bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic study of thermal dehydrochlorination of poly(vinyl chloride) in the presence of oxygen. I. Fundamental relations
Authors: Valko L. 
Published: June 2010

AbstractStarting from the assumption that the mechanism of the elimination of the HCI molecule and of cleavage of the C–C bonds represents a monomolecular stochastic process, a differential equation has been constructed that describes the thermal destruction of PVC in oxygen. Here one has started from the step mechanism of destruction, this being associated with the formation of weak points in the polymer chain system. The influence of dissipative factors, which prevent transferring the system into a truly thermodynamic equilibrium, has been considered too. The introduced kinetic parameters and relations between them make it possible to evaluate quantitatively the kinetics of destruction of PVC in oxygen, treated to various degrees of reaction.
A new equation for polymer oxidation reactions
Authors: Kovarskaya B. M. 
Published: June 2010

AbstractAn empirical equation permitting the description of oxygen absorption as a function of time for all steps of oxidation of a number of heterochain polymers of linear and three‐dimensional structure: polycarbonate, polycaproamide, epoxy resin, etc., is proposed. A suggestion is made that a compound inhibiting oxidation is formed along with the oxidizing product.
Anionische Polymerisation in Schwach Solvatisierenden Lösungsmitteln
Authors: Figini R. V. 
Published: June 2010

AbstractThe anionic polymerization of styrene initiated by cumylsodium and carried out in cumyl methyl ether has been examined with use of conversion kinetics and molecular weight distribution. The solvent has a weaker solvation power than THF and THP, which have been studied with the same experimental technique. The polymerization rate is first order relative to monomer and the rate constant has a value of ca. 1 mole−1 1. sec.−1 at − 20.5°C. The constant is only slightly dependent on the initiator concentration, but the molecular weight distribution is broader than a Poisson function. Added electrolyte has little effect on the propagation constant but it greatly alters the molecular weight distribution. These experimental results are discussed in connection with two‐state polymerization.
Wechselwirkung Zwischen Chloriertem Polyolefin und Lösungsmittel. III. Einfluss von Bedingungen der Filmbildung auf die Eigenschaften von Chlorierten Niederdruckpolyäthylen‐Filmen
Authors: Kriston Pal , Dimitrov Miklos 
Published: June 2010

AbstractThe influence of film‐forming conditions on the properties of chlorinated low pressure polyethylene films has been examined. The film‐forming temperatures have been found to cause not too large but measurable differences in yield strength of the films. The concentration of the film‐forming solution has no important effect on the properties investigated. but the solvent‐diluent ratio markedly influences viscosity, tearing strength, and permeability. An inverse dependence of yield strength on solvent vapor permeability has been established.
Untersuchung der Kationischen Copolymerisation von Cyclischen Anhydriden mit Cyclischen Äthern
Authors: Habermeier J. , Reichert K.‐H. , Hamann K. 
Published: June 2010

AbstractThe preparation of linear polyesters by the well‐known base‐catalyzed copolymerization of carboxylic dianhydrides and cyclic ethers is possible only with epoxides or in the essentially slower reaction with 4‐membered cyclic ethers. It is not possible with higher cyclic ethers. The reaction of 5‐7‐membered cyclic ethers (tetrahydrofuran, tetrahydropyran, hexamethylene oxide) and succinic and phthalic anhydride can be carried out with varied reaction conditions. Using complex Lewis acid/co‐initiator type initiators, e.g., SbCl5‐MeCOCl or Et3O+BF4‐ producing reactive cations polyesters with molecular weights up to 3200 are formed within 3 hr. in the melt at 120°C. with 70‐95% yield. The products obtained contain ether bond units in the polymer chain. The ether content not only depends on the molar ratio of the reactants but is strongly influenced by the nature and especially by the concentration of initiator. On the basis of this fact a two‐step reaction mechanism is postulated: (1) polymerization of the cyclic ether to the corresponding poly(alkylene oxide); (2) subsequent transacylation inserting the anhydride between the polyether chain units. The occurrence of the secondary reaction could be confirmed by short‐time experiments. Similarly, polyethers and carboxylic dianhydrides are converted to the corresponding polyesters by complex cationic initiators. This further proves the two‐step mechanism postulated above.
The investigation of polymerization at high pressures
Authors: Zharov A. A. , Berlin Al. Al. , Enikolopyan N. S. 
Published: June 2010

