated oxidation of cumene
Authors: Berlin A. A. , Aseeva R. M. , Ivanov A. A. , Kotova A. V. 
Published: June 2010

AbstractThe inhibiting activity of poly (2‐methyl‐5‐ethynylpyridine) (PEP) has been studied in the cumene oxidation reaction initiated by azobisisobutyronitrile at 55–65°C. According to the kinetic data the reaction between RO2 radical and PEP is irreversible. About 12% of the most active macromolecules of PEP react during the induction period followed by retarded oxidation of cumene. The quantity of terminated peroxy radicals reaches 1.5 per molecule of the inhibitor. This quantity is not altered when PEP concentration changes. Macromolecules of PEP differ in their radical reactivity. An increase of PEP molecular weight leads to the increase in PEP reactivity and in the fraction of active molecules. The paramagnetic centers of PEP interact with peroxy radicals at the maximum rate and disappear at the initial stage of oxidation.