bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of fiber heat treatment. II. Poly(ethylene terephthalate) fibers
Authors: Peszkin Perla N. , Schultz J. M. , Lin J. S. 
Published: April 2003

AbstractMicrostructural changes occurring during the process of crystallization in as‐spun poly(ethylene terephthalate) (PET) have been monitored using wide‐ and small‐angle X‐ray scattering, optical birefringence, shrinkage measurements, and specific gravity.Shrinkage and birefringence results show a competition between two processes: chain re‐coiling on the one hand and crystallization on the other hand. A consistent correlation among WAXS, SAXS, shrinkage, and birefringence results is demonstrated. SAXS data show a fibrillar morphology. On the basis of WAXS results, the crystallization is envisioned as a two stage process: first, the formation of defective fibrils, and then the formation of more perfect crystals. WAXS results also demonstrate a remelting phenomenon in samples which have experienced positive shrinking.
Dynamic light scattering of polystyrene single chains in a semidilute solution of poly(methyl methacrylate) and benzene
Authors: Numasawa N. , Hamada T. , Nose T. 
Published: April 2003

AbstractTranslational diffusion and internal motion have been observed by dynamic light scattering of optically labeled single chains of polystyrene (PS) in a semidilute solution of poly(methyl methacrylate) and benzene for the case in which the dimension Rg of the PS chain is comparable to the correlation length of the matrix solution. The molecular weight Mw dependence of the hydrodynamic radius Rh is expressed as Rh ∼ M, while Rh ∼ M in pure benzene. The average linewidth Γ for internal motions (KRg > 1) appears to depend on the magnitude K of the scattering vector approximately as Γ ∝ K4 at higher KRg ( > 1), in contrast with the fact that Γ ∝ K3 approximately for KRg > 1 in pure benzene. The scaling law for the K dependence of Γ does not hold in low‐molecular‐weight PS owing to the K dependence of Γ/K2 for KRg < 1.
Rheological behavior of thermotropic flexible main‐chain polyesters based on 4,4′‐dioxy‐2,2′‐dimethyl azoxybenzene mesogens. I. Oscillatory shear behavior
Authors: Blumstein A. , Thomas O. , Kumar S. 
Published: April 2003

AbstractThe rheological properties of fractionated thermotropic nematic polyesters 4,4′‐dioxy‐2,2′‐dimethyl azoxybenzenenonanediyl (n = 7) (AZA‐9) and dodecanediyl (n = 10) (DDA‐9)
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have been determined under oscillatory shear in the nematic and isotropic phase. A markedly more pronounced shear thinning characterizes the polydisperse DDA‐9 polymer as compared to the fractionated polymer in the nematic state. This difference becomes less pronounced in the isotropic phase. In all cases, the elastic compliance J′ in the isotropic state is much lower than in the nematic state. The values of relaxation time λ, although lower in the isotropic state, are not very different in the nematic state. The loss tangent tan δ is significantly higher in the isotropic phase for lower molecular weights. For molecular weights of 13,000 and above, this difference becomes smaller and shifts to lower angular frequencies. For AZA‐9 and DDA‐9, η→0 the limit of the dynamic viscosity can be represented by η* = M with a value of α similar for both phases and approximately equal to 4.
Drawing of ultrahigh‐molecular‐weight polyethylene single‐crystal mats: The crystallinity
Authors: Furuhata Kenichi , Yokokawa Takuya , Seoul Chang , Miyasaka Keizo 
Published: April 2003

