bluuebunny/crossref_metadata_2025 huggingface dataset:
The rheology of polymer solutions in oil
Authors: Philippoff W.
Published: April 2003

The flow birefringence and viscosity of solutions of two samples of polyisobutylene in 14 different solvents were measured in a wide range of rates of shear and concentrations. For a match of refractive index of solvent and polymer, the conditions could be completely described by the stress‐optical coefficient C over the whole range, the value being equal to the one measured on the 100% rubberlike polymer. For nonmatching solvents, according to the occurring form effect, the C becomes dependent on both molecular weight, concentration, and shear stress. These statements are independent of the viscosity of the solvent, but depend only on the index of refraction n of the solvent. This has been proved by measurements in low viscosity solvents and in hydrocarbon oils with a change of the viscosity of the solvent of about 100‐fold. The performed measurements on higher concentrations (up to 30 wt.‐%) give essentially the same results as those extrapolated to zero concentration. For these relations, allowance has to be made for viscosity and birefringence of the solvents. One therefore can conclude that the viscosity of the solvent as such does not affect either the viscosity or flow birefringence of polymer solutions, the conditions being fully described by the intrinsic viscosity [η]v and the index of refraction of the solvent. The main factor in the flow birefringence is the shear stress set up in the flowing solution.
Shear dependence in solutions of fractionated dextran: A variable‐shear capillary viscometer for use with aqueous solutions
Authors: van Oene H. , Cragg L. H.
Published: April 2003

The viscosity behavior of a high molecular weight fraction (M̄w = 9.8 × 106) of dextran (B‐512) in aqueous solutions was studied at low and medium shear stresses, and its intrinsic viscosity was shown to be independent of shear stress. A convenient and precise multibulb Ubbelohde‐type viscometer, especially designed for use with aqueous solutions is described. The calibration of the viscometer and the evaluation of surfacetension corrections of relative flow times measured in it are discussed in detail.
Velocity of dissolution of polymers. Part I
Authors: Ueberreiter Kurt , Asmussen Frithjof
Published: April 2003

A short description is given of the apparatus for the solution of a macromolecular substance in a solvent and the mathematical treatment of the curves. A relation is obtained for the velocity of penetration ⋅ (cm./sec.) of the solvent into the polymer:

where D is the integral, mutual diffusion coefficient and δ the thickness of the swollen layer on the surface of the polymer. The dependence of the process on the temperature is

The swollen layer δ is investigated in detail. It consists first on the side of the solvent of a streaming layer (liquid layer) δ1. Below this is a rubberlike layer δ2. These layers are made visible by dispersed carbon black particles. The total layer δ increases with the temperature:

The liquid, swollen polymer is removed from the surface and its polymer content measured. The mean content of polymer in the double layer δ1 + δ2 increases with the temperature. Viscosity measurements are made to draw final conclusions regarding the stability of δ. The mean viscosity in δ can be taken from these viscosity curves, as the content of polymer in δ is known. The stability (viscosity) increases with the temperature. The reason for it is the decrease of the solid, swollen layer below the rubberlike layer. The polymer content in the rubberlike layer increases to the same extent as the solid, swollen layer decreases. The total swollen layer δ is built up of four layers: a liquid layer δ1, a rubberlike layer δ2, the solid, swollen layer δ3, and an infiltration layer δ4. δ3 contains so few solvent molecules that its state at the temperature of solution is still solid and swollen. δ4 is a solid, glassy polymer, the holes and channels of which have only been filled with solvent molecules without swelling the structure. All four layers exist at temperatures of solution below the glass temperature of the polymer. δ3 and δ4 disappear at the glass temperature, and at the flow temperature the polymer and its layer are liquid. The variation of the concentration in δ is measured interferometrically. The concentration of solvent decreases sharply in δ3 + δ4 and linearly in δ1 + δ2 down to zero. The streaming of the solvent influences mostly δ1. The slope of the log ⋅ versus 1/T curves differs above and below the glass transition. The coefficient of diffusion can be calculated from the solution formula and, independently, from time lag measurements. Both values agree well.
Velocity of dissolution of polymers. Part II
Authors: Asmussen Frithjof , Ueberreiter Kurt
Published: April 2003

Polystyrenes of molecular weight 429 to 973,000 were prepared by fractionation of a pure thermal polymerizate. The velocity of dissolution ⋅ (in cm./sec.) of these fractions in a solvent follows the relation ⋅ = kM−A over a wide range of molecular weight. Only the parameter k is temperature‐dependent and changes with the speed of stirring in the bath. A is constant. ⋅ can be very accurately measured in the molecular weight range from 1000 to 20,000. This offers a new means for determining the molecular weight in a range which otherwise presents difficulties. The swollen surface layer δ increases with the square root of the molecular weight. It increases abnormally above M ≈ 150,000 due to the strong entanglement of large macromolecules. The velocity of dissolution is thereby considerably diminished. The mean mutual diffusion coefficient D is independent of the chain length of the polymer. Its value can be determined from the slope of the ⋅ vs. δ−1 curve and agrees well with those values calculated from the time lag and dissolution formulae data. The assumption that macromolecular coils are the units building up the swollen surface layer can be proven. The average number of coils in a line of the length δ seems not to depend upon molecular weight and is approximately 104 coils. A distinction between two fundamental definitions of the quality of a solvent is necessary. The thermodynamical definition depends upon the value of the second virial coefficient B in the expression for the osmotic pressure. The kinetic definition is simply based on the value of ⋅. High values of these qualities indicate good solvents. However both properties are independent of each other. Whether or not a solvent is suitable from the thermodynamic standpoint depends upon the chemical constitution of the solvent and its interaction with the polymer. Suitability from the kinetic standpoint is related to a small molecular size and viscosity which creates no difficulties for the penetration into the channel system of the polymer.
Shear dependence of the reduced viscosity—concentration slope constant
Authors: Van Oene H. , Cragg L. H.
Published: April 2003

