bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyimide fibers
Authors: Irwin R. S. , Sweeny W. 
Published: June 2010

AbstractThe excellent high temperature properties of aromatic polyimides, well known in films and enamels, have also been demonstrated in fibers. Current investigations show that experimental aromatic polyimide fibers have a very high level of thermal and dimensional stability and property retention at high temperatures, as well as a good, all‐round level of other fiber properties.
Methods of single fiber evaluation
Authors: Schulman Stanley 
Published: June 2010

AbstractResearch and development directed at improved fibers and fibrous materials normally utilizes relatively conventional apparatus for fiber, yarn, and fabric characterization. When desired, material properties are dictated by end‐use requirements which represent extremes in temperature resistance, strength‐to‐weight ratio, high impact velocities, etc.; novel equipment and techniques are likely to be necessary for such research. This is the case with the Air Force's effort in the area of materials evaluation. Techniques now in use are, for the most part, suitable for materials being researched, but improvements must be made for the next generation of fibrous materials. New methods of characterization will be needed to overcome shortcomings of present techniques and to adapt to an ever‐increasing requirement for the properties of all types of materials. For example, evaluation of thermally stable abrasion‐resistant finishes will require long‐term, high temperature flex testing. The laboratory equipment herein described represents a small fraction of the total in‐house capability of the Air Force Materials Laboratory for conducting exploratory research and development on advanced fibrous materials for aerospace systems.
Continuous filament ceramic fibers via the viscose process
Authors: Wizon I. , Robertson J. A. 
Published: June 2010

AbstractThe process for making AVCERAM (FMC Corporation) fibers involves incorporation of lattice‐forming inorganic materials, molecularly dispersed in a viscose batch, spinning, weaving, or winding the resultant fiber on conventional, production‐type machinery, and firing the fiber or fabric so as to retain the unique, single, or multicomponent continuous filament structure. The versatility and practicality of the process give promise for new and unusual fiber compositions and fabric constructions in quantities and at prices attractive to the ultimate consumer. Of particular interest is the indication that in composite applications the carbon‐silica fabric exhibits some advantages of both carbon and silica reinforcemeuts which may be partly due to in situ conversion to silicon carbide.
Gel permeation chromatography: Its inception
Authors: Moore J. C. 
Published: June 2010

AbstractThe early history of the author's contributions to the origin and development of gel permeation chromatography is recounted. Previous experiences with chromatography and with polymer characterization were of value at the inception. Early problems involved the control of gel structure and particle size, column‐packing techniques, design, and test methods for the instrumentation. Aid from co‐workers is acknowledged.
A method for high‐temperature exclusion chromatography of polyethylenes
Authors: Ross J. H. , Casto M. E. 
Published: June 2010

AbstractSoft polystyrene gels compact and degrade at high temperatures. Therefore, recalibration at frequent intervals is required. Suitable solvents for swelling the gel appropriately are needed. Although the universal applicability of differential refractometry as a detector for exclusion chromatography is desirable, in certain instances, when demands are high, it has several drawbacks. Among these are its extreme sensitivity to temperature changes, the variation of refractive index with molecular weight, and the lack of sufficient sensitivity to certain polymers. The system described herein, employing infrared spectrophotometric monitoring and porous glass beads as column packing, was developed to circumvent the problems inherent in the commercially available gel permeation chromatograph.
Application of gel permeation chromatography to crosslinking in irradiated paraffins
Authors: Salovey R. , Falconer W. E. , Hellman M. Y. 
Published: June 2010

AbstractGel permeation chromatography is shown to be a feasible technique for the absolute measurement of crosslinking yields in irradiated, high molecular weight paraffins. For solid n‐eicosane (n‐C20 paraffin) the yield of radiation‐induced crosslinking is independent of dose with a G value of 1.0 ± 0.1, derived from gel permeation chromatography, and of 0.9, from gas chromatography. A radiolytic yield of dimer in liquid n‐eicosane of 1.5 ± 0.1 with no evidence of dose dependence is derived from gas chromatography. However, an increase in crosslinking yield with dose for irradiated liquid n‐eicosane is inferred from gel permeation studies. The yield of radiation‐induced crosslinking in solid n‐hexatriacontane (n‐C36 paraffin) is about 0.8, with little dose dependence, from gel permeation chromatography.
The investigation of parallel‐column systems in gel permeation chromatography
Authors: Alliet David F. , Pacco Jeanne M. 
Published: June 2010