AbstractSingle‐crystal mats of ultrahigh‐molecular‐weight polyethylene can be drawn uniformly to high draw ratios, more than 20χ at the highest, after the necking process is completed. The dynamic mechanical modulus of the drawn mats increases markedly during the uniform drawing stage. The structural changes induced by the uniform drawing at 100°C have been followed by wide‐angle and small‐angle x‐ray scattering, infrared absorption, differential scanning calorimetry, and birefringence. The crystallinity is estimated from the x‐ray amorphous scattering intensity, the IR absorbance of gauche bands, the heat of fusion from DSC, and the density. The estimated crystallinities of the drawn mats are all very high and increase slightly and monotonically with increased drawing after necking, though the values of the crystallinity depend on the method of estimation. IR gauche bands and the SAXS peak due to the long period disappear at a draw ratio of about 80χ. All the results suggest that the uniform drawing after necking destroys the two‐phase structure made up of alternately stacked crystalline and amorphous regions and then reorganizes it into a single‐phase crystalline structure.
Electron diffraction structure analysis of epitaxially crystallized n‐paraffins
Authors: Dorset Douglas L. 
Published: April 2003

AbstractElectron diffraction data from a series of paraffins epitaxially crystallized on benzoic acid are used to determine their crystal structures. Even‐chain paraffins from n‐C32H66 to n‐C60H122 are shown to crystallize isostructurally as the orthorhombic polymorph described for n‐C36H74. Like the even‐chain compounds, odd‐chain paraffins do not crystallize in their lowest‐energy form. A quantitative zonal crystal structure analysis for n‐C33H74 suggests that the molecular packing is in the B‐polymorphic form proposed earlier by other workers.
Environmental stress cracking of low‐density polyethylene in normal alcohols
Authors: Ogata Nobuo , Yanagwa Teruaki , Yoshida Koukichi 
Published: April 2003

AbstractFracture mechanics was used to investigate the environmental stress cracking of low‐density polyethylene with 4.0 melt flow index. Annealed samples were prepared; a single edge notch was made and then the samples were fractured under constant load in four different liquid alcohols. The relation between the stress intensity factor K and the crack speed a˙ has been investigated. The log a˙ vs. logK curves are influenced not only by temperature but also by the alcohol used as the environment. This influence has been studied in detail. The conclusions are as follows: the crack speed at high K is determined by the diffusion mechanism, and this mechanism cannot be explained in terms of hydrodynamics but can be explained in terms of thermally activated molecular motion. On the other hand, the crack speed at low K is strongly related to the plasticization and the stress relaxation of the crack tip material.
Sorption of CO2, C2H4, N2O and their binary mixtures in poly(methyl methacrylate)
Authors: Sanders E. S. , Koros W. J. 
Published: April 2003

AbstractSorption of carbon dioxide, ethylene, and nitrous oxide in poly(methyl methacrylate) (PMMA) at 35°C has been characterized for each gas as a pure component and for mixtures of carbon dioxide/ethylene and carbon dioxide/nitrous oxide. Pressures up to 20 atm were examined. Pure‐component sorption isotherms are concave to the pressure axis for each of the gases. This behavior is accurately described by the dual‐mode sorption model. Using only the purecomponent dual‐mode parameters and the generalization of the model for gas mixtures, one can predict the total concentration of gas sorbed in the polymer to within an average deviation of ±2.01% for the CO2/C2H4/PMMA system and ±0.98% for the CO2/N2O/PMMA system. In both systems, for each component of the mixture, sorption levels were lower than corresponding pure‐component sorption levels at pressures equal to the partial pressure of the respective components in the mixture. Depression of the sorbed concentration in mixture situations appears to be a general feature of the above systems and can be substantial in some situations. For the CO2/C2H4/PMMA system, use of pure‐component sorption data to estimate the total sorbed concentration in the mixture would be in error by as much as 40% if one failed to account for competition phenomena responsible for depression in mixed‐gas situations. Mixture pressures as high as 20 atm were studied for both systems and in the CO2/N2O/PMMA system sorbed concentrations reach 33.90 [cm3(STP)/cm3 polymer] without any significant deviation from model predictions.
Mesogenic random copolymers. II. Copolymers with one flexible and two rigid segments
Authors: Watanabe Junji , Ikeda Kenichi , Krigbaum W. R. 
Published: April 2003