The variation with shear of the concentration dependence of the reduced viscosity was studied in the system polystyrene‐toluene at 20, 40, and 60°C. The slope constant k′ was determined at constant shear stress k′T and at constant shear rate k′D; k′T was found to increase, k′D to decrease, with increasing shear. Alternatively, the concentration dependence was expressed in terms of Peterlin's effective viscosity. For this system the effective viscosity at constant shear stress was independent of shear but the effective viscosity at constant shear rate decreased with shear. The decrease in k′D, and in effective viscosity at constant shear rate with shear are attributed to molecular entanglement and an explanation is proposed for the observed differences in behaviour at constant shear stress and constant shear rate. In appendices a new formula for the calculation of viscosity ratios from the relative flow times is derived, and a procedure is outlined to compute intrinsic viscosities and limiting slope constants that will be free from absorption effects.
Diffusion de la lumière par les solutions de copolymères
Authors: Leng Marc , Benoit Henri
Published: April 2003

On montre comment l'étude de la diffusion de la lumière par un copolymère dans des solvants d'indices différents permet d'obtenir des informations précises sur la masse moléculaire de chacun des constituants, la structure de l'échantillon et sa polydispersité en masse et en composition. Dans une première partie, on analyse du point de vue théorique les données fournies par les mesures de masses moléculaires et de rayons de giration. Dans une deuxième partie, on étudie un copolymère séquencé du type polyméthacrylate de méthyle—polystyrène—polyméthacrylate de méthyle préparé par voie anionique, étude qui permet de caractériser ce produit de façon assez complète. On décrit enfin une série d'expériences qui permettent de mettre en évidence d'une façon très directe, “l'effet de volume.”
The viscosity behavior of linear and branched dextran sulfates
Authors: Pasika W. M. , Cragg L. H.
Published: April 2003

Linear and branched samples of potassium dextran sulfate have been prepared without significant degradation from samples of linear and branched dextran having similar intrinsic viscosities. The dilute solution viscosity behavior of these polyelectrolytes has been studied with particular reference to the effect of branching and degree of sulfation. A comparison of the reduced viscosity—concentration curves, in aqueous 0.001N and 0.0005N KCl, of linear and branched potassium dextran sulfate with the same degree of sulfation revealed a significant difference in their viscosity behavior. This difference is attributed to a greater charge density in the nonlinear sample resulting from its branched structure.
Statistical computation of distribution functions of dimensions of macromolecules
Authors: Schatzki T. F.
Published: April 2003

Random walks of 100 steps or less in a three‐dimensional tetrahedral lattice have been generated by means of the ILLIAC computer. Excluded volume has been introduced by forbidding double occupancy of lattice sites. The distribution function of end‐to‐end lengths has been collected and expanded in terms of Hermite polynomials. One finds that the distribution can be expressed as a two‐term expansion, the second term contributing 10% at 100 steps. For walks of a given number of steps and a given end‐to‐end length the spatial distribution of monomer segments has been investigated and compared to the (no excluded volume) expression of James. One finds that the introduction of excluded volume swells the chains and increases the moment of inertia along the major axis.
Fractionnement des polyamides par une méthode en continu
Authors: Duveau N. , Piguet A.
Published: April 2003

Les auteurs présentent un procédé rapide de fractionnement des polyamides. Ce procédé est basé sur la mise en continu de la méthode développée par G. B. Taylor [J. Am. Chem. Soc., 69, 638, (1947)], utilisant le partage du polymère entre deux phases liquides phénol—eau M, dont la composition est variable en fonction du temps. A chaque instant, la solution contenue dans la cellule de fractionnement forme deux phases; le mélange M arrive dans la phase inférieure; la phase supérieure s'écoule goutte à goutte dans les tubes d'un collecteur; au cours du temps le volume de la phase inférieure décroǐt, pour s'annuler lorsque tout le polymère est extrait. L'exploitation des fractions se fait par la méthode classique: précipitation, séchage, détermination de la viscosité intrinsèque. Le choix de conditions opératoires appropriées (débit, gradient de composition du mélange M) permet d'obtenir une courbe de répartition correcte, comme il est possible de s'en rendre compte en travaillant sur des échantillons de polydispersité connue (répartition de Flory). La méthode développée pour le polyamide 66 est applicable à d'autres polyamides. La durée d'une opération est de l'ordre de quinze heures.
The morphology and internal structure of poly(ethylene oxide) spherulites
Authors: Price Fraser P. , Kilb Ralph W.
Published: April 2003

