bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibers of thermally stable ordered heterocycle–amide copolymers
Authors: Preston J. , Black W. B.
Published: June 2010

Thermostable fibers were spun from several ordered heterocycle‐amide copolymers. Tenacities up to 8 g./den. at standard conditions were obtained. The polymers were prepared by condensation of arylene diacid chlorides with aromatic diamines containing preformed heterocyclic units of types known to be thermally stable (oxadiazole, thiazole, and bithiazole). Fiber tensile properties were determined at temperatures up to that at which the fiber failed. Each fiber had a zero strength temperature of over 515°C. in nitrogen, and each had appreciable strength at 400°C. In general, the fiber showed excellent retention of tenacity after heat aging for long periods of time at 300°C. in air. An oxadiazole‐amide fiber retained three‐fourths of its original tenacity after 168 hr. under these conditions.
Formation of metal filaments and their characterization
Authors: Ross J. H.
Published: June 2010

A technique has been established for the drawing of bundles of sheathed superalloy wires. Reduction of the individual filaments to a final diameter of 0.0005 in. was accomplished for Chromel R and René 41 with as many as 100 filaments per bundle. The problems of sheathing, stress‐relieving, and desheathing were solved. However, the problem of interfilament welding and/or oxide bonding still requires extensive explanation, first, to define more clearly the causes of welding or bonding, second, to develop techniques for separating the welds or bonds, and third, to accomplish this with a minimum of loss in strength and elongation while achieving the flexibility and bending recovery of yarns formed by stranding single‐drawn superalloy fibers. The successful achievement of these goals will yield high strength, flexible superalloy yarns capable of being woven and fabricated, systems requiring the thermal stability provided by super‐alloys.
Influence of the structure of unsaturated imides on their polymerizability and on the polymer properties
Authors: Sheremeteva T. V. , Larina G. N. , Tsvetkov V. N. , Shtennikova I. N.
Published: June 2010

On the basis of the comparison between the polymerization rates, intrinsic viscosities and molecular weights of the polymers of N‐substituted maleimides and citraconimides a conclusion is drawn that the methyl group in citraconimide causes a decrease in the reactivity of its double bond. Fractions of poly‐N‐isobutylmaleimide (P‐N‐IBMI) were investigated by the methods of translational diffusion, sedimentation, and flow birefringence. In the range of molecular weights from 0.19 × 106 to 3.6 × 106 relationships are obtained between the molecular weight M of the fractions investigated, their intrinsic viscosity [η], diffusion coefficient D, and sedimentation coefficient S. The hydrodynamic data obtained indicate that macromolecules of P‐N‐IBMI exhibit high rigidity due to the presence of cycles in their main chain. A marked optical anisotropy of the P‐N‐IBMI molecules is positive and indicates that molecular chains of P‐N‐IBMI in solution have a trans conformation.
Reaction of nickel carbonyl on halogenated olefins obtention of polymers
Authors: Asfazadourian M. , Prillieux M.
Published: June 2010

The reaction of nonsaturated dihalogenated hydrocarbons (halogen atoms in the a position of the double bond) with nickel carbonyl. 1,4‐dichlorobutene‐2 and nickel carbonyl magnified image gives almost quantitatively a powdered, colored solid, insoluble in all common solvents. Physical studies showed this solid to be a new polymeric complex, Ni 2+ bound to a hydrocarbon skeleton. Derivatives from dichloroparaxylene were also prepared and studied. The complexes are decomposed by water and methanol, giving polymers and a nickel halogenide solution. The polymers obtained are described. They are insoluble in all common solvents and of good thermal stability up to 350°C.
Possibility of a new method of polycondensation
Authors: Turska E. , Dems A.
Published: June 2010

It has been suggested, on the basis of theoretical considerations, that a polycondensation process in solution can be performed with a shifting of the equilibrium by precipitation of the highest fractions of polymer. A series of condensations of polycarbonates was carried out, starting with 2,2‐di(p‐hydroxyphenyl) propane (bisphenol A) and its dichloroformate in two different solvents, for preparation of polymers under equilibrium conditions and under conditions of equilibrium disturbance by an addition of nonsolvent. The molecular weights and distribution functions of both products were determined. It was found that the products obtained by this precipitation polycondensation, in agreement with the theoretical assumptions, have considerably higher molecular weights and molecular homogeneity.
Effect of conditions of glass formation on the density and energy of polystyrene
Authors: Allen Geoffrey , Ayerst R. C. , Cleveland J. R. , Gee Geoffrey , Price Colin
Published: June 2010

Samples of fluid polystyrene are converted into the glassy state at 20°C. and 1 atm. pressure by two different routes: (a) by cooling at 1 atm. pressure and (b) by cooling at 1250 atm. and then decompressing. The heats of solution of the samples are determined in toluene at 30°C. The samples are found to have similar enthalpies, although their densities are different. An attempt is made to explain the results in terms of freezing of rotational isomerism at the glass transition temperature.
A study of the elastic deformation of butyl rubber at constant volume
Authors: Allen Geoffrey , Gee Geoffrey , Kirkham M. C. , Price Colin , Padget John
Published: June 2010

