bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrolyzed starch ‐ polyacrylonitrile graft copolymer solutions: Effect of shear history on transient and steady ‐ state viscoelastic behavior
Authors: Bagley E. B. , Taylor N. W. 
Published: June 2010

AbstractBoth viscosity ζ and primary normal stress difference (P11 ‐ P22) of water solutions of hydrolyzed starch‐polyacrylonitrile graft copolymers have been investigated, with a cone and plate rheometer, as a function of time and sample history at a variety of shear rates. At a constant shear rate the highly viscoelastic fluids show strong stress overshoot effects, both ζ and (P11 ‐ P22) rising to a maximum and then falling to a steady‐state value. Both equilibrium levels and peak heights strongly depend on sample history. Unexpectedly, oscillatory shearing of certain samples at low frequency and amplitude, before steady shearing at constant shear rate, had an extreme effect on observed peak heights of both ζ and (P11 ‐ P22) but little on equilibrium levels. Magnitude of the effect depends on the time for which the oscillations are imposed. Such behavior may be characteristic of some high molecular weight polymers in solution and useful in identifying long‐range entanglements which strongly influence the elastic properties of these solutions.
Viscoelastic properties of polyurethane block polymers
Authors: Seymour Robert W. , Cooper Stuart L. 
Published: June 2010

AbstractOrientation measurements using differential infrared dichroism experiments have been applied to the study of the viscoelastic properties of polyurethane block polymers. The time dependence of the orientation function reflects the influence of both the viscoelastic nature of the blocks and of the two‐phase microstructure. A study of the effect of hard block length on the orientation response suggests the presence of an interlocked hard phase structure for most compositions. Such a structure severely restricts relaxation of orientation under strain. At very short hard segment lengths, this morphology is not present and extensive relaxation does occur.
Preparation of block copolymers by use of some new polymeric peroxides and characterization of the products
Authors: Baysal B. M. , Orhan E. H. , Yilgör I. 
Published: June 2010

AbstractBlock copolymers containing prepolymer segments such as poly(ethylene oxide), poly‐(propylene oxide), polybutadiene, and butadiene‐styrene copolymer and segments of a vinyl polymer such as styrene and methyl methacrylate were synthesized. A commercially available low‐molecular‐weight dihydroxyl‐terminated prepolymer was reacted with an aliphatic diisocyanate and with 2, 5‐dimethyl‐2, 5‐bis‐(hydroperoxy) hexane. The resulting polymeric peroxycarbamates were used as free radical initiators of vinyl polymerization. Various modes of preparation and the properties of the copolymers are described. Formation of block copolymers was illustrated by several characterization methods such as IR spectroscopy, elemental analysis, and elastic modulus versus temperature measurements. The modulation of the mechanical properties of the copolymers with respect to homopolymers was observed and reported by impact strength as well as other certain ASTM properties.
Macronet isoporous gels through crosslinking of dissolved polystyrene
Authors: Davankov V. A. , Rogoshin S. V. , Tsyurupa M. P. 
Published: June 2010

AbstractMacronet isoporous polystyrene gels, obtained by cross‐linking of linear polystyrene in solution with p‐xylylenedichloride or 4, 4′‐bis‐chloromethylbiphenyl, differ from conventional styrene‐divinylbenzene (DVB) copolymers by high solvent‐uptake capacity, high inner surface area, and the ability to increase their volume in any solvent, including hexane, methanol, and water.
Changes in the structure of chloromethy‐lated polyethylene modified with styrene and divinylbenzene foils due to friedel‐crafts catalysts
Authors: Czarczynska Henryka , Trochimczuk Witold 
Published: June 2010

