bluuebunny/crossref_metadata_2025_split huggingface dataset:
A kinetic study of ziegler‐natta propylene polymerization
Authors: Keii T. , Soga K. , Saiki N. 
Published: June 2010

AbstractThe kinetics of the propylene polymerization with TiCl3‐AlEt3 has been investigated in the temperature range (30‐70°C.), the pressure range of propylene (100‐700 mm. Hg), and the concentration range of the catalysts (2 g. TiCl3/liter, [A]/[Ti] = 0.4‐3.0). The polymerization rate R increases rapidly with the polymerization time t at first (stage I), which is followed by a gradual decrease to the stationary value Roo, (stage II). The kinetic behavior in stage I in the case when propylene is introduced after the addition of AlEt3 is expressed by

and that in the case when propylene is introduced before the addition of AlEt3 is expressed by

The kinetic behavior in stage II, which is independent of the above procedure, is expressed by

where R∞ is the stationary rate represented by

and Ro a constant. The activation energies are E1 = 15, E2 = 17, Et3 = 2‐3, E3″ = 12, and EP = 10 kcal./mole, respectively. The heat of adsorption of AlEt3 was obtained as 12 kcal./ mole from the temperature dependence of K. Stage I is explained on the basis of the formation of polymerization centers from Al2Et6 and a propylene monomer on the surface of TiCl3. Stage II is attributed to an irreversible deactivation of the polymerization centers localized on unstable surface sites due mainly to a spontaneous process and partially to a propylene monomer (or polymer) attack.
The morphology of fibers from deformed polymer crystals
Authors: Ingram P. , Kiho H. , Peterlin A. 
Published: June 2010

AbstractElectron diffraction and microscopy have been used to investigate the fine structure of fibrils pulled from deformed polyethylene and polyoxymethylene crystals. Since on annealing close to the melting point the striations developed transverse to the fibril axis are thought to be folded chain lamellae, we looked for evidence whereby folds could be detected prior to annealing. In addition to striations observed by allowing iodine vapors to diffuse into polyethylene fibrils, and by dark‐field observation, both reported earlier, we found (1) similar striations in polyoxymethylene by exposure to phosphotungstic acid, and (2) the presence of some monoclinic phase remaining in polyethylene from initial stages of deformation of orthorhombic folded chain crystals. It is suggested that blocks less than 200 A. long of the original crystals break off during deformation. On annealing, tie molecules and some unfolded chains relax and are incorporated into the blocks. The striation periodicity increases with annealing temperature and decreases with molecular weight. Little annealing time dependence is found. The periodicity was independent of draw temperature between 40 and 160°C. in polyoxymethylene indicating that folded chain lamellae could not be formed during deformation.
A study of the interaction of Ni(II) and Cu(II) with poly(acrylic acid)
Authors: McLaren J. V. , Watts J. D. , Gilbert A. 
Published: June 2010

AbstractPotentiometric titrations have been carried out on a sample of poly(acrylic acid) of very high molecular weight (Mw = 1.92 × 106). At polymer concentrations greater than about 1 × 10−4 equiv./liter, this material behaves as a weaker acid, under given conditions, than when it is heat degraded, and also compared with a lower molecular weight sample of poly(acrylic acid) (Mw = 3.52 × 105). Only at very high dilutions are there indications that the three materials have the same pKa values. The titration curves reveal a conformational transition in poly (acrylic acid) in the range of α's of 0.2–0.5. Formation curves for the complexes between the high molecular weight poly‐(acrylic acid) and Cu2+ and Ni2+ have been calculated from the titration curves. At a polymer concentration of 2.4 × 10−3 equiv./liter, these metals form complexes in which two carboxylate groups are involved, whereas at a polymer concentration of 1.5 × 10−4 equiv./liter, the formation curves suggest the existence of complexes involving more than two carboxylate groups. This is thought to be due to enhanced intermolecular interaction which results in a reversible physically crosslinked system.
Strahlenchemische Darstellung von Polysulfonen bei Verschiedenen Temperaturen
Authors: Schneider Christel , Denaxas Jannis , Hummel Dieter 
Published: June 2010