Stress–temperature measurements have been obtained for a butyl rubber strip, held in simple elongation at constant volume. The results have been used to evaluate the energetic component of the total elastic force. The results are compared with similar data, previously reported, for natural rubber, and with data based on indirect estimates of (∂ƒ/∂T)LV. The energetic contribution to the elastic retractive force was found to be of opposite sign to that reported for natural rubber, being small and negative. Dilation coefficients have also been estimated from a subsidiary experiment and the results compared with the predictions of current elasticity theory.
Influence of some friedel‐crafts halides on the polymerization of isobutylene catalyzed by aluminum bromide
Authors: Marek M. , Chmelíř M.
Published: June 2010

The rate of polymerization of isobutylene catalyzed by AlBr3 in the presence of some Friedel‐Crafts halogenides (TiCl4, TiBr4, and SnCl4) in nonpolar medium and in the absence of H2O is much higher than in polymerization catalyzed by AlBr3 alone. The catalytic activity increment decreases in the order TiCl4, SnCl4, and TiBr4. In the system AlBr3TiCl4 the conversion is dependent only on the concentration of AlBr3. A new mechanism of initiation by complex compounds is proposed.
Dependence of the steady‐state compliance on concentration and molecular weight in polymer solutions
Authors: Holmes Larry A. , Ferry John D.
Published: June 2010

Low‐frequency dynamic viscoelastic measurements have been made on solutions of four polystyrenes with nearly uniform molecular weights (M) ranging from 19,800 to 860,000, in three chlorinated diphenyls covering a wide range of viscosities, at concentrations (c) up to 0.35 g./ml. The steady‐state compliances (Je), derived from these measurements, are proportional to M/c for M ≥ 82,000 and c ≥ 0.08 g./ml., and their magnitudes agree with the prediction of the Rouse theory. For M = 19,800, Je is abnormally small, and the frequency dependence of the viscoelastic properties also deviates from both Rouse and Zimm theories, suggesting that the molecular length is too small for applicability of the Rouse‐Zimm model. At decreasing concentrations deviations from M/c proportionality occur for two reasons: the magnitude of Je shifts from the Rouse prediction to the Zimm prediction, and the concentration dependence shifts from inversely proportional to directly proportional. Both changes are attributed to the disappearance of coil interpenetration with decreasing concentration, and in qualitative agreement with this interpretation they appear to be correlated with the product of concentration and intrinsic viscosity when data for different molecular weights are compared.
The conformational transformation in macromolecules of atactic poly‐β‐vinylnaphthalene
Authors: Eskin V. E. , Serdjuk I. N.
Published: June 2010

Light scattering, viscosity, and dilatometric studies of poly‐β‐vinylnaphthalene solutions indicate the conformational transformation in the macromolecule near 50–60°C. This transformation separates two states of the macromolecule, characterized by the different temperature coefficients of the partial specific volume dv̄/dT. The transformation is accompanied by a decrease of the optical anisotropy of the macromolecules. These phenomena can reflect disordering of the regular short sequences in the macromolecule or overcoming the barrier to the rotation of their naphthalene groups. It is possible to admit the coexistence of these two mechanisms in some cases.
Mechanical dispersions of polar polymers sensitive to the presence of low molecular weight substances below the glass transition temperature: The influence of the side‐chain length and the end hydroxyl group of swollen poly(methacrylic acid) esters
Authors: Janáček Josef
Published: June 2010

Characteristic features of mechanical low‐temperature dispersions which arise in polymers with polar groups are studied. In poly(methacrylic acid) esters swollen to various extents by low molecular weight substances of different types the influences of side‐chain length and of OH and CH3interchange in the side‐chain endgroup are compared. In the case of poly(diethyleneglycol methacrylate) two types of dispersion were found: the temperature of one was dependent, the other independent, of the concentration and composition of the low molecular weight substances. An attempt at interpretation is given.
Glass transition and relaxation in the amorphous phase of isotactic polypropylene
Authors: Wada Yasaku , Hotta Yasuko , Suzuki Ryuji
Published: June 2010

Two breaks are observed in the temperature dependence of both specific volume and logarithmic retardation time in isotactic polypropylene, indicating two glass transitions. In correspondence with two transitions, two loss peaks are found in isochronal measurement of dynamic mechanical loss at 3 Mc./sec. The lower transition Tg1 is assigned to the amorphous phase, which is rich in atactic chains (A1 phase); the upper transition Tg2, to the amorphous phase, rich in isotactic chains (A2 phase). The lower transition shifts to high temperature with room temperature aging time owing to recrystallization in the A1 phase, accompanying the increase in flexural stiffness. The upper transition shifts to high temperature through annealing above 100°C. on account of recrystallization in the A2 phase. The situations of the two phases in the spherulite of polypropylene are suggested by variations of long period with annealing temperature and birefringence with aging time. The effects of molecular weight on Tg1 and Tg2 and on impact strength and brittle point are discussed.
Application of two‐phase mechanical model to viscoelastic properties of blends of high‐density and low‐density polyethylene
Authors: Okamoto T. , Takayanagi M.
Published: June 2010