AbstractWe have investigated copolyesters based on a single aliphatic dibasic acid flexible segment and two rigid segments arising from 4,4′‐dihydroxybiphenyl (PB) and 2,6‐dihydroxynaphthalene (PN). Homopolyesters based on the latter rigid segment exhibit no enantiotropic mesophase for 5 ≤ n ≤ 8. The copolymers are designated PBN‐n where n is the number of methylene units in the dibasic acid. From the temperature–composition phase diagram, the odd‐membered PBN‐5 and PBN‐7 exhibit only a nematic phase. The temperature range of the nematic phase decreases progressively with increasing mole fraction of naphthalene units. The even‐membered PBN‐6 and PBN‐8 exhibit a smectic SH mesophase and a newly induced nematic phase. Comparison with a previous study of copolymers involving a single rigid segment and two flexible segments reveals that the smectic SH phase is more easily disrupted, and converted to a less ordered nematic phase, by different rigid segments than by different flexible segments. The isotropization entropy of a series of nematogenic equimolar copolymers exhibits a marked odd–even effect, with the observed ΔSNI values being quite large for the even‐membered copolymers.
Characterization and properties of polyethylene blends I. Linear low‐density polyethylene with high‐density polyethylene
Authors: Hu Shi‐Ru , Kyu Thein , Stein Richard S. 
Published: April 2003

AbstractA blend system of linear low‐density polyethylene (LLDPE) (ethylene butene‐1 copolymer) with high‐density (linear) polyethylene (HDPE) is investigated by differential scanning calorimetry (DSC), wide‐angle x‐ray diffraction (WAXD), small‐angle x‐ray scattering (SAXS), Raman longitudinal‐acoustic‐mode spectroscopy (LAM), and light scattering (LS). For slowly cooled or quenched samples, one single endotherm is evident in the DSC curve which depends on the composition. No separate peaks are observed in the WAXD, SAXS, Raman‐LAM, and LS studies on the LLDPE/HDPE blends. This observation along with the fact that no peak broadening is observed suggests that these peaks are associated with the presence of a single component. In no case did we see double peaks or a broadened peak that might be associated with two closely spaced unresolved peaks. This suggests that segregation has not taken place at the structural levels of crystalline, lamellar, and spherulitic textures. A single‐step drop in the scattered intensity (IHv) as a function of temperature is seen in the LS studies. It is therefore concluded that cocrystallization between the LLDPE and HDPE components occurs. The mechanical and optical α, β, and γ relaxations of these blends are explored by dynamic birefringence. The 50/50 blend displays the intermediate relaxation behavior between those of the components in all α, β, and γ regions. This observation is reminiscent of the characteristic of the typical miscible blends.
Characterization and properties of polyethylene blends II. Linear low‐density with conventional low‐density polyethylene
Authors: Kyu Thein , Hu Shi‐Ru , Stein Richard S. 
Published: April 2003

AbstractMelting and crystallization phenomena in blends of a linear low‐density polyethylene (LLDPE) (ethylene butene‐1 copolymer) with a conventional low‐density (branched) polyethylene (LDPE) are explored with emphasis on composition by differential scanning calorimetry (DSC) and light scattering (LS). Two endotherms are evident in the DSC studies of the blends, which suggests the formation of separate crystals. Light‐scattering studies indicate that the blend system is predominantly volume filled by the LLDPE component whereby the LDPE component crystallizes as a secondary process within the domain of the LLDPE spherulites. In contrast to those of the LLDPE/HDPE blends, the mechanical and optical relaxation behavior of the LLDPE/LDPE blends are dominated by the LLDPE component in the vicinities of γ and β regions, whereas the trend reverses at high temperature α regions. This observation is accounted for on the basis of the relative restrictions imposed by the deformation of spherulites (which are primarily made up of the LLDPE component) at different time scales.
Quantitative small‐angle light‐scattering studies of the melting and crystallization of LLDPE/LDPE blends
Authors: Ree Moonhor , Kyu Thein , Stein Richard S. 
Published: April 2003