AbstractThe polymerization kineties of three types was investigated under high pressure: redieal propylene polymerization, eationie styrene polymerization, and trioxane polymerization in the solid state. Two first rections are accelerated by pressure and the rate of solid‐state polymerization of trioxane is decreased by pressure. A kinetic scheme ac counting for the experimental results is suggested.
Zum Mechanismus der Thermische Abspaltung von Chlorwasserstoff aus Polyvinylchlorid. I. Mitteilung: Thermische Zersetzung von Copolymeren aus Vinylchlorid und Fumarsäurediäthylester, Isobutylen, Vinylbromid und 2‐Chlorpropen
Authors: Braun Dietrich , Thallmaier Manfred 
Published: June 2010

AbstractInvestigation of the thermal behavior of copolymers of vinyl chloride (VC) and diethylfumaric ester (FDE), isobutene (IBu), vinyl bromide (VBr), and 2‐chloropropene (2CP) gives an insight into the mechanism of thermal dehydrochlorination in an inert atmosphere. The rate of decomposition at 180°C. increases in the following order: VC‐homopolymer < VC–FDE‐copol. < VC‐IBu‐copol. < VC‐VBr‐copol. < VC‐2CP‐eopol. The thermal elimination of hydrogen chloride from the copolymers in a nitrogen atmosphere starts from the comonomer unit. The first step of the decomposition of the VC‐VBr and the VC‐2CP‐copolymers requires a sequence of at least two neighboring comonomer units. The behavior of the 2CP‐copolymers indicates that the thermal decomposition of PVC can start from branches. The growth of the forming polyene sequences is stopped at the FDE‐ or IBu‐units Thus shorter sequences result, in reference to the VC‐homopolymer. However, the length of the polyene sequences increases from PVC to VC‐VBr‐copolymers to VBr‐homopolymer. The activation energies of hydrogen halide elimination from VC–VBr‐ and VC–2CP‐copolymers are lower than that of PVC.
Cationic copolymerization of isobutene. IV. Copolymer degree of polymerization in cationic polymerization
Authors: Okamura Seizo , Higashimura Toshinobu , Imanishi Yukio , Yamaiamoto Ryuji , Kimura Kuninobu 
Published: June 2010

AbstractThe lowering of degree of polymerization in cationic copolymerization was investigated for the isobutene–styrene copolymerizations in particular. In this system the simultaneous presence of a reactive isobutene cation and reactive styrene monomer acting as a chain transfer agent, a situation which cannot be visualized in homopolymerization, was proved to be responsible for giving low molecular weight copolymers. The ratios of rate constant for the monomer transfer reaction from isobutene cation to styrene monomer, a cross–transfer reaction, were determined kinetically. Carrying out the copolymerizations in solvents of different dielectric constant, in solvents of similar dielectric constant but of different solvating power, and with the Wichterle catalyst, and comparing the results with those by homogeneous catalyst, the polar and the nonpolar, possibly solvation effects of the solvent, and the effect of a heterogenity of catalyst on the crosstransfer reaction were investigated. A mechanism for the reaction was proposed. The choice of a comonomer or reaction conditions to minimize the cross‐transfer reaction in isobutene copolymerization was discussed in the light of the information about the styrene‐type monomer transfer reaction which has been reported previously by the present authors.
Solid‐ and liquid‐states polymerization of tetrafluoroethylene induced by ionizing radiation
Authors: Tabata Yoneho , Shibano Hiroshi , Oshima Keichi , Sobue Hiroshi 
Published: June 2010