AbstractGel permeation chromatography (GPC) is a new technique for characterizing the molecular weight distribution of polymeric materials. The separation of species is based upon the depth to which each molecular species in a polymer will diffuse into a crosslinked polystyrene gel. The selection of the proper gel to use for separating molecular species depends upon the degree of homogeneity in a polymer. For a better understanding of the separating ability of the various gels an investigation was carried out, to establish the molecular weight limitations of gel porosities in the 105, 104, and 103 A. ranges. The study was carried out with a series of anionically polymerized, narrow molecular weight, standard polystyrenes, which have been characterized by light scattering and membrane and vapor‐pressure osmometry. Molecular weight distribution curves, called chromatograms, are characteristically described in terms of average molecular weights: weight‐average molecular weight Mw and number‐average molecular weight Mn. The range of distribution ratios Mw/Mn is quite large in synthetic polymers. To give the weight average or number average from a GPC chromatogram, the average chain lengths have to be multiplied by a Q factor, the molecular weight per angstrom of equivalent straight‐chain length. The results for narrow molecular weight distributions show that the separating ability of the 105, 104, and 103 A. gels is limited to specific ranges of molecular weight. The 104 A. column system gave the best correlation of results between GPC and the absolute methods.
Characterization of HB polymer with gel permeation chromatography
Authors: Law Ronald D. 
Published: June 2010

AbstractA low molecular weight liquid polymer, polybutadiene‐acrylic acid‐acrylonitrile (HB), is used as a binder‐fuel fraction in solid composite propellants. The molecular weight distribution of this polymer, previously undetermined and uncontrolled, is being determined routinely with gel permeation chromatography (GPC). Analytical conditions are described and the precision and accuracy of the determination are discussed. Correlation of GPC determinations of low molecular weight materials in HB polymer (100 through 500 molecular weight range) with final propellant physical properties is statistically significant. These low molecular weight materials are being characterized, and studies of their role in determining propellant mechanical properties are being conducted. Use of a Waters Model 100 instrument for fractionating and isolating low molecular weight species in the molecular weight range of 100–500 yielded milligram quantities. Analysis of these materials with semimicrotechniques has permitted tentative indentification of the molecular species present.
Analysis of carboxy‐terminated polybutadienes by GPC: A preliminary investigation
Authors: Screaton R. M. , Seemann R. W. 
Published: June 2010

AbstractThe use of gel permeation chromatography (GPC) for the rapid determination of molecular weight distributions of carboxy‐terminated polybutadienes is demonstrated. Whole polymer samples and fractions prepared by elution fractionation were characterized by GPC and viscosity measurements with two different solvents for each method. Variable functionality (COOH group) dependence of the polystyrene gel columns is shown. Thus there is a need to pretest the columns for COOH absorption before use with materials containing carboxylic acid. Effects of sample size and also of carboxy termination as compared with hydrogen termination are discussed. Correlations between tetrahydrofuran and CHCl3 chromatograms are given. As a first approximation the Q factor of 16 is indicated for molecular weight determination from a standard polystyrene calibration in both tetrahydrofuran and CHCl3.
Préparation de Macromolécules à Structure en Etoile, par Copolymerisation Anionique
Authors: Zilliox Jean‐Georges , Rempp Paul , Parrod Jacques 
Published: June 2010

AbstractStar‐shaped macromolecules have been obtained by anionic block copolymerization of a monofunctional monomer and a divinyl compound with cumylpotassium or butyllithium as initiator. The polymer molecule is a crosslinked nodulus, to which n linear, solvated chains are attached. The shielding effect of these chains is such that more than 40% difunctional monomer is necessary to induce gel formation in the reaction medium. Star‐shaped polystyrenes, polyisoprenes, polyvinylpyridines and poly(methyl methacrylate) were obtained by this method, the crosslinking agent being divinylbenzene or glycol dimethacrylate. The individual branches of the star molecules may be considered identical, but a polydispersity arises from the fact that within a sample the number of branches of the star molecules fluctuates appreciably. Fractionation remains possible, though it is not very easy to get monodispersed samples. The molecular dimensions of the star‐shaped polymers, as determined from their intrinsic viscosities or from their radii of gyration, are smaller than those of the corresponding linear polymers, and this may be considered a proof of their highly branched structure.
The numerical evaluation of the composition of products in polymer analogous reactions
Authors: Szántó J. I. 
Published: June 2010