AbstractSmall‐angle light‐scattering (SALS) patterns were obtained during melting and crystallization of blends of linear low‐density polyethylene (LLDPE) with conventional low‐density polyethylene (LDPE). Quantitative measurements of these SALS patterns using a two‐dimensional optical multichannel analyzer apparatus (OMA2) indicate that the LLDPE which is miscible with the LDPE component in the molten state crystallizes first, forming volume‐filling spherulites. The LDPE then crystallizes within the preformed spherulites. These findings are supported by optical microscopy studies showing that the blend samples were volume filled with one kind of the spherulites having a radius comparable to that of the pure LLDPE. The SALS intensity curve changes with composition of the blends in a manner that may be interpreted by considering the orientation of crystals within spherulites. It has been observed that the spherulites in the blend have more diffuse boundaries as the LDPE content increases. The lattice spacing and long spacings in blends were obtained by wide‐angle and small‐angle x‐ray scattering, respectively. The SALS technique along with differential scanning calorimetry (DSC) is shown to be useful for determining the crystallization behavior of a crystallizable polymer blend system.
Photophysical investigations of interpolymer interactions in solutions of a pyrene substituted poly(acrylic acid), poly(vinyl amine), poly(1‐aminoacrylic acid), and poly(1‐acetylaminoacrylic acid)
Authors: Arora Kartar S. , Turro Nicholas J. 
Published: April 2003

AbstractPhotophysical properties of the pyrene chromophore covalently bound to poly(acrylic acid) were used to investigate the interactions of a pyrene substituted poly(acrylic acid) (1) with poly(vinyl amine hydrochloride) (PVAm), poly(1‐aminoacrylic acid) (PDA), and poly(1‐acetylaminoacrylic acid) (PADA) in aqueous solutions. A number of photophysical parameters were obtained from fluorescence emission and excitation spectra, the deconvolution of decay curves for pyrene monomer, and excited state complex fluorescence and the quenching of pyrene monomer fluorescence by nitromethane in polymer solutions. These photophysical parameters were considered to reflect the inter‐ and intrapolymer interactions in solutions of 1, PVAm, PDA, and PADA. The formation of interpolymer complexes between 1 and PVAm was noticed at low (< 4) as well as high (> 8) values, whereas PDA and 1 formed interpolymer complexes at low pH only. No interpolymer complex formation was detected in solutions of 1 and PADA under low or high pH conditions. The structures of interpolymer complexes formed between 1 and PVAm under low and high pH conditions were found to be determined by the conformation of 1. There were significant differences in the interpolymer interactions of 1 and PDA in comparison to those of 1 and PVAm; in particular, the fluorescence from the excited state complex was enhanced in solutions of 1 and PVAm but quenched in solutions of 1 and PDA. The investigations of terpolymer solutions of 1, PVAm, and PADA indicated that the nature of interpolymer complexes formed in terpolymer solutions was determined by Coulombic interactions of the amino and carboxylic group containing polymers.
Synthesis and electrical and optoelectronic properties of poly[(N‐benzyldiphenylamino)methane]
Authors: Akhter Md. Aquil , Pramanik Panchanan , Biswas Mukul 
Published: April 2003

AbstractPoly[(N‐benzyldiphenylamino)methane] was synthesized by the condensation polymerization of benzyldiphenylamine and formalin (30% HCOH in water) and examined for electrical and optoelectronic properties. Dark conductivity and photoconductivity of the polymer film were investigated by steady‐state measurements. Current‐voltage characteristics and intrinsic photoconduction of the polymer in the visible wavelength range were studied. A superlinear current increase is tentatively explained in the light of the Poole‐Frenkel effect. Dielectric constant and dielectric loss parameters of the polymer are independent of frequency (50 Hz–10 kHz) and temperature (273–323 K), respectively. The growth and decay rates of the photocurrent depend on the applied voltage, and the photocurrent varies directly with the light intensity. The activation energies for dark conductivity and photoconductivity are 1.16 eV and 1.05 eV, respectively, and the optical energy band gