bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscoelastic behavior of polymers undergoing crosslinking reactions
Authors: Moacanin J. , Aklonis J. J.
Published: June 2010

Previously a method was developed for predicting the viscoelastic response of polymers undergoing scission reactions. These results are now extended to include crosslinking reactions. As for scission, at any given time the character of the network chains is determined by the instantaneous crosslink density. For scission all chains were assumed to carry the same stress; for crosslinking, however, the stress is distributed between the “new” and “old” chains. Equations for calculating the creep response of a system which experiences a step increase in crosslink density are derived.
Die swell and recoverable shear strain in polyethylene extrusion
Authors: Mendelson R. A. , Finger F. L. , Bagley E. B.
Published: June 2010

The present paper treats die swell as unretarded recovery of elastic strain imparted during flow into and through the die. Three mechanistic models are developed. All three models treat the material as an elastic solid for the purpose of elucidating die swell, and two models utilize rubber‐like elasticity theory. Equations relating swelling ratio, recoverable shear strain (SR), axial normal stress, shear stress, and shear modulus are derived for the three models. While the forms of the results differ somewhat from model to model, the numerical results are quite similar. Experimental die swell data were obtained for four high density polyethylene resins in several large L/D capillaries using an Instron Capillary Rheometer. A procedure for obtaining equilibrium, or strain‐free, values of the swelling ratio by annealing the extrudates above the melting point is discussed. Values of SR and normal stress were calculated and compared to corresponding quantities obtained directly from measurements using a cone‐and‐plate Weissenberg Rheogoniometer. Excellent agreement between results from the widely divergent methods of measurement was obtained.
Oxidative reactions of cellulose initiated by free radicals
Authors: Arthur Jett C. , Hinojosa Oscar
Published: June 2010

Oxidative reactions in cellulose are commonly initiated by thermal, ultraviolet, and high‐energy radiations and by chemical oxidation. Long‐lived free radicals, formed in cellulose on the localization of energy from thermal, ultraviolet, and high‐energy radiations, and short‐lived free radicals, formed in cellulose by oxidation, e.g., by ceric ion or redox reactions, were investigated by electron spin resonance spectroscopy. Dehydrogenation and oxidative depolymerization reactions of cellulose are indicated. The physical, chemical, and morphological effects of these free‐radical initiated reactions on cellulose are summarized. The formation of free radicals in cellulose also increases the chemical reactivity of cellulose, particularly for chain copolymerization reactions with vinyl monomers. Preparation of cellulose‐poly(vinyl) copolymers, using free‐radical initiation, yields paper, film, wood, and textile products with new physical and chemical properties.
The distribution of aqueous solutions within wood
Authors: Fengel D.
Published: June 2010

One of the basic reactions during pulping processes is the penetration of wood chips by the delignifying solution. For the study of the distribution of fluids within the cell walls, dry and green samples of pine wood (Pinus sylvestris L.) were treated with aqueous solutions of staining compounds, only by dipping‐in (diffusion), under vacuum, and under pressure. Best penetration was achieved by vacuum treatment in dry wood and by pressure treatment in green wood. The studies made by electron microscopy and by electron probe microanalyzer showed that the staining material is not equally distributed in the cell wall. In all samples the compound middle lamella is intensively stained. In some places there is a high concentration of staining material in the secondary wall 1 (S1), in other places there is a high concentration in a zone of the secondary wall 2 (S2) adjoined to the secondary wall 1. In most cases the tertiary wall (S3) and the adjoined part of the S2 is stained more intensively than the residual S2. Also the tori of the bordered pits are penetrated by the staining substance. The connection between the passage and the distribution of fluids within the cell wall and the ultrastructure of the cell wall is discussed.
Twisting energy of holocellulose fibers
Authors: Mark R. E. , Thorpe J. L. , Angello A. J. , Perkins R. W. , Gillis P. P.
Published: June 2010

Freely drying fibers exhibit collapse and twist behavior that is only infrequently observed in the formation of a paper web. Anisotropic fiber shrinkage models are employed that enable calculation of the twisting energy of a freely drying fiber as well as the reverse case (dry to wet). The twisting energy appears to be highly significant in relation to the fiber and bond energies associated with paper strength. Some experimental results with southern pine fibers have been obtained using specially designed testing devices.
Graft copolymerization of ethyl acrylate with γ‐irradiated cotton cellulose I and II
Authors: Nakamura Yoshio , Hinojosa Oscar , Arthur Jett C.
Published: June 2010

The graft copolymerization of ethyl acrylate from methanol‐water solutions with γ‐irradiated cotton cellulose I and II was investigated by electron spin resonsance spectroscopy and by the formation of cellulose‐poly(ethyl acrylate) copolymer. The rate and extent of graft copolymerization reactions in these heterogeneous systems were dependent on conditions of storage of the irradiated celluloses prior to reaction, the composition of the methanol‐water solutions, reaction time, agitation during the reaction, and cellulose crystal lattice type. Agitation of the heterogeneous system during reaction decreased both the rate and extent of copolymerization. From water the extent of copolymerization of ethyl acrylate with irradiated collulose I was greater than with cellulose II; from methanol the extent of copolymerization with irradiated cellulose II was greater than with cellulose I. From methanol(40 vol‐%)‐water(60 vol‐%) maximum extent of copolymerization occurred with both irradiated celluloses; however, the extent of copolymerization was less with irradiated cellulose II than with cellulose I. The extent of copolymerization was directly related to the initial concentration of free radicals in the irradiated cellulose. However, a fraction of the radicals, about 10% of the maximum concentration in cellulose obtained at a dosage of 5.2 × 1019 eV/g, was apparently in the highly ordered regions of the cellulosic structure. These radicals were not scavenged and did not initiate copolymerization reactions.
Grafting of cellulose and derivatives by means of diazonium salts
Authors: Simionescu Cristofor I. , Dumitriu Severian
Published: June 2010

New amino aromatic esters and ethers of cellulose were synthetized. Then grafting processes were performed on these derivatives by using acrylic, methacrylic and N‐vinyl pyrolidone monomers. Finally, chemical structure and physicomechanical properties were determined. Industrial experiments proved the utility of this grafting method.
The effect of vinyl monomer grafting on the water sorption kinetics and equilibria in cellulose
Authors: Lepoutre P. F. , Hopfenberg H. B. , Stannett V.
Published: June 2010

Wood pulp cellulose was grafted with styrene and a number of other vinyl monomers using the mutual radiation technique. The effects of the level of grafting, type of monomer, and the grafting conditions on the water sorption equilibria and kinetics were determined. Styrene was studied in considerable detail. Styrene grafting reduced the equilibrium water content but water diffusivities increased as a consequence of styrene grafting. Conversely, the grafting of polar monomers such as acrylonitrile, ethyl acrylate, and acrylic acid led to somewhat higher water regains but to decreased diffusion constants.

The swelling conditions used during the mutual grafting process with styrene significantly affected the grafting rates and the properties of the resulting grafts. For example, the equilibrium water contents at the same level of grafting, was a function not only of percent graft but also of the specific swelling conditions. These moisture regains were inversely related to the density of the grafted fibers. These results are discussed in terms of the conformation of the grafted side chains which is determined by the various grafting conditions.
Hydrodynamically induced crystallization of polymers from solution. V. Tensile properties of fibrillar polyethylene crystals
Authors: Pennings A. J. , Schouteten C. J. H. , Kiel A. M.
Published: June 2010

A study has been made on the tensile properties of mats of fibrillar polyethylene crystals grown at various temperatures from stirred xylene solutions in a Couette‐type instrument. The stress‐strain behavior of fibrillar crystals precipitated above 100°C was found to be essentially Hookean, and the maximum values determined for Young's modulus and tensile strength at break amounted to 27 × 104 kg/cm2 and 10 × 103 kg/cm2, respectively. The elongation at break for these high temperature fibers was 6%. Stress‐strain diagrams for fibrillar polyethylene crystals grown at temperatures below 100°C were curved and the elongations at break amounted to roughly 12%. Both the Young's modulus and the tensile strength were found to increase strongly with the crystallization temperature; this trend is attributed mainly to the decrease in the amount of lamellar overgrowth and the improvement in orientation.

Microscopic examinations have shown that the mats can be regarded as assemblies of macrofibers having diameters in the micron range. Homogeneous fracturing is found in samples with extensive lamellar overgrowth, whereas carefully washed samples fractured into fibrils. Electron micrographs reveal that the elementary fibrils (the shish‐kebabs) develop brittle fractures and that the lamellar overgrowth is capable of transmitting stresses normal and parallel to the backbones. Digestion of the fibrillar crystal material with fuming nitric acid causes a decrease in tensile strength and elongation at break, but the Young's modulus remains approximately unaltered.
The influence of supermolecular structure on the strength and deformation characteristics of linear polyethylene
Authors: Marichin V. A. , Miasnikova L. P. , Sutchkov V. A. , Tuchvatullina M. Sh. , Novak I. I.
Published: June 2010

The influence of supermolecular structure on the mechanical properties of linear polyethylene has been studied. The change in film structure has been realized by means of variation of isothermal crystallization conditions. The films obtained had either lamellar structure, or consisted of spherulites. It has been shown that the tensile strength of unoriented films with small spherulite structure is twice as great as that of films with well developed lamellae. This mechanical difference remained after 20‐fold drawing of the specimens at high‐temperature (102°C) for short times. The study of the structure of oriented films showed that in all the cases the transverse size of microfibrils remained constant. However, with the help of infrared spectroscopy it has been found that the amorphous phase orientation here was different, while the degree of elongation was the same.
Morphological changes during the melting of bulk‐crystallized polymers
Authors: Fulcher K. U. , Brown D. S. , Wetton R. E.
Published: June 2010

The melting behavior of some bulk‐crystallized, high molecular weight polymers has been studied in relation to morphology. Small‐angle x‐ray scattering results from two polymers, polytetramethylene oxide and polyethylene, are presented and discussed.

Theoretical correlation functions have been calculated from models based on randomly oriented regions of alternating crystalline and amorphous layers, and have been compared with experimental correlation functions obtained from desmeared x‐ray scattering data. With this approach it has been possible to study changes in the thickness and widths of distributions of both crystalline and amorphous regions, over the temperature range from the crystallization temperature to the melting point.

Evidence has been obtained in favor of a “surface melting” mechanism in which fusion occurs by the progressive transfer of chain segments from the “fold surfaces” of the crystalline lamellae to the amorphous or melt‐like phase. This involves the progressive thinning of each lamella towards its center.
Morphology of the fracture surface layer of poly (methyl methacrylate) and the fracture mechanism
Authors: Lednicky F. , Pelzbauer Z.
Published: June 2010

Optical and electron microscopic methods were used to investigate the morphology and optical properties of the fracture surface layer of poly (methyl methacrylate). A new method developed by us made it possible to evaluate, from interference phenomena, the optical thickness of the layer which in the proximity of the secondary fracture center always exhibited a minimum and attained maximum values (1.1‐1.6 μm) at the boundaries of the conic fracture formation. After mutual correlation, the local refractive index of the surface layer was calculated and found to be 1.31 to 1.35. Although the macromolecular chains are oriented in crazes, no chain orientation in the fracture surface layer was detected. The lower refractive index of the surface layer is therefore interpreted in terms of material dilution of about 35% by volume of small holes. When the sample is subjected to thermal treatment, the profile of the optical thickness of the fracture surface layer remains unaltered, only the interference colors gradually disappear. This fact is attributed to a change in the reflectivity on the upper or lower boundary of the surface layer caused by local changes in the material density. The replica electron micrographs of the fracture surfaces showed pits in the foci of the conic markings which had various shapes and diameters about 1 μm. Using the facts established about the geometry and morphology of the fracture surface layer, a mechanism for the initiation and propagation of fracture has been suggested.
Calculation of minimum potential energy of folds and kinks in polyethylene crystals
Authors: Petraccone V. , Allegra G. , Corradini P.
Published: June 2010

We have performed calculations of potential energy minima for the possible conformations of folds and kinks in a polyethylene crystal. Unlike previous work, the calculations take into account the possibility of coupled variations of internal rotation angles as well as of bond angles in the search for energy minima.

The conformations of minimum energy found by us for tight folds in the 200 and 110 planes of polyethylene structure have energies of the order of 3 and 4 kcal/mole, respectively, less by a factor of say 2.5 than the figures obtained by previous authors, even when the earlier results were recalculated with our “softer” energy functions. Possible conformations for a “Reneker kink” have also been calculated; their energy turned out to be of the order of 7 kcal/mole.

In all cases, a wide variety of geometrical models is almost isoenergetic in the neighborhood of the conformations studied.
Entropy of mixing of polymer and solvent as derived from the free‐volume concept
Authors: Dayantis Jean
Published: June 2010

A theory is proposed for the entropy of mixing of polymer and solvent. The theory is an extension of Hildebrand's derivation of the Flory‐Huggins combinatorial entropy of mixing by use of free‐volume concepts. The noncombinatorial (or equation of state) entropy of mixing originates, according to the proposed theory in the different free volume fractions which characterize ordinary simple solvents and high polymers. Two parameters are introduced: a parameter ρ, which is the ratio of the free volume fractions in the polymer and in the solvent, and a parameter c, which describes the external degrees of freedom of the polymer segments and is equivalent to Prigogine's parameter c. The noncombinatorial entropy of mixing, as derived from the present theory is equivalent (but not identical) to that derived from the newer theory of Flory et al. Concomitantly, the agreement with experiment of the calculated interaction parameter × for the athermal system polyisobutylene‐cyclohexane is about the same as that obtained from the theory of Flory et al.
Influence sur la viscosite intrinsèque d'un copolymère de son mode de dissolution dans un mélange binaire solvant‐non‐solvant
Authors: Vial J.
Published: June 2010

There are two ways of dissolving a polymer in a binary mixture of a solvent and a nonsolvent: direct dissolution or dissolution in the solvent followed by dilution with the nonsolvent. The two methods have been applied to two types of vinylacetochloride copolymers, one containing 6% by weight of hydrolyzed groups, with a series of solvents diluted with polar nonsolvents (butyl alcohol, acetronitrile). The thermodynamic quality of the resulting solutions has been evaluated by intrinsic viscosity measurements. The addition of butyl alcohol to a moderately good solvent greatly improves the solvent power, particularly if solution is effected directly in the mixture. This does not happen with the nonhydroxylated polymer for which results are identical regardless of the mode of dissolution. These phenomena are also observed in some cases with both polymers when acetonitrile is used. None of the above phenomena occurs with a very good solvent regardless of the mode of dissolution.
Polymeric UV absorbers of the 2‐hydroxybenzophenone type. II. On the mechanism of the polymerization of 2‐hydroxy‐4‐(2,3‐epoxypropoxy) benzophenone with phthalic anhydride
Authors: Lustoň J. , Schubertová N. , Maňásek Z.
Published: June 2010

Simultaneously with the preparation of 2‐hydroxybenzophenone light stabilizers with a reduced extractability from polypropylene, the mechanism of the propagation reaction of 2‐hydroxy‐4‐(2,3‐epoxypropoxy) benzophenone with phthalic anhydride was studied under different concentrations and temperature conditions, with tert‐amines, potassium benzoate, and potassium hydroxide being used as catalysts. If the polymerization of epoxide with anhydride is performed in melt at 125°C, an alternating copolymer is formed whether an equimolar ratio or a molar excess of anhydride with respect to epoxide has been used. Provided epoxide is present in molar excess with respect to anhydride in the reaction system, some changes in ultraviolet absorption spectra are observed in comparison with the spectra of alternating copolymers which indicate that some undesirable reactions of the orthophenolic groups of benzophenone occur simultaneously with the catalyzed polyaddition reaction, and that the polymeric stabilizer is impaired.
Antioxidants and stabilizers. XLIV. Properties of halogenated dihydric phenols
Authors: Lerchová J. , Obali M. , Kotulak L. , Pospíšil J.
Published: June 2010

The effect of halogenated and alkylated dihydric phenols on the autoxidation process of tetralin and cumene initiated at 65°C with AIBN has been investigated. The character of substitution effects the antioxidative activity of the derivatives of the pyrocatechol and hydroquinone series in a different way. All halogenated pyrocatechols were less active than unsubstituted pyrocatechol. Their antioxidative activity increased in both substrates proportionally to the number of the halogen atoms. On the other hand the introduction of chlorine atoms into the hydroquinone ring led to a considerable increase in the antioxidative activity compared to hydroquinone and to its alkyl derivatives. In both substrates isomeric dihydric phenols exhibited different retardation of the oxidation course in the step following the induction period. The reasons for the different behavior are discussed.
Pressure‐induced diffusion in swollen butyl rubber membranes
Authors: Paul D. R. , Carranza D. H.
Published: June 2010

Membranes were prepared from butyl rubber of different levels of chain unsaturation to produce membranes with four different well characterized cross‐link densities. Pressure‐induced permeation rates through them were measured for various organic liquids which highly swell the membranes. The data conformed to and were analyzed by previously published theories. It was found that the product of the diffusivity of the liquid in the membrane and the pure liquid viscosity is very nearly a constant which is approximately 20% less than observed earlier for polyisoprene membranes. More lightly cross‐linked membranes yielded higher liquid fluxes at fixed pressures. Most of the effect is attributed to the higher degree of swelling of these membranes. The diffusion coefficient is essentially independent of crosslink density over the range studied.
Effect of monomer‐active filler system structurization on thin layer polymerization
Authors: Morozova E. M. , Yeliseyeva V. I. , Travnikova L. A.
Published: June 2010

The polymerization of monomers in a thin layer in air is very sensitive to the variations in the initial composition of the polymerized system. A study of the effect of initial mixture composition on the regularities of the polymerization kinetics elucidates the specific features of the process, and thereby facilitates its control. This paper reports the effect of active fillers (aerosil) on the kinetics of bulk polymerization of aminoalkylmethacrylates in a layer of specific thickness and in volume. The rheological parameters of the polymerized system were measured. Such investigations revealing the kinetics of the variations in the rheological parameters during polymerization are of considerable significance for establishing a relationship between both processes. Besides, they have practical value for the production technology of polymer coatings by direct polymerization of monomers. The data obtained in this work clearly demonstrate the effect of coagulation structure developed by adding an active filler into system to be polymerized on the polymerization process.
Anionic copolymerization of acrolein with aldehydes. III
Authors: Lapena A. , Mateo J. L. , Sastre R.
Published: June 2010

Unsaturated polyacetals have been prepared by anionic copolymerization of acrolein with aldehydes, such as, acetaldehyde, propionaldehyde, isobutylaldehyde, pivaldehyde, and benzaldehyde. The new copolymers have essentially an acetal structure as the result of the acrolein preference to copolymerize through the carbonyl group when alcaline cyanides are used as catalysts. The influence of temperature, nature of the aldehyde and monomer composition on the molecular size, polymerization rate, and composition and structure of the copolymer are studied. These copolymers undergo cross‐linking when exposed simultaneously to oxygen and light. The variables affecting the oxidation process and the products obtained were studied.
Anionic polymerization of caprolactam. XLV. Decay and regeneration of catalytic activity in anionic polycaprolactam via 3‐oxoamides
Authors: Bukač Z. , Šebenda J.
Published: June 2010

N, 2‐Diethyl‐3‐oxohexaneamide was chosen as a model compound for the investigation of transformations of the 3‐oxoamide structures in anionic polycaprolactam. Dipropyl ketone, ethyl butyramide, N,N′,2‐triethyl malonamide, 1,3,5‐triethyl‐6‐propylpyrimidine‐2,4‐dione are formed under the conditions of anionic polymerization, along with carbon dioxide and traces of ethyl isocyanate, ethyl amine, and N,N′‐diethylurea. The formation of these compounds can be explained by the cleavage or rearrangement of the 3‐oxoamide N‐anion and by secondary reactions of isocyanate with the initial 3‐oxoamide. Some of the reactions of the 3‐oxoamide give rise to growth centers as well as a strong base, thus causing regeneration of the catalytic activity. However, one part of the activity vanishes irreversibly, owing to the formation of stable acid products.
Suggested interpretation for the anomalous kinetics of acrylonitrile polymerization in homogeneous solution
Authors: Patron L. , Mazzolini C. , Moretti A.
Published: June 2010

The polymerization in homogeneous solution of acrylonitrile shows an anomalous kinetic behavior. The reaction order in respect to the monomer appears higher than 1, and approaches the order of 2 at low acrylonitrile concentrations (< 2M). This behavior was given various interpretations. No completely satisfactory explanation is, however, available. By taking into account some secondary radical reactions recently discovered (polymerization through CN), a new interpretation of the kinetic anomalous behavior is suggested, and a kinetic model is given which also takes into account the propagation through the triple CN bond.

The equations so fully derived justify the experimental results. A reaction order of 2 in respect to the monomer for (AN) tending to zero, and approaching 1 for (AN) > 2M, is deduced from the assumptions made. According to the proposed mechanism, the kinetic deviations from theory do not depend on the initiation rate, as confirmed by experimental results, but only on monomer concentration.
Charge transfer complexes of maleic anhydride in radical homo‐ and copolymerization
Authors: Rzaev Z. M. , Bryksina L. V. , Sadykh‐Zade S. I.
Published: June 2010

Radical copolymerization of maleic anhydride (MA) with a number of electron‐donor monomers has been investigated. Charge transfer complexes (CTC) of MA with vinyltriethoxysilane (VTES), vinylcyclohexylcetone (VCHC), and styrene (St) have been fixed. On the basis of NMR and ultraviolet spectroscopy data, the equilibria constants of complexation (K)1 and extinction coefficient (ε) for various pairs of donor‐accepting monomers have been determined. The terpolymerization has been carried out involving the mentioned monomeric CTC (complexomer). Copolymerization constants r2 and r2), specific activity (Q), and polarity (e) factors for monomer and complexomer pairs, constituting the systems: MA‐St‐VTES, MA‐St‐NCH, and MA‐St‐VCHC have been determined. Some regularities of terpolymerization with MA complexomers present have been revealed. It has been shown that the three‐component system polymerizes at the stage two‐component polymerization of either complexomer MA‐St with VTES (or NCH) or two complexomers MA‐St with MA‐VTES (or MA‐NCH).
Influence of orientation on the relaxation and ultimate properties of polypropylene
Authors: Retting Wolfgang
Published: June 2010

As is known, the relaxation maxima of polymers are often shifted within the time or temperature scale if the materials are stretched or drawn. This behavior is due to changes of the free volume and/or of the crystallization and orientation of the stretched specimens. Since the relations between these parameters and the shift of the maxima are not yet known very well, an examination was made using polypropylene as a suitable example. The knowledge of these relations is of technical importance, too, because the shift of the maxima is often accompaned by a shift of corresponding brittle‐tough transitions.

The relaxation maxima were determined in a good approximation by measuring the time‐dependent moduli of elasticity and by differentiating the modulus curves. It was found that the main maximum of polypropylene shifts with increasing draw ratio to longer times. At the same time the activation energy of the maximum decreases. Tensile tests, carried out on the unstretched and on the stretched specimens, yielded the same shift of the brittle‐tough transition as that of the main maximum. The molecular causes of this behavior are discussed.
Conductivity of two semiconducting poly‐2, 4‐diamino compounds
Authors: Löfgren B. , Virtanen J.
Published: June 2010

The electrical conductivity of poly‐2, 4‐diaminoanisole is compared with the conductivity of poly‐2, 4‐diaminotoluene in the temperature range 293–450°K. The conductivity obeys the exponential law σ = σ0 exp {−Ea/kT} for both polymers, Poly‐2,4‐diaminoanisole conducts better than poly‐2, 4‐diaminotoluene, and the σ0 value for poly‐2, 4‐diaminoanisole is one decade higher than for poly‐2,4‐diaminotoluene, while the activation energies are equal at equivalent molecular weights.
A study of short‐range order in amorphous polymers by diffraction methods
Authors: Markova G. S. , Ovchinnikov Ju. K. , Bokhyan E. B.
Published: June 2010

The structure of amorphous polymers and polymer melts differing in chemical composition and molecular configuration have been studied by means of electron and x‐ray diffraction methods. The final result of the investigation are differential radial distribution curves (DRD), which correspond to fluctuations of the potential (electron diffraction method) or to fluctuations of electron density (x‐ray diffraction method). It was found that for all investigated systems on the DRD‐curves, from two to three intermolecular peaks have been obtained. The appearance of such a number of intermolecular maxima on the DRD curves for strongly asymmetrical molecules was explained only by the parallel packing of the chain molecules. The ordered areas have been established over a wide temperature range. The sizes of these ordered areas have been estimated.
Swelling equation for gaussian networks. Networks formed by random crosslinking of primary chains
Authors: Dušek K.
Published: June 2010

The expression for the chemical potential of the solvent in a swollen extracted net‐work, obtained by the quasi‐chemical equilibrium treatment of crosslinked polymer solutions, has been transformed into the form of Flory's swelling equation Δμs/RT = In φs + φg + χφg2 + veg (Vs/Vp) (φφ – Bφg), where μs is the chemical potential of the solvent, φs and φg are the volume fractions of the solvent and polymer in the gel, respectively, φ is the value of φg at network formation, χ is the polymer‐solvent interaction parameter, φs and φp are partial molar volumes of the solvent and polymer segment, respectively, and veg is the number of elastically active network chains per polymer segment. For random crosslinking of primary chains, B = 1 – (vg – 2/rng)/2veg (vg is the fraction of crosslinked segments in the gel and rng is the number average degree of polymerization of primary chains bound to the gel). The parameter B is independent of the coordination number of the lattice and varies from 2/3 at the gel point to 1/2 for networks formed of infinitely long primary chains. The interaction parameter χ is a complex function of the interaction free energy, lattice coordination number, and network parameters, and usually increases with increasing degree of crosslinking. Possible variations of B and χ are demonstrated for a number of primary chain distributions. The network parameters have been calculated by using the theory of cascade processes.
Relationship between rheological behavior of solutions and composition of acrylamide and acrylic acid copolymers
Authors: Jaćović Mihailo S. , Rajić Živojin
Published: June 2010

The rheological behavior of aqueous solutions of ten acrylic acid and acrylamide copolymers was studied. The mole fraction of acrylic acid in the copolymer ranged from 0.042 to 0.443. Fifteen aqueous solutions for each copolymer were prepared by including all combinations for five values of the degree of neutralization and for three solution concentrations. All other parameters being constant, solution viscosity increases with the degree of neutralization of carboxylic groups in a copolymer. We introduced the expression (ηn –/(η0n), where ηn and η0 are the viscosities of solution at the degree of neutralization n and 0, respectively, and called it the neutralization viscosity number. It has been found that the limiting neutralization viscosity number for n = 0 is a linear function of the acrylic acid mole fraction in the copolymer with acrylamide and that it is independent of the copolymer molecular weight and solution concentration.
Some new ideas in liquid state physics and their impact on polymer science
Authors: Gaeta F. S.
Published: June 2010

Thermal agitation in liquids consists of high‐frequency elastic waves. Thermal conductivity being a measure of how easily these waves drift down a gradient of temperature can be expressed as a function of the speed of sound in the liquid. The proposed expression agrees with experimental results.

More important is the consideration that energy propagating in the form of waves entails propagation of mechanical momentum, the flux of momentum being equal to the flux of energy divided by the velocity of wave propagation. This momentum transported by the waves can be transferred to the bulk of the liquid, thereby contributing to viscosity.

Another consequency of the propagation of momentum connected with thermal waves is that whenever heat flows within a solution, radiation pressures are developed, which make the disperse particles migrate along the temperature gradient. This is the physical explanation of thermal diffusion. The analytical expressions which are derived allow us to develop a new method of characterization of polymers and of macromolecules of biological origin. Furthermore, the measurable forces produced by the flow of heat on macroscopic blocks of polymeric materials, suspended by appropriate means within a liquid, show a dependence on the state of the polymeric material and on its thermal and mechanical history.
Some properties of copolymers containing phosphoryl groups
Authors: Kosolapoff G. M. , Voris F. S.
Published: June 2010

Copolymers were prepared from tertiary phosphine oxides containing a vinyl group, on the one hand, and esters of vinyl‐ and p‐vinylphenylphosphonic acids, the hydrolysis of which afforded a series of copolymers containing a polyvinyl chain with side chains of R2P(O) and (HO)2P(O) types. The interaction between these afforded considerable variability of viscosity of solutions of such substances in media with various pH values.
Synthesis and thermal stability of poly‐n‐α‐naphthylmaleimides
Authors: Barrales‐Rienda J. M. , Gonzalez Ramos J.
Published: June 2010

Two samples of poly‐N‐a‐naphthylmaleimide (PNNMI) prepared by free radical polymerization under different experimental conditions have been characterized. The elemental analysis of both samples indicates the same chemical composition, although they are different from a structural point of view. Their structures have been established by spectroscopic methods.

Rates of thermal degradation for both PNNMI samples have been analyzed by programmed thermogravimetry using a multiple‐heating‐rate procedure. Overall activation energy and order of reaction have been calculated. Values of 40 and 24 kcal/mole for the overall activation energy and a value close to unity (1.2 and 0.8) for the order of reaction for both polymers have been found.
Degree of polymerization and polydis‐persity of native cellulose
Authors: Holt C. , Mackie W. , Sellen D. B.
Published: June 2010

Cellulose trinitrate was prepared from cotton (Deltlapine) under a variety of conditions and investigated in solution using the techniques of light scattering, osmotic pressure, viscometry, and gel permeation chromatography. Gel particles associated with incompletely nitrated material were shown to be present in the more mildly nitrated samples and calculations were made to find the true weight‐average molecular weight of the coil component. As the nitration time increased, the measured degree of polymerization fell, and due to lower solution viscosities removal of gel particles by centrifugation became easier. It was possible to show that samples obtained by nitration for times in the range of 2 to 25 hr at 20°C had a low degree of polydispersity with DPw/DPn in the range 1.3 to 1.5. Assuming this also to be the case for the more mildly nitrated samples, extrapolation back to zero time of nitration, assuming a random degradation process, suggests a virtually monodisperse starting material with a degree of polymerization of about 8000. However, it is possible that molecules of this size result from some morphological feature of the cell wall and do not represent the true length of the cellulose chains.
Grafting of acrylonitrile on cellulose xanthate
Authors: Ehrnrooth Elsa
Published: June 2010

A study has been made of the grafting of acrylonitrile onto a bleached kraft pulp by application of the xanthate method developed by Faessinger and Conte. Acrylonitrile was grafted to the cellulose in aqueous suspension at 25°C, with cellulose xanthates of gamma numbers from 3 to 13. The reaction system contained 1–2 percent xanthogenated pulp, 0.2–0.9 mole/1. hydrogen peroxide, 0.45–1.0 mole/1. acrylonitrile, and the reaction time was 45 min. In some cases 0.6–60 mmole/1. sulfuric acid was added to the reaction system. The grafting yield was calculated from the nitrogen content of the grafts. The degree of polymerization (DP) of the grafted polyacrylonitrile, after hydrolytic removal of the cellulose, was calculated from the limiting viscosity number of dimethylformamide solutions of the polymer at 25°C, and use of the formula [ε] = 2.43 × 10−4 (M)0.75. The grafts were found to contain 10–35 percent polymer of DP = 350–1000, and an average number of 1–4 grafted polymer chains per cellulose chain, i.e., less than 5 percent of the number of xanthate groups initially present in the cellulose xanthate. The number of grafted polymer chains was dependent upon the pH, and the DP of the grafted polymer was dependent upon the monomer and xanthate concentrations; the higher the monomer concentration was, and the lower the xanthate concentration was, the higher it became. Possible mechanisms for grafting are discussed.
Polymerization and copolymerization of vinyl phosphonic (acid) diethylamide and vinyl pyrrolidone
Authors: Usmanov Kh. U. , Nazhmiddinov Sh. , Nurmukhamedov Sh.
Published: June 2010

Synthesis of phosphoramide high molecular weight analogs presents interest polymerization of vinyl phosphonic (acid) diethylamine and its copolymerization with vinyl pyrrolidone are suggested for discussion.
High‐speed thin‐foil calorimetry
Authors: Hager Nathaniel E.
Published: June 2010

A method is described for performing adiabatic scanning calorimetry on thin samples heated at high speeds. Sample sheets are inserted between layers of a folded metal foil heater to form a stacked array. A thin‐foil thermocouple is inserted near the median plane of the array. The sample assembly is heated by passing a current through the foil heater. There is a brief initial period during which the sample interior heats adiabatically. During this period, the thermocouple signal is traced as a function of time on a chart recorder.

Analysis of the chart yields the sample heating rate dT̃/dt at selected values of the mean sample temperature T. Specific heat values are calculated from dT̃/dt, using an energy‐conservation equation. The sample thickness is kept small to permit attaining rapid heating rates without excessive temperature gradients. The overall thickness of the stacked array is designed to make the adiabatic period sufficient in duration, so that results are valid over the desired temperature range.

Results are shown for polytetrafluoroethylene and polyethylene terephthalate at various heating rates up to 600 K/sec. At low speeds, results agree with previously published data, but at higher speeds radically different curves are obtained. Above the glass transition temperature of the polyethylene terephthalate, it is observed that the positions of inflections in the specific heat curve vary sharply with sample heating speed.
Thermo‐optical analyses of poly(2‐methyl‐6‐benzyl‐1,4‐phenylene oxide)‐poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends
Authors: Shultz A. R. , Gendron B. M.
Published: June 2010

Blends of poly(2‐methyl‐6‐benzyl‐1,4‐phenylene oxide) (PMBPO) with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO® resin) form clear, transparent films. Thermo‐optical analyses of solvent‐cast and compression‐molded films comprising PMBPO‐PPO resin mixtures at 0.1 weight fraction composition intervals over the complete composition range prove these blends to be homogeneous. True thermodynamic compatibility of the polymers is thus indicated. The thermo‐optical transition temperatures, TTOA, defined as the temperatures at which birefringence disappears in scratches on the films during 10°/min heating, are found to increase monotonically with increasing PPO resin weight fraction w2, in the manner: TTOA (°C) = 120 + 101 w2. Differential scanning calorimetry on the pressed films also indicates polymer compatibility yielding single glass transition temperatures Tg (DSC) increasing monotonically from 99°C for the PMBPO to 209°C for the PPO resin.
Interfacial morphology and mechanical hysteresis in S‐B‐S triblock copolymers
Authors: Kaelble D. H. , Cirlin E. H.
Published: June 2010

Significant aspects of the interfacial phase continuity and mechanical stress‐strain hysteresis in S‐B‐S triblock copolymers, where S is polystyrene and B is polybutadiene, are analyzed in terms of a cavitation model for interfacial debonding. Extension‐recovery data in tensile deformation at temperatures from −120°C to 90°C include the glass temperatures of both the S and B phases. The correlation of rheological response at low deformation ϵ = ΔL/LO ⩽ 0.02, where the interfacial phase is intact, with high deformation response ϵ ⩾ 1.0, where interfacial debonding is substantially complete, isolates the strain‐time‐temperature function B(t,ϵ) which defines the interfacial continuity. Analysis of this function by use of the Halpin‐Polley model for kinetics of micro defect growth isolates an intial cavity nucleation process and subsequent propagation and coalescence of cavities at distinct levels of B(t,ϵ). At temperatures above 20°C the work lost WL due to mechanical hysteresis in stress‐strain response is correlated directly with the interfacial work of adhesion Wa between S and B phases of Kraton 101 by means of the model for interfacial morphology.
Hydrodynamic properties of complexes of polymethacrylic acid‐polyvinylpyrroli‐done in solutions
Authors: Bimendina L. A. , Roganov V. V. , Bekturov E. A.
Published: June 2010

The intrinsic viscosities and sedimentation constants of polymethacrylic acid‐poly‐vinylpyrrolidone (PMAA‐PVP) mixtures have been measured in water and dimethylsulf‐oxide. By conductometric method it has been shown that the composition of those complexes is stoichiometric.

The value of intrinsic viscosity of the complexes in water is about 0.10 dl/g which is close to the viscosity of globular proteins. This value seems to be almost independent of the concentration and molecular weight of the macromolecular components of the complex (both PMAA and PVP have been used as an oligomer and as an matrix), and in the case of high molecular weight of both the components as well.

In an organic solvent a sharp increase of intrinsic viscosity is observed. This is probably connected with the weakening of hydrophobic bonds stabilizing the compact structure of complex in water. In dimethylsulfoxide reduced viscosity depends on concentration and intrinsic viscosity on the molecular weight of the matrix (PMAA). The values of hydrodynamic‐average molecular weights of complexes establish the intermolecular association of complexes particles in water, and the degree of association depending on the molecular weight of the matrix. In dimethylsulfoxide probably not only the weakening of hydrophobic interactions but the destruction of hydrogen bonds occurs, following which the dissolution of the complexes takes places. In water‐dimethylsulfoxide mixtures a gradual destruction of the complex is observed at the transition from water to organic solvent.
The mechanism of formation of polymer particles during turbidimetric titration of polymer solutions
Authors: Klenin V. J. , Shchyogolev S. Yu. , Fein E. G.
Published: June 2010

Stages of formation in the structure of precipitated polymer phase have been found by the method of spectroturbidimetric titration (STT) during precipitation titration of a number of polymer systems. In the first stages of formation of polymer particles, a sharp decrease was observed in the particle size, rCλ, which may be related to a fall in large fluctuations in the postcritical region if the transition of the system through the binodal curve were to be identified with phase transition of the second kind. In the second stage, rλ remains constant at the minimal level, rλ = rλ(γ) = rλ 0 const. The extension of plateau rλ 0 in terms of γ depends on the polymer‐solvent‐precipitant system(P‐S‐P) and conditions of titration. The value of rλ 0 differs insignificantly for different systems, rλ 0 = 0.2–0.3 μm, which is possibly related to the existence of an optimum of particle size in colloid systems of this type. The third stage is determined by the process of particle coagulation, here the kinetics are subject to the equation of Smolukhowskii and the rate depends on the P‐S‐P system. A value of v was determined which appears to be antibate to the effectiveness of attractive forces produced between polymer particles and defines the coagulation process in a specific P‐S‐P system. General conditions for the preservation of particle size during titration were established. Under these conditions, however, an effective separation of fractions with respect to molecular weights can not be attained from the point of view of relaxation thermodynamics. These contradictions are minimized by the use of the STT method. It is shown that the coagulation of particles during turbidimetric titration by the conventional approach leads either to fallacious underestimation or overestimation of the polymolecularity of a polymer depending on the time of beginning of such coagulation, before or after complete precipitation of the polymer.
Temperature dependence of polystyrene Raman depolarization in cyclohexane, methyl ethyl ketone, and deuterobenzene solutions
Authors: Speak R. , Shepherd I. W.
Published: June 2010

The depolarization ratio ρ of the 1002 cm−1 band in polystyrene has been measured as a function of temperature (20 < T < 60°CC) in the solvents cyclohexane, methyl ethyl ketone, and deuterobenzene. The largest changes in ρ were observed in the poorest solvent, cyclohexane and no changes were detectable in benzene. The ratio, 〈r2〉/n/2, measured in the same solvents over the same temperature range by conventional light scattering, is compared with the ρ data. The corresponding changes in rotational isomer population are calculated and the dependence of ρ on these populations is demonstrated.
Electric birefringence, conformation, and rigidity of the molecules of cellulose esters in solutions
Authors: Lavrenko P. N. , Rjumtsev E. I. , Shtennikova I. N. , Andreeva L. N. , Pogodina N. V. , Tsvetkov V. N.
Published: June 2010

Electro‐optical properties of solutions of several cellulose esters in dioxane have been investigated. It was shown that macromolecules of these esters are characterized by high equilibrium and kinetic chain rigidity. The coincidence in signs of the Kerr and Maxwell effects in solutions of the samples reveals general relationships exhibited by all rigid‐chain polymers for which the longitudinal geometric axis of the molecule (direction of the greater geometric length) is also the symmetry axis of its polar and optical properties.

Experimentally found dependences of hydrodynamic and electro‐optical properties of solutions of cellulose carbanilate (CC) on molecular weight (Mw) show that with the increase in Mw the conformation of the CC molecules varies from a faintly curved rod to a rigid Gaussian coil. A study on the dependence of the equilibrium constant of the Kerr effect on Mw leads to the same conclusion. Besides, in Gaussian region (high Mw) the Kerr effect depends on the longitudinal (with respect to the chain) component of the dipole moment formed by the C‐O bonds making a part of the glucoside ring. At low M the transverse components of the monomer dipoles begin to play an important part in birefringence.