AbstractUnder the influence of 60Co‐γ‐rays copolymers of vinyl chloride and sulfur dioxide have been prepared at various temperatures between + 20 and − 75°C.; the molar ratio of vinyl chloride and sulfur dioxide in the polysulfone formed at + 20°C. is about 2. With decreasing temperatures the sulfur content of the polysulfone increases, and at −75°C. the molar ratio VC/SO2 in the copolymer averages about 1.4. For all temperatures used the composition of the polysulfone is independent of the composition of the reaction mixture. However, the polymerization rate is dependent on the vinyl chloride concentration in the feed. The temperature coefficient of the polymerization rate is negative for vinyl chloride concentrations up to 50 mole‐% in the reaction mixture. The reaction mechanism‐according to the reaction temperature–is presumed to be a radical copolymerization between the vinyl chloride monomer and a 1:1 vinyl chloride/SO2 complex, or between two vinyl chloride/SO2 complexes. Furthermore, the eopolymerization of 2‐vinylpyridine, 4‐vinylpyridine, and 4‐vinylcyclohexene with SO2 was investigated. No polysulfone was formed in the case of the vinylpyridines, neither at room temperature nor at low temperatures. 4‐Vinylcyclohexene, on the other hand, formed a polysulfone.
The mechanism of particle formation in polymer hydrosols. I. Kinetics of Aqueous Polymerization of Methyl Methacrylate
Authors: Fitch Robert M. , Prenosil Michael B. , Sprick Karen J. 
Published: June 2010

AbstractThe polymerization of an aqueous solution of methyl methacrylate has been shown to obey classical steady‐state homogeneous kinetics at low initiator concentrations ([I] < 0.463 mM) even though the system is colloidal. At higher [I] (> 0.925 mM) classical heterogeneous kinetics are found. Particle formation, observed by Tyndall scattering, occurs when the polymer concentration reaches approximately 0.03 g/100 ml regardless of the rate of polymerization. This is taken as evidence that in this system particle formation is thermodynamically controlled. The particles are formed during the earliest stages of the polymerization when nonsteady‐state kinetics obtain. In this region the molecular weight of the polymer increases rapidly. After the steady‐state is attained, the average molecular weight remains constant until the Norrish‐Trommsdorff “gel effect” becomes important.
Instabilities in theoretical chemistry. II. Mixing of different instabilities
Authors: Trig C. 
Published: June 2010

AbstractAs discussed in the preceding paper, the Hartree‐Fock instabilities have now been shown1‐3 to occur in a rigid symmetrical lattice, giving rise to lower energy states than the Hartree‐Fock symmetrical wave function. It has also been pointed out already4a, 15 that the charge density waves (“singlet instability”) may possibly enhance a core distortion. As a matter of fact, as far as polyenes are concerned, there are experimental indications that core alternation occurs: for linear polyenes, the relevant experimental data consists of x‐ray analysis of carotenoid crystals, vibrational frequencies spectra,4a and, perhaps less directly, the vibrational coupling in optical spectra4b; even in cyclic polyenes (18‐annulene), core alternation may possibly take place.5 Thus, the first question arises: how can different instabilities coexist in the same ground state? This problem has been partially studied by different authors2a,6, but, as Paldus and Čížek pointed out1,2b, they generally disregarded the possibility that “number density fluctuations” take place between the atoms, inducing or enhancing bond order alternation, and not only on the atoms, inducing alternating electronic charges. Indeed Harris and Falicov6 have considered core alternation together with spin density waves, but, by replacing the long range exchange potential by a constant mean value, they really miss its specific effect on bond alternation. So the question of the nature of the Hartree‐Fock ground state of long chain polyenes is still open. The different types of instability are each characterized by the symmetry properties of the wave function with respect to time reversion, and to the one‐electron space and spin coordinate transformations.2a As these transformations involve different coordinate spaces, they may be compatible; however the onset of one instability generally lessens the other instabilities: in a variational procedure, mixing with excited states is less favorable as soon as an energy gap already exists. Our purpose is to develop some examples of these consistency conditions.
Thermal dehydrochlorination of poly(vinyl chloride) models in the liquid phase
Authors: Mayer Z. , Obereigner B. , Lim D. 
Published: June 2010