AbstractSolid‐state polymerization of tetrafluoroethylene was carried out by initiating with γ‐rays from Co60 and electrons from a Van de Graaff generator. Apparent activation energy of the polymerization in the solid state was about 0.3 kcal./mole. The polytetrafluoroethylene which was obtained both in liquid‐ and solid‐state polymerizations was examined by the infrared and x‐ray diffraction methods. From these experiments it was clearly demonstrated that the crystalline structure is quite different between both polymers. It indicates that the polymerization in the solid state is strongly influenced by the crystal lattice of the monomers.
Conformation of methacrylic acid radicals in solid‐state polymerization
Authors: Bamford C. H. , Bibby A. , Eastmond G. C. 
Published: June 2010

AbstractRecent work has shown that the familiar ESR spectrum of methacrylic acid radicals can be modified when the radicals are formed in the solid state by irradiation. For example, the conventional 9‐line spectrum may be replaced by one of 13 lines. The nature of the radicals depends critically on the conditions of irradiation and crystal formation. The factors influencing the structure and concentration of the radicals are discussed and correlated with broadline NMR observations in this paper.
New organic systems for the study of electrical conduction mechanisms
Authors: Andres Raymond J. 
Published: June 2010

AbstractAn organic structure embodying a π‐electron chain of carbon atoms which terminates in an electron‐bridging structure at each end is proposed as a promising class for evaluation as organic semiconductors. A quantum mechanical argument is presented on which is built a model simulating conduction electrons within a band and an energy gap between bands like that present in inorganic semiconductors. Results are reported on the polymerization of diamines and dibasic acids containing π‐electron structures. These polymers are of limited value in studying the mechanism of conduction since they are thermally intractable and are insoluble in useful solvents. Study of monomeric substances based on similar structures is now in progress and evaluation of electrical characteristics of well‐formed crystals is planned.
Charge‐transfer exciton and ionic levels in organic crystals
Authors: Pope Martin 
Published: June 2010

AbstractBy means of external photoelectric emission produced by double‐exciton annihilation within the crystal, a mobile charge‐transfer (CT) state consisting of a hole and an electron on adjoining lattice sites has been identified in tetracene and anthracene. The energy of this state is 2.9 e.v. in tetracene and 3.45 e.v. in anthracene; there can be no intrinsic charge‐carrier generation in these materials at energies less than these CT energies. A study of delayed electroluminescence in anthracene provides evidence for the existence of a broad, upper conductivity band; measurements of the efficiency of generating CT excitons as a function of the energy of the exciting light indicate that in anthracene, the broad upper conductivity level starts at about 4 e.v., and in tetracene, at about 3.5 e.v. From photoconductivity measurements made in the short ultraviolet region, it appears that the lowest, narrow‐band conductivity level in tetracene appears 3.1 e.v. above the ground state of the crystal, and at about 3.7 e.v. in anthracene. A maximum value for the CT exciton‐exciton recombination coefficient (β) in anthracene is estimated to be 10−9 cm.3 sec.−1. From an examination of the delayed fluorescence produced in anthracene by α‐particle bombardment, it is concluded that the lifetime of the CT exciton T(CT) is less than 10−6 sec. The efficiency of generating the CT exciton in anthracene using light of energy 4.4 e.v. is about 2%, based on the values for β(CT) and T(CT) given above.
The nature of the lamellar crystalline structure in branched polyethylenes as deduced from melting point and branching determinations
Authors: Knox Jack R. 
Published: June 2010

AbstractIn a semicrystalline polymer chain, if n is the total number of backbone units and a is the number of nonlattice backbone units, then the per cent crystallinity is (n – a)/n. By an empirical approach it is found that if a is set equal to ca. 40 for branched polyethylenes and n is determined from a melting point‐fold length relationship that the calculated values of per cent crystallinity are in good agreement with experiment. It is also shown that 100/(n – a) is equivalent to the total number of branches per 100 methylenes for branched polyethylene. A sinusoidal random coil is postulated for the melt state in order to rationalize why chain folding with adjacent reentry should occur if as many as 40 methylenes per fold are noncrystalline.
Fractions of linear polyethylene as moleculary dispersed eutectic systems
Authors: Asbach G. I. , Kilian H. G. , Müller F. H. 
Published: June 2010

