bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fourier transform infrared study of uniaxially oriented atactic polystyrene
Authors: Jasse Bruno , Koenig Jack L. 
Published: April 2003

AbstractInfrared measurements of the dichroic ratio of atactic polystyrene absorption bands provide a valuable method of determination of the overall orientation of chains as well as the particular orientation of the trans conformational segments. The orientation process produces the alignment of the chains as well as an increase in the amount of trans conformational segments. A linear relationship is observed between birefringence and dichroic ratio for the absorption bands characteristic of overall orientation. A value of 35° ± 3° is obtained for the angle between the normal to the plane of the benzene ring and the chain axis from both infrared and birefringence determinations.
Fourier‐transform infrared studies of polymer blends. II. Poly(ϵ‐caprolactone)–poly(vinyl chloride) system
Authors: Coleman M. M. , Zarian J. 
Published: April 2003

AbstractFourier‐transform infrared (FTIR) studies of the poly(ϵ‐caprolactone) (PCL)–poly(vinyl chloride) (PVC) blend system are presented. The results indicate that there are specific interactions between the PCL and PVC in both the molten and solid states which could be responsible for the apparent compatibility of the amorphous component of these blends. Additionally, FTIR difference spectra are presented to illustrate the potential of this technique for following the kinetics of crystallinity in polymer blend systems.
Dielectric relaxation of polydimethylsiloxane
Authors: Adachi Hiroshi , Adachi Keiichiro , Ishida Yoichi , Kotaka Tadao 
Published: April 2003

AbstractDielectric studies were performed on crystallized and amorphous polydimethylsiloxane which had been characterized by differential thermal analysis and polarized light microscopy. The crystallized specimen displayed one relaxation near 160 K at 1 kHz while the amorphous specimen showed absorption peaks at 155 and 165 K. For the latter material the high‐temperature peak was not due to a true relaxation but resulted from crystal nucleation at 160 K and the subsequent growth of spherulites. The low‐temperature peak at 155 K resulted from the relaxation associated with the glass transition. A sharp decrease of dielectric constant was observed for both specimens at the melting point (235 K). For the dielectric relaxation associated with the glass transition in crystallized specimens, the values of the dispersion amplitude, the apparent activation energy at 160 K, and the half‐width of the absorption curve are 0.43 and 29 kcal/mole, and 5.6 decades, respectively, which are in marked contrast to the corresponding values of 0.82, 18, and 2.2 for amorphous specimens.
Geometrical effects in the measurements of mechanical properties in parallel superposed flows
Authors: Powell R. L. , Schwarz W. H. 
Published: April 2003

AbstractThe shear‐dependent complex viscosity η*12, which governs the linear time‐dependent stresses in a viscoelastic fluid undergoing infinitesimal shearing oscillations in‐line with a viscometric motion, has been investigated. Formulas relating η*12 to measured quantities have been derived for the cone‐and‐plate and parallel‐plate geometries. In the former case, the formula has the same form as that found when there is no steady shearing present. For the parallel‐plate geometry, the formula is different because of the radial variation in the viscometric shear rate. In order to determine the empirical significance of this formula, η*12 data were obtained for two fluids, NBS nonlinear sample No. 1 and a 4.3 g/dl aqueous polyethylene oxide (molecular weight, 5 X 106) solution using a Weissenberg rheogoniometer Model R‐18. Data were acquired and analyzed using a minicomputer on‐line with the rheogoniometer. The obtained data indicate that good agreement between the η*12 measured using the two geometries is obtained only if the derived formulas are used. Also, it is shown that theoretical results of simple‐fluid theory are valid for these data.
An examination of the crystal structures present in nylon‐6 fibers
Authors: Stepaniak R. F. , Garton A. , Carlsson D. J. , Wiles D. M. 
Published: April 2003