AbstractIn chemical reactions of polymers the functional groups on the chains are gradually converted, and so the eventual structure of the products depends on the degree of conversion. The conversion of polymer analogous reactions is generally not complete, and so copolymers are formed from homopolymers (as well as from copolymers) by chemical transformations. The elementary analysis of products obtained by polymer analogous reactions gives useful information primarily on the conversions in the reactions. In a set of consecutive reactions the conversion in a given reaction depends on the degrees of conversion in the previous steps. In the numerical evaluation of analytical results mathematical formulae based on stoichiometric principles have been used. In some instances theoretical elementary compositions were computed on the basis of a known degree of conversion and the results compared with the measured values. The degrees of conversions in simultaneous polymer analogous reactions may be characterized by a matrix equation having the form Aa = c, where the values of a, a vector characterizing the conversion, may be computed from the elementary compositions and from the initial conditions. By a comparison of computed and measured values some conclusions on the direction of the reactions may be drawn.
Relative reactivity of initiator radicals in polymerization of vinyl monomers
Authors: Pavlinec J. , Lazár M. 
Published: June 2010

AbstractRelative reactivities of primary initiator radicals in substitution reactions with an atactic polypropylene are compared with their reactivities in additions to styrene and methyl mechacrylate in the system monomer–polymer–initiator. For calculations the results of a kinetic analysis of reactions in the system were used. The calculations were made from determination of the weight fraction of grafted branches per total amount of newly formed polymer and from kinetic constants of polymerization of the monomer. It was possible to determine the relative reactivities of different monomers in relation to radicals of the same initiator. The relative reactivities of styrene and methyl methacrylate to benzoyloxy radical were 1:0.125 at 50°C. The ratio of the reactivities of the same monomers to a cumyloxy radical was 1:0.04 at 130°C. The transfer constant of polystyrene and poly(methyl methacrylate) radicals with atactic polypropylene at 50°C. were C = 2.5 × 10−6 and C = 4 ×; 10−6, respectively, and at 130°C. they were C = 3 × 10−5 and C = 4.2 × 10−5, respectively.
Sur un Cas Particulier de Réarrangement Intramoléculaire des Copolymères Séquencés en Solution
Authors: Brendle M. , Koeppel R. , Banderet A. 
Published: June 2010

AbstractFor some polystyrene–poly(methyl methacrylate) block copolymers whose second blocks are prepared in a free‐radical reaction, a decrease in intrinsic viscosity appears by simple heating in a solvent. Contrary to our previous explanation, this decrease is now explained as related, not to a cleavage of a covalent bond, but to an intramolecular rearrangement of the structure. This was shown by viscosity light‐scattering and gel chromatography measurements. It seems that the free‐radical polymerization leads to an unstable structure, which is transformed into a more stable one during the heating. It is possible that in the first form the different blocks are intermingled and that they become segregated in the stable form. Under the same conditions no variation appears when the block copolymers are entirely formed by an ionic mechanism. In this case we may believe that they are already formed in the stable structure.
Polyaniline compounds. II. The linear oligoaniline derivatives tri‐, tetra‐, and hexaanilinobenzene and their conductive complexes
Authors: Honzl J. , Tlusťáková M. 
Published: June 2010

AbstractOligomeric oligoaniline derivatives of diethyl Δ1,4‐dihydroterephthalate (V–VIb–d) of diethyl terephthalate (VIIb–d) and linear oligoanilines (Ib–d) were synthesized. Ultraviolet spectra and polarographic half‐wave potentials corresponding to the first degree of oxidation of linear oligoanilines of type (I) were studied, their iodine complexes prepared, and their electric and magnetic properties studied. Increase of chain length of the base causes increase of λmax of ultraviolet bands, decrease of ionization potential, and increase of electric conductivity of iodine complexes in solid state. The properties of the five‐membered oligomer (Ic) differ only slightly from analogous properties of the seven‐membered oligomer (Id); the same holds in the case of their iodine complexes. Such substances may be regarded as in some respects models of a linear polyaniline polymer or its complexes.
Influence of the structure of polypropylene fibers on the rate of grafting and the structural changes caused by grafting
Authors: Odor Louise 
Published: June 2010