AbstractThe purpose of the present work was to investigate the influence of Friedel‐Crafts catalysts—SnCl4, ZnCl2, and AlCl3,—on the structure and other properties of chloromethy‐lated polyethylene (PE) foil modified with styrene (S) divinylbenzene (DVB) (S + DVB). The high‐pressure PE foil (d = 0.927) used in chloromethylation was previously modified with S and DVB in the presence of benzoyl peroxide. The foil contained 30 % (by weight) of S + DVB. The DVB content was 0.5 %‐15% related to the total of monomers, or 0.15‐4.5 % related to all other compounds (PE + S + DVB). Chloromethylation of unmodified PE foil has also been carried out.Chloromethylation parameters have been optimized. It has been established by means of extraction that in the chloromethylation process, additional binding of PE occurs, using AlCl3—20%, ZnCl2—30%, and SnCl4—35% of bound PE. The crystallinity degree, which is 47% for modified foil, decreases after chloromethylation to 15%. The chlorine substitution ratio apparently depends on the DVB content in modified foils. For AlCl3 and SnCl4 with 0.5 and 5% DVB content, the substitution degree is ca. 90%; for 2% DVB, 80%; for ZnCl2, ca. 75 and 60%, respectively. The structure changes have been shown in photomicrographs, tensile strength and relative elongation have also been tested.
Water transport joined with ion exchange in resins
Authors: Dickel Gerhard 
Published: June 2010

AbstractThe exchange of ions in an ion exchanger is combined with a variation of the water sorption which results from the effect of osmosis and the osmotic pressure difference. If the ion exchange is connected with an increase of water, the process of swelling is in accordance with the result deduced from the transport scheme. This is not the case if a decrease of water takes place. In this event, a temporary formation of a pure water phase must be supposed.
On the measurement of the polymer microenvironment polarity and the effect of the polymer microenvironment polarity to some reactions on polymers
Authors: Strop P. , Mikes F. , Kalal J. 
Published: June 2010

AbstractThe effect of the polymer microenvironment polarity on some reactions of polymers is briefly discussed. The polymer microenvironment polarity has been measured using the Kosower semiempirical polarity scale based on the energy of the solvatochromic chargetransfer absorption band. The microenvironment polarity of synthetic vinylic polymers due to the nonpolar contribution of the polymer chain has been found to be lower than that of a solvent. Furthermore, the photochemical isomerization of the stilbene moiety in the side chain of poly (2‐hydroxyethylmethacrylate), a reaction sensitive to the medium polarity, was investigated. A satisfactory correlation was found between the determined polymer microenvironment polarity and the rates of the isomerization.
Polyphosphazene elastomers
Authors: Tate D. P. 
Published: June 2010

AbstractPoly (dichlorophosphazene) rubber was discovered eighty years ago. Its rapid hydrolysis in moist air has hitherto precluded applications. The polymer was intractable and could not conveniently be modified chemically until Allcock (1965) reported that a soluble form could be obtained by careful control of the polymerization. This polymer could be substituted quantitatively with alkoxides or amines to give polymers of good thermal and hydrolytic stability. The polymers produced often have high crystalline melting points. Rose (1968) showed that use of mixed alkoxy substituents gave elastomers with low glass‐transition temperatures. Fluoroalkoxy substituents are particularly useful since elastomers with good resistance to swelling by petroleum fluids are obtained. Glass transition temperatures as low as −68°C have been observed so that the limitations of other oil‐resistant elastomers at low temperatures are absent. Toughness and dynamic flex resistance are comparable with hydrocarbon polymers and much better than in siloxane polymers. Fluoroalkoxyphosphazene vulcanizates show adequate retention of properties at 150‐200°C and withstand prolonged heating in aqueous alkali. They can be processed on conventional rubber machinery. Silica, carbon black, or clay fillers may be used. Vulcanization can be achieved with either peroxide or sulfur‐accelerator systems.
The mechanics of rubber elasticity
Authors: Treloar Leslie R. G. 
Published: June 2010

AbstractThis paper reviews the various attempts which have been made to represent the mechanical properties of rubber in terms of the strain‐energy function W for the most general types of strain. The inadequacy of the Mooney equation is shown by the early work of Rivlin and Saunders and also by the recent work of Obata, Kawabata, and Kawai. Of recent theories, those of Ogden and of Valanis and Landel, both of which depart from the restrictions on the form of W postulated by Rivlin, show possibilities for a more direct representation of experimental data, as well as for the simplification of mathematical analyses. General biaxial strain data by the author are shown to be capable of accurate representation on the basis of the Valanis‐Landel theory in terms of a function w(λ) of the single strain parameter λ. This function may also be expressed as an algebraic series, corresponding to the Ogden formulation.
Factors influencing the strength of rubbers
Authors: Thomas Alan G. 
Published: June 2010