AbstractAn investigation was made of the kinetics of thermal dehydrochlorination of 8‐chlorohexadecane, 2,4‐dichloropentadecane, 4‐chloro‐2‐dodecene, 8‐chloro‐6‐tridecene, 6‐chloro‐2,4‐octadiene, and 7‐chloro‐3,5‐nonadiene in the liquid phase in an inert gas.The course of the reaction is accelerated by the presence of free hydrogen chloride and slowed down by conjugated dienes and trienes. Destruction of the model compounds leads to the formation of oligomers and telomers, some of which were isolated and their elementary composition and molecular weight determined. The reaction occurs much faster in nitrobenzene, compared with the dehydrochlorination of a model without solvent.With respect to its complicated mechanism, the dehydrochlorination reaction was characterized from the kinetic viewpoint by its initial rate kO. Parameters E and A were estimated from the temperature dependence kO = A exp(−E/RT).It follows from the experimental results and from the comparison of thermal dehydrochlorination reactions in the gas and liquid phases and in poly(vinyl chloride) that the reaction under investigation occurs by a ionic mechanism in the liquid phase, and most probably also in the polymer.
Spectroscopy of protein monolayers: A transition in β‐lactoglobulin films
Authors: Loeb George I. 
Published: June 2010

AbstractInfrared studies of the amide I band of transferred films of β‐lactoglobulin‐B spread on 0.5 M KC1 have been obtained via the multiple internal reflection (MIR) technique. The spectra indicate that the conformations of the films change with surface pressure. The data are consistent with a denatured molecule as the predominant species at high area per molecule and a species whose secondary structure is similar to that of the native molecule at high degree of compression. The transition may be reversed by re‐expansion of the film after compression. Approximately equal amounts of native‐type and denatured type spectral components are found at 6 dynes/cm at room temperature.
The substructure of crystalline cellulose and chitin microfibrils
Authors: Gardner K. H. , Blackwell J. 
Published: June 2010

AbstractThe fine structures of the highly crystalline cellulose microfibrils from the cell walls of the marine algae Valonia ventricosa, and the extra cellular chitin spines of the euryhaline diatoms Thalassiosira fluviatilis, have been investigated by observation of deformed and un‐deformed specimens in the electron microscope. On treatment with ultrasonic vibrations, the purified Valonia cell wall broke down into long microfibrils, with approximate cross section 210 Å × 110Å Some of these microfibrils appeared to have been disruptedby the ultra‐sonic treatment, and consisted of elementary fibrillar fragments, with a regular width of ∼35 Å, or multiples thereof. Deformation by stretching or mylar films separated the micro‐fibril into smaller fibrils with width of ∼35 Å. Striations on the intact microfibrils are in‐terpreted in terms of a substructure of these elementary fibrils.A similar substructure is observed for the crystalline chitin of the diatom spines. The spines have a lamella morphology, and break down into ribbons with widths of 200‐300 Å, and a thickness of 20 Å. These ribbons were generally observed as lateral or stacked aggregates. Further disruption by ultrasonic vibrations and deformation shows that these ribbons are made up of smaller fibrils with a width of ∼35 Å Striations are observed on the intact ribbons indicating the presence of substructure.
Elementary cellulose fibrils possess an entropic deformation mechanism
Authors: Stöckmann Volker E. 
Published: June 2010

AbstractIn order to obtain information on the structure of cellulose elementary fibrils, temperature coefficients of equilibrium tensile forces were determined. A force‐temperature coefficient is identical with the negative amount of entropy change during deformation. Thus, data on thermoelasticity can provide insight into the basic mechanism of deformation, hence, into the structure of the deformed specimen. The thermoelastic behavior of native and mercerized ramie fibers was investigated as a function of moisture content. All of the measured force‐temperature curves possess positive slopes. The effect of temperature on undeformed length and on moisture content required that temperature coefficients be corrected accordingly. After incorporating the corrections, only moisture‐free fibers possess positive slopes. Water‐swollen fibers show large negative slopes, whereas air‐dried fibers exhibit a behavior between the two extremes. Positive slope implies entropy‐elastic deformation. Because dry fibers deform in an entropy‐elastic manner, disordered regions within elementary fibrils must exist. The degree of disorder must be higher in the mercerized than in the native fibers. Rearrangement of water molecules during deformation towards higher disorder is evoked to account for the increasing entropy of the water‐swollen fibers.
Synthesis of cellulose graft copolymers with mixtures of N‐vinyllactams and vinyl monomers
Authors: Ibraghimov F. , Mukhamedaliyev D. , Gafurov T. G. , Usmanov Kh. U. 
Published: June 2010