AbstractAn investigation of the relation between the structure of polypropylene fibers and grafting shows that the grafting process takes place in the amorphous phase of the fiber up to 50% grafted polymer content and that the crystals are destroyed only above 75%. This is proved by the diffusion constant of the monomer in the grafted fibers and also by x‐ray diffraction. The studies of grafting rates and diffusion rates of monomers show that the differences in diffusion rate of monomer in fibers of different structures do not affect the rate of chain growth but do affect that of chain termination. The initial rate of grafting is affected by the amount, orientation, and segment mobility of the amorphous part. The chains of the basic polymer are disoriented by grafting, which is indicated by the sudden decrease of birefringence and crystalline orientation. The tensile strength of grafted fiber decreases as the structure changes.
Macropolymerization of Polyethylene by Anhydrous Alkalis and Effective Inhibition of Polyethylene Destruction at High Temperatures
Authors: Paushkin J. M. , Losev G. P. 
Published: June 2010

AbstractThe polyolefin transformation at 200 to 450°C. in the presence of alkali metals and their hydroxides is described. A twofold to fourfold increase of the molecular weight of polyethylene in contact with alkali melts is observed at 200 to 300°C. This phenomenon was given the name “macropolymerization” of polyolefin. At 350 to 450°C. a high retarding action of polyolefin destruction is observed.
On the structure and solution properties of radically polymerized poly(vinyl chloride). III. Discussion of some anomalies
Authors: Kratochvíl P. , Bohdanecký M. , Šolc K. , Kolínský M. , Ryska M. , Lím D. 
Published: June 2010

AbstractDilute poly(vinyl chloride) solutions exhibit a number of anomalies, such as dependence of solution properties on polymerization conditions, strong aggregation in some solvents, low solubility of the fraction with the highest molecular weight, and considerable polydispersity of fractions with higher molecular weights. On the basis of the authors' work and the literature data a survey of these anomalies is given, followed by an attempt to explain them from a unitary viewpoint. Most of the phenomena mentioned can be ascribed to the enhanced crystallization capability of syndiotactic sequences in the chain.
Polymerization of methyl methacrylate by alkali metal compounds
Authors: Lím D. , Čoupek J. , Jůzl K. , Báča J. , Sýkora S. , Schneider B. 
Published: June 2010

AbstractThe structure of poly(methyl methacrylate) prepared by anionic polymerization was followed. Compounds of lithium, sodium, and potassium were used as initiators. The influence of the structure of the initiator and its amount and of the monomer concentration, conversion, and temperature on the structure of the polymer in the polymerization without the presence of complexing solvents was studied. By analysis of NMR spectra tacticity and stereoblock structure, characterized by the parameter η = pis/(pis + pss), was determined. The results made possible the conclusions concerning the factors controlling the growth reaction.
Influence of branching length on structuration and crystallization of stereoregular and irregular polymers
Authors: Platé N. A. , Shibaev V. P. , Petrukhin B. S. , Kargin V. A. 
Published: June 2010

AbstractStereoregular and irregular long‐side‐chain poly(alkyl acrylates) and poly(vinyl esters) have been obtained. A study of the structure these polymers showed that their crystallization took place as hexagonal cells, regardless of the stereoregularity. Studies of the effect of polymer branching length on supermolecular structure have shown that the minimal length of side chain required for crystallization probably is 10 carbon atoms, regardless of the stereoregularity of the backbone chains.
Amine salts of polypyromellitamic acids
Authors: Reynolds R. J. W. , Seddon J. D. 
Published: June 2010

