bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of toluene‐soluble polymers at the toluene–water interface
Authors: Huber Hans F. , Thies Curt
Published: April 2003

The adsorption of several toluene‐soluble polymers at the toluene–water interface has been investigated by using the duNouy ring method of measuring interfacial tension γT/W. Polystyrene and poly(ethylene‐co‐vinyl acetate) (11.1 mole‐% vinyl acetate) have little affinity for this interface at 29°C, but poly(methyl methacrylate) (PMMA) (M̄n = 420,000) and ethyl cellulose (EC) (M̄n = 50,100; 49.1% ethoxyl) adsorb significantly at concentrations as low as 1.0 × 10−4 g/100ml. A plot of interfacial tension lowering versus initial logarithm of initial bulk phase polymer concentration is linear from 1.0 × 10−4 to 1.0 × 10−1 g/100 ml for EC and 1.0 × 10−4 to 1.0 × 10−2 g/100 ml for PMMA. When the PMMA concentration increases to 1.15 × 10−1 g/100 ml, its adsorption behavior changes markedly. Prolonged time effects occur and adsorption becomes dependent upon dissolved water content of the toluene prior to formation of the toluene/water interface. Such effects are not observed with the other solutions studied. Increasing temperatures have variable effects on values of γT/W for the polymer solutions studied. Experiments with various polymer mixtures indicate that the polymer lowering T/W the most is preferentially adsorbed at the toluene–water interface and rapidly displaces less strongly adsorbed polymers.
Universal calibration in GPC: A study of polystyrene, poly‐α‐methylstyrene, and polypropylene
Authors: Coll H. , Gilding D. K.
Published: April 2003

The theoretical justification for using M[η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly‐α‐methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly‐α‐methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experimental error.
Lamellar and interlamellar structure in melt‐crystallized polyethylene. I. Degree of crystallinity, atomic positions, particle size, and lattice disorder of the first and second kinds
Authors: Kavesh S. , Schultz J. M.
Published: April 2003

An x‐ray diffraction method for the simultaneous determination of crystallinity (including intracrystalline defects), effective Debye‐Waller factors, and atomic positions has been developed and applied to semicrystalline polyethylene. It was found that this material unambiguously constitutes a two‐phase system. Measurements of intracrystalline lattice disorder in the chain direction and perpendicular to the chain direction show these to be in the ratio 1:2.5. Lattice disorder was principally of the first kind. Paracrystalline disorder in the [110] direction was less than 2.4% at all experimental conditions. Results include measurements of degree of crystallinity, particle size, space group, and unit cell parameters and variation of these quantities with crystallization temperature, ambient temperature, and time.
General dynamic theory of macromolecular networks. II. Dynamics of network deformation
Authors: Takserman‐Krozer R. , Ziabicki Andrzej
Published: April 2003

On the basis of the general concepts of a macromolecular network as defined in the preceding paper, a detailed analysis of forces acting on a network chain is given. In all types of networks the chain tension involves elastic, diffusional, contact friction and internal viscosity terms; in entanglement networks there appears also an additional term associated with chain–chain friction at entanglement junctions. The force balance equation for a tetrafunctional network junction is derived. It is shown that exact formulation of this equation requires knowledge of the simultaneous configurations of all the network chains in the system. For energetic networks, solution of the force balance equation is not required for the determination of the distribution function; and the dynamics of such networks can be discussed in terms of a distribution function for a single chain. On the other hand, for entanglement and contact networks, where the force balance equation is a source of information about sliding rates, some simplified equations can be formulated and solved, by using a 4(N + 1)‐dimensional distribution function for a single macromolecule with N network junctions. It is shown that for both network classes with nonlocalized junctions the position of a network chain within the macromolecule plays an essential role and is a source of the effects of molecular weight on the physical behavior of the system.

The analysis of forces acting on a network chain reveals also some essential differences in the dynamic behavior of energetic, entanglement and contact networks and thus confirms the significance of the classification proposed in the preceding paper.
General description of orientation factors in terms of expansion of orientation distribution function in a series of spherical harmonics
Authors: Nomura Shunji , Kawai Hiromichi , Kimura Itsuro , Kagiyama Mitsuyasu
Published: April 2003

A mathematical representation of orientation distribution of structural units within the bulk polymer is given in terms of an expansion of the distribution function in a series of spherical harmonics. Each coefficient of the expanded series is discussed in general relation to the orientation factors, average degrees of orientation distribution, defined by several different authors independently. Several optical techniques to evaluate the orientation factors, the second and fourth moments of orientation distribution of crystalline and noncrystalline structural units from optical dichroic quantities, are discussed. Some graphical representations of the state of orientation are proposed, and the estimation of orientation distribution from the orientation factors of different orders is discussed quantitatively.
Determination of the width of a narrow molecular weight distribution by gel‐permeation chromatography
Authors: Waters J. L.
Published: April 2003