AbstractSynthesis of cellulose graft copolymers with mixtures of N‐vinyllactams (VL) and vinyl monomers (VM), the definition of the copolymer composition of the grafted chain, coefficients of relative monomers reactiveness, solubility, characteristic viscosity, and the effect of the initial monomer ratio on the obtained products properties are reported.N‐vinylpirrolidone, N‐vinylcaprolactam, and methylmethacrylate butylmethacrylate, acrylonitrile, and β‐hydroxyacrylate glycidic ether were used in the investigations as well as preparations of cotton fibers, fibers of diacetylcellulose, and fibers of viscose staple rayon.VL and VM were grafted onto cellulose in the oxidative‐reductive systems of bivalent ferrous and hydrogen peroxide at various molar ratio (0.1:0.9; 0.25:0.75; 0.5:0.5; 0.75:0.25; 0.9:0.1). The VL‐VM copolymer side chains were hydrolytically isolated from the grafted part of cellulose. The values of rVL and rVM were plotted as those of rVL and rVM for the static polymerization. It is found that the composition of the grafted cellulose side chains was identical with that of the copolymers, which have been obtained by the bulk method. The copolymers solubility remained the same after the grafted cellulose chain was isolated by the classic method of copolymerization in the absence of cellulose.The graft copolymers were identified by IR spectra. The mechanism of the graft copolymerization is given for all the abovementioned monomers and cellulose.
The effect of ultraviolet irradiation on photo‐oxidation and crosslinking reactions in a poly(vinyl alcohol)‐ammonium dichromate system
Authors: Bravar M. , Rek V. , Kostelac‐Biffl R. 
Published: June 2010

AbstractThe chemical transformations of poly(vinyl alcohol) (PVA) film by ammonium dichromate on exposure to ultraviolet irradiation have been investigated. The oxidative transformation was followed spectrophotometrically and the extent of crosslinking reaction by measuring the solubility and the viscosity changes of the exposed film. The influence of the time of exposure as well as the concentration of ammonium dichromate on the above reactions has been established.The ultraviolet and infrared data of exposed film showed that hydroxyl groups are oxidized to carbonyl groups. Absorption bands at 230, 270, and 330 mm, attributed to the presence of the double bond conjugated with carbonyl, were increased during the exposed period.The bromination and hydrogenation of the dissolved films decreased those absorptions. This indicated that the content of the carbonyl groups and double bonds were increased during the irradiation.The partial insolubilization of the exposed film was attributed to the formation of complexes of alcohol and carbonyl groups to chromic ions formed by reduction of the dichromate.
Effectivity of organic phosphites
Authors: Kovács E. , Wolkóber Z. 
Published: June 2010

AbstractThe behavior of organic phosphites as antioxidants for polyethylene, costabilizer, and metal‐deactivator for poly(vinyl chloride) (PVC), has been studied by Thermox‐meter and Brabander plastograph. It was found, that their antioxidative effectivity is determined by the self‐stability of the investigated phosphites, namely the volatility, the hydrolysis and oxidation sensitivity. At the same time, the stabilizing and metal‐deactivating effect for PVC with this technique did not show significant differences.
Inhibiting activity and thermooxidative stability of the oxidative dehydro‐polycondensation products of diphenylamine
Authors: Berlin A. A. , Ivanov A. A. , Mirotvortsev I. I. 
Published: June 2010

AbstractOxidative dehydropolycondensation of diphenylamine (DPA) at 200–260°C leads to the formation of polymers with a system of conjugation, this process being a first order reaction with an activation energy of 20 kcal/mole. Polymeric products of the reaction (PDA) are found to contain fragments of quinone imine and triphenylamine structures and an insignificant quantity of NH groups. PDA reactivity towards peroxide radicals is significantly lower than that of DPA. PDA has higher activity than DPA by the inhibition of thermal oxidation of 1,4‐cis‐polybutadiene, ceresine, and SKN‐26 rubber, the largest effect being observed when PDA mixtures with DPA are used. PDA has high thermal and thermooxidative stability. PDA loses its solubility at the initial stages of destruction, then its destruction rate increases in air and remains constant in argon. Paramagnetic centers of PDA take part in the inhibition of destruction in air until the polymer completely loses its solubility.
Aqueous diffusion through partition membranes
Authors: Lyman Donald J. , Kim Sung Wan 
Published: June 2010