AbstractThe pyromellitamic acid prepared from pyromellitic anhydride and p:p′‐diamino‐diphenyl ether (the precursor of the heat‐resistant polyimide) can be dissolved in aqueous organic bases to form solutions which, unlike those of the free acid dissolved in highly polar organic solvents, are resistant to hydrolytic degradation. These solutions on drying and heating evolve the base to yield the pyromellitimide polymer and can be employed in fabrication processes, particularly for the formation of films and surface coatings. Data are presented on the properties of the solutions and derived films.
The influence of complexing agents on the polymerization of vinyl and allyl monomers
Authors: Zubov V. P. , Lachinov M. B. , Golubev V. B. , Kulikova V. F. , Kabanov V. A. , Polak L. S. , Kargin V. A. 
Published: June 2010

AbstractAcceleration of photo‐induced polymerization of methyl methacrylate (MMA) has been found in the presence of AlCl3 and AlBr3. On the basis of the kinetic data it has been supposed that at lower concentrations of AlX3 ([AlX3]/[MMA] ≤ 0.1) the role of the complexing agent is reduced to acceleration of propagation with complexed radicals. The peculiar behavior of these radicals has been revealed by ESR. We have proposed that the mechanism of activation of propagation by the complexing agent consists of electron transfer from the radical to the adding monomer molecule through the metal atom of the complexing agent. At higher concentrations of the complexing agent its role is also reduced to ordering of the monomer molecules into mobile organized arrays. Acceleration of radical polymerization of allyl acetate and allyl alcohol has also been found in the presence of ZnCl2. The mechanism of acceleration involves activation of allyl radicals of chain transfer and formation of mobile, organized arrays of the monomer molecules.
Alkaline polymerization of caprolactam. XXIX. Mechanism of chain growth in anionic lactam polymerization
Authors: Šebenda J. 
Published: June 2010

AbstractWhen butyrylenantholactam is used as acyllactam and sodium caprolactam as the source of lactam anions, the position of the lactam anion incorporated in the first chain‐growth step may be determined. To avoid the interference of transacylation leading to butyrylcaprolactam and sodium enantholactam the reaction was stopped at very low extents. Determination of the structure of the reaction products revealed that the incorporated caprolactam anion is present as the end‐standing acylated lactam unit and the enantholactam unit is inside the chain. This position of monomer units proves that the chain‐growth reaction consists of acylation of lactam anions by the cyclic carbonyl group of an acylated lactam and not by insertion into imide or β‐ketoamide groups. At 50°C. the rate of transacylation was found to proceed 5 times faster than the chain growth; the rate of condensation reactions of imide groups amounts to 20% of the rate of the chain‐growth reaction.
Some new redox resins
Authors: Manecke Georg , Bourweig Gerhard , Creutzburg Klaus , Ramlow Gerhard 
Published: June 2010

AbstractWith the aim to synthesize chemically stable redox polymers the following investigations have been performed. Homopolymerization investigations of nucleus‐methylated 1‐vinyl‐3,6‐diacetoxybenzenes showed that a methyl group in the 5 position seems to have a severe negative effect on the polymerizability of vinyl hydroquinone compounds. Sulfonated copolymers of the vinyl hydroquinone derivatives with styrene and DVB having ion exchange capacities of 3.4 meq./g., redox capacities of 2.1 meq./g., and midpoint potentials of 520 mv. (pH 0.36) were prepared. 2,3‐Dimethyl‐2,3‐epoxy‐5‐vinyl naphthoquinone‐(1,4) is the only polymerizable derivative of this naphthoquinone. A copolymer of epoxide, methacrylic acid, and DVB was converted to the quinone by reaction with KJ, yielding a redox copolymer with a redox capacity of 2.3 meq./g. Oxidative degradation experiments on sulfonated styrene–DVB cation exchange resins, wherein styrene and DVB are partially replaced by α‐methylstyrene and diisopropenyl‐benzene, showed that the resins become more stable as more tertiary H atoms are substituted by methyl groups. Bead‐shaped and macroreticular redox copolymers of 2‐isopropenyl‐anthraquinone‐(9,10), styrene, or methacrylic acid and DVB were prepared having redox capacities of 2–4 meq./g., ion exchange capacities of 1–4 meq./g., and midpoint potentials of 170 mv. (pH 0.2). Oxidative degradation investigations on the bases of capacity decrease and swelling increase measurements generally showed that these resins can be stabilized if a major portion of tertiary H atoms is replaced by methyl groups.