AbstractA thermodynamic theory of melting for linear stereoregular homopolymer systems with a molecular weight distribution has been derived. The homopolymer system is regarded as a eutectic multicomponent system. The components of the system are the molecules themselves. Under conditions of thermodynamic equilibrium the molecules of different lengths should crystallize as extended‐chain crystals. The thickness of the crystals equals the molecular length. During crystallization of stereoregular homopolymer systems the molecular weight fractionation is usually not completely established. This can be described by only one additional internal parameter in the theory. To test the theory, fractions of linear polyethylene as the simplest examples of regular homopolymers were investigated by means of DTA and low‐angle x‐ray diffraction methods. The maximum melting points, the molar mass fractions of crystals as a function of temperature, and the long periods depend on the data of the molecular weight distribution, as predicted by the theory. Both the theory and the experiment agree quantitatively provided that only extended‐chain crystals exist. Under normal pressure conditions molecular folding processes occur, beginning above a critical molecular length. This critical molecular length is determined by kinetic factors.
Military applications of high temperature fibers
Authors: Gloor W. H. 
Published: June 2010

AbstractThe interest of the Air Force and other military organizations in high temperature fibers spans a broad range of fiber types and applications. Fibers and yarns with a high degree of flexibility and good thermal capabilities are required for flexible fibrous materials for use in decelerators and expandable and/or rigidizable structures. High temperature fibers with outstanding modulus‐to‐weight ratio are needed for reinforcement of composite structural materials. In most instances, a high strength‐to‐weight ratio, at temperature, is desirable. To meet these space‐age requirements, research is being conducted by the Air Force Materials Laboratory on a wide variety of fiber types, including polymeric, metallic, graphite, glass, and ceramic. The results of this, and similar research being conducted by industry, while maintaining our military superiority, will, in many instances, also be felt in the commercial world.
Aromatic ordered copolyamides for temperature‐resistant fibers
Authors: Preston J. , Smith R. W. , Stehman C. J. 
Published: June 2010

AbstractFibers were spun from five different wholly aromatic ordered copolyamides. Each polymer contained units derived from aminobenzoic acids, arylene diamines, and arylene diacids. Structural differences in the ordered copolyamides were made by variations in combinations of para‐ and meta‐phenylene units, 2,6‐naphthalene units, and 4,4′‐bi‐phenylene units. Tensile properties of the fibers were obtained at standard conditions, at elevated temperatures, and after heating at 300°C. in air. All of the fibers had tenacities of about 6 g./den. and all were crystalline after drawing. Easy of crystallization, initial modulus, elongation, and retention of tensile properties at elevated temperatures in air were, in general, consistent with variations in the structure of the polymers. Fiber properties were retained to a high degree at temperatures up to 400°C., and fibers heat aged at 300°C. showed remarkable retention of tensile properties. Radiation resistance (γ source, 2.92 × 105 rads/hr.) of these fibers was good and resistance to ultraviolet light appeared to be better than that of unstabilized nylon 66.
Aspects of the structure of α‐Keratin derived from mechanical properties
Authors: Chapman B. M. , Feughelman M. 
Published: June 2010

Abstractα‐Keratin fibers such as wool and hair may be considered in terms of the two‐phase model of organized microfibrils arranged parallel to the fiber direction and embedded in a disorganized matrix. The microfibrils contain α‐helices responsible for the crystalline x‐ray diffraction pattern of α‐keratin; the length stability of the microfibrils depends on the stability of α‐helices. Modifications to the matrix in parallel with the microfibrils are masked by this lengthwise stabilization but can be revealed by placing the fibers in 98% formic acid. In this medium a large proportion of the α‐helices are randomized and much of the stabilization due to the microfibrils is removed. Wool fibers in which portions of the microfibrils were modified by different levels of extension in boiling water were also examined by mechanical properties in concentrated formic acid. The results are considered in terms of relationships between mechanical properties and molecular structures already proposed.
Reshaping: A computational method of resolving gel permeation chromatograms
Authors: Pickett Harry E. , Cantow Manfred J. R. , Johnson Julian F. 
Published: June 2010