With a two‐phase mechanical model the complex dynamic tensile modulus of blends of high‐density and low‐density polyethylene were calculated from viscoelastic properties of the components by a high‐speed computational technique. Agreement of the calculated values with the experimental values was satisfactory. For a given volume fraction of one component the mixing state of blends can be expressed by only one parameter, which is affected by crystallizing conditions. Differential thermal analysis of the blends was made to supplement information on the mixing state. Results of high‐speed tensile tests are discussed on the basis of the mixing state of the blends.
The role of crystallinity of polymer in the adhesion between chlorinated isotactic polypropylene and isotactic polypropylene
Authors: Aoki Yoshihide
Published: June 2010

Chlorinated isotactic polypropylene (CIP) has good ability to bond to isotactic polypropylene. The bonding strengths between the two polymers are affected by the preparation conditions of CIP, chlorine contents of CIP, isotacticity of raw polymer, and conditions of making joints. However, these factors are related to the crystallinity of CIP, and it is considered that the crystallinity of CIP is responsible for the bonding strengths between the two polymers. By using x‐ray diffraction and electron diffraction measurement the role of crystallinities of these polymers in bonding are discussed.
Patterns in terpolymerization
Authors: O'Driscoll Kenneth F.
Published: June 2010

A program has been written and used to compute vinyl terpolymer compositions as a function of monomer feed. The results are presented as a set of triangular contour maps. Six hypothetical monomers of typical reactivity have been investigated in their 20 possible terpolymerizations. With respect to composition it is concluded that variation in electronegativity is less important than the variation in resonance stabilization commonly encountered in vinyl monomers. The approach of these terpolymer systems to azeotropic behavior is graphically derived from the contour maps. Loci of partial azeotropy are drawn for a number of systems. No true ternary azeotropes have been observed.
Calculation of relative reactivity ratios from composition–conversion data through use of a computer
Authors: Montgomery Donald R. , Fry Charles E.
Published: June 2010

The classical methods of determining relative reactivities of monomers to free‐radical polymerization, namely polymerization to low conversion of several initial monomer compositions, purification of the polymers formed, compositional analysis, and fitting of the data to the differential form of the copolymer equation by any of several techniques, suffer from several problems. In particular, the various methods of treating the data assume no change in monomer composition at low conversion. This is a reasonable approximation when the reactivities are similar, but when they are grossly different (e.g., r1/r2 > 100), even 2 to 3% conversion can cause highly significant shifts in the monomer composition, particularly for those points where the more reactive monomer is present in relatively small amounts. Illustrations of the potential magnitude of these errors are provided. A computer program has been written that utilizes one of the integrated forms of the copolymer equation and thereby includes the conversion corrections in the treatment of the data. This procedure should yield more precise r1 and r2 values than the classical techniques, with less direct computational effort on the part of the investigator.
Particle size analysis of polymer latexes by light scattering. II. Computer analysis
Authors: Wallace T. P. , Kratohvil J. P.
Published: June 2010

Angular light scattering by polymer latex dispersions is used for determining the particle size distribution. The analysis consists of calculating the experimental Rayleigh ratios Vθ,v and Hθ,h for vertically and horizontally polarized components of scattered light. Corrections for solvent scattering and reflection effects are also applied. The polarization ratios are calculated for each concentration and extrapolated to infinite dilution, thereby correcting for multiple scattering at finite concentrations. The polarization ratios at infinite dilution are converted to polarizations and compared with theoretical values corresponding to anticipated possible size distributions. A topographical map of the root‐mean‐square deviations on a plot of the size parameter versus the distribution parameter is obtained. This map gives an indication of the uniqueness of the fit over the range of theoretical values searched. Data obtained on a Dow polystyrene latex are used for an example analysis. Details of the computer routine are discussed. Similar programs exist for the size distribution analysis and determination of number concentration of spherical particles utilizing the angular absolute specific intensities.
On semicontinuous emulsion polymerization
Authors: Gerrens Heinz
Published: June 2010

Semicontinuous emulsion polymerization of styrene and methyl acrylate with a feed of either monomer or monomer emulsion has been investigated. Feeding rate Rz and initial charge were varied, reaction rate Rp, degree of polymerization Pζ, number of latex particles N, and particle size distribution were measured. With both monomers Rp and Pζ are independent of Rz as long as Rz is large enough to maintain the saturation value of monomer concentration [M] in the latex particles. If [M] falls below this value a steady state is reached with monomer feed as well as with emulsion feed, Rp equals Rz, and Pζ increases with increasing Rz. Taking the Smith‐Ewart theory as a basis for calculation, the propagation rate constant kp was determined for both monomers in the steady state. Emulsion feed produces less, i.e., larger particles than monomer feed or batch polymerization, the overall charge being kept constant. Emulsion feed gives a narrower particle size distribution, and the initial rate of polymerization and N are proportional to the initial charge, if formation of new latex particles during the emulsion feed can be avoided. If not, particle size distribution is broadened and can eventually become even broader than with the other two methods.
Electron microscope investigations on fibril formation
Authors: Bittiger H. , Husemann E. , Kuppel A.
Published: June 2010

In order to gain a better understanding of the formation and structure of natural fibrils as found in cellulose, chitin, etc., transitions from coils into fibrillar solid structures were investigated with some suitable polymers as model substances. Preliminary precipitation experiments of cellulose out of solution yielded no clear results. With cellulose tricarbanilate, rod‐like single molecules or single crystals with folded chains are formed at low concentrations and fibrils of different diameter with preferentially extended chains at higher concentrations. The results are discussed in terms of nucleation and chain stiffness. In the amylose iodine complex the transition from coils to fibrils with a uniform diameter of 40 Å could be shown. Alcohol complexes yielded only single crystals. With mannan and cellulose tribenzoate ribbon‐like fibrils are found. Trimethyl cellulose finally formed fibrils with a uniform diameter of 200 Å and a helical periodicity of 200 Å along the chain. On the basis of the above‐mentioned results a modification of Manley's model of the cellulose elementary fibrils is proposed and discussed in relation to properties and biosynthesis of cellulose.
On the biosynthesis of cellulose in higher and lower plants
Authors: Marx‐Figini M.
Published: June 2010

Kinetic experiments on cotton cellulose and cellulose from the alga Valonia show, that the degree of polymerization during the biosynthesis of the secondary wall is independent of conversion and reaction conditions. During the whole synthesis period it remains constant at a DPw ∼ 13,000 for cotton and 16,500 for Valonia, respectively. Fractionation experiments indicate complete uniformity of the degree of polymerization at every stage of the biosynthesis. This means that the biosynthesis of secondary wall cellulose for both higher and lower plants must be a structure‐controlled process and not a time‐controlled one. Contrary to this evidence the synthesis of primary wall cellulose takes place by another mechanism which results in a lower average degree of polymerization and a nonuniform distribution. Both, secondary wall and primary wall synthesis can occur simultaneously. Recent results of electron diffraction experiments on native cellulose and fibrils, precipitated from the original material, seem to indicate that crystalline and supermolecular structure of the cellulose fibrils are not determined by the biosynthetic process.
Interaction of cellulose with liquid water: Accessibility determined from thermal expansion
Authors: Neal J. L. , Goring D. A. I.
Published: June 2010

The apparent specific volumes in water of glucose and of three different types of cellulose were measured at 3° intervals between −5 and 25°C. The extent of the destructuring of the liquid water by the carbohydrate surface was determined from the thermal expansion near 0°C. If glucose in aqueous solution was taken to be 100% accessible, the accessibilities of cellophane, wood pulp and cotton linters ranked 50, 29 and 20 per cent respectively. These values are considerably lower than accessibilities measured by isotope exchange techniques. Possible reasons for this discrepancy are discussed.
Preparation and properties of grafted membranes for desalination. Part I
Authors: Hopfenberg H. B. , Kimura F. , Rigney P. T. , Stannett V.
Published: June 2010

Styrene grafting to cellulose acetate has been studied in an attempt to synthesize a cellulose acetate reverse osmosis membrane with improved resistance to compaction. The studies reported here involved grafting to homogeneous cellulose acetate

E‐398‐3 Eastman Chemical Company.

film and evaluation of the tensile creep and water sorption behavior of the resulting grafts. The grafting studies involving homogeneous cellulose acetate films indicated that the kinetics of grafting were rate controlled by monomer diffusion to the growth site. By controlling the ratio of styrene to pyridine (monomer/swelling agent) and controlling total dose, reproducible and predictable grafts were prepared. The tensile creep rate of wet cellulose acetate–styrene grafts decreases sharply with increasing styrene content up to 40% styrene and then decreases more slowly as styrene content is further increased. The creep rate of grafts containing 40% styrene is 7.5 times lower than that of ungrafted cellulose acetate. Unsteady‐state water vapor sorption experiments revealed that the equilibrium water content was decreased as a consequence of grafting although water diffusivities were increased or decreased as percent graft was increased according to the method and level of grafting. Water sorption deviated slightly from Henry's law behavior. The water diffusivity, as measured by the rate of sorption, was concentration dependent, decreasing with increasing water concentration. Membrane constants for water transport (defined as D 1C1 g‐cm/cm2‐sec) could be increased or decreased as a consequence of grafting.
High temperature superconductivity
Authors: Ginzburg V. L.
Published: June 2010

The critical temperature, Tc, for all presently known superconductors does not exceed 21'K. This fact obviously limits the range of applications of superconductivity in technology in a very fundamental way. On the whole, the reason why the value of Tc for “ordinary” superconductors would not exceed 20‐40oK is fairly well understood. At the same time, there apparently could exist high temperature superconductors for which Tc would reach liquid air temperature or even room temperatures. Possible means of producing high temperature superconductors are considered in this article which is based on the review published in Contemporary Physics, 9, 355 (1968), but includes also some new material. Special attention is paid to what can be called the exciton mechanism of superconductivity and its application to systems of the “sandwich” type and metallic conductors with layer structures.
Solid state possibilities of porphyrin structures
Authors: Adler Alan D.
Published: June 2010

The structures and chemical, physical, and biological properties of porphyrins are generally described. The problems inherent in their employment in physical studies are summarized. A semiconduction study of Langmuir films of ms‐tetraphenylporphin showing a cubic thickness dependence in resistance is detailed. Possibilities for employing these materials in organic superconduction research are presented.
The molecular weight dependence of lower and upper critical solution temperatures
Authors: Delmas G. , Patterson D.
Published: June 2010

The molecular weight dependence of the Lower Critical Solution Temperature in polymer solutions has been derived using the Prigogine smoothed potential cell model. Satisfactory agreement is obtained with experimental results for a number of systems. It is found that the new structural term (or equation of state term) in χ introduced by the Prigogine theory accounts for the LCST. Any difference in chemical nature between the polymer and solvent molecules may be largely ignored. The structural term also has an effect on the molecular weight dependence of the familiar Upper Critical Solution Temperature. It is predicted that fractionation of a polymer could be improved by choosing a solvent for which the UCST and LCST were separated by only a small temperature interval. Fractionation at the LCST should not be more efficient than at the UCST.
Simulation of the brownian motion of macromolecular chains in solution
Authors: Monnerie Lucien , Geny Francois
Published: June 2010

The first study by the Monte‐Carlo method of the dynamical comportment of macromolecular chains in solution was made by Verdier and Stockmayer. We have adapted the method proposed by these authors to the case of a chain built in a tetrahedral lattice with volume‐excluded‐condition, for analyzing the brownian motion of a macromolecular in solution. This is done by submitting the chain to a very great number of elementary motions of 1, 2, 3 or 4 bonds.
The lifetimes and intensities of positron states in several solid polymers as an indication of structure
Authors: Stevens J. R. , Edwards M. J.
Published: June 2010

Positrons which penetrate and become trapped in polymeric solids form states which display complex annihilation time spectra. The average lifetimes and intensities of the posiltron states can be obtained from the exponentially decaying components of the time spectra. Usually three components can be resolved for solid polymers; with long, Intermediate and short average lifetimes. Experimental results of lifetimes and intensities for positrons annihilating in trans 1–4 polybutadiene, polyethylene, polyethyleneterephthalate are used to conclude that the intensity can be associated with regions of short range order and the intermediate lifetime and intensity with regions of long range order. It is also concluded that for both regions of long range and short range order there is a tightening of the microstructure in the polymer as the amount of long range order increases and/or molecular weight decreases.
On the general theory of polymer absorption at a surface
Authors: Hoeve C. A. J.
Published: June 2010

Previous theoretical work dealt with polymer adsorption in which the adsorbed segments (trains) interact in the surface layer only. In this work the treatment is extended to Include also interaction between the loops dangling in solution. Fortunately, the excluded volume effects for adsorbed polymer chains are found to be small. Therefore an approximate treatment is possible that leads to equations that govern polymer chains under a wide variety of conditions.
Solution of water in polymers: The keratin‐water isotherm
Authors: Rosenbaum Shlomo
Published: June 2010

The uptake of water by polar polymers was shown by Simha and Rowen to be described by the Flory‐Huggins solution treatment at high relative vapor pressures. The breakdown at lower vapor pressures is attributed here to the effect of water content on the free volume of the system. By using data for the wool keratin‐water system, similar agreement is obtained for the rest of the isotherm by taking account of the volume changes observed at low vapor pressures. These are shown to set in at a characteristic composition with properties generally associated with a glass transition.
Reaction kinetics in dilute solutions of chain molecules carrying randomly spaced reactive and catalytic chain substituents. I. Estimation of ring closure probabilities from kinetic data and computer simulation
Authors: Goodman Neil , Morawetz Herbert
Published: June 2010

Acrylamide was copolymerized with small proportions of monomers containing a p‐nitrophenyl ester group and a small amount of a monomer containing a pyridine residue. The hydrolysis of the ester groups was studied under conditions where the rate of the process was controlled by interaction with pyridine residues attached to the same chain. Variables studied included the mode of attachment of the ester groups to the chain backbone, the concentration of the catalytic pyridine residues in the chain and the fraction of the pyridine present in the unprotonated, catalytically active form. Kinetic data obtained at different pH values gave the same results if the extent of reaction was expressed as a function of the product of the experimental time and the fraction of pyridine residues in the basic form. This proves that the intramolecular process is not controlled by the rate at which cyclic conformations are formed but by their probability. The reaction deviated from first‐order kinetics because the reactive groups had varying spacings from the catalytic groups. Experimental data were in good agreement with the kinetics derived by computer simulation if the probability of group interaction was made inversely proportional to the square of their separation along the chain molecule. Initial apparent first‐order rate constants were about 40% of the value predicted on the basis of a simple theory based on the average extension of the polymer coils.
Spectroscopic study of the n‐π* transition of oriented poly (γ‐benzyl L‐glutamate) in solution
Authors: Hoffman S. J. , Ullman Robert
Published: June 2010

