bluuebunny/crossref_metadata_2025 huggingface dataset:
Elution fractionation of atactic and isotactic polypropylene
Authors: Shyluk Shirley
Published: April 2003

Procedures and an apparatus for the elution fractionation of polypropylenes are described. The isotactic polymer is precipitated onto a sand column from p‐xylene solution by cooling slowly from 126°C. to room temperature. After removal of the solvent and the atactic fraction soluble at room temperature, the column is heated to 156°C. Fractions are eluted with mixtures of a high boiling hydrocarbon fraction as solvent and 10% ethylene glycol in 2‐butoxyethanol as nonsolvent. The dissolving power of the eluents is periodically increased to fractionate the polymer. Upward solvent flow is used. Recovery is usually quantitative, and good reproducibility is demonstrated. Polymer degradation during fractionation has been reduced to generally less than 5% by suitable techniques. Molecular weight distribution curves for three samples are shown. Good selectivity is established by the fact that the ratio of the molecular weight of the highest to that of the lowest fraction is usually in the range of 50 to 200. A description of the fractionation of atactic polypropylene is given also. The atactic material was used to show the effect of depositing the polymer selectively or randomly on the surface of the support as well as the effect of diffusion on fractionation efficiency.
Structural dependence of the electrical conductivity of polyethylene terephthalate
Authors: Amborski Leonard E.
Published: April 2003

The direct current conductivity of three different forms of polyethylene terephthalate was studied over a wide temperature and voltage range to determine the structural dependence of the conduction process. From the films in the amorphous, crystallized, and oriented and crystallized forms it was determined that crystallization reduces the conductivity by more than one order of magnitude. Orientation results in a sixfold decrease in conductivity. The conductivity does not change over a wide range of molecular weight or carboxyl end group concentration. As shown from model polymers and copolymers, disruption of chain symmetry and molecular packing, introduction of side chains, or any other modification which reduces the crystallinity and order, results in greater conductivity. The structural dependence of conductivity, the temperature dependence, and the current–voltage relationships of polyethylene terephthalate are consistent with a proposed ionic mechanism for the conduction process.
Infrared specturm of cellulose I in relation to its structure
Authors: Saksena B. D. , Agarwal K. C. , Jauhri G. S.
Published: April 2003

The infrared data for cellulose I have been critically analyzed and are found to show two parallel and four perpendicular bands in the region of OH stretching. In the region of CH stretching there are two parallel bands and four perpendicular bands. If we imagine that the chains have random phase and a twofold screw axis passes down each chain we should expect six OH frequencies. From the coordinates of O2, O3, and O6 it is shown that two modes should show parallel and four modes perpendicular dichroism. It is also shown that the mode which represents the oscillation of hydrogen atoms against oxygen atoms parallel to the line joining hydroxyl oxygen atoms O2 and O3 can produce intramolecular hydrogen bonding and should be a parallel mode. This is identified with the strong parallel band at 3350 cm.−1 Since each band should become double by virtue of symmetry and antisymmetry with respect to the screw axis we should have two parallel modes, and these are identified with parallel bands at 3350 and 3275 cm.−1. The position of the oxygen atom O6 and of hydrogen atoms H61, H62 of groups CH2 have been calculated. It is shown that the oscillating dipole moment in symmetric CH stretching mode makes an angle of 39°17′ and in the CH antisymmetric stretch an angle of 50°43′ with the fiber axis and therefore both should show parallel dichroism. These are respectively identified with bands at 2853 and 2967 cm.−1. The remaining CH vibrations belonging to the hydrogen atoms of the glucopyranose ring should show perpendicular dichroism. Four vibrations at 2945, 2910, 2897, and 2870 cm.−1 are identified with these CH vibrations. Thus all the infrared predictions are explained on the basis of the Meyer and Misch structure of cellulose I provided we assume that the chains have a random phase relationship. That a two‐fold screw axis runs along each chain direction is also in agreement with the infrared data.
Some polymers and copolymers of vinyl ketostearates
Authors: Marvel C. S. , Dykstra T. K. , Magne F. C.
Published: April 2003

Vinyl esters of 4‐ketostearic acid, 9(10)‐ketostearic acid, and 12‐ketostearic acid have been homopolymerized and copolymerized with vinyl chloride. Reactivity ratios have been determined for the three vinyl ketostearates with vinyl acetate and vinylidine chloride. Also reactivity ratios for the 4‐ and 10‐ketostearates with vinyl chloride and those of the 9(10)‐ketostearates and 12‐ketostearate with acrylonitrile were determined. The mechanical properties of typical vinyl chloride‐vinyl ketostearate copolymers have been examined and compared with a similar vinyl chloride‐vinyl stearate copolymer and with a plasticized vinyl chloride‐vinyl acetate copolymer. The copolymers of vinyl chloride with vinyl 9(10)‐ketostearate and with vinyl 12‐ketostearate compare favorably with the compolymer of vinyl chloride and vinyl stearate in general properties.
Dynamic mechanical properties of high molecular weight nylon 66 fiber
Authors: Murayama Takayuki , Silverman Bernard
Published: April 2003