AbstractIn this paper we present a rigorous argument for the validity of a new technique for obtaining greatly increased resolution of the chromatograms of a gel permeation chromatograph. The method is phenomenological in that no assumptions are made about the separation process, although certain simple assumptions are made about the characteristics of this process. Instead, the method makes use of the observable behavior of narrow polymer fractions of presumably known composition. From a pragmatic point of view, this is an important aspect of the method, since the results predicted by the method depend only upon what the chromatograph is observed to do, and not upon what it is assumed to do. This method has been implemented in FORTRAN IV for the IBM 7094 computer.
Elution behavior of model compounds in gel permeation chromatography
Authors: Edwards G. D. , Ng Q. Y. 
Published: June 2010

AbstractAlthough gel permeation chromatography (GPC) was developed primarily for measuring the molecular size distribution of polymers, it has been extremely useful for analyzing materials of intermediate and low molecular weight. It is also in this range that properties of compounds other than molecular size appear to have the greatest effect on the elution characteristics of solutes. Therefore, in order to increase the effectiveness of GPC as an analytical tool, the elution behavior of about 100 model compounds was studied and this information used to assist in the interpretation of chromatograms.
Gel permeation chromotography: New applications and techniques
Authors: Bombaugh K. J. , Dark W. A. , King R. N. 
Published: June 2010

AbstractRecent advances in GPC technology are described. These advances include the development of column packings which are compatible with aqueous systems and permit the fractionation of water‐soluble materials such as dextrans, polyphosphates, and lignin sulfonates. Small molecule separation capability in both aqueous and organic systems is also demonstrated. New equipment is described which is capable of both analytical and preparative scale separations. Utilizing 2½‐in. ID columns 1.5‐g. sample loads were fractionated with resolution comparable to the analytical system.
Unsaturation changes and other radiolytic reactions in polyethylene. II. An examination of crosslinking with gel permeation chromatography
Authors: Lyons Bernard J. , Fox Adrian S. 
Published: June 2010

AbstractA simple method of determining crosslink yields and examining crosslink statistics in polymers is described. In this method the soluble fraction of materials crosslinked to well above their gel point is examined with gel permeation chromatography and compared with the original material. The results of such an examination of the soluble fractions of irradiated polyolefins indicate that the random statistical crosslinking mechanism first suggested by Charlesby is followed closely by low‐density polyethylenes. The high‐density polyethylenes examined show deviations from statistical behavior, which may be attributed to dimerization or endlinking through vinyl decay. However, other factors may also be involved. The results suggest that G (crosslinks) does not change significantly with dose and that the ratio of chain scission to crosslinks is less than 0.03 in the range up to 80 Mrad in a low‐density polyethylene.
The use of gel permeation chromatography in guiding polymer syntheses
Authors: Pavelich William A. , Livigni Russell A. 
Published: June 2010

AbstractGel permeation chromatography can contribute significantly to the guidance of polymer synthesis activities. Qualitative information about the effect of reaction variables on molecular weight distribution is satisfactory for such studies. Reaction mixtures can be analyzed without isolating the products of interest. Data are available soon after the reaction is completed, enabling future work to benefit from the information generated. The polymerization of propylene oxide in the presence of 1,5‐pentanediol and hydrocarbon solvent was shown to proceed in two steps. All the diol first reacted with propylene oxide to form an adduct at each hydroxyl function. Propagation with propylene oxide then proceeded with no further initiation and no termination reactions. Attempts to synthesize block copolymers in hydrocarbon solvent at 50°C. by the addition of a second monomer to polystyryl anions gave binodal molecular weight distributions. Polystyryl anions were shown to form species inactive toward further polymerization. Gel permeation chromatography also demonstrated the presence of a chemical composition heterogeneity in these products.