AbstractDiffusion data obtained from Leonard‐Bluemle cell was interpreted in terms of the extent of interaction between solute and membrane matrix. A new equation was developed to provide linear fit curve for the half‐time data measurements. To develop an understanding of these partition type membranes on the molecular basis, the absolute reaction rate theory has been explored.
Investigation of thermal and thermooxi‐dizing degradation of irradiated polyethylene
Authors: Leshtchenko S. S. , Pavlova Zh. D. , Egorova Z. S. , Karpov V. L. 
Published: June 2010

AbstractThe peculiarities of thermal and thermooxidizing degradation of low‐ and high‐density polyethylene (PELD, PEHD) and the ethylene‐propylene copolymer (CEP‐7) irradiated over the range of 1 to 300 Mrad have been studied.It was established that the change of structure of polymer by irradiation resulted in an increase of thermostability and a decrease of thermooxidation stability.The change of content of double bonds as a result of pyrolysis was studied. It was suggested that trans‐vinylene double bonds promoted the development of thermal degradation of irradiated polymer and vinylidene double bonds were slowing down this process. It was found that in nonirradiated branched PELD and CEP‐7 side groups and tertiary carbon atoms oxidized. In nonirradiated linear PEHD the oxidation occurred mainly with the partipation of secondary carbon atoms. The initial polymer structure had an influence on the process of oxidation of irradiated polymers.Cross‐linking bonds and tertiary carbon atoms were the most vulnerable to the oxidation of irradiated polymers.Simultaneously with the degradation, during oxidation of irradiated polymers a structuralization with the formation of ether bonds R‐O‐R takes place.
Enzymes covalently bound to acrylic gel beads. II. Practical application of hydrolases covalently bound to hydrophilic anionic gel beads
Authors: Krämer D. M. , Lehmann K. , Plainer H. , Reisner W. , Sprössler B. G. 
Published: June 2010

AbstractDNase‐free protease covalently bound to hydrophilic anionic gel beads1 can be used to isolate DNA from animal tissue homogenate by simply degrading the protein moiety and precipitating the DNA with isopropanol from the supernatant, the yield being close to 80%. Glucoamylase bound to AM retains 100% activity as compared to the free enzyme. Thus, 30 % solutions of dextrins in water were degraded to glucose and the procedure was repeated with the same beads for 42 times without apparent loss of enzyme activity. From a technical point of view, this system is more efficient than using the free enzyme.
Aminolysis of monoacetyl derivatives of 2,2′ ‐dihydroxydiphenylmethanes
Authors: Böhmer Volker , Wörsdörfer Klaus , Kämmerer Hermann 
Published: June 2010

AbstractA neighboring group effect was found for the aminolysis of the second acetyl group in acetates of 2,2′‐dihydroxydiphenylmethane derivatives containing a nitrophenol and a methylphenol unit. Kinetic measurements with an excess of n‐butylamine in dioxane were done with 2‐(2‐hydroxy‐3, 5‐dinitrobenzyl)‐4‐methylphenyl acetate (1), 2‐(2‐hydroxy‐5‐nitro‐benzyl)‐4‐methylphenyl acetate (2), and 2‐(2‐hydroxy‐3‐nitro‐5‐methylbenzyl)‐4‐methyl‐phenyl acetate (3). The maximum rate was found for compound 2. When the concentration of n‐butylamine was varied over a large range, the results obtained for compound 2 could be explained best, by assuming that the acetyl group in the methylphenol unit is aminolized faster in the ionic form than as a neutral molecule.
Etude des Activités Catalytiques du Trichlorure de Titane Violet Dans la Polymérisation Haute Température de L'Ethylène
Authors: Machon J. P. , Hermant R. , Houzeaux J. P. 
Published: June 2010

AbstractDes techniques et méthodes expérimentales développées en réacteurs discontinus et continus permettent d'évaluer les vitesses des réactions concurrentes (polymérisation, désactivation, dimérisation) mises en jeu au cours de la polymérisation Ziegler de l'ethylène à haute tempeéature (160 à 280°C).