AbstractThe strength behavior of rubbers is discussed in terms of fracture mechanics which treats fatigue and tensile failure as crack growth processes from small flaws. Crack growth can be influenced by the presence of oxygen or ozone. The nature of the vulcanizing system affects strength: crosslinks probably rupture and reform under stress. A new approach to the problem of abrasion is presented using fracture mechanics. Schallamach has shown that rubber often develops a pattern of ridges perpendicular to the direction of abrasion. In the simplest case abrasion is produced by a line contact (e.g., a razor blade) which pulls a tongue of rubber from the ridge producing crack growth at the base of the tongue. Provided the surface configuration is in a steady state, the quantity of rubber abraded can be related quantitatively to the frictional force and the crack growth characteristic of the rubber on some reasonable assumptions. Good agreement with experiment is found for noncrystallizing rubbers but the behavior of strain crystallizing natural rubber suggests that crystallization cannot occur under the conditions used so that the rubber is not strengthened by this means.
Factors affecting the sensitivity of positive electron resists
Authors: Bowden M. J. 
Published: June 2010

AbstractPositive electron resists are polymeric film‐forming materials which undergo predominantly main‐chain scission upon exposure to high‐energy electrons. The irradiated regions of a selectively “patterned” film may be removed by fractional dissolution, enabling processes such as chemical etching to be carried out on the exposed substrate. Foremost in determining sensitivity (the minimum dose required to render an image developable, i.e., to produce a molecular weight distribution significantly removed from the original distribution) is the G(scission). Poly(methyl methacrylate) (PMMA) has a sensitivity of ∼10−5 C/cm2 (G(s) ∼ 1.9) compared with poly(butene‐1 sulfone) (PBS) whose sensitivity is ∼10−6 C/cm2 (G(s) ∼ 12). The molecular weight and molecular weight distribution are also of extreme importance, e.g., the sensitivity of PBS can be increased to ∼4–5 × 10−7 C/cm2 using molecular weights > 106 with low dispersitivity. Obviously, care must be taken when comparing sensitivities of two different materials.
Catalysis by polymers
Authors: Overberger C. G. , Smith Thomas W. , Dixon Kenneth W. 
Published: June 2010

AbstractPoly(4(5)‐vinylimidazole) poly(4(5)‐Vlm) has been shown to be an effective catalyst, as compared to monomeric imidazole, for the hydrolysis of various nitrophenyl esters. The catalytic activity of synthetic macromolecules in general and poly(4(5)‐VIm) in particular has been attributed to the approximation of substrate and catalyst by electrostatic‐ or apolar‐bonding and to certain bifunctional interactions. In an effort to exploit the enhancement in catalytic activity derived through hydrophobic interactions between polymer and substrate, 1‐methyl‐5‐vinylimidazole, 1‐methyl‐4‐vinylimidazole, 1‐butyl‐5‐vinylimidazole, and 1‐butyl‐4‐vinylimidazole, have been synthesized and polymerized. The kinetics of the poly‐1‐methyl‐4‐vinylimidazole (poly‐1,4‐Me) and the poly‐1‐methyl‐5‐vinylimidazole (poly‐1,5‐Me) catalyzed hydrolysis of various nitrophenyl esters will be discussed presently. Poly‐1,5‐Me has been proven to be an efficient catalyst, as compared to the model compound, 1,5‐dimethylimidazole (1,5‐DMIm), towards the hydrolysis of nitrophenyl esters. The poly‐1,5‐Me catalyzed hydrolysis of the negatively charged ester 3‐nitro‐4‐acetoxybenzoic acid exhibits a bell‐shaped pH‐rate profile with a maximum at pH 5 where about 40% of the pendant imidazole groups are protonated. When long‐chain nitrophenyl esters are hydrolyzed by poly‐1,5‐Me, order of magnitude rate enhancements over 1,5‐DMIm are realized. The kinetics of the poly‐1,5‐Me catalyzed hydrolysis of long‐chain nitrophenyl esters has been analyzed in terms of the rate‐determining decomposition of an intermediate polymer‐substrate complex. In support of such a mechanism, saturation and inhibition phenomena typical of enzymatic systems have been observed.Graft copolymers have been prepared from linear and branched polyethylenimine. These graft copolymers were studied as catalysts for the hydrolysis of activated esters in an aqueous system.The rate enhancements for the hydrolysis catalyzed by the polymer were attributed to electrostatic and hydrophobic effects.A study of the hydrolysis of p‐nitrophenyl acetate at varying pH showed that there were no cooperative effects between imidazoles or between imidazole and amine. The lack of cooperativity was attributed to the stereochemistry of the system.Electrostatic effects were investigated by a study of the hydrolysis of 4‐acetoxy‐3‐nitrobenzoic acid at varying pH. A bell‐shaped pH‐rate profile was obtained indicative of an electrostatic attraction between the positive polymer and negative substrate at the maximum rate.The large rate enhancements obtained in the hydrolysis of the esters of long‐chain fatty acids were explained by hydrophobic effects. This system was complicated by the precipitation of the acylated polymer intermediate, which caused decelerative behavior.
The gaussian chain in the theory of rubber elasticity
Authors: Staverman A. J. 
Published: June 2010

AbstractThe importance of the conception of the kinetic theory of rubber elasticity is comparable to that of the kinetic theory of gases. In the theory of rubber elasticity the concept of the Gaussian chain is comparable to that of the Maxwell distribution in a gas. However, whereas the theory of gases has been refined in successive approximations to a coherent set of equations relating meaurable macroscopic properties to the field of force between the molecules and thus allowing the collection of detailed information on molecular forces, no similar progress has been made in the theory of rubber elasticity since its conception 40 years ago. The molecular forces appear in the theory of the Gaussian chain in the quantity r02, the mean square end‐to‐end distance of the “free” chain. In a bulk rubber and also in a swollen rubber this quantity depends on intra‐ and intermolecular forces. If the definition of a Gaussian chain is a chain in which magnified image is independent of r (F(r) being the free energy of the chain with fixed end‐to‐end distance r), then the observation of the Rivlin‐Mooney term in measurements of rubber elasticity appears to be incompatible with the assumption of Gaussian chains. Starting from James's theory of networks of Gaussian chains, it is shown that the Rivlin‐Mooney term can be explained by assuming that the chains are indeed Gaussian, but that r02 depends on the internal pressure pi. However, in order to explain what was observed, the effect of pi on r02 should be much larger than one expected, and hence additional effects are needed to explain the behavior. The additional effects can consist of higher terms in the development of r02 with respect to pi and also in anisotropic terms giving rise to differences between the 3 components of r02 in a nonisotropic stress field. In order to answer the question whether Gaussian chains exist at all in rubber much more experimental information on deformation under different pressures and stress tensors should be available. By ignoring the effect of pressure on r02 one can derive equations between measurable quantities from which r02 is eliminated. These equations should be considered unfounded since already a small effect of pressure in r02 will invalidate them. In the introduction it is shown, in accordance with an earlier conclusion of Lodge, that James's theory of networks of Gaussian chains predicts isotropic elastic behavior of the network, irrespective of any anisotropy of the topology of the network. It is also shown that the expression for the elastic free energy is insensitive to the choice of the junctions and of the chains between junctions.
Recent advances in man‐made fibers
Authors: Magat E. E. , Morrison R. E. 
Published: June 2010

AbstractAdvances in man‐made fiber technology are reviewed. The two main topics are second‐generation fibers and specialty fibers. Chemical or physical modification of polymers or fibers through additives or alteration of polymer backbone has led to a variety of second‐generation fibers. Incorporation of dye sites, antioxidants, antistatic and flameproof modifiers into fibers are discussed. Specialty fibers engineered to meet specific market needs are described. These include heat‐ and flame‐resistant fibers, reinforcing fibers and low‐density pneumatic‐cellular fibers. Energy consumption in the preparation and use of polyester garments is compared to that of corresponding cotton garments. The outlook for continued growth and advances in man‐made fibers continues to be highly promising.
Anionic polymerization mechanism of n‐carboxy‐α‐amino acid anhydrides
Authors: Sekiguchi Hikaru , Froyerd̊ Gerard 
Published: June 2010