A recycle gel‐permeation chromatography (GPC) method for extrapolating to infinite resolution is proposed. From the GPC calibration curve, the extrapolated elution peak width volume can be converted into peak width in decades of molecular weight. For an essentially Gaussian distribution, the weight‐average/number‐average molecular weight ratio can be determined from a calculated conversion table.
A dynamic approach to diffusion and permeation measurements
Authors: Pasternak R. A. , Schimscheimer J. F. , Heller J.
Published: April 2003

A dynamic method for investigating the mechanism of permeation and diffusion through polymers has been explored. The permeation cell consists of two compartments separated by the membrane. The permeant (gas, vapor, or liquid) is introduced into one compartment; a carrier gas (helium) flows at constant rate through the other and sweeps the permeant which diffuses through the membrane to the thermal conductivity detector. Both compartments are at atmospheric pressure; thus no or little membrane support is required, and leakage problems are minimal. Moreover, the same membrane can be used over a wide temperature range and for diverse permeants. The detector signal is at any instant proportional to the permeation rate. A simple mathematical formalism for deriving the diffusion coefficient from the transient permeation rates has been developed. The measured diffusion and permeability coefficients of CO2, O2, and N2 through low‐density polyethylene closely agree with literature values. Permeation of hexane and benzene through polyethylene follows a complex diffusion law, and the rate depends on the thermal history of the system. The dynamic method is particularly suited to the study of transitions in polymers. Changes in permeation rates, usually occurring at transition points, can easily be discovered by slow temperature scanning of the system.
Multiple melting transitions in fractions of partially isotactic poly(propylene oxide)
Authors: Booth C. , Devoy C. J. , Dodgson D. V. , Hillier I. H.
Published: April 2003

Three transitions are detected dilatometrically when partially isotactic poly(propylene oxide) melts. One transition, the temperature of which is independent of the crystallization temperature over a wide range below 60°C, is ascribed to the melting of lamellar crystallites which are limited in thickness by the average isotactic sequence length alone. The other two transitions, the temperatures of which vary with the crystallization temperature, are ascribed to the melting of lamellar crystallites with thickness determined predominantly by three‐ and two‐dimensional primary nucleation acts. The theory of Flory is adapted and applied quantitatively to the melting points of three crystalline fractions of poly(propylene oxide), obtained from a polymer produced via the zinc diethyl and water catalyst system. This method leads to a thermodynamic melting point of isotactic poly(propylene oxide) near 82°C.
Dilute solution parameters of polymethylphenylsiloxamers
Authors: Buch Robert R. , Klimisch Helen M. , Johannson O. K.
Published: April 2003

Dilute solution parameters were determined for polymethylphenylsiloxamer fractions (5 × 104 < M < 1.5 × 106) in toluene, cyclohexane, and diisobutylamine (θ ≈ 30.4°C). The data are interpreted by the procedure suggested by Flory and Fox. Minor deviations from theory are noted. Polymers from both cis‐ and trans‐cyclotrisiloxanes were investigated. The major portion of the work, however, was concentrated on fractions derived from the trans form. From the data obtained, a characteristic ratio of dimensions (r/r)½ of 1.56 was determined. The hydrodynamic parameter Φ was determined to be (2.0 ± 0.3) × 1021. The appropriate model for the polymer is indicated to be the impermeable random coil with slight hindrance to rotation about backbone skeletal bonds.
Viscoelastic and relaxation properties of a polystyrene melt in axial extension
Authors: Vinogradov G. V. , Fikhman V. D. , Radushkevich B. V. , Ya. Malkin A.
Published: April 2003

On axial extension of polymer melts at constant deformation rates, the development of high‐elastic deformation is of predominant importance during the initial period. High‐elastic deformation is accompanied by a rise in viscosity and in the modulus of high‐elasticity and by retardation of the relaxation processes in the region of large relaxation times. At relatively low deformation rates, the rise in viscosity and high‐elasticity modulus and the retardation of relaxation processes may give way to a decrease in viscosity and high‐elasticity modulus and acceleration of relaxation processes, so that stationary flow regimes are attained. The transition from strain regimes with increasing viscosity and modulus of high elasticity to those with a decrease of these quantities corresponds to an increase in the rate of accumulation of irreversible deformation. Accordingly, a competing influence due to the orientation effect and to destruction of the network of intermolecular bonds becomes evident while stationary flow is being attained. The orientation effect must be responsible for the retardation of the relaxation processes, whereas rupture of the intermolecular network bonds results in structural relaxation accelerating relaxation processes. In contrast to shearing, during extension the orientation effect is of predominant importance. Hence in stationary flow regimes the viscosity may not only remain independent of the rate of strain, but even increase with it. In this case the contribution of the large relaxation times to the relaxation spectrum increases with increasing stress in stationary flow regimes. The fact that the longitudinal viscosity and the modulus of high elasticity are independent of the stress in stationary flow regimes does not guarantee linearity of the mechanical properties of the polymer in the prestationary stage of deformation when complex changes occur in its relaxation characteristics. At high deformation rates the viscosity and the modulus of high elasticity keep rising with increasing deformation until rupture occurs. Determination of the strength of polystyrene samples vitrified after extension showed that it is due not to the entire degree of extension, but only to the value of accumulated high‐elastic deformation. The strength of the vitrified samples is to a first approximation independent of the rate at which the melt was extended.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. I. Effect of concentration, temperature, pH, and ionic strength
Authors: Priel Z. , Silberberg A.
Published: April 2003

The reduced specific viscosity of poly(methacrylic acid) has been studied in ethanol–0.002N HCI solvent mixtures as a function of polymer concentration, alcohol concentration, and temperature. In addition, experiments were performed at different HCI concentrations and with KCI instead of HCI. Both intrinsic viscosity and Huggins coefficient were shown to undergo unusually strong variations. Two minima and two maxima could be demonstrated in intrinsic viscosity. The Huggins coefficient seems to show corresponding variations. The first minimum in intrinsic viscosity indicates that the coil volume has collapsed almost to an Einstein sphere. In this region the Huggins coefficient is extremely large (of order 102) and is controlled by coil association. It was shown that several forms of intramolecular interaction must be assumed to be competing to account for this behavior. The presence of HCI, particularly in the preponderantly aqueous phase, is required to suppress the polyelectrolyte effect. It is found, however, that the behavior of the solutions at relatively high ethanol concentrations is more sensitive to HCI content than is that of highly aqueous solutions. KCI can be used to replace HCI over most of the range. Increase in temperature shifts the turning points of the curves to lower alcohol concentrations. Some evidence has been found that the association constant giving rise to dimers increase with rate of shear. The importance of poly(methacrylic acid) as a chemically simple model substance for various biopolymer effects is stressed.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. II. Methanol, ethanol, n‐propanol, and 1,2‐ethanediol
Authors: Priel Z. , Silberberg A.
Published: April 2003

The intrinsic viscosity of poly(methacrylic acid) has been studied in mixtures of 0.002N HCI and a series of aliphatic alcohols. The behavior found previously with ethanol is shown to apply in the case of admixture with methanol, n‐propanol, and 1,2‐ethanediol. The intrinsic viscosity first drops to a minimum and then increases sharply to a maximum. With ethanol and n‐propanol the maximum is followed by another minimum and maximum. With methanol and 1,2‐ethanediol this effect is absent or much smaller. Methanol and 1,2‐ethanediol are equivalent, molecule for molecule, in their influence on the intrinsic viscosity. With ethanol and n‐propanol there are in addition one and two shoulders, respectively, in the passage from the first minimum to the first maximum. Good correlation of the data is obtained if alcohol concentration is plotted as the mole fraction of carbon atoms per OH group (in the alcohol). The first maximum in particular was shown to correspond to the point where the number of water molecules per alcohol in the solvent mixture equals the number of C atoms per hydroxyl in the alcohol. The shoulders and first minima were found to correspond to other simple ratios. This behavior reflects changes in alcohol–water structure. The maximum in the case of ethanol was found to be the most pronounced and ethanol seems to possess optimal properties from this point of view.
Conformation of poly(methacrylic acid) in alcohol–water mixtures. III. Dependence on molecular weight
Authors: Priel Z. , Silberberg A.
Published: April 2003

Poly(methacrylic acid) has been studied in 0.002N HCl–ethanol mixtures as a function of molecular weight. A different dependence on molecular weight is noted at different alcohol concentrations. Since the intrinsic viscosity passes through a series of extrema with changes in alcohol concentration, the dependence on molecular weight has been considered in two regions of alcohol concentration in particular. The region of the first minimum and the region of the second minimum (or overall maximum). In the region of the first minimum, intrinsic viscosity is proportional to M½, just as in 0.002N HCl. The Huggins coefficient k′ is large (ca. 60) but drops to about 10 when the molecular weight exceeds 320,000. In the region of the second minimum the dependence on molecular weight is complex. Intrinsic viscosity is proportional to molecular weight both at low and at high molecular weight and thus indicates freely draining structures. There is a conformational contraction, however, at molecular weight about 320,000 leading from one type of structure to the other. The structure at higher molecular weight may involve a specially strong bond between specifically grouped segments in the chain. The positions of the extrema along the alcohol concentration axis are not molecular weight dependent, particularly above 320,000. Results available for molecular weight dependence in methanol agree well with this picture. The present results confirm prediction inherent in the model of Silberberg and Priel and Silberberg.
Dielectric relaxation in ethylene–methacrylic acid copolymers and their salts
Authors: Phillips P. J. , Macknight W. J.
Published: April 2003

Dielectric relaxation data have been obtained for two ethylene–methacrylic acid copolymers (containing about 4 mole‐% methacrylic acid units and about 8 mole‐% methacrylic acid units, respectively) and the lithium, sodium, and calcium salts prepared by partial neutralization of the polyacids. The frequency range employed was from 50 Hz to 10 kHz and the temperature range was from −130°C to 100°C. Attention is focused on three dielectric loss regions labeled β, β and α in order of increasing temperature. The β′ process (−10°C at 100 Hz in the salts only) correlates with a mechanical loss process previously reported and is attributed to microbrownian motion taking place in an amorphous hydrocarbon phase. The β′ process (20°C at 100 Hz) has also been observed mechanically and is attributed to the same mechanism as the β process. The higher temperature of this relaxation compared to the β relaxation is attributed to the presence of acid groups which form crosslinks composed of interchain hydrogen bonds. The α process (>50°C at 100 Hz in the salts only) correlates with dielectric and NMR data previously reported for a sodium salt and is assigned to motions within ionic domains formed by the clustering of salt groups.
NMR study of molecular motion in oriented long‐chain alkanes. I. Theoretical part
Authors: Olf H. G. , Peterlin A.
Published: April 2003

Several molecular mechanisms, proposed in the literature for the low‐ and high‐temperature relaxation processes in linear polyethylene and commonly referred to as γ and α processes, are examined, and their effect on the second moment of the broad line NMR absorption is predicted quantitatively. The following models for the α process are discussed: rotational oscillation of the long chain molecules around their axes, general two‐site models where the chain performs thermally activated rotational jumps through an angle τ between two equilibrium positions, a particular two‐site model (τ = 180°) denoted as flip‐flop motion, and the kink model. For the γ process, the following molecular mechanism are considered: the kink model, a vacancy with a chain end, the crankshaft mechanism. The decrease of the second moment caused by these motions is considered. Characteristic differences between the motional models are predicted with respect to the anisotropy of the decrease in second moment in a uniaxially oriented sample and/or the magnitude of the overall decrease. These differences allow an experimental distinction between the different models.
NMR study of molecular motion in oriented long‐chain alkanes. II. Oriented mats of polyethylene single crystals
Authors: Olf H. G. , Peterlin A.
Published: April 2003

Measurements of the NMR second moment of a uniaxially oriented sample of polyethylene single crystals in the range of temperatures from −196°C to 130°C and its dependence on the alignment angle γ between the orientation axis (preferential direction of the molecular chains) and the NMR magnetic field are presented. The experimental results are discussed mainly with respect to the high temperature relaxation, called the α process, in polyethylene. They are compared to theoretical predictions made for a number of mechanisms of molecular motion in Part I of this work. Only one of the mechanisms considered is found to be in quantitative agreement with experiment, the mechanism here referred to as flip‐flop motion. This consists of thermally activated rotational jumps of the crystalline chain segment between folds around its axis between two equilibrium sites in the lattice. Each rotational jump through 180° is accompanied by a shift of the molecule along its axis by one CH2 group. The discussion of the low‐temperature relaxation of polyethylene, the γ process, is based partly on the above measurements and partly on measurements of second moments for unoriented polyethylene samples varying widely in morphology and noncrystalline content. The decrease of the second moment observed with these samples between −196°C and 20°C is taken as a measure of the intensity of the γ process. A linear correlation is found between the decrease in the second moment, designated ΔS, and the noncrystalline content, 1 − αm; this can be represented by ΔS = 1.4 + 22.1(1 − αm). It is shown that neither the crankshaft mechanism not the kink mechanism is able to account quantitatively for this result. The model of a chain end moving in a vacancy fails to adequately describe the angle dependence of ΔS in oriented polyethylene single crystals. The “sandwich model” of a polyethylene single crystal, in which the crystalline core is covered by noncrystalline surface layers, is in better agreement with observations.
Phase‐distribution chromatography (PDC) of polystyrene
Authors: Casper R. H. , Schulz G. V.
Published: April 2003

A chromatographic technique is described where the stationary phase is a layer of a very high molecular polystyrene fraction (M = 107) on glass beads (ballotines). The mobile phase is cyclohexane passing the column at a constant temperature below the theta‐temperature. A polystyrene sample of sufficiently low molecular weight (M ≤ 106) injected as a small plug at the top of the column is fractionated because the distribution between the mobile and the stationary phase depends on the molecular weight. Since the large molecules preferentially remain in the stationary phase, the smaller molecules leave the column first. The fractionation effect is inverse to that found in GPC experiments. The separation efficiency is rather good and can be described by a simple thermodynamic theory.
Internal motion in organosilicon polymers. II. Dimethylpolysilazanes crosslinked through silicon
Authors: Model F. S. , Rochow E. G.
Published: April 2003

An investigation of the internal motion in organosilicon polymers by wideline nuclear magnetic resonance has been extended to a pair of dimethylpolysilazanes crosslinked through trifunctional silicon. The data suggest that there is considerable internal motion in all silazanes at 77°K. Evidence is presented for the presence of C3 rotation of the methyl groups, as well as rotation or torsional oscillation of the Si(CH3)2 groups about the polymer backbone. Upon warming the NMR line is seen to narrow, and this is associated with the onset of additional motion, including chain translation and chain flexing or bending. Crosslinking through silicon increases the barrier to chain translation while decreasing the barrier to chain flexing or bending.
Scattering of light by disordered spherulites
Authors: Stein R. S. , Chu W.
Published: April 2003

The scattering of light by a two‐dimensional spherulite of radius R is calculated when there is disorder of optic axis orientation with respect to the radius. Special cases are considered when (1) the disorder occurs in the radial direction only, (2) the disorder occurs in the angular direction only, (3) there is combined radial and angular disorder, and (4) the optic axis makes a constant angle with the radius but there is disorder in the twist angle about the axis. In all of these calculations, a correlation function for disorder is defined and the scattering pattern depends on the ratio of the associated correlation distance to the size of the spherulite. With decreasing correlation distance, the azimuthal dependence of the scattering becomes less and there is a change in the variation of scattered intensity with scattering angles in a manner dependent upon the type of disorder.
ESR and electrical conduction in polypropiolamide
Authors: Michel R. E. , Chapman F. W.
Published: April 2003

ESR and electrical conductivity measurements have been made on a recently prepared polymer, polypropiolamide. The polymer was obtained as a fine powder which exhibited a nearly Lorentzian line with a width between derivative maxima of 5.2 ± 0.1 gauss and a g value of 2.0036 ± 0.0005. The signal intensity increased with increasing molecular weight. The signal was retained in a dilute solution in formic acid with a slight narrowing of the line. Permanent changes were produced in the spectra at room temperature by heat treatments of the polymer at temperatures up to 800°K. The changes were similar for samples sealed in tubes containing air, dry nitrogen gas and a vacuum of 3 × 10−5 mm of Hg. Spectra obtained at temperatures up to 500°K showed no dependence on the presence or absence of oxygen in the ambient atmosphere. The deresistance of pressed pellets of the polymer was measured in the temperature range 450°K to 525°K, and the results were described by the relation R = R0cE/kT. The activation energy E had a value of 1.2 ± 0.2 ev and the resistivity at 500°K was approximately 1013 ohm‐em. The ESR signal is attributed to an intrinsic property of the polymer which is associated with a conjugated bond system along the polymer backbone. Neither the activation energy nor the magnitude of the resistivity suggest that the delocalized electrons associated with the conjugated bond system have produced unusual electrical characteristics in the polymer.
Methods of description of orientation in polymers
Authors: Roe Ryong‐Joon
Published: April 2003

The nonrandom orientational distribution of structural units, such as crystallites and chain segments, prevailing in an anisotropic bulk polymer sample can be represented fully by an orientation distribution function. Measurements of fluorescence polarization and wide‐line NMR are, in principle, capable of yielding information on the moments of the distribution function up to the fourth order. This work presents the method of analysis required to determine these moments. For this purpose, the distribution function is expanded in a series of generalized spherical harmonies. The method is an extension of a similar technique previously proposed for analysis of x‐ray diffraction data for determination of a complete crystallite orientation distribution function.
Study of molecular orientation in poly(ethylene terephthalate) fibers by fluorescence polarization
Authors: McGraw Gary E.
Published: April 2003

Molecular orientation in poly(ethylene terephthalate) (PET) fibers was studied by polarized fluorescence. The observed amorphous orientation of the spun as fiber was not random but uniaxial along the fiber axis. This orientation increased with draw ratio up to about 2 and then remained fairly constant. The amorphous regions of PET fibers were disoriented when the fibers were heated while unconstrained. The fluorescence data obtained were correlated with shrinkage measurements. Fluorescence data indicated that spin drawing had more effect upon orientation than subsequent drawing of the fiber, whereas birefringence data indicated the opposite. The reason for this behavior is discussed.
Dependence on strain rate of the nucleation of cracks in polystyrene at 293°K
Authors: Murray J. , Hull D.
Published: April 2003

The processes associated with the deformation and fracture of polystyrene tested in uniaxial tension have been studied over a range of strain rates from 1.4 × 10−2 to 4.3 × 10−7 sec−1 and at constant stresses between 4.1 and 2.9 kg/mm2. The effect of strain rate on the surface craze distribution prior to fracture, the fracture stress, the mechanism of nucleation of cracks, and the nature of fracture surfaces associated with slow and fast crack propagation have been determined. The changes in fracture surface appearance have been studied using optical and stereoscan microscopy. The observations are consistent with the model presented in a previous paper. Fracture is preceded by craze formation, cavitation in the craze, coalescence of cavities to form large planar cavities which propagate slowly until a critical stage is reached at which fast crack propagation occurs. The effect of changes of strain rate and material variables on these processes is discussed.
Studies on biaxial stretching of polypropylene film. IV. Overall orientation during one‐step biaxial stretching and its application to the estimation of the principal refractive indices of isotactic polypropylene
Authors: Masuko Toru , Tanaka Hiroshi , Okajima Saburo
Published: April 2003

Polypropylene film was biaxially stretched in one step in air at 140°C or 152°C, and the deformation was studied optically. A linear relation held between Δnss and vA−½ for vA > 10, at both temperatures, where Δnss is the birefringence with respect to the normal to the film and vA is the degree of stretching expressed as the factor by which the area of the film is increased. Extrapolation of data in this linear region yielded a value of 20 × 10−3 for −Δnss at infinite vA. Since it is presumed that the polypropylene molecules lie completely parallel to the film surface when the film is stretched infinitely, −Δnss at vA−½ = 0 must be just half Δn°, the intrinsic birefringence in the case of completely parallel orientation. Thus, Δn° must be 40 × 10−3. This value was obtained experimentally in uniaxial stretching when the birefringence with respect to the direction of drawing was extrapolated to infinite extension. Similar relations held between np, the average of the refractive indices in the two stretching directions, and vA, and between nss, the index normal to the film, and vA. By similar extrapolations, (1/2)(n′γ + n′β) and n′β = n*α′ were estimated, and thence nα′ was obtained. Here, n′α and n′β are the refractive indices along the c axis (molecular chain axis) and b axis. All these optical parameters refer to a density of 0.900 g/cm3. Hence by applying a density correction to those values, the principal refractive indices and the intrinsic birefringence of polypropylene crystal were evaluated as follows: nα = 1.5522, nβ = n*α = 1.5106 and Δnc° = 4.16 × 10−3, where n*α is the refractive index prependicular to the b and c axes of the crystal.
Superposition of dynamic mechanical properties in the glassy state
Authors: Cuddihy Edward F. , Moacanin Jovan
Published: April 2003

Superposition of the loss tangent curves could be achieved for the β‐transition of a series of homologous epoxy resins. It was found that both a vertical and horizontal shift were necessary to achieve superposition when the curves were plotted as the logarithm of the loss tangent versus reciprocal absolute temperature. Resins from the diglycidyl ether of bisphenol A (DGEBA) were prepared with five different curing agents and their loss tangent curves measured on a free‐oscillation torsion pendulum (ca. 1 cps). The β transition is caused by DGEBA, which was found via molecular models to contain a mobile group. The intensity of the loss for three of the resins was found to be proportional to the concentration of DGEBA, molecular models revealing that no additional mobile groups were introduced by these curatives. The remaining two curing agents introduced mobile groups into their systems and for these two, no separate transitions were identified but the intensity of the DGEBA β transition was increased. This may be caused by a coupling of the DGEBA mobile groups through the flexibility of the curative‐introduced mobile groups.
Measurement of the optical activity of some stereoregular vinyl polymers in the crystalline state
Authors: Bonsignori O. , Lorenzi G. P.
Published: April 2003

The general problems presented by the determination of the optical activity of polymers in the crystalline state are considered. The necessity of using unoriented samples, if the polarimetric data are to be compared with analogous data measured in solution, is emphasized. The optical activity in the crystalline state of a number of stereoregular vinyl polymers has been measured by employing either suspensions of fine powders or thin plates with no detectable orientation. The results of optical rotatory dispersion studies in the crystalline state suggest that, at least in the case of the poly‐α‐olefins investigated, the same chromophores are responsible for the optical activity in the crystalline state and in solution.
Transcrystallinity and x‐ray diffraction in trans‐1,4‐polyisoprene
Authors: Lovering Edward G.
Published: April 2003

Middle range fractions of mimusops balata, a natural trans‐1,4‐polyisoprene, exhibit transcrystallinity when crystallized in the 35–40°C range. The presence of transcrystallinity was established by x‐ray diffraction and optical microscopy. Diffraction peak intensities change due to transcrystallinity, suggesting x‐rays be used to detect transcrystallinity and that caution be exercised in using x‐ray diffraction techniques to determine the phases present in bulk material and in calculating the degree of crystallinity. The tendency toward transcrystallinity may depend upon molecular weight.
Mechanical and optical properties of an anelastic polymer at intermediate strain rates and large strains
Authors: Weiss R. T. , Goldsmith Werner , Chase K.
Published: April 2003

The mechanical and optical properties of a polyester–styrene copolymer have been investigated by means of drop tests at strain rates from 38 to 113 sec−1 for strains less than 50%. Over this range of rates, the optical behavior was found to be linear with strain and independent of strain rate while the elastic–plastic mechanical behavior was only slightly dependent on strain rate. Comparison with the results of similar experiments at lower strain rates achieved by means of an Instron tester reveals that both mechanical and optical properties vary significantly with strain rate. The variation of flow stress with strain rate was found to obey a power law.
A theory of the influence of branching on the crystallinity of bulk polyethylene
Authors: Des Cloizeaux J.
Published: April 2003

The temperature dependence of the crystallinity of bulk polyethylene is calculated in terms of branching (methyl or ethyl side groups on the chain). In the model, the chains are approximately parallel and they pass through alternating amorphous and crystalline layers forming a periodic structure. The crystalinity and the thicknesses of the layers are determined by minimization of the free energy. The theory shows that the temperature at which the polymer begins to crystallize is lower than the melting point of pure polyethylene and that the thicknesses of the layers becomes smaller as the temperature decreases.
Raman spectra of poly(ethylene glycols) in solution
Authors: Koenig J. L. , Angood A. C.
Published: April 2003

Raman spectra have been obtained from poly(ethylene glycol) (PEG) in the solid and molten phases and in aqueous and chloroform solutions. Several new lines are observed or resolved in the Raman spectrum of the solid state as a result of using a high‐power argon‐ion laser as a source. The Raman spectra of the molten polymer and the chloroform solutions are indicative of a disordered structure, since additional Raman lines appear as a result of the additional rotational isomers. The Raman spectrum of the aqueous solution shows that considerably less structural change occurs upon dissolution in water.
Gel‐permeation chromatography: Examination of universal calibration procedures for polydimethylsiloxane in a poor solvent
Authors: Dawkins J. V. , Maddock J. W. , Coupe D.
Published: April 2003

Various procedures for universal calibration in gel‐permeation chromatography with polystyrene gels are examined for polystyrene and polydimethylsiloxane fractions. For o‐dichlorobenzene at 138°C, experimental intrinsic viscosity–molecular weight data show that the Mark‐Houwink exponents are 0.70 and 0.57 for polystyrene and polydimethylsiloxane, respectively. In principle, this difference permits a distinction between the various polymer size parameters proposed for universal calibration. An interpretation of the experimental polydimethylsiloxane calibration for o‐dichlorobenzene at 138°C requires a consideration of errors in average molecular weights and errors arising from the use of average molecular weight instead of peak molecular weight. When calibration procedures utilizing hydrodynamic volume and unperturbed dimensions are examined, the difference between them is comparable with experimental error. If the Flory‐Fox viscosity expression is employed, the perturbed end‐to‐end distance (or radius of gyration) and the hydrodynamic volume give equivalent universal calibrations. The experimental data are sufficiently accurate to show that the perturbed dimension determined with the Ptitsyn‐Eizner relation does not give an adequate universal calibration.
Thermodynamic study of deformation of crosslinked ethylene–propylene copolymer
Authors: Romanov A. , Pollák V.
Published: April 2003

The thermodynamics of deformation of ethylene–propylene copolymer crosslinked by dicumyl peroxide with addition of sulfur or maleic anhydride has been studied. Both the entropic (fS) and energetic (fU) components have been studied at elongations α up to 65%. It was found that the course of fU/f, where f is equilibrium stress, in dependence on α agrees with the determined difference in both chemical and physical bonds.
A light‐scattering photometer for use at elevated pressures
Authors: Schulz G. V. , Lechner M.
Published: April 2003

A new light scattering photometer has been designed in order to perform light‐scattering measurements at various temperatures and under pressures of 1–1000 atm. Since the scattering angle is constant (90°C), the dimensions of the dissolved molecules are determined by measuring the intensity at different wavelengths. The method of measurement, the calibration of the instrument, and the treatment of data are described. By a series of test measurements on polystyrene in trans‐decalin solutions it is shown that one obtains reliable results and finds considerable effects of pressure on the radius of gyration and the fundamental thermodynamic properties of the system.
Effect of long‐chain branching on the relation between steady‐flow and dynamic viscosity of polyethylene melts
Authors: Shroff Ramesh N. , Shida Mitsuzo
Published: April 2003

The steady‐state viscosity η, the dynamic viscosity η′, and the storage modulus G′ of several high‐density and low‐density polyethylene melts were investigated by using the Instron rheometer and the Weissenberg rheogoniometer. The theoretical relation between the two viscosities as proposed earlier is:\documentclass{article}\pagestyle{empty}\begin{document}$ \eta \left( {\dot \gamma } \right){\rm } = {\rm }\int {H\left( {\ln {\rm }\tau } \right)} {\rm }h\left( \theta \right)g\left( \theta \right)^{{\raise0.7ex\hbox{$3$} \!\mathord{\left/ {\vphantom {3 2}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{$2$}}} \tau {\rm }d{\rm }\ln {\rm }\tau $\end{document}, where \documentclass{article}\pagestyle{empty}\begin{document}$ \theta {\rm } = {\rm }{{\dot \gamma \tau } \mathord{\left/ {\vphantom {{\dot \gamma \tau } 2}} \right. \kern-\nulldelimiterspace} 2} $\end{document}; \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \gamma } $\end{document} is the shear rate, H is the relaxation spectrum, τ is the relaxation time, \documentclass{article}\pagestyle{empty}\begin{document}$ g\left( \theta \right){\rm } = {\rm }\left( {{2 \mathord{\left/ {\vphantom {2 \pi }} \right. \kern-\nulldelimiterspace} \pi }} \right)\left[ {\cot ^{ - 1} \theta {\rm } + {\rm }{\theta \mathord{\left/ {\vphantom {\theta {\left( {1 + \theta ^2 } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 + \theta ^2 } \right)}}} \right] $\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$ h\left( \theta \right){\rm } = {\rm }\left( {{2 \mathord{\left/ {\vphantom {2 \pi }} \right. \kern-\nulldelimiterspace} \pi }} \right)\left[ {\cot ^{ - 1} \theta {\rm } + {\rm }{{\theta \left( {1{\rm } - {\rm }\theta ^2 } \right)} \mathord{\left/ {\vphantom {{\theta \left( {1{\rm } - {\rm }\theta ^2 } \right)} {\left( {1{\rm } + {\rm }\theta ^2 } \right)^2 }}} \right. \kern-\nulldelimiterspace} {\left( {1{\rm } + {\rm }\theta ^2 } \right)^2 }}} \right] $\end{document}. Good agreement between the experimental and calculated values was obtained, without any coordinate shift, for high‐density polyethylenes as well as for a low density sample with low nw, the weight‐average number of branch points per molecule. The correlation, however, was poor with low‐density samples with large values of the long‐chain branching index nw. This lack of coordination can be related to nw. The empirical relation of Cox and Merz failed in a similar way.
Fatigue as monitored by the torsion pendulum
Authors: Schrager M.
Published: April 2003

This paper describes the use of a new air‐bearing torsion pendulum as a nondestructive monitor of torsional fatigue in epoxy resin castings. Results indicate that both G′ and tan δ undergo significant changes as fatigue is induced in the specimen. In those specimens that have not been sufficiently post‐cured, cyclic fatiguing induces further crosslinking. However, this is accompanied by a competing reaction of crack formation and propagation leading ultimately to failure.
A theory of die‐swell
Authors: Tanner R. I.
Published: April 2003

An elastic‐fluid theory of die‐swell for long dies is presented. The theory predicts a swelling ratio De/d asymptotically proportional, for large values of swelling, to the cube root of the recoverable shear evaluated at the die wall. Here the recoverable shear is defined to be half the ratio (first normal stress difference/shear stress). Excellent agreement is shown between predicted De/d and measured De/d for experiments on melts and solutions for which adequate data are available.
Numerical solutions of the lamm equation. VI. Effects of hydrostatic pressure on velocity sedimentation of two‐component systems
Authors: Dishon Menachem , Weiss George H. , Yphantis David A.
Published: April 2003

We present the results of accurate numerical solutions to the Lamm equation, including the effects of hydrostatic pressure, in order to check methods for the estimation of parameters based on a diffusionless theory. Some estimates of boundary spreading due to diffusion are given. The results indicate that parameter estimates based on the position of the maximum concentration gradient lead to fairly accurate results.
NMR spectrum of poly(propene sulfide)
Authors: Ivin K. J. , Navrátil M.
Published: April 2003

The 100 MHz spectra of polymers of propene sulfide and propene‐2‐d1 sulfide have been determined in CDCl3, CCl4, and C6D6. In the deuterated polymer the main‐chain protons give rise to two overlapping AB quartets in which the two pairs of upfield B lines are coincident and the two pairs of downfield A lines are resolved. With CdCO3 as polymerization catalyst the downfield quartet is twice as strong as the upfield quartet. The former is ascribed to an isotactic dyad:

magnified image
and the latter to a syndiotactic dyad:
magnified image
Other catalysts (ZnCO3, CuCO3, SiO2/Al2O3, Na) produce an essentially atactic structure. The values τA = 7.125, τA′ = 7.155, τB = 7.45, JAB = −12.9 Hz, derived from the spectrum of the deuterated polymer (in CCl4) were used to obtain the following values from the spectrum of the undeuterated polymer (tertiary proton = Hc): τC = 7.131, JBC = 10.0 Hz, JCA = 4.1 Hz. The magnitudes of the vicinal coupling constants indicate a preferred trans conformation for the mainchain CC bond. τA, τB, and τC are somewhat dependent on solvent; τCH3 = 8.63, independent of solvent, and JCH3, HC = 6.2 Hz.
Mechanochemische aufpfropfung von polymeren an der oberfläche von füllstoffen als methode ihrer aktivierung
Authors: Taubman A. B. , Yanova L. P. , Blyskosh G. S.
Published: April 2003

Peculiarities in the process of the mechanochemical grafting of polystyrene on freshly formed surface of particles of calcium carbonate on grinding in styrene were studied. It was established that the formation of homopolymer in this process is the result of rupture of individual chains of macromolecules, which are bound to the surface. If a small quantity of water is present in the monomer, the grafting is enhanced, due to an increase of the specific surface of the powder as a result of the reduction of its durability due to adsorption (Rehbinder effect). The grafting of polystyrene makes the solid surface hydrophobic and increases the activity of calcium carbonate as a filler for rubber.
Effects of nonionic surfactants on seeded polymerizations
Authors: Napper D. H. , Netschey A. , Alexander A. E.
Published: April 2003

The rate of polymerization of vinyl acetate in systems containing poly(vinyl acetate) seed particles was investigated. A significant reduction in rate was observed when nonionic surfactants were adsorbed onto the particles prior to polymerization. The molecular weight of the poly(ethylene oxide) moieties in the surfactants was varied over two decades. The diminution in rate was relatively insensitive to this molecular weight variation, at least for higher molecular weights (≥20,000). A minimum in the rate was apparent at lower molecular weights. No new nucleation was detectable in any of these systems. The results have been interpreted in terms of two properties of the dissolved poly(ethylene oxide) layers through which the oligomeric free radicals must diffuse in order to reach the major loci of polymerization inside the particles. These two properties, the effective thickness of the dissolved poly(ethylene oxide) layer and its average microscopic viscosity, are expected theoretically to be approximately self‐compensating when the molecular weight is varied.