Dynamic mechanical properties of the ultrahigh molecular weight nylon 66 film and fiber produced by thermally induced solid‐state polycondensation are presented. The α peak temperature of tan δ of these treated films and fibers is shifted 8–32°C higher than that of the appropriate control nylon 66 (film and fiber) while the maximum height of the tan δ peaks is decreased. The treated fibers have higher moduli at all temperatures (20–145°C) and humidities (30% RH) than do their control counterparts. The moduli of the treated fibers at 30% RH compare favorably with control yarn at 0% RH. These yarns also have a greater per cent of the 25°C modulus retention as temperature increases.
Griffith fracture of a phenol–formaldehyde polymer
Authors: Nelson B. E. , Turner D. T.
Published: April 2003

Cast samples of a phenol–formaldehyde polymer with a crack of length defined by a metallic foil inclusion were fractured in tension. The stress at fracture was inversely proportional to the square root of the crack length, in agreement with the Griffith equation for brittle fracture. The behavior did not conform to the Griffith equation with respect to the experimental value of surface free energy, which was several orders of magnitude higher than a theoretically calculated value. However, as the temperature of tensile testing was raised, the experimental value did approach the calculated value. Consistently the appearance of the fracture surface was observed to change from one showing evidence of plastic deformation at room temperature to a featureless appearance, characteristic of brittle fracture, at higher temperatures.
Infrared dichroism of polyethylene crystallized by orientation and pressure in a capillary viscometer
Authors: Miller Philip J. , Jackson John F. , Porter Roger S.
Published: April 2003

Polarized infrared absorption spectra have been obtained by Fourier‐transform spectroscopy for several crystalline and noncrystalline absorption bands of polyethylene crystallized by orientation and pressure in capillary viscometer. An analysis of data obtained at room temperature yielded degrees of crystallinity which are in good accord with values obtained from calorimetry and density measurements. The dichroism of the infrared absorption bands for the crystalline region revealed an extreme degree of orientation consistent with previous x‐ray studies and also demonstrated that the degree of orientation is a good or better than that obtained from drawn polyethylene films with extension ratios of 20. Dichroism of bands from the amorphous phases revealed that the noncrystalline chain segments are in a comparatively relaxed state compared with results for drawn films having extension ratios of about 2 to 7. This is 1/10 to 1/3 the extension ratio of drawn polyethylene which shows maximum crystalline orientation. The results also indicated that the ratio of the GTG′ to GG segment conformations in the amorphous regions is larger than that of amorphous portions in unoriented polyethylene. The vinyl endgroups were shown to be highly oriented, while the main bulk of the amorphous polymer was fairly relaxed, i.e., of low orientation. It is concluded that the amorphous polyethylene state is strongly dependent on the nature of the crystalline–amorphous interface.
A constitutive equation for composite systems
Authors: Chen Y. T.
Published: April 2003

By the differential operator representation of constitutive equations for linearly viscoelastic materials, general theoretical expressions are developed for the physical parameters of a composite system in relation to those of the constituents. The interfacial tension between the dispersed phase and continuous matrix is included in the derivation. The results show that it has effect only on the shear parameter but not on the bulk parameter of the composite system. The general expressions developed in this article represent a unified theory for composite systems. The results are shown to reduce to many special cases obtained by other investigators.
Interpretation of fracture surface features in polycarbonate
Authors: Hull D. , Owen T. W.
Published: April 2003

The fracture surface of notched impact specimens of polycarbonate tested in the range 130°C to −196°C have been studied by use of optical microscopy and scanning electron microscopy. The morphological features associated with the initiation and propagation of fracture have been determined and interpreted in terms of the processes which occur in association with fracture, notably crazing. The fracture processes are similar to those observed in poly(methyl methacrylate) and polystyrene. The transition from ductile to brittle fracture is attributed to the case of crazing relative to shear yielding.
Infrared spectroscopic studies of polymer transitions. III. Effects of sodium ion on glass transitions in styrene‐based ionomers
Authors: Ogura Katsuyuki , Sobue Hiroshi , Nakamura Shigeo
Published: April 2003

The glass transition in styrene‐based ionomers was investigated by means of infrared spectroscopy and differential scanning calorimetry (DSC). Transition temperatures were determined from the temperature dependence of the peak absorbances of the 1700 and 1745 cm−1 bands. These transition temperatures agreed with glass transition temperatures (Tg) determined by DSC. With increasing degree of ionization, Tg and the enthalpy ΔH of the residual intermolecular hydrogen bonding increased. The values of Tg obtained were analyzed by the theory of Fox and Loshaek for the effect of crosslinks. It is concluded that sodium ions probably from ionic domains and act as crosslinks to reinforce the residual hydrogen bonding and may increase Tg. The absorbance at 1560 cm−1 (νCOO−) did not change at Tg. This suggests that the glass transition observed here is not due to the onset of the mobility in ionic domains, as has been proposed for ethylene‐based ionomers on the basis of dielectric measurements.
Drag reduction in turbulent flow by polymer additives
Authors: Lumley J. L.
Published: April 2003

A brief survey is given of the drag reduction phenomenon, emphasizing the aspects which must be explained by any theory: onset, the existence of intrinsic drag reduction, the Newtonian plug, saturation with increasing concentration, and the maximum drag reduction asymptote. In addition, the polymer properties observed to be favorable are noted. Experimental and theoretical arguments are cited, indicating that sublayer stability arguments are not relevant. Recent evidence is given, linking the onset phenom‐enon to a molecular time scale. The behavior of isolated molecules in flow fields is briefly surveyed, indicating the possibility of large increases in viscosity in relatively rotation free strain rate fields; indirect experimental evidence for such behavior is cited, and it is shown how, by reducing the intensity of the smallest eddies, this can explain the various aspects noted. The maximum drag reduction asymptote is discussed, in connection with recent measurements of turbulent fluctuations in drag reducing flows, and it is shown how both of these may be related to changes in the large eddy structure caused by the polymer induced changes in the small eddies.
Correlations between types of absorbed water molecules and water permeability in swollen polymer membranes
Authors: Chang Y. J. , Chen C. T. , Tobolsky A. V.
Published: April 2003

A series of poly(vinyl formal) membranes was synthesized by formalization of poly(vinyl alcohol) membranes. Representative pieces were selected for this study. Some cellulose acetate membranes cast from dioxane were used for comparison. The main experimental techniques employed included water absorption measurements and direct osmosis measurements. Aqueous solutions of sodium chloride at various concentrations were used for the studies of permeation through the membranes by direct osmosis.

The plot of water permeability coefficient Pw versus volume fraction Vw of water absorbed in a membrane was interpreted in terms of the effect of two different types of absorbed water molecules. The individual diffusion coefficients were evaluated from asymptotic slopes of the curves. Similar analyses applied satisfactorily to data found in the literature.
Calorimetric study of free‐radical polymerized poly(p‐biphenyl acrylate) and poly(p‐cyclohexylphenyl acrylate)
Authors: Frosini V. , Magagnini P. L. , Newman B. A.
Published: April 2003

DSC traces and specific heat data for poly(p‐diphenyl acrylate) (PPBA) and poly(p‐cyclohexylphenyl acrylate) (PPCPA) obtained by radical polymerization are reported. The results indicate the existence of a definite ordered phase and of a reversible firstorder solid–liquid transition in both polymers although x‐ray diffraction studies showed that they are not crystalline in the conventional sense. The extent of the ordered phase present in each polymer is calculated, and the problems involved in such determination by thermal measurements are discussed. On the basis of the experimental results reported here in conjunction with the x‐ray data, models are proposed for the morphology of these polymers.
Free‐radical decay in irradiated PMMA
Authors: Davis L. A.
Published: April 2003

Data from the literature are analyzed to show that decay of the chain‐end radical of PMMA in the regime of 80–130°C and 1–13000 atm occurs by two mechanisms operating in parallel. These processes are characterized by activation volumes of ca. 70 Å3 (I) and ca. ∼7.5 Å3 (II), suggesting that decay by process I occurs by chain‐end diffusion and decay by process II occurs by unzipping of the polymer radical to the monomer.
Thermally stimulated chemiluminescence in photo‐oxidized poly(ethylene 2,6‐naphthalene dicarboxylate)
Authors: Richards R. R. , Rogowski R. S.
Published: April 2003

Poly(ethylene 2,6‐naphthalene dicarboxylate) exhibits thermally stimulated chemiluminescence after exposure to ultraviolet radiation and oxygen. The chemiluminescence spectrum is essentially the same as the fluorescence spectrum of the polymer with a maximum intensity at 430 nm. Upon heating, the decay of the luminescence follows a first‐order law with an activation energy of 26.3 ± 0.3 kcal/mole. A comparison of the ultraviolet absorption spectra of the polymer before and after exposure to ultraviolet light and oxygen indicates that the naphthalene ring is oxidized. Heating the polymer above 80°C causes decomposition of the initial photo‐oxide to produce luminescence.
Optical anisotropy of polyisobutylene: Strain birefringence
Authors: Liberman M. H. , Debolt L. C. , Flory P. J.
Published: April 2003

Strain birefringence measurements on crosslinked polyisobutylene (butyl rubber) confirm earlier work of Stein and Tobolsky on the linear polymer indicating the optical anisotropy to be much greater than should have been expected from the structural symmetry of the polyisobutylene (PIB) chain. The configuration–optical anisotropy parameter Δa for PIB at 25°C is 4.1(±0.1) × 10−24 cm3, or about half the value for crosslinked polymethylene, both polymers being undiluted and amorphous. Swelling with cyclohexane, CCl4, and CBrCl3 lowers Δa to values of 3.8, 3.4, and 2.8 × 10−24 cm3, respectively. Contributions from intermolecular correlations in the bulk polymer and from form anisotropy in the diluted systems are small, if not negligible. Temperature coefficients measured isometrically yield d In Δa/dT ≈ 0.2 × 10−3 deg−1. Both Δa and its temperature coefficient are much greater than calculated from rotational isomeric state theory assuming additivity of bond polarizabilities. The disparity (more than tenfold for Δa) cannot be relieved by any rational adjustment of the structural parameters. It is suggested that the severe crowding of groups in the PIB chain may affect the anisotropies of group polarizabilities.
Macromolecular nucleation
Authors: Wunderlich Bernhard , Mehta Aspy
Published: April 2003

The rate‐determining step of crystallization of macromolecules from melt and solution is shown to be molecular nucleation. Molecular nucleation is described by using classical nucleation theory. Good agreement is found between the molecular nucleus size and the critical length of the rejected species. Molecular nucleation has a higher free‐energy barrier than secondary nucleation; it might thus lead initially to independent patches of each molecule on the crystal surface. A possible reason for secondary nucleation on extended surfaces is suggested.
Crystallization of poly(ethylene terephthalate) induced by inorganic compounds. I. Crystallization behavior from the glassy state in a low‐temperature region
Authors: Groeninckx G. , Berghmans H. , Overbergh N. , Smets G.
Published: April 2003

The kinetics of isothermal crystallization from the glassy state at low temperatures and the morphology of poly(ethylene terephthalate) (PET) filled with additives are reported. Talc, kaolin, silicon oxide, and titanium oxide have been used as fillers; they act as effective nucleating agents for PET. The overall rate of crystallization depends on the volume concentration, the size distribution, and the nucleating ability of the additives. An electron microscopic study reveals a transcrystalline morphology at the surface of the filler particles. The occurrence of transcrystallinity is attributed to extensive heterogeneous nucleation induced at the filler surface. From the shape of the crystallization isotherms, it can be concluded that the crystallization mechanism depends on the type of filler.
Studies on amylose and its derivatives. X. Dilute solution conformation of amylose tripropionate
Authors: Cowie J. M. G. , Maconnachie Ann
Published: April 2003

Some dilute solution parameters have been measured for linear amylose tripropionate samples in ethyl acetate and tetrahydrofuran. Mark‐Houwink relations for the molecular weight range 104 to 1.5 × 105 have been established, and the exponents are 0.58 and 0.61 in ethyl acetate and tetrahydrofuran, respectively. This indicates that the coil is only slightly expanded in these solvents. A value of 6.21 was calculated for the characteristic ratio C∞ leading to a steric parameter of σ = 2.32. The temperature dependence of the unperturbed dimensions (d In C∞/dT) was found to negative and of the order −4.05 × 10−3°K−1.
Synthesis and dynamic mechanical properties of heterogeneous network polymers from poly(L‐glutamic acid) and poly(oxyethylene glycol)
Authors: Mori Tetsuo , Kuchihara Yutaka , Tanaka Ryuichi , Tanaka Takehide
Published: April 2003

Heterogeneous network polymers composed of rigid polypeptide chains and flexible polyether chains were synthesized. That is, poly(L‐glutamic acid) (PLGA) was crosslinked with poly(oxyethylene glycol) (PEG) at various carboxy/hydroxyl mole ratios K. The solubility tests and hydrolysis of heterogeneous network polymers suggest that the crosslinking reaction proceeds by esterification. The dynamic mechanical properties of these polymers(100 Hz, −100–200°C) are greatly influenced by the presence of a trace of water and the weight per cent of PLGA. In addition, some of these polymers show only one maximum in the temperature dispersion of dynamic loss modulus E″ and tan δ, although their shape is rather broad. The x‐ray photographs of these polymers show an amorphous halo or weak Debye‐Sherrer rings. These findings suggest that these polymers are not simple adducts; neverthless PLGA and/or PEG domains exist.
Crystal structure of polyisobutylene
Authors: Tanaka Tamotsu , Chatani Yozo , Tadokoro Hiroyuki
Published: April 2003

The crystal structure of polyisobutylene was determined by x‐ray analysis. The orthorhombic cell, with a = 6.88 Å, b = 11.91 Å, c (fiber axis) = 18.60 Å (space group: P212121 − D), contains two molecular chains each consisting of eight monomeric units in the fiber identity period. The chain conformation is essentially an (8/3) helix, but deviates appreciably from the exact (8/3) helix symmetry. The symmetry of the molecular chain is only a twofold screw axis in exact sense, and a crystallographic asymmetric unit consists of four monomeric units. The torsional angles are

equation image

where M denotes the methyl group. The averaged skeletal CCH2C and CCM2C bond angles are 128° and 110°, respectively. The large CCH2C bond angles may be due to steric respulsion between the adjacent methyl groups, giving intramolecular distances larger than 3.09 Å.
Light scattering and x‐ray characterization of amylose films
Authors: Unbehend John E. , Sarko Anatole
Published: April 2003

Small‐angle light scattering (SALS) in the solid state and x‐ray diffraction were used to investigate the development of anisotropic structure in water‐cast amylose films prepared under various conditions. The conditions investigated were different temperatures and relative humidities maintained during the drying of the films and different aging times and temperatures of the amylose solution prior to the casting of films. As revealed by SALS, the predominant morphology developing in these films was based on rod‐like scattering units of considerable size. At times, a low degree of spherulitic character was also evident in the films. All four experimental conditions affected the development of anisotropic structure, with the aging time and temperature producing the most noticeable effects. Increasing aging time and/or decreasing aging temperature markedly increased the rod‐like morphology of the films. On the other hand, crystallite sizes as measured by x‐ray diffraction remained constant at 24–28 Å, indicating no influence on the part of experimental conditions. These findings are discussed in the light of starch retrogradation.
Mechanical properties of ultra‐oriented polyethylene
Authors: Weeks Norman E. , Porter Roger S.
Published: April 2003

Semicrystalline polymers generally exhibit moduli well below their theoretical limit due to chain folding and to lack of crystal alignment. Modulus increases attainable through standard drawing procedures are limited by sample fracture before large draw ratios are reached. Using an Instron capillary rheometer which allowed a draw ratio of > 300, transparent polyethylene strands of unusually high c‐axis orientation have been produced by a combination of pressure and shear. The virtually perfect crystalline orientation and evidence for extended chains confirm that a significant improvement in modulus can be realized by this technique. The dynamic tensile storage modulus was measured by Vibron over the temperature range −160°C to +120°C. Room‐temperature moduli were 7 × 1011 dyne/cm2, higher than any reported values for drawn polyethylene. Values also remained above 1011 dyne/cm2 even at 120°C. The moduli and morphological data have been related by a model consisting of an extended‐chain component in paralled with a conventional drawn morphology. Experimental and calculated moduli are compared and related to available theory.
Diamagnetic susceptibility effects in NMR measurements of the properties of water in polymeric membranes
Authors: Shporer Mordechai , Vega Alexander J. , Frommer Moshe A.
Published: April 2003

The NMR spectra of water adsorbed at various relative humidities on various cellulose ester membranes have been studied. Membranes of cellulose acetate (CA), cellulose triacetate (CTA), and cellulose acetate butyrate (CAB) were investigated. It was found that the resonance peak of a liquid imbibed in or adsorbed on membranes from high relative humidity is very sensitive to the angle between the membrane plane and the direction of the magnetic field, shifting 5–7 ppm to higher fields as the membrane plane is rotated from a perpendicular to a parallel position with respect to the direction of the external magnetic field. This phenomenon was found to be independent of the nature of the polymeric material (namely CA, CTA, or CAB), porosity of the membrane (varying from an “all bulk” dense sheet to an 80% porosity and 0.2 μm average pore size membrane), nature of the magnetic nuclei (H2O or D2O), intensity of the external magnetic field (60 Mcps or 100 Mcps), and nature of the liquid in the membrane (water, methanol, or n‐hexane). It is therefore concluded that the dependence of the position of the resonance peak on the position of the membrane plane with respect to the external magnetic field, is a geometrical phenomenon due to the magnetic “bulk susceptibility” of the medium. Quantitative estimations of the magnitude of the diamagnetic susceptibility effect in a cylindrically rolled sheet are given. These estimates agree well with the experimentally observed “splittings.”
Effect of solvent and carbon black species on the rubber–carbon black interactions studied by pulsed NMR
Authors: Nishi T.
Published: April 2003

The spin–spin relaxation time T2 and the fraction of short T2 component for composites of natural rubber with carbon black prepared under various conditions have been measured by pulsed NMR. Effect of swelling with a solvent (CCl4), carbon black species (SAF, HAF, SRF) with different surface areas, and different initial carbon black loadings (35, 50, 70 phr) have been determined. Molecular motion in the rubber phase not in the immediate vicinity of the carbon black surface increases rapidly with increasing solvent concentration, yet it is still slightly restricted compared to rubber with solvent alone. On the other hand, molecular motion in the immobilized layer around carbon black and the fraction rubber in that layer are not affected by the solvent. This indicates strong restriction of molecular motion of polymers at the surface. For estimation of the thickness of the immobilized layer, the necessity of using an appropriate measure of surface area accessible to polymer molecules is pointed out. The degree of immobilization in the layer and the thickness of the layer do not vary appreciably with the nature of carbon black or the initial loading of carbon black.
Raman scattering in uniaxially oriented samples of planar zigzag poly(vinylidiene fluoride)
Authors: Cessac Gerald L. , Curro John G.
Published: April 2003

Band assignments of phase‐I PVF2 have been Revised by using additional data obtained by laser Raman spectra of oriented samples. A set of least‐squares refined force constants was obtained which reproduce the experimental data to an average error in frequencies of 1.3 cm−1. In order to determine the effect of electrical polarization on the spectra, a Gaussian distribution of the dipole axis was assumed. The calculation shows that polarizations of less than 60% will not significantly affect the Raman spectra.
Effect of interference between anisotropic scattering entities on light scattering from polymer films. II. The correlation function approach
Authors: Yoon Do Yeung , Stein Richard S.
Published: April 2003

A theory is developed by use of the correlation function approach for calculating both the Hv and Vv intensity of scattered light for a concentrated assembly of spherulities. The scattering becomes a function of the radial and tangential polarizabilities of the spherulite αr and αt, the polarizability αm of the medium, surrounding the spherulites, and the volume fraction ϕs of spherulites. The “effective polarizability of the surroundings” αs, which appeared in previous theories, becomes function of these variables. The theory can explain, for example, why the Vv scattered intensity passes through a maximum during the course of crystallization.
Analysis of fractionation of ethylene–propylene copolymers
Authors: Ogawa Toshio , Inaba Tadami
Published: April 2003

Analysis of the solution fractionation of ethylene–propylene copolymers was carried out by assuming a bivariate normal distribution function for the distribution of molecular weight and chemical composition. It was found that the variation of the molecular weight and composition distributions in fractions was complicated, because two distribution characteristics of the original copolymer affect fractionation to differing extents. The hypothetical cumulative weight distribution curves thus obtained agreed essentially with those obtained experimentally.
Rheological properties of internal viscosity models with stress symmetry
Authors: Bazúa Enrique R. , Williams Michael C.
Published: April 2003

Internal viscosity models (IVM) for dilute‐solution polymer dynamics differ in how they define the deformational force Fd which includes φ, the IV coefficient, and in how they treat polymer rotational velocity Ω. Here, the handling of angular momentum is shown to be crucial. A torque balance in simple shear flow at shear rate G leads to stress symmetry and specification of Ω(G) which differs greatly from the conventional Ω = G/2. This determines the G dependence of viscosity η and normal stress coefficient ζ. There are also implications of a transition in rotational behavior as φ approaches a critical value. Predictions of η(G), ζ(G), and η*(ω) are presented for two versions of Fd: one derived recently by the authors and one being most commonly used at present. Limiting cases for high and low φ, and for high and low G and ω, are discussed. Some differences exist between predictions of the two Fd models, but these are surprisingly minor.
Investigation of the interaction of a polyelectrolyte with low molecular weight electrolytes containing nonidentical counterions by differential refractometry
Authors: Stejskal Jaroslav , Kratochvíl Pavel , Pouchlý Julius
Published: April 2003

If the counterion of a polyelectrolyte is not identical with any of the ions of a low molecular weight electrolyte added to the solution, the system may be regarded as a four‐component system. Relations for the refractive index increments have been derived which allow the determination of the coefficient of selective sorption of the added electrolyte from the refractive index increments of the components independent of the original counterion of the polyelectrolyte. Equilibrium dialysis and differential refractometry were used to study the interaction of KCl, KBr and NaI with poly[‐1(2‐hydroxyethyl)pyridiniumbenzenesulfonate methacrylate] or with an analogous polymer containing a toluenesulfonate counterion in aqueous solutions. The coefficient of selective sorption increases in the series Cl− < Br− < I− from strongly negative to strongly positive values; the specific interaction of these counterions with the macroion increases in the same order.
Nuclear magnetic resonance studies on microstructure of ethylene copolymers. VI. Carbon‐13 spectra of ethylene–vinyl acetate copolymers
Authors: Wu Ting Kai , Ovenall Derick W. , Reddy Gade S.
Published: April 2003

The 22.6‐MHz Fourier‐transform noise‐decoupled 13C (carbon‐13) NMR spectra of several ethylene–vinyl acetate (E–VA) copolymers were obtained. We found that triad information on monomer placement can be deduced from carbonyl resonances, triad and pentad information can be deduced from methine carbon resonances, and triad information is available from the methylene carbon resonances. The random comonomer distributions in E–VA polymerizations were demonstrated up to pentad placements. In addition, the use of model‐compound data in the analysis of copolymer spectra was shown.
Kinetics of polymer crystallization from the melt (calorimetric approach)
Authors: Godovsky Yu. K. , Slonimsky G. L.
Published: April 2003

Crystallization kinetics for 12 polymers including polyolefins, polyesters, polyurethanes, polysiloxanes was measured by the evolution of heat in a modified Calvet‐type calorimeter over wide temperature ranges. The results are analyzed in terms of the Avrami equation and a comparison between calorimetric and dilatometric results is carried out. It is concluded that, although in the majority of cases experimental results do not obey the Avrami equation, for some polymers the agreement is rather good. The Avrami parameter obtained, however, depends on the experimental technique. Possible reasons for this disagreement are discussed. Analysis of the calorimetric crystallization rate in the vicinity of the melting point by using the kinetic theory of crystallization shows that the growth is controlled by surface (two‐dimentional) nucleation. Energy parameters for the crystallites were determined and it is shown that the surface energy of the crystallites depends on the molecular structure of the polymer. Temperature dependence of the calorimetric crystallization rate of the polymers for which crystallization rates could be determined above and below the maximum rate are analyzed using a kinetic equation with common approximations for the transport term. The influence of melting conditions on the crystallization rate was studied. The results indicate heterogeneous nucleation in the polymer melt. It is concluded that this may be due both to impurities and to high regularity of macromolecules in the polymer melt.
Electron trapping and luminescence mechanism in thermoluminescence of irradiated polycarbonate
Authors: Hama Yoshimasa , Nishi Kunihiko , Watanabe Kazuo , Shinohara Kenichi
Published: April 2003

Thermoluminescence of polycarbonate irradiated by electron beams was observed in order to investigate the trapping of electrons and the luminescence mechanism. The thermoluminescence glow curve is composed of three components. The peaks appear at −150°C (α peak), −120°C (β peak), and −30°C (γ peak). The α peak is attributed to recombination of cations with electrons released from trapping sites formed by carbonate groups. The β peak is attributed to small amounts of impurities. The γ peak is perhaps due to untrapping of electrons from the phenoxy anion. The luminescence intensity of the α peak is linearly dependent on the absorbed dose, and that of the β peak is approximately proportional to the cube of the dose. The appearance of these peaks is presumably closely related to local molecular motions.
Electron microscope study of low molecular weight fractions of linear polyethylene
Authors: Kloos F. , Go S. , Mandelkern L.
Published: April 2003

Electron microscope studies are reported for crystals of linear polyethylene formed in dilute solution from very sharp low molecular weight fractions. Emphasis is placed on molecular weights in the range of 1.1 × 103 to 15.1 × 103. The dependence of the crystal habit on the crystallization temperature is very similar to that which has been found for the higher molecular weight species. However, the demarcation temperature for the crystallization of the different morphological forms is very molecular weight‐dependent. The conditions under which interfacial dislocation networks form can be clearly defined. The molecular weight must be less than 3000, so that these structures are restricted to very small chain lengths. However, not all crystallization conditions within this allowable molecular weight range yield such dislocations. The formation of interfacial dislocation networks are shown to occur only under very special circumstances. Their occurrence clearly cannot be offered as evidence, as has been done in the past, for a regular, chain‐folded interfacial structure.
Electron spin resonance study of free radicals in the radiation grafting of butadiene to poly(vinyl chloride)
Authors: Hamanoue Kumao , Shimizu M. , Higaki H. , Block Ira , Silverman Joseph
Published: April 2003

The kinetics of the disappearance of propagating butadiene radicals produced in the grafting of butadiene to poly(vinyl chloride) was followed by electron spin resonance measurements. The radical species observed in the temperature range 213–298°K is the conjugated allylic radical:

The reaction conditions were adjusted to provide a highly viscous medium in which the propagation reaction took place. Under these conditions the radicals were stabilized and a precise ESR spectrum was obtained. Arrhenius plots of the second‐order decay rate constants yield an activation energy of 5 kcal/mole. This suggests that the bimolecular termination reaction is controlled by the segmental motion of the grafted side chains.
Further comments on the relation between hydraulic permeation and diffusion
Authors: Paul D. R.
Published: April 2003

We feel that the lengthy comments given here come down to a few simple points. For uniform, homogeneous swollen membranes the internal driving force for transport in hydraulic permeation experiments is a concentration gradient not a pressure gradient. Equation (1) is in error because it neglects the frame of reference term 1/(1 − ν1). Equation (19) shows properly the connection between K0 and the various diffusion coefficients. In the particular case discussed here and previously we see no evidence to say that a viscous flow mechanism is operative since we can explain all of the K0 data in terms of reasonable diffusion coefficients if proper consideration is given to the frame of reference correction. This is not to say that in many other cases a viscous flow mechanism will not be present or even predominate.
Radiothermoluminescence. I. Radiothermoluminescence for investigation of thermal and radiation‐induced crosslinking of rubber mixtures
Authors: Nikolskii V. G. , Zlatkevich L. Yu. , Borisov V. A. , Kaplunov M. Ya.
Published: April 2003

Phase heterogeneity of vulcanizates based on cis‐polybutadiene (cis‐Europrene) and SBR (Europrene 1500) blends obtained by radiation, thermal, two‐stage radiation‐thermal, and two‐stage thermal‐radiation processes was investigated by the radiothermoluminescence method. Unvulcanized blends of these polymers are found to be heterogeneous, exhibiting two glass transition temperatures Tg, which coincide with the values for the initial components. Following vulcanization, the difference between the two Tg values for a polyblend decreases. The decrease is more distinct for polyblends crosslinked at high temperatures. When the vulcanization temperature exceeds 140°C and the crosslink density (or 1/Mc) exceeds 5 × 10−5–1 × 10−4 mole/cm3, the glass temperature ranges of the crosslinked blend are practically superimposed. Such crosslinked mixtures should be considered pseudohomogeneous in phase.
Radiothermoluminescence. II. Radiothermoluminescence of polyethylene with different chain conformations
Authors: Nikolskii V. G. , Zlatkevich L. Yu. , Konstantinopolskaya M. B. , Osintseva L. A. , Sokolskiĭ V. A.
Published: April 2003

Molecular relaxation processes in the 77–260°K interval and the structure of polyethylene melt‐crystallized under normal and high pressures have been studied. The positions of relaxation transitions and activation energy for molecular relaxation were determined by radiothermoluminescence. The most intense maximum in the glow curve of the sample crystallized under normal pressure is observed in the 200–240°K interval, i.e., in the range of the β transition. In this temperature interval the β relaxation activation energy changes from 15 to 25 kcal/mole. An increase of the pressure under which crystallization takes place results in a substantial decrease of the intensity of the β maximum. This indicates that the β transition of polyethylene is most probably due to the mobility of segments on the chain‐folded lamellar surface. For samples melt‐crystallized under pressure between 5000 and 7000 atm, relaxation transitions were found at 150 and 190°K. Various processes of molecular relaxation appear to be associated with the maxima observed on the polyethylene glow curve.
Thermostimulated depolarization currents and thermoelectret effects in poly(methyl methacrylate)
Authors: Solunov H. , Vassilev T.
Published: April 2003

The electrical dipole relaxation in PMMA has been studied by measuring thermostimulated depolarizing currents. A master curve for the segmental component of the dielectric constant has been constructed. The increment of the dielectric permittivity due to the α‐relaxation has been determined. The distribution function of the relaxation times and the average relaxation times in the region from 70°C up toTg= 105°C have been obtained. A way of describing the electret properties of the polymer is discussed.
Correct measurement of birefringence in a nonuniform medium
Authors: Ong C. , Yoon D. Y. , Stein Richard S.
Published: April 2003

The birefringence of an object is usually obtained from its retardation. For an object of variable refractive index and optic axis orientation, a matrix procedure should be used for relating the retardation to the birefringence. There are many cases in the literature where this correct procedure has not been used. The correct procedure is illustrated for the case of a polymer spherulite.
Preparation of crosslinked polymers with increased modulus by high‐pressure polymerization
Authors: Rackley F. A. , Turner H. S. , Wall W. F. , Haward R. N.
Published: April 2003

p‐Divinylbenzene has been polymerized by heating at pressures ranging from atmospheric to 2.5 GN/m2, and the moduli (Young's, shear, and bulk), density, and residual unsaturation of the products have been determined. The results show a marked effect of polymerization pressure upon density and upon the degree of conversion of the second double bond. Linear relations are indicated between modulus and either density or an intermolecular force function based on a 6–12 potential field. These results and others on the densification of polystyrene are discussed and it is concluded that the moduli of the poly‐p‐divinylbenzene samples prepared under these conditions are still at a level largely determined by intermolecular forces.
Small‐angle light scattering and crystallization processes in solid polymer films
Authors: Samuels Robert J.
Published: April 2003

Information, not previously measurable, about the internal crystallization processes occurring within spherulitic films can now be obtained by combining refractive index, birefringence, and small‐angle light‐scattering measurements. The surroundings of a spherulite in a solid film are composed of both the adjacent spherulites and their interstices (boundaries), and it is shown that different crystallization processes can occur in each of these regions. Upon annealing a quenched isotactic polypropylene film, the rate of crystallization within the interstices of the space‐filling spherulites is observed to be greater than the rate of crystallization within the spherulites themselves.
Crystallite size determination of nylon 6 by wallner's method
Authors: Kaji Keisuke , Sakurada Ichiro
Published: April 2003

The crystallite sizes of α and β forms of nylon 6 along the chain axis were determined by Wallner's method. First the shifts of the maximum positions of meridional reflections from their ideal reciprocal‐lattice positions were calculated for the various crystallite sizes. Second, using these relationships, crystallite sizes were estimated from the observed maximum positions of reflections. The estimated values agree well with those from the integral widths of reflections by the method of Hosemann and Wilke.
Solid‐state synthesis of large polymer single crystals
Authors: Baughman R. H.
Published: April 2003

Criteria for the solid state synthesis of large, nearly defect‐free, polymer crystals are derived and related to experimental observations. Polydiacetylene single crystals are of principal concern, although the concepts presented can be easily generalized. In particular, a least‐motion criterion is developed whereby the solid‐state reactivity of different diacetylene phases and the most likely polymerization mode of a particular phase can be predicted from a two‐parameter description of the relationship between neighboring monomer molecules. Phase stability criteria are considered for four characteristic free energy diagrams which explain the phase behaviors that have been observed for various polymerizing diacetylenes. Reaction uniqueness criteria are discussed as they relate to monomer site point group symmetry, symmetry relations between mutually reacting monomer molecules, and dimensional changes during polymerization.
Specific interactions of polyelectrolytes with counterions
Authors: Prokopová E. , Stejskal J.
Published: April 2003

Free electrophoresis, differential spectral UV analysis, and the determination of the coefficients of selective sorption were used to investigate, in aqueous solutions of halides, the behavior of two polycations, poly[1(2‐hydroxyethyl)pyridinium methacrylate] and poly[1(2‐hydroxyethyl)trimethylammonium methacrylate]: i.e., one species with and the other without a pyridine ring in the side chain. Electrophoretic data were used to estimate the length of the electrophoretic segment and the approximate charge of the polyion in solutions of the individual salts. A comparison of the data showed that the interaction is not due to the presence of the pyridine ring in the side chain and that the order of activity of the halide anions is the same for both types of polymers.
Approximate theory of the viscoelasticity of chain‐molecule solutions not infinitely dilute
Authors: Wang Francis W. , Zimm Bruno H.
Published: April 2003

The theories of viscoelasticity of chain‐molecule solutions, based on the bead‐spring model, have been modified to take into account approximately the effect of interactions among chain molecules. The motion of a given chain molecule has been analyzed in detail while all other chain molecules have been treated as a background of uniformly distributed beads in which the given chain molecule is suspended. The inclusion of intermolecular interactions leads to a hydrodynamic interaction tensor, which after averaging, differs from that of Kirkwood by a concentration‐dependent correction term. The modified theory correctly predicts the transition from the non‐draining to the free‐draining behavior which has been observed in chain‐molecule solutions as their concentrations are increased.
Effect of chain defects on the morphology and thermal behavior of solution‐grown single crystals of syndiotactic polypropylene
Authors: Marchetti A. , Martuscelli E.
Published: April 2003

The morphology of solution‐grown single crystals of syndiotactic polypropylene with different degree of stereoregularity is compared. A sector formation phenomenon, found in some monolayer single crystals, is discussed in terms of possible crystallographic fold planes, growth planes, and gemination planes. A correlation between thermodynamic and morphological properties such as apparent enthalpy of fusion, critical long spacing, critical annealing temperature, and the number of configurational chain defects along the macromolecule has been found. Two endothermic peaks are observed in the DSC thermograms of single‐crystal aggregates of syndiotactic polypropylene. The low‐temperature peak is attributed to melting of crystals or parts of crystals with incorporated chain defects. The high‐temperature peak corresponds to the melting endotherm of more regular crystalline zones. The peak‐area ratio seems to depend on the degree of stereoregularity.