The development of spherulites in thin films has been observed. At low supercoolings they develop scalloped edges, with each scallop sector having a branched structure reminiscent of a fern frond. At high supercoolings they develop smooth circular boundaries. An x‐ray diffraction study has been made both of the fronded structures and of the more perfect spherulites formed at higher supercoolings. Only one of the latter types of spherulites was examined. Here it appears that the crystallites have a rotation axis perpendicular to the spherulite radius. This axis is the 4, 0, 1 direction in the crystal which has a monoclinic unit cell. The fronded spherulites, when examined along the radial frond spine, have the same rotation axis of the crystallites, both ±45° to the radius. This double orientation of rotation axis also occurs in material crystallized in a fine capillary, where the spherulite radial direction is presumably along the capillary axis. Low‐angle x‐ray diffraction shows spacings of about 200 A. (sometimes to sixth order) parallel to the spherulite radius for both fronded and perfect spherulites.
A study of the molecular dimensions of fractions of high pressure polyethylene
Authors: Schuurmans H. J. L.
Published: April 2003

A sample of high pressure polyethylene was fractionated and subsequently characterized by means of osmometry, light scattering, and viscometry. The molecular weight distributions of the fractions as calculated by means of the numerical approximation method of Beall were compared with those obtained from the osmometry and light‐scattering experiments. Also a comparison was made between the molecular dimensions calculated respectively from light‐scattering data, viscometry, and second virial coefficients. It is shown that an application of current theories to the data gives vastly different values for the molecular dimensions depending on what measurements are taken as a starting point. For calculations on the branching, it appears necessary to take into consideration the difference in the width of the molecular weight distribution of the branched polymer and the linear polymer with which it is compared.
The effect of pressure and temperature on the specific volume of polyethylene
Authors: Matsuoka Shiro
Published: April 2003

A spherulitic crystallization process can be divided into three successive stages: the formation of spherulite centers, the growth by means of crystalline fibrils with many branches extending into the melt, and finally crystallization of the intervening regions between these already crystallized fibrils. The three stages were identified with parts of a typical dilatometric isotherm for crystallization from the melt. The last stage of the isotherms was analyzed as crystal growth accompanied by the predetermined nucleation of one‐dimensional character. Isothermal annealing was also studied dilatometrically and was found to be similar in mechanism to the last stage of crystallization from the melt. The influence of the thermal history, including the conditions of crystallization, on the degree of crystallinity were summarized as a kinetic factor, and was distinguished from the thermodynamic consequence of branches on the equilibrium degree of crystallinity. Specific volumes of the crystal (estimated) and the melt were determined at various temperatures and pressures. The relationship between the entropy of fusion and pressure was determined from the volume of fusion by utilizing Clausius‐Clapeyron's equation. The entropy of fusion at atmospheric pressure thus obtained was found in agreement with values obtained elsewhere by other methods. The compressibility of the melt and the true volume of fusion decreased substantially under high pressure, while the entropy of fusion was essentially unchanged. This was ascribed to the change of the melt property from the familiar free‐volume type of behavior to a more solidlike one without an increase in structural order.
Effect of carbon black on chain mobility and structure of synthetic rubbers
Authors: Baccaredda M. , Butta E.
Published: April 2003

Dynamic mechanical properties of polyisobutylene, butyl rubbers, Paracril, cis‐1,4‐polybutadiene, reinforced with EPC black, were determined in the temperature range −150‐+170°C., in the frequency range 2–20 kcycles/sec. In the amorphous polymers, reinforcement causes an increase of sound velocity at any temperature, while the glass transition point Tg and the thermal coefficient of sound velocity dV/dT remain practically unchanged. Only at high temperatures, near the softening region, are lower values of the damping factor Q−1/dT found for the filled samples, as compared with the corresponding unfilled ones. Addition of reinforcing carbon black to cis‐1,4‐polybutadiene causes an increase of sound velocity at any temperature, and a little shift of the maximum damping point toward lower temperatures. In the reinforced sample, the Q−1 − T curve, in the region of high dissipation, becomes more unsymmetrical, showing a flat region at temperatures just above the maximum. A comparison of the mechanical spectra of the unfilled vulcanized samples of cis‐1,4‐polybutadiene with those of the corresponding filled vulcanized ones (with the same sulfur content and the same heat treatment) shows a shift of the glass transition point and of the maximum damping toward lower temperatures with addition of the filler. The experimental results are discussed and the conclusion is drawn that neither structural changes nor appreciable variations of chain mobility are caused by addition of carbon black in the examined rubbers.
Experimental determination of the elastic modulus of crystalline regions in oriented polymers
Authors: Sakurada Ichiro , Nukushina Yasuhiko , Ito Taisuke
Published: April 2003

The elastic modulus of the crystalline regions in some oriented polymers was determined. An x‐ray diffractometer specially constructed for this purpose was used, and the lattice extension in the direction of the fiber axis was measured under application of a direct load. Usually a meridional reflection was used for the measurement of the lattice extension, but in the case where no strong meridional reflection exists a reflection from planes which are almost perpendicular to the fiber axis of the crystallites was used. The elastic modulus was calculated under the assumption of a simple series model. The values found are as follows: polyvinyl alcohol, 255 × 104 kg./cm.2; polyethylene, 240 × 104 kg./cm.2; polypropylene, 42 × 104 kg./cm.2; polyoxymethylene, 54 × 104 kg./cm.2; cellulose, 137 × 104 kg./cm.2; polyvinylidene chloride, 41.5 × 104 kg./cm.2.
Influence de la température sur le greffage du styrène sur des films de polytetrafluoroéthylène et de poly(chlorure de vinyle) par la méthode radiochimique directe
Authors: Chapiro Adolphe , Matsumoto Akira
Published: April 2003