AbstractThe anionic polymerization mechanism of N‐carboxy‐α‐amino acid anhydrides (NCAs) is studied. Polymerization of α‐aminoisobutyric acid NCA in the presence of triethylamine as catalyst is fairly accelerated by addition of ring amide compounds, namely 2‐oxazolidone and 3‐methyl hydantoin. Similar effects are noted when N‐acetyl derivatives of such compounds are used. This observation corroborates the usual hypothesis which presumes a N‐acylated NCA ring structure for the growing chain end.By comparing this polymerization with that of lactams, one reveals some common features as well as differences between these two reactions. Theoretical considerations supported by some experimental data lead us to assume two hypotheses in interpreting the anionic polymerization of NCAs: first, the 2‐carbonyl group is the most electrophilic of the three carbonyls present at the active site of chain growth, and second, the NCA anion has a pronounced oxanionic character.Thus, the anionic polymerization mechanism of NCAs we propose, involves attack of the 2‐carbonyl group of the terminal ring unit by NCA oxanion. In the resulting reaction intermediate, the attacking unit then swings to the 5‐carbonyl through a series of electron transfers by mesomerism, helped by the release of carbon dioxide after the neutralization of the ionic charge of the polymer chain.This mechanism is an improved version of the “activated monomer” mechanism, and is based on the same principle as the latter. Thus, not only can our own results be explained without difficulty by this mechanism, but also the experimental facts presented in support of the conventional mechanism in the literature agree with it.
Etude De La Reticulation Thermoreversible De Copolymeres Porteurs De Fonctions Anhydride
Authors: Decroix J. C. , Bouvier J. M. , Roussel R. , Nicco A. , Bruneau C. M. 
Published: June 2010

AbstractCette étude sur des copolymères ethylène‐anhydride maléique (EAM) modifiés par des réactifs polyalcools ou aminoalcools met en évidence par deux méthodes leur possibilité de réticulation par formation de liaisons ester: une méthode indirecte, par la variation de l'indice de fluidité en fonction de la température; et une méthode quantitative, par spectroscopie IR, permettant la détermination des paramètres thermodynamiques de l'équilibre de la réaction entre fonctions anhydride et fonctions alcool.
The role of microparacrystallites in polymer network
Authors: Hosemann R. , Loboda‐Čačkovič J. 
Published: June 2010

AbstractA two‐dimensional analysis of the wide‐ and small‐angle x‐ray scattering (WAXS, SAXS) of well‐oriented polymers allows us to calculate some of the gik parameters of the paracrystalline superlattice that are built up by the centers of the microparacrystallites, which comprose the “crystalline phase.” The dependence of gik upon mechanical deformation, heat treatment, and graft copolymerization of the sample is explained by a three‐dimensional network of chain segments, which not only connect the “crystalline lamellae” of the two‐phase model, but also run through lateral grain boundaries of neighbored microparacrystallites within one “crystalline lamella.” These microparacrystals act, therefore, as special knots of the network. They generally have a much larger volume than the chemical crosslinks and instead of having one strong chemical bond there is a series of much weaker physical bonds, creating the single microparacrystallite. The importance of this model for “amorphous” polymers is also pointed out.
Collagen low angle diffraction patterns and crosslinking reactions
Authors: Bieńkiewicz K. J. , Bukowska‐Strzyźewska M. 
Published: June 2010

AbstractCrosslinking reactions exert some influence on low‐angle diffractograms. In samples crosslinked with Cr (III) salts a significant shortening of the identity period was observed, as well as some changes in the intensity of particular reflexes. A similar, although less expressed change, was observed in the samples crosslinked with formaldehyde. This phenomenon is supposedly due to the easier penetration of the crosslinking agents into the nonpolar regions. The change in the intensity of the reflexes may be explained in the same way. A “fan effect” in the reflexes is due to the isolating effect of acetone in the course of dehydration. Identity subperiods are proposed, probably connected with charge distribution along the molecule.
Temperature dependence of elastic constants of rubbers
Authors: Shumskaya A. G. , Priss L. S. , Popov V. F. 
Published: June 2010

AbstractOn the specially designed dynamometer with automatic control of λ = constant condition at temperature alteration (λ is the extension ratio), there were studied the temperature dependence of stress, f, in uniaxial tension tests of butyl and butadiene‐acrylonitrile vulcanisates at various λ. Temperature coefficients of C2 constant in the Mooney‐Rivlin equation, calculated from these data, are represented reasonably well by the semiempirical formula (β is the bulk thermal expansion coefficient, T is the absolute temperature, To is the constant temperature), derived using molecular theory which revealed the origin of the C2 term and the empirical generalization of the dependence of C2 on swelling degree.The published data on the temperature dependence of C2 and the methods of further experimental examination of conception suggested are discussed.