AbstractThe variety of wide‐angle x‐ray scattering (WAXS) patterns exhibited by nylon‐6 fibers with different fabrication histories is rationalized using a model comprising three limiting structures, viz., an α, a γ, and a pleated α structure. The γ and pleated α structures both have a single broad reflection in the range 2θ = 19° −25°, but differ in their annealing behavior. At 205° (in vacuo), the pleated α structure converts to the normal α structure by removal of the pleats, without breaking any hydrogen bonds. The γ structure, however, remains unchanged under this annealing condition since it is necessary to break all the hydrogen bonding in the structure to convert it to the α form. Different fabrication routes produce fibers which resemble the three ideal structures to varying extents. Fibers extruded at low speeds (and hence low spinline tension) resemble a mixed conventional α/pleated α structure with only a small γ component. Increasing the take‐up speed (and hence the spinline tension) of the as‐spun fiber, or in‐line drawing of the low orientation fiber (without prior storage), increases the γ content. If drawing of the low orientation fiber takes place after several hours storage (off‐line drawing), a largely α structure is produced. The intensity of the 020 reflection in the γ structure is shown to be very dependent on the degree of crystalline orientation in the sample.
Electron microscopic investigation of the molecular mechanism of plastic deformation of polyethylene and isotactic polystyrene crystals
Authors: Petermann J. , Kluge W. , Gleiter H. 
Published: April 2003

AbstractThe molecular process involved in the plastic deformation of crystals of linear polyethylene and isotactic polystyrene by necking was investigated by transmission electron microscopy (TEM). The results for the draw ratio, the height, and the shape of the neck and the molecular structure of the deformed material suggest that plastic deformation occurs basically by the unfolding and bending of the molecules in a deformation region only a few nm wide. The observations are at variance with deformation models involving complete unfolding of the molecules or the breaking off of folded‐chain blocks and the incorporation of these blocks into the deformed material.
Properties of amorphous and crystallizable hydrocarbon polymers. I. Melt rheology of fractions of linear polyethylene
Authors: Raju V. R. , Smith G. G. , Marin G. , Knox J. R. , Graessley W. W. 
Published: April 2003

AbstractThe dynamic moduli G′(ω) and G″(ω) for two groups of linear polyethylene fractions (reported Mw/Mn < 1.2) were measured in the melt state using the eccentric rotating disk method. Values of zero shear viscosity η0 were obtained and compared with published results on similar fractions. Molecular weight data were converted to a common basis through intrinsic viscosities in trichlorobenzene (TCB) at 135°C. With recent data on Mw (light scattering) vs. [η]TCB, for linear polyethylene, the relationship at 190°C, η0 = 3.40 × 10−14(Mw)3.60, was obtained. The flow activation energy Ea was 6.4 kcal (T = 140–195°C). The plateau modulus G at 190°C was determined from the area under the loss modulus peak in one high‐molecular‐weight sample. The value obtained, G = 1.58 × 107 dyn/cm2, corresponds to an apparent molecular weight between entanglements of 1850. The storage compliance J′(ω) becomes anomalously large at low frequencies. The recoverable compliance J could not be determined for any of the fractions.
Properties of amorphous and crystallizable hydrocarbon polymers. II. Rheology of linear and star‐branched polybutadiene
Authors: Rochefort W. E. , Smith G. G. , Rachapudy H. , Raju V. R. , Graessley W. W. 
Published: April 2003

AbstractSome results are reported on the linear viscoelastic properties of polybutadienes with narrow‐molecular‐weight distributions. The zero shear viscosity η0 varies as M3.4 in the linear samples, and viscosity enhancement is found in star‐branched samples with long arms, in good agreement with results reported earlier by Kraus and Gruver. The temperature coefficient of viscosity appears to be slightly larger in stars when the arms become long. The steady state recoverable compliance J is 2.1 × 10 −7 cm2/dyn in linear samples of high molecular weight, but it increases to values as much as 10 times larger in the stars. The plateau modulus G, obtained from a composite curve for the linear samples, is 1.32 × 107 dyn/cm2. The terminal relaxation spectrum of the stars is too broad to allow an evaluation of plateau modulus.
Properties of amorphous and crystallizable hydrocarbon polymers. III. Studies of the hydrogenation of polybutadiene
Authors: Rachapudy H. , Smith G. G. , Raju V. R. , Graessley W. W. 
Published: April 2003

AbstractThree methods for hydrogenating anionically prepared polybutadiene (containing about 8% vinyl double bonds) were investigated: homogeneous catalysis (alkylated transition metal salts), heterogeneous catalysis (nickel on kieselguhr; paladium on calcium carbonate), and stoichiometric reaction with in situ generated diimide. The products were characterized by intrinsic viscosity, gel permeation chromatography, infrared spectroscopy, and melt viscosity. Only the heterogeneous catalysts were found to yield completely hydrogenated products without incorporation of foreign groups and without significant change in the large‐scale molecular structure of the chain. The 195°C melt viscosity of linear polybutadiene hydrogenated with heterogeneous catalysts is virtually identical with that of linear polyethylene with the same intrinsic viscosity in trichlorobenzene at 135°C. The solid state properties of hydrogenated polybutadiene, containing about 20 ethyl branches/1000 main chain atoms, closely resemble those of commercial branched polyethylene.
Effect of hydrogen bonding on the anisotropy of the hydrostatic compressibility of polymer crystals
Authors: Ito T. , Hirata T. , Fujita S. 
Published: April 2003

AbstractCorrelations between the crystal structures of polymers consisting of the hydrogen‐bonded molecular sheets and anisotropy of the linear compressibility (K0) of the crystal were studied at 20°C under hydrostatic pressures up to 6 kbar. For nylon‐6, it was found that K0 is more than four times larger in the direction normal to the hydrogen‐bonded sheet than in the parallel direction. The inversion of the sheet direction involved in the α → γ transition of nylon‐6 was clearly reflected in the anisotropy of the linear compressibility. For atactic poly(vinyl alcohol), K0 in the c‐axis direction was 1.6 times larger than that in the a‐axis direction, which is consistent with a structure model with the hydrogen‐bonded sheet parallel to the a‐axis. Theoretical calculations by Tashiro et al. indicate, however, the anisotropy does not necessarily correspond to the sheet structure when the direction of the hydrogen bonds strongly deviates from the plane of the sheet.
Studies of orientation and structure of crazed matter in polystyrene. II. Electron diffraction measurements
Authors: Brown H. R. 
Published: April 2003

AbstractThe technique of selected area electron diffraction in the transmission electron microscope is used to examine the degree of orientation of crazed matter. The theories of electron and x‐ray diffraction are compared and it is shown experimentally, by comparison with published x‐ray results, that it is possible to obtain electron diffraction patterns from uncrazed polystyrene that are reasonably free of both radiation damage and multiple scattering problems. Electron diffraction patterns from crazes show a considerable degree of orientation but otherwise are very similar to those from uncrazed material, showing that crazes have no structure different from that of bulk material. Diffraction patterns are also obtained from thin films drawn to draw ratios of 4.5 and 6 at 90°C. These agree well with published x‐ray results from oriented polystyrene but show less anisotropy than the craze diffraction patterns.
Hydrogen bonding effects on the skeletal optical and the longitudinal acoustical modes in long chain molecules and polymers
Authors: Rabolt John F. 
Published: April 2003

AbstractRaman spectra of stearyl alcohol (n‐C18H37OH) indicate that vibrational bands in both the skeletal optical (1000‐1200 cm−1) and longitudinal acoustical (0–500 cm−1) regions are considerably perturbed by intermolecular hydrogen bonding. The zone interior skeletal stretching mode reflecting phonon dispersion in the v4 branch of the infinite polyethylene chain is found at 1105 cm−1, approximately 20 cm−1 higher than in the corresponding n‐alkane. Similarly the single nodal longitudinal acoustical mode (LAM‐1) is found shifted by 12 cm−1 to higher frequency when the expected “mass effect” produced by the OH group is considered. This shift is further increased to 16 cm−1 at −100°C indicating a further perturbation on this accordion mode due to the increased strength of the hydrogen bond at the low temperatures. The positions of the higher multinodal vibrations, LAM‐3 and LAM‐5, are also perturbed by the hydrogen bond but by differing amounts. The observation of a low‐frequency Raman‐active LAM in polytetrahydrofuran [(CH2CH2CH2CH2O)n] is discussed in conjunction with the expected effects of hydrogen bonding at the lamellar surface.
Effect of nonhomogeneous shear rates on the flow‐induced crystallization of flexible macromolecules
Authors: Silebi C. A. , McHugh A. J. 
Published: April 2003

AbstractSeveral observations are made regarding the role of nonhomogeneous shearing rates in the process of flow‐induced fibrillar crystallization from solution. The flow geometry chosen in the present analysis is that occurring in the annular region between two concentric cylinders. Computational evaluation and discussion of the effect of stress‐induced diffusion is presented in terms of the elastic dumbbell model. Significant variations in concentrations in the annular region are predicted at full development. Estimates of the dynamics of development of these profiles indicate that the length to capillary radii for full development depends upon the molecular weight of the polymer and the relative dimensions of the concentric cylinders. These results indicate the important role of stress‐induced diffusion in the process of thickening of fibrillar crystals.
Dielectric relaxation in some polyacrylate solutions
Authors: Murthy V. R. K. , Kadaba P. K. , Bhagat P. K. 
Published: April 2003

AbstractThe dielectric constant ϵ′ and loss factor ϵ″ of poly(butyl acrylate), poly(butyl methacrylate), and poly(isobutyl methacrylate) solutions are reported in the frequency region of 1 kHz to 24.42 GHz at four different temperatures of 27, 40, 50, and 60°C. Cole–Cole plots are plotted to obtain the distribution parameter and relaxation time. The activation energies are evaluated assuming dielectric relaxation to be a rate process in these solutions. A possible relaxation mechanism is discussed.
Photon correlation spectroscopy of polystyrene near the glass–rubber relaxation
Authors: Lindsey C. P. , Patterson G. D. , Stevens J. R. 
Published: April 2003

AbstractPolarized Rayleigh scattering is studied near the glass‐rubber relaxation in atactic polystyrene using photon correlation spectroscopy. Average relaxation times determined from the data agree well with previous results obtained using depolarized Rayleigh scattering. The light scattering results follow the same trend observed by dielectric and mechanical relaxation studies, but the times for orientational relaxation are longer by approximately two orders of magnitude. Also, an extensive discussion of the experimental techniques necessary to use photon correlation spectroscopy of polymers near the glass‐rubber relaxation is presented.
Structure of diepoxide–diamine network polymers. I. Average network properties
Authors: Charlesworth John M. 
Published: April 2003

AbstractA study of some of the average chemical properties of a variety of diepoxide–diamine network polymers has been carried out. The weight fraction of sol, the quantity of unreacted epoxide in the sol, and the number‐average molecular weight of the sol have been measured for polymers prepared from both stoichiometric and nonstoichiometric ratios of diamine and diepoxide. Theoretical expressions for these quantities have been calculated using the methods recently developed by Macosko and Miller. These relationships were found to give close agreement with the experimental behavior.
Structure of diepoxide–diamine network polymers. II. Soluble chemical species
Authors: Charlesworth John M. 
Published: April 2003

AbstractGel permeation chromatography has been used to separate diepoxide–diamine oligomers, produced at a variety of stoichiometric ratios, into individual chemical species. Probability theory has been applied to calculate expressions for the amounts of each of these compounds and close agreement has been found with the experimental results. In conjunction with previous conclusions, this provides compelling evidence in favor of a purely random reaction mechanism, contrary to the inhomogeneous network‐forming mechanism suggested by other workers. The effect of adding an inert diluent prior to reaction has been investigated and it is evident that the fraction of intramolecularly formed bonds increases as the concentration of polymer decreases.
Studies on partially polymerized 2,4‐hexadiyn‐1,6‐bis(p‐toluenesulfonate)
Authors: Patel G. N. 
Published: April 2003

AbstractAn improved procedure for the synthesis of high‐purity 2,4‐hexadiyn‐1,6‐bis(p‐toluenesulfonate) (PTS) is described. The melting point of partially polymerized PTS increases monotonically with increasing polymer conversion (<12%). The increase in melting point is due to formation of a solid solution of unreacted monomer and polymer chains. The relation between the melting point and polymer conversion can be used for determination of polymer conversion. The low‐conversion (<12%) poly PTS is soluble in dimethylformamide. The solution is yellow (λmax ≃ 450 nm) and does not undergo a color change when the temperature is lowered or a nonsolvent is added. Gel permeation chromatography (GPC) studies show that the molecular weight distribution of poly PTS is very broad and does not change with increasing polymer conversion up to <12%. The degree of polymerization for the low‐conversion polyPTS is very low, about 20 repeat units. The G value for initiation centers (radicals) is about 2. The properties of the low‐conversion partially polymerized PTS are compared with the corresponding properties of poly(diacetylene diurethanes).
Rheological study of an aromatic polyamide‐hydrazide
Authors: Baird D. G. , Ciferri A. , Krigbaum W. R. , Salaris F. 
Published: April 2003

AbstractRheological and rheo‐optical data are reported for the poly(terephthalamide of p‐aminobenzhydrazide), X‐500, in dimethyl sulfoxide solutions in the concentration range 0.2 to 6.0 g/100 ml. The objective of these measurements is to seek evidence of shear‐induced isotropic → nematic phase transition. Three types of measurement, Couette, cone and plate, and capillary rheometer, all indicate that this system exhibits flow instabilities at high shear rates and concentrations. In this region both the viscosity and the primary normal stress difference decrease with time under shear. In the capillary rheometer the apparent viscosity is smaller for shorter capillaries and, for short capillaries, there is a range of shear rates in which plug flow and a coiled extrudate are observed. These instabilities may arise from the existence of a mixture of isotropic and nematic phases. At lower shear rates, where the flow behavior appears normal, the concentration dependence of the flow birefringence increases at a critical polymer concentration C This value is in reasonable accord with the concentration corresponding to the change of slope of logη (measured at low shear rate) vs. logCp. Both the latter measurements appear to be sensitive to the onset of the phenomenon, which may be due to a shear‐induced transition or the rheological effect of chain entanglements.
Thermal behavior of co[poly(ethylene terephthalate)‐p‐oxybenzoate]
Authors: Lader Harry J. , Krigbaum W. R. 
Published: April 2003

AbstractIn a previous investigation of a co[poly(ethylene terephthalate)‐p‐oxybenzoate] containing 30 mole % oxybenzoate units (referred to as T2/30), Krigbaum and Salaris identified the endotherm at tIII = 244°C as a nematic → isotropic transition. Subsequent investigation revealed that the tIII endotherm disappeared if the polymer is heated to the isotropic melt or dissolved and reprecipitated. The loss of the tIII transition might be due to molecular weight reduction, sequence randomization, or erroneous identification of the transition. Viscosity and high‐field NMR data eliminate the first two explanations. Annealing studies at temperatures higher than those of the earlier work demonstrate that the tIII transition, in fact, represents the melting of crystallites formed during a high‐temperature annealing operation. Moreover, we cannot determine the thermodynamic melting temperature of the copolymer from solid‐state annealing studies. Hence, the principal objective of the study of Krigbaum and Salaris, to compare the enthalpies and entropies of the nematic → isotropic and crystal → isotropic transitions, must be fulfilled in future work.
Statistical mechanical model of diffusion of complex penetrants in polymers. II. Applications
Authors: Pace R. J. , Datyner A. 
Published: April 2003

AbstractThe theory of Part I is applied to the diffusion of several aromatic diffusants in two “smooth chained” polymers: poly(ethylene terephthalate) (PET) and natural rubber. Modifications of the theory necessary to accommodate vinyl polymers are discussed and applied to benzene in PMA and PEA. In all cases the theory agrees satisfactorily with the experimental D(0,T) and D(c,T)/D(0,T) data, and the values of the disposable rg and Δ parameters are of the expected order. The limiting Arrhenius behavior of benzene in natural rubber appears to be correctly predicted. The cell model is definitely more appropriate than the free volume model for the calculation of enfolding chain effects in highly crystalline PET. For the three amorphous polymers the two models give comparable results, the cell model being somewhat superior for natural rubber and PMA.
Diffusion in a multicomponent inhomogeneous system with moving boundaries. I. Swelling at constant volume
Authors: Rudolph F. B. 
Published: April 2003

AbstractA medium B contains a substance C which can diffuse. This mixture of B and C is brought into contact with a medium A which itself can diffuse into B. Now C diffuses through a swollen layer of A and B into A. The present study examines mathematically this process which, among other things, could serve as a model for migration in a system consisting of plastic packaging (polymer plus an additive) and the contents of the package. It is assumed that medium A (contents) with a constant diffusion coefficient diffuses into medium B (plastics) and that the diffusion of substance C (additive) in the pure B and into A can also be described by constant diffusion coefficients. The diffusion coefficient of substance C in the zone of mixed A and B is taken to be dependent on the concentration of A in B. Partition coefficients are assumed to exist at all interfaces between the media. The general equations of this coupled diffusion process are solved explicitly. The solutions are discussed and illustrated by several special cases. Furthermore, the total amount of C in A is calculated as a function of the diffusion coefficients of the partition coefficients of time, and of the concentration of A in B.