Le greffage radiochimique direct du styrène sur des films de polytetrafluoroéthylène a été étudié à 40 et à 60°C. A 40°C, la réaction présente des caractères cinétiques analogues à ceux que l'on avait observés au cours d'une étude antérieure conduite à 19°C. On trouve en particulier qu'au dessus d'une certaine intensité “critique,” le greffage ne se fait plus dans la masse mais est limité à une zone superficielle du film. La valeur de cette intensité critique est voisine de 6 à 8 rads/sec à 40°C tandis qu'à 19°C, nous avions trouvé une valeur de 1,0 rads/sec. A 60°C, l'intensité critique est supérieure à la plus grande intensité examinée, soit 35,1 rads/sec. Les courbes de conversion obtenues pour des intensités inférieures à la valeur critique mettent en évidence une autoaccélération. En représentant ces courbes en échelles logarithmiques, on obtient des droites dont la pente est 1,5–1,6 à 40°C et 1,0–1,2 à 1,0–1,2 à 60°C. A 19°C, la pente des droites correspondantes était comprise entre 2,5 et 3,2. Cette pente, qui est l'exposant du temps dans la relation C = Ktβ est désignée sous le nom de coefficient d'autoaccélération. Ce coefficient β permet de caractériser le comportement cinétique des différentes réactions autoaccélérées. Le déplacement de l'intensité critique vers les grandes valeurs, lorsque la température s'élève, est interprété par une augmentation de la vitesse de diffusion du monomère et à 60°C, on suppose que cette dernière cesse de contrǒler la cinétique de la réaction dans les conditions expérimentales utilisées. D'un autre cǒté, on pourrait penser que la diminution du coefficient d'autoaccélération β, lorsque la temperature croǐt, est dǔe à une diminution de la contribution de l'effet de gel, en raison de la mobilité accrue des chaǐnes croissantes. Cependant l'exposant α de l'intensité dans la relation V = KIα, qui est égal à 0,5–0,55 à 19°C, passe à 0,68 à 40°C et à 0,70–0,72 à 60°C, ce qui montre que, malgré la forme linéaire des courbes de conversion à 60°C, la réaction n'atteint pas l'état stationnaire. Le greffage radiochimique du styrène sur des films de poly(chlorure de vinyle) a été étudié à 60°C. Contrairement à la réaction étudiée antérieurement à 20°C, cette réaction n'est plus controlée par la vitesse de diffusion du monomère et la cinétique du greffage est “normale.” C'est ainsi que les courbes de conversion sont pratiquement linéaires et que la vitesse de la réaction est proportionnelle à la racine carrée de l'intensité. Une certaine courbure vers l'axe des abscisses persiste sur les courbes de conversion obtenues aux faibles intensités. Elle pourrait, soit résulter d'une diffusion non homogène du monomère, soit d'un phénomène de “protection” radiochimique du poly(chlorure de vinyle) par les noyaux phényliques du styrène greffé.
The dynamic birefringence of high polymers
Authors: Stein Richard S. , Onogi Shigeharu , Keedy Daniel A.
Published: April 2003

The simultaneous measurement of the birefringence and strain of a sample subjected to sinusoidal strain is proposed as a means for elucidating the molecular mechanism of the response of high polymers to mechanical deformation. A linear phenomenological theory is proposed in which strain‐optical coefficient distribution functions are assigned to the elastic and viscous members of a distribution of Maxwell elements. An apparatus has been constructed to determine the dynamic strain‐optical coefficient at frequencies between 0 and 600 cycles/sec. by means of mechanical excitation of vibration at low frequencies and electromagnetic at high frequencies. The dynamic birefringences of polyethylene has been studied at room temperature over this frequency range.
Kinetics of polymerization of vinylidene chloride. IV. Copolymerization of vinylidene chloride and acrylonitrile
Authors: Marker Leon , Sweeting Orville J. , Wepsic James G.
Published: April 2003

The emulsion polymerization of vinylidene chloride is divisible into three stages: (I) a normal emulsion polymerization at a rate dependent on the 0.6 power of both the catalyst and surfactant concentration; (II) at a rate less than half that of I; (III) at a rate which increases in direct proportion to the catalyst concentration and independently of surfactant concentration. A careful examination of stirring rate has shown that the slowdown in stage II probably results from monomer starvation caused by slow diffusion of coalesced droplets, and that recovery in stage III is the result of transfer of monomer at the time of collision between a polymer particle and a monomer droplet. Extension of this work to copolymers of vinylidene chloride and acrylonitrile has shown a similar kinetic effect at high ratios of vinylidene chloride. The rate of polymerization for a system containing 90% vinylidene chloride decreases sharply after 15% conversion. The polymer formed increases in acrylonitrile content with conversion, reaches a maximum, and then decreases during stage III of the reaction. A run containing 70% vinylidene chloride in the charge did not show a slowdown but gave evidence of a maximum in the curve relating conversion and composition. At higher acrylonitrile content, no slowing occurred, and the polymer composition changed monotonically with conversion. Since acrylonitrile is partially soluble in water, the partition coefficient of acrylonitrile between vinylidene chloride and water was determined at concentrations similar to those used in the polymerizations. The partition coefficient decreases with increasing acrylonitrile concentration in the water phase. Apparent reactivity ratios were calculated on the basis of the monomer composition corrected for the water solubility of acrylonitrile and the initial composition of the copolymer. These values are r1 = 0.390 and r2 = 0.585, vinylidene chloride being considered to be the first monomer. The existence of a unique reactivity ratio indicates that the composition of the initial polymer is controlled only by the relative reactivities of the comonomers and the water solubility of acrylonitrile. The polymer formed later is also influenced by the rate of transport of vinylidene chloride to the reaction site. This is confirmed by the conversion curves and the manner in which composition changes with conversion.
Kinetics of the γ‐radiation‐induced polymerization of ethylene
Authors: Wiley Richard H. , Lipscomb N. T. , Johnston F. J. , Guillet J. E.
Published: April 2003