Circular dichroism, optical rotation, and ultraviolet absorption studies have been carried out on oriented solutions of poly(γ‐benzyl L‐glutamate). The orientation of the molecules was achieved by use of an electric field parallel to the direction of propagation of the light wave. This was possible because of the design of conducting electrodes which are largely transparent in the ultraviolet. It was accomplished by putting a very thin coating of stannous oxide on optical silica. The results of these measurements show that the magnitude of the circular dichroism and optical rotation decrease substantially in the n‐π* region of the ultraviolet (∼ 2200 Å). The decrease agrees with the calculation of Woody and Tinoco.
Morphology and deformation mechanisms of crystalline polymers
Authors: Stein Richard S.
Published: June 2010

Crystalline polymers consist of regions of varying order ranging from perfectly crystalline to random and rubber‐like assemblies of polymer chains. Such structures may thus be represented in terms of statistical parameters characterizing the size and shape of ordered regions, degree of order and orientation of these regions. These parameters may be characterized by such techniques as x‐ray and light scattering. A study of the deformation of such polymers requires the specification of the change in these descriptive parameters with time, temperature, and morphology. The application of a number of optical techniques to this determination is discussed and typical results are presented. A deformation mechanism for crystalline polymers is proposed which is consistent with these observations.
Crack propagation and arrest in polymethylmethacrylate
Authors: Rosenfield A. R. , Mincer P. N.
Published: June 2010

By use of a double‐cantilever‐beam specimen, fast fracture and crack arrest were studied in PMMA. The observation, that the heavily deformed region at the crack tip was confined to a thin wedge of material was confirmed. This result provided support for a onedimensional solid‐mechanics analysis. The computations suggest that the average energy to propagate fast fracture from a sharp crack is only ∼2/3 of that required to initiate it. In addition, the process of very slow crack propagation, leading to arrest, was examined microscopically. At very slow rates the crack was seen to advance in a series of small jumps. The implications of these results with respect to materials development are discussed.
Chain scission and plastic deformation in the strained crystalline polymer
Authors: Peterlin A.
Published: June 2010

Depending on temperature and load rate an unoriented polymer solid under sufficiently large applied stress either deforms plastically (high temperature, low rate of loading) or undergoes brittle fracture (low temperature, high rate of loading). The fracture proceeds through the areas of minimum strength, i.e., along the boundaries between adjacent spherulites and between parallel lamellae. Very few chains, i.e., interlamella tie molecules and molecules bridging the crack if a crystal lamella is broken, are ruptured during this process. Hence the number of radicals per cm2 of new surface is small, about 1013/cm2.

The plastic deformation gradually transforms the sample into the extremely well oriented fiber structure of much higher elastic modulus and strength but of smaller strain to break. The basic element of the fiber structure is the long and narrow microfibril formed by micronecking of the crystal lamella. The microfibril consists of fully oriented folded chain blocks connected by a great many tie molecules obtained by partial chain unfolding in the micronecks. Their number per amorphous layer increases with the draw ratio and so does the tensile strength of the microfibril.

Under load the fiber structure breaks at very small strain. The fracture proceeds through the weakest elements of the structure, i.e., through the boundary between adjacent microfibrils and the amorphous layers between subsequent blocks of the microfibrils. With axial stress the fracture must cut at least one full cross section of the fiber and hence rupture about 1014 intrafibrillar tie molecules per cm2. ESR experiments show long before the final break a much higher number of radicals throughout the whole strained sample upto 1017/cm2. The number of broken chains depends on strain and not on stress. One imagines that at every applied strain one breaks the most strained tie molecules which as a consequence of stress concentration have to carry most of the load. The stress concentration caused by the special morphology of the microfibrils and tie molecules reduces the tensile strength of the polymer far below the theoreticall limit calculated for uniform stress field even if one considers that the number of chains passing through the fracture plane is only a fraction of the maximum number calculated with all macromolecules extended and perfectly aligned.
Chemical structures of surface‐oxidized and grafted polyethylene: Adsorption and wetting studies
Authors: Baszkin Adam , Ter‐Minassian‐Saraga Lisbeth
Published: June 2010

Surfaces of thin low‐density polyethylene films are chemically modified either by oxidation or by grafting with maleic acid. The oxidation is performed at constant tempera‐ture by sulfuric acid and potassium chlorate mixtures of variable compositions. Grafting was carried out at constant temperature and time in the solution of maleic anhydride in acetic anhydride in the presence of benzoyl peroxide initiator. Isotherms of calcium adsorption at these surfaces have been established by the use of the radioactive tracer technique. The chemical composition (number of obtained polar sites) of these modified polyethylene surfaces is thus determined. The measurements were conducted at different pH and salt concentrations. Wettability of the modified surfaces is determined by contact angle measurements. It was found that the wettability of these films is directly related to the chemical composition of their surfaces.
Determination of the high frequency viscoelastic properties of polymers using shear mode strip delay lines
Authors: Hunston Donald L.
Published: June 2010

A recently developed technique for measuring the high frequency shear mechanical properties of a wide range of samples is discussed. The technique involves the propagation of a shear wave in a thin strip of metal. When a sample coating is applied to the metal, the attenuation of the wave in the strip increases and the velocity decreases slightly. Previously, an expression was developed for the relationship between these changes in the wave and the mechanical properties of the sample; however, a simplified derivation is presented here for the special case where the sample is a liquid. At present the method has been used only at 2 MHz, but it can be adapted to frequencies between 1 MHz and 20 MHz quite easily and with careful work to frequencies outside this range. The sensitivity of the technique makes it possible to measure a range of samples extending from liquids with viscosities of only a few centipoise to deformable solids and in some cases rigid solids.
Solvent effects on the viscosity of moderately concentrated polymer solutions
Authors: Gandhi K. S. , Williams Michael C.
Published: June 2010

Viscosity ηo and osmotic pressure π were measured for polymer solutions at 25°C, for concentrations up to 30 g/dl. To elucidate the effects of polymer‐solvent interactions of various types, the systems chosen were polystyrene in toluene (good solvent) and decalin (poor solvent), and poly(methylmethacrylate) in chlorobenzene (good) and m‐xylene (poor). The surprising result was the generalization that ηo for poor‐solvent systems increases with concentration faster than for good‐solvent systems, so that eventually ηo becomes far greater with poor solvents. This behavior is enhanced with polar polymers, and is not explainable on the basis of entanglements in the usual sense. It is believed that polymer aggregation occurs in poor solvents, independent of molecular weight effects.

Data were correlated with both the powerlaw and the Simha methods. Characteristic shapes of such curves were related to polymer‐solvent effects. Theories for the Huggins constant were found to be inadequate, as was a model proposed earlier (by MCW) for concentrated solutions. The latter was modified by adopting an ad hoc friction constant, which proved successful with good solvents and could be correlated with π to incorporate the poor‐solvent data as well.
Hydrogenation of kraft lignin
Authors: Benigni J. D. , Goldstein I. S.
Published: June 2010

A series of high temperature hydrogenolyses‐hydrogenations of kraft lignin in water, organic solvents and aqueous alkali using a variety of catalysts were run. The liquefaction and distillation yields for the resulting products were measured. The products from these reactions were characterized by titration for acidic materials, elemental analyses, catechol content, ultraviolet absorption, and NMR.
ESR study of interactions of γ‐irradiated cellulose I and cellulose II with ammonia, water, and sodium hydroxide solutions
Authors: Hinojosa Oscar , Nakamura Yoshio , Arthur Jett C.
Published: June 2010

The types of long‐lived free radicals formed in predried cellulose I and cellulose II, after irradiation in a nitrogen atmosphere at 25°C by γ‐radiation from 60Co, were resolved by selectively scavenging some of the radicals and then recording the ESR spectra generated. The effects of anhydrous ammonia (both gas and liquid), water, solutions of sodium hydroxide, and temperature of heating on the ESR spectra generated by the irradiated celluloses were recorded. Most of the free radicals formed in the irradiated celluloses are apparently trapped in the amorphous or less ordered regions of the cellulosic structure. About 70% of the radicals formed in irradiated cellulose I and about 90% of the radicals formed in irradiated cellulose II are scavenged by contacting the samples with water. The ESR spectra of the free radicals scavenged by water are almost identical for both irradiated celluloses. Contact of the irradiated celluloses with ammonia (liquid) scavenged most of the trapped free radicals. It also appears likely that the long‐lived free radical sites in the highly ordered regions in both irradiated celluloses are the same. As shown by the effects of orientation of irradiated cellulosic fibers in the magnetic field on the ESR spectra recorded, differences in spectra for the irradiated celluloses are probably related to conformations of the trapped radicals which are dependent on differences in crystal lattice types of cellulose I and II.
Structural characterization of grafted cotton fibers by microscopy
Authors: Goynes Wilton R. , Harris James A.
Published: June 2010

The structure of cotton fibers grafted by radiation induced polymerization with butyl methacrylate and acrylonitrile was investigated by light and electron microscopy. Degree and uniformity of dye uptake was used to indicate uniformity of reaction. The internal structure of the fibers was studied with the transmission electron microscope using ultrathin cross sections and solubility tests. Changes in the fiber surface, and types of damage caused by abrasion were evaluated with the scanning electron microscope. These tests indicated that the grafting procedure had changed the surface as well as the internal fibrillar character of the fibers and the extent of such changes increased with increasing content of graft polymer.
Effect of molecular weight on the crystallization and morphology of poly (ethylene oxide) fractions
Authors: Godovsky Yu. K. , Slonimsky G. L. , Garbar N. M.
Published: June 2010

The temperature dependence of the isothermal growth rate of spherulites and overall crystallization kinetics of different fractions of poly (ethylene oxide) over the range of molecular weight from 300 to 20,000 were studied by calorimetry, dilatometry, and polarized light microscopy, in order to establish the dependence of the kinetic parameters upon molecular weight. The morphology of crystallites was studied by small‐angle x‐ray scattering. In the course of this study it has been established that the growth rates of spherulites and the overall crystallization rates at any fixed supercooling essentially depend upon molecular weight. The minimum in the crystallization rate which occurs at molecular weight 4000 is a consequence of transition from extended‐chain crystallization to folded‐chain crystallization. Small‐angle x‐ray scattering study of the morphological features confirmed this conclusion. This minimum depends very strongly on the degree of supercooling, increasing rather sharply at small supercooling. The temperature and molecular weight dependence of the growth rates of spherulites and the overall crystallization rates has been analyzed by means of the theoretical expression given by Hoffman and Lauritzen. The product of the lateral and basal surface free energies of the crystallites σσe increases with molecular weight and reaches a limiting value at molecular weight 6000. Such behavior is in agreement with morphological transformations.
Growth rate and morphology of polyoxymethylene supermolecular structures
Authors: Pelzbauer Z. , Galeski A.
Published: June 2010

The connection between the growth rate and morphology of supermolecular structures was investigated for polyoxymethylene which was isothermally crystallized from the melt at various temperatures. Optical and electron microscopy showed that below 158°C the crystallization occurred in the spherulite form, while above this temperature hedrites and, sporadically, ovoids were obtained. Although the radial growth rate itself does not exhibit a break around the critical temperature (158°C), a more detailed analysis based on the kinetic theory of crystallization has revealed a sudden drop in the interfacial free energy of the fold surface around this temperature. For the growth model represented by two‐dimensional surface nucleation, which seems the most probable representation, values of 183 and 95.5 erg/cm2 were found for the temperature regions of growth of spherulites and hedrites, respectively. Morphologically, the two types differ by a larger extension of monocrystalline lamellae in hedrites, the mode of their arrangement, and the final external shape. The increasing extension of the lamellae, due to a decrease in the radial growth rate, which can be understood in terms of the segregation theory by Keith and Padden, is probably the reason that at a certain critical size (near 158°C), the hedritic growth becomes stabler than the spherulitic growth. A further investigation will be needed to elucidate the part played by a simultaneous drop in the free energy of the fold surface.
A study of the elongation ratio of deformed spherulites
Authors: Pakula T. , Kryszewski M.
Published: June 2010

In order to describe mathematically small‐angle light scattering in samples containing undeformed spherulites or spherulites deformed by tensile forces we assume a function for the light scattering intensity distribution for Hv patterns. This assumed function is a very good approximation to Stein's equations but has a simpler mathematical form. It is also a good approximation of the distributions experimentally obtained for light scattered from spherulites.

By using this function, a new method of calculating the elongation ratio λS of deformed spherulites is elaborated. It consists of measuring the azimuthal angle μmax for which the value of the intensity of light scattered at the vertical angle 0 < θ < π/2 is a maximum.

Using this method, the spherulite deformation in PE films was studied. The results are compared with those obtained by Samuels' method.
Anisotropy of the physicochemical properties of single‐textured polymer samples in relation to morphology
Authors: Goffin A. , Dosiere M. , Point J. J. , Gilliot M.
Published: June 2010

Single‐textured samples of high pressure polyethylene were prepared by rolling. The anisotropy of the variations of macroscopic dimensions of these samples produced by thermal expansion or by swelling with solvent allows us to test the classical models. The anisotropy of the expansion coefficients at low temperature for three different samples (respectively annealed at 90, 100, 105°C) show that the structure changes progressively, going from a morphology wherein sample dimensions along the chain axis are stabilized by partially uncoiled molecules to the ideal lamellar structure. The anisotropy of the thermal expansion coefficients at high temperature suggests that there exist distinct phases arranged in layers parallel to the rolling plane, one of which melts on raising the temperature of the sample. A new model explains these results. It describes the samples as composed of two phases: a lamellar one and another without regular structure in the 100 Å range. The anisotropy of the dimensional changes due to the swelling by solvents strongly supports this model. It is shown that swelling at low temperature produces a minimum of expansion perpendicular to the lamellar faces. The fringed fibril model modified by folded chains cannot explain the observed anisotropy. By using the new proposed model a plausible mechanism is proposed to explain the experimental facts. At high temperature, the swelling is due to the dissolution of the lamellar phase and the results obtained are in good agreement with the model.
Thermodynamic limitations on interaction functions and the theta temperatures of polymer solutions
Authors: Kennedy J. W.
Published: June 2010

A limiting critical point of a binary solution of a homodisperse polymer of molecular weight M, is any point in a (concentration, Φ, temperature, T)‐plane which is a critical point for a limit M → ∞. At any such point four conditions subsist for a function Φ defined in terms of the free enthalpy of mixing for (polymer) solutions. Because this definition is quite general, the conditions are universal and are not limited by any interpretation of Φ in terms of a particular model. Thus they are to be regarded as thermodynamic constraints on any model which may be applied to polymer solutions over conditions which extend to a critical region. If the limiting critical concentration, ΦL, is zero, then the limiting critical temperature, TL, is identical to the theta temperature, Tθ. If ΦL is not zero, Tθ can be obtained from Φ and is less than TL in a Flory (upper critical) system, or greater than TL in a Rowlinson (lower critical) system. It is concluded that theta temperatures have been seriously misestimated by classical extrapolation procedures.