Studies of the rates of γ‐radiation‐initiated polymerization of ethylene in the gas phase at 22°C., 40–70 atm. and 380,000 r/hr. have shown that the rate expressions show a good correlation with the relations expected from kinetic considerations if the density is used to express the ethylene concentrations. In this range of temperature and pressure, the density, pressure, and fugacity relations for ethylene differ significantly from those at the elevated pressures which have been used in previous rate studies. Use of fugacities in the rate expression log (rate) = a + b log x, where x = p, f, or d, gives a value of 10.4 for the b term; use of pressure gives a value of 5.0; and use of density gives a value of 2.4. This last value is closest to that predicted (2.0) from a kinetic analysis which takes into consideration an initiation step dependent on monomer concentration and termination by primary radicals. Studies of the liquid‐phase polymerization over the temperature range of 5 to −40°C. give an activation energy of 4.4 ± 1.8/kcal./mole. Infrared analysis of the product indicates that short‐chain branching is much less (0–1.2 vs. 2–3 branches per 100 carbon atoms) than for polyethylenes prepared at higher temperatures. Relations between solution and melt viscosities indicate a high degree of long‐chain branching in the polymer.
Preliminary studies of the effects on crystal structure of introducing aromatic rings into linear polyamides. Polyamides made from p‐xylylenediamine and dicarboxylic acids
Authors: Vogelsong Donald C.
Published: April 2003

X‐ray diffraction has been used to study molecular packing in the crystalline regions of fibers of the polyamide made from p‐xylenediamine and sebacic acid, PXD‐10. Many of the diffraction spots are displaced from the layer lines. This has been attributed to the crystallites assuming a preferred orientation of about 5° off the fiber axis. No amount of drawing orients the crystallites parallel to the fiber axis. Unit cell dimensions and indices have been determined from normal fiber photographs. The unit cell is triclinic with the following dimensions: a = 5.74 A., b = 4.87 A., c = 20.6 A.; α = 75°45', β = 55°13', γ = 65°19'. A structure is proposed in which the chains pack together in hydrogen‐bonded sheets. The sheets pack together to form a three‐dimensional lattice. No evidence has been found to indicate a second crystalline phase as is usually found in linear polyamides. Fiber photographs of the polyamides PXD‐6 and PXD‐8 show packing and orientation similar to that found for PXD‐10. Fiber photographs of the polyamides PXD‐7 and PXD‐9 show a different type of triclinic packing Long fiber identity periods, combined with the fact that many of the diffraction spots are displaced from the layer lines for these latter two polyamides, prohibit any quantitative interpretation of the diffraction patterns.
Study of the mechanism of synthesis of protein molecules
Authors: Goto Seichu
Published: April 2003

Glutamic acid undergoes cyclization to form 2‐pyrrolidone‐5‐carboxylic acid as an intermediate cyclic monomer in some mechanisms of the synthesis of protein molecules. Two molecules of leucine undergo cyclization to form a dioxopiperazine derivative useful as an intermediate, closed ring dimer for some high protein copolymerization reactions. Leucyl‐leucine has also been cyclized by heating to obtain a similar six‐membered ring dimer as an intermediate. Glutamic acid (1 mole) with leucyl‐leucine (1 mole) react in the same way to form leucyl‐leucyl glutamate without cyclization. Glutamic acid (1 mole) with leucine (2 moles) interact to make α,β‐dileucyl‐glutamate as an intermediate useful for some high protein copolymerization reactions. These intermediates and almost all amino acids will copolymerize to form higher polymers by the method used in this fundamental research investigation.
Etching of polyethylene terephthalate
Authors: Baker William P.
Published: April 2003

A degradative etching technique has been employed with polyethylene terephthalate films to demonstrate the existence of several different structures, the size of which vary from hundreds of microns to hundreds of Angstroms. The micron‐sized structures are a function of the processing and orientation of the film and occur in regular geometric patterns. Thus, parallel stretch‐direction lines are etched into one‐way stretched film, the number of lines being dependent upon film history. Etched, two‐way stretched films reveal a lamellate composition, each layer possessing a brick wall‐like structure. This general structural pattern has been found in other types of film by similar methods. Examination of the etched areas by electron microscopy demonstrates that the micron‐sized blocks are composed of spheres, 700 A. in diameter, which are aligned over moderate distances.
The Newtonian melt viscosity of polyethylene: An index of long‐chain branching
Authors: Schreiber H. P. , Bagley E. B.
Published: April 2003

The relationship at 190°C. between Newtonian melt viscosity η0 and the weight‐average molecular weight, M̄w for polyethylenes has been developed by use of melt viscosities obtained from capillary viscometry and molecular weights from intrinsic viscosity and bulk flow measurements in addition to the usual light‐scattering determinations. The same η0 vs. M̄w relationship is obeyed by whole and fractionated linear polyethylenes and also by ethylene–butene and ethylene–propylene copolymers. The Newtonian viscosity therefore seems virtually independent of molecular weight distribution and the influence of short (ethyl, methyl) chain branches. Low density polyethylenes have consistently lower Newtonian melt viscosities at given M̄w than their linear counterparts. At constant M̄w and temperature, therefore, η0 depends primarily on long‐chain branching. A viscosity index of long‐chain branching (v.b.i.) is defined by the ratio of Newtonian viscosities of a linear and a branched polyethylene of the same M̄w. The v.b.i. correlates well with an intrinsic viscosity branching index provided long branch incidence is high. The correlation breaks down otherwise, because the intrinsic viscosity is also sensitive to molecular weight distribution and the presence of short‐chain branches. The v.b.i. is therefore more useful as a long branching index. It is a comparative index, however, and not an absolute evaluation of the number of long branches per molecule. The η0 vs. M̄w relationship of linear polyethylenes does not obey the often reported 3.5 power law for linear polymers, but is well fitted by a 4.2 power factor. The present work indicates the necessity of using polyethylenes which have been stabilized against the effects of thermally induced changes if meaningful values of Newtonian viscosity are to be obtained.
Effect of molecular weight distribution and branching on the viscosity of polyethylene melts
Authors: Busse W. F. , Longworth R.
Published: April 2003

The effects of molecular weight distribution and branching on the viscosity of polyethylene melts were studied by making mixtures of paraffin wax with 0 to 100% of various types of high and low density polyethylenes of known weight‐average molecular weights, M̄w and measuring their Newtonian melt viscosity at 150°C. The range of molecular weights from about 400 to 106 gave about a billionfold range in the viscosities (10−2 to 10+7 poises). The results showed that the melt viscosity did not vary with M̄w3.4, since samples with the same M̄w might differ by up to 100,000‐fold in viscosity. An analysis of the flow process in melts suggested that the viscosity‐average molecular weight M̄v might be more significant than the M̄w. Within the accuracy of our knowledge of the initial molecular weight, the viscosities of all mixtures having viscosities above about 10 poises fit the equation

where w1 and w2 are the weight fractions, and M1 and M2 are the molecular weights of the paraffin and polyethylene, respectively, and M̄v is a viscosity‐average molecular weight of the mixture. Theory and experiment show that the value of α may be obtained without any knowledge of the initial molecular weight, from the slope of the curve for log η0 versus log concentration at small concentrations of wax. Polyethylenes with large amounts of long‐chain branching had low values of α (down to about 0.25), while polymers with relatively little long‐chain branching had values of α up to about 0.8. Where the comparisons could be made, the value of α determined from a polymer melt was surprisingly close (∼ +0.15) to the value of α in the intrinsic viscosity equation for the same polyethylene dissolved in paraffin wax.
Determination of the mechanical properties of high polymers at high speeds of testing
Authors: Richard K.
Published: April 2003

Three impact testing devices for different test purposes are described and the measuring, amplifying, and indicating equipment for the plotting of stress–strain curves is shown in diagrammatic form. The problem of evaluating the impact strength of high polymers for specified applications is discussed for the case of diverse semifinished and finished parts. In the case of safety belts for motor vehicles, the difference between plastic and elastic deformation energy for various belt materials is shown. With films, a distinction is made between the amount of energy used in deformation until the first tear and the total impact energy. For sheet specimens subject to tensile stress, the stress‐strain curves for slow and shock stresses are contrasted. Further experiments must show whether, with the help of the new testing equipment, the usability of high polymers for specified applications may also be forecast quantitatively.
Effects of cupric salts on the polymerization of acrylonitrile in aqueous solution
Authors: Watanabe Masamoto , Kiuchi Hiroshi
Published: April 2003

The polymerization of acrylonitrile in aqueous solution initiated by ammonium persulfate in the presence of cupric salts was studied by a dilatometric method. The presence of cupric sulfate, nitrate, or acetate has a pronounced effect on polymerization, leading to an increase in the rate, and both cupric chloride and bromide retard or inhibit polymerization beyond certain salt concentrations. The increased rate is explainable by the following reactions:

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The polymerization of acrylonitrile can be initiated by an oxidizing agent such as cupric sulfate, ferric sulfate, stannic chloride, nitric acid, or periodic acid. The decreased rate can be explained by assuming that the complexes of Cu+ ion with a halide ion X− such as CuX2−, CuX3=, CuX4≡, or Cu2X3− shows lower reactivity in the reaction with S2O8=. The cupric‐terminated reaction depends on the coexisting anion. The effect of sulfate, nitrate, acetate, phosphate, chlorate, or fluoride anions is negligible, while that of the chloride is marked, and that of the bromide is overwhelming. The CuX+(X = Cl, Br) ion appears to terminate polymer chains more efficiently than does Cuaq++. Apparent transfer constants of cupric sulfate in the presence of sodium chloride or bromide and the transfer constant of CuCl+ are given. It is suggested that the possibility of the termination reactions by halogen atom transfer is large under conditions of high halide ion concentration:
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Behavior of primary radicals in vinyl polymerization
Authors: Manabe Tomonobu , Utsumi Tadashi , Okamura Seizo
Published: April 2003

The reciprocal of the viscosity‐average degree of polymerization (P̄v−1) vs. rate of polymerization (V) relation is expressed as:

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where [η] = K′P̄vα, β = ktd/kt, k = rate of primary radical formation out of cages/concentration of initiator, \documentclass{article}\pagestyle{empty}\begin{document}$ \sum {_i k'} _{pi} [R_i \cdot][{\rm M}] = {\rm rate of initiation of polymerization} $\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}$ \sum {_i k'} _{ti} [R_i \cdot][{\rm M} \cdot] $\end{document} = rate of termination of growing chains M· by reaction with primary radicals Ri·. From this equation, several, important constants can be determined. In the polymerization of styrene at 60°C. with 2,2′‐azobisisobutyronitrile, the results obtained are as follows: kp2/kt = 5.52 × 10−4 (or 5.86 × 10−4) l.‐mole.−1‐sec.−1. ktrM/kp = 6 × 10−5, ktrS/kp 1.1 × 10−2 (carbon tetrachloride as solvent), k = 1.57 × 10−5 (or 1.48 × 10−5) sec.−1, \documentclass{article}\pagestyle{empty}\begin{document}$ \sum {_i k'} _{pi} [R_i \cdot]/\sum {_i k'} _{ti} [R_i \cdot] = 1.20 \times 10^{- 7} $\end{document}. These values agree well with those obtained by the other authors. The rate of initiation \documentclass{article}\pagestyle{empty}\begin{document}$ \sum {_i k'} _{pi} [R_i \cdot]{\rm -}[{\rm M}] $\end{document} and the rate of termination \documentclass{article}\pagestyle{empty}\begin{document}$ \sum {_i k'} _{ti} [R_i \cdot][{\rm M} \cdot] $\end{document} between the growing chains and primary radicals are calculated, respectively, from the equations:

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The rate of disappearance of the primary radicals through the reaction among themselves is negligible in comparison with the other termination rates in the usual conditions. The ratio of concentrations of the primary radicals R· and growing chains M· is expressed under an ordinary condition as:

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where VR is the rate of primary radical formation and k′p the rate constant of initiation.
The behavior of polysilicic acid. I. Surface charge effects
Authors: Greenberg S. A. , Chang T. N. , Jarnutowski R.
Published: April 2003

The influences of surface charges on polysilicic acid on light‐scattering, electrokinetic, viscosity, and emf measurements were examined. It was substantiated that the potential‐determining ions are hydrogen and hydroxyl, which control the dissociation of the acidic silanol groups, SiOH → SiO− + H+. The zeta potentials are also influenced by the ionic strength of the solutions. The effect of cations on the surface charges increase with valence: Na < Ca < Al. Molecular weights of silica solutions can be determined by light scattering or viscosity measurements. In order to obtain reliable measurements an ionic strength of 0.1 is recommended to suppress the influence of surface charges.
Emulsion polymerization of vinyl acetate
Authors: Okamura Seizo , Motoyama Takuhiko
Published: April 2003

It is generally admitted that the Smith‐Ewart equation is not applicable to the emulsion polymerization of vinyl acetate. This is considered to be due to two factors, namely, (1) the great solubility in water of vinyl acetate and (2) the fact that vinyl acetate is easily subject to the influences of retarders or chain transfer agents. However, examination of the polymerization of vinyl caproate and of styrene leads to the conclusion that the special features pertaining to the polymerization of vinyl acetate are to be attributed to its solubility in water. The reason is that vinyl caproate, which is less soluble in water but subject to the influences of retarders or chain transfer agents in the same degree as vinyl acetate, follows the Smith‐Ewart equation in emulsion polymerization, and styrene, when polymerized in aqueous methanol, in which the solubility of styrene increases, shows a diminished Smith‐Ewart exponent.
Packing of aliphatic molecules
Authors: Ivanovszky Leo
Published: April 2003

It is generally not appreciated that almost all physical properties of solids depend primarily on the shape of the molecule, which controls regularity and density of packing and thus such properties as melting point, specific gravity, hardness, etc. The melting point is of special interest; it characterizes the solid → melt transition.

This contribution follows a novel method of assessing shape and packing arrangement of molecules, based on four considerations: (1) common‐sense probability, (2) packing characteristics, relative to compactness and balance of structure, (3) comparative studies of the melting‐point/chain‐length curves of a number of related series of homologous compounds of known and unknown configuration, and finally (4) actual packing experiments with different types of molecular models. The data so gained should also agree with known x‐ray measurements.

Of importance and comparatively widely studied is the configuration of the fatty acid glycerides. For triglycerides, two (principal) arrangements have been proposed so far, namely, the “tuning fork” and the “chair” structures; these are assumed to be universally accepted. An unnamed third arrangement, not unlike a capital letter E might be regarded the basic shape. The symmetrical one‐acid diglycerides are thought to form a U‐type structure.

It is shown that none of the arrangements named above is really the most probable. The symmetrical or more generally all 1,3‐diglycerides take the shape of straight‐axis molecules which form twin molecules held together by hydrogen bonds. The triglycerides also form straight‐axis molecules; the chain of the acid‐radical in the 2‐position runs parallel to the axis. The composite chain of all the glycerides can be regarded as truly planar, since it shows one negligible deviation only. The twin diglyceride molecules constitute ideal packing units with respect to both closeness and regularity. The packing structure of the triglycerides, particularly of the one‐acid type, is not much less ideal. The latter can form two kinds of twin molecule, i.e., one molecule and one‐and‐one‐half molecules long, as well as multiple (in particular eightfold molecules) two molecules long. The importance of hydrogen bonding is discussed in connection with all types of glycerides. Reference is also made to the packing of ringmolecules of planar symmetry and of aliphatics of spherical symmetry. It is pointed out that the concept of the unit cell offers little advantage in discussion of packing properties of molecular crystals, in particular in the case of long‐chain compounds; rather, it complicates the issue.
Copolymerization studies of radiation‐induced polymerization at low temperature
Authors: Tsuda Yoshizo
Published: April 2003

Copolymerization of acrylonitrile with styrene or methyl methacrylate was performed by gamma‐irradiation at low temperatures in various solvents. Both an anionic copolymerization and a free‐radical reaction were observed to proceed simultaneously. However, when water, alcohol, or ester is present, the anionic polymerization is inhibited. On the other hand, when the content of styrene increases, the free‐radical polymerization is retarded. From results of the fractionation of styrene–acrylonitrile copolymer obtained it was concluded that an anion‐radical of acrylonitrile formed by irradiation at low temperatures initiates both an anionic and a free‐radical copolymerization. The resultant copolymer consists of a block of anionic copolymer attached to a block of free‐radical copolymer.
Röntgenographische Strukturanalyse von amorphem Polystyrol. VI
Authors: Kilian H.‐G. , Boueke K.
Published: April 2003

Es wurden Rötgenaufnahmen von amorphem Polysryrol VI zwischen 20 und 160°C mit monochromatischer Cu Kα‐Strahlung ausgeführt. Das Beugungsbild bei 160°C wurde nach einem bekannten Verfahren, der Fourieranalyse unterworfen, und so die radiale Verteilungsfunktion des amorphen Polymeren ermittelt. Die Berechnung des Beugungsbildes, das von den intramolekularen Interferenzen herrührt, führt auf die Bestimmung einer effektiven permanenten Gruppe. Diese stellt ein Mass für die mittlere statistische Reichweite dar, über die die Lage benachbarter Atome im Makromolekül durch gegenseitige Korrelation bestimmt wird. Es ergeben sich für die Länge der effektiven permanenten Gruppe 11 Å. Über diese Länge stellt sich im Mittel dieselbe Molekülspirale ein, die von der Struktur des isotaktischen Kristalls bekannt ist. Die Struktur bestimmende Bedeutung des Benzolkerns im Polystyrol wird anhand der Streudiagramme bei verschiedenen Temperaturen diskutiert. Nach demselben Analysenverfahren wurde amorphes Phenolphtalein untersucht. Am Beispiel dieses niedrigmolekularen Glases sollten Methode und Ergebnis der Untersuchung am hochpolymeren Polystyrol indirekt überprüft werden.
Graft copolymerization to cellulose by sodium periodate
Authors: Toda Takao
Published: April 2003

It has been shown that acrylic monomer is easily grafted to cellulose by sodium periodate. The apparent activation energy of graft copolymerization is found to be 10.5 Kcal./mole, which indicates that polymer radicals formed by the attack of sodium periodate on cellulose initiate the graft copolymerization. The rate of the reaction increases with increasing reagent concentration of the reagent up to a certain concentration. At higher concentrations, sodium periodate produces more aldehyde groups in the graft copolymer and the grafted chains become shorter. The apparent number of graft‐initiating points is almost constant and independent of the sodium periodate concentration. Studies of homogeneous polymerization indicate that sodium periodate seems not to terminate the reaction of growing polymer radicals. On the other hand, when dialdehyde cellulose prepared previously by sodium periodate oxidation is grafted with methyl methacrylate, the grafted chain is shorter in the range of high content of aldehyde. The above observation indicates that the aldehyde groups formed in cellulose during the grafting reaction are likely to terminate the growing graft chains. The chain transfer constants for several sugars and alcohols with acrylonitrile as monomer were measured. The constants for sugars were found to be always higher than those for alcohols. The x‐ray diffraction patterns of the grafted cellulose with acrylonitrile give, in addition to the typical patterns of crystalline cellulose, lattice distances of 5.2 and about 3 A. which are attributed to the grafted polyacrylonitrile. The intensity distribution curve along the Debye‐Scherrer ring at the lattice distance of 5.2 A. leads to the conclusion that the crystallites of grafted polyacrylonitrile might be oriented along the direction of the fiber axis of the preexisting stock polymer. Studies on samples of cellulose of different fine structure would support the inference that, in the range of relatively low per cent grating the growing grafted chains on the surface of cellulose crystallites are oriented with the formation of crystallites along the lamellar plane of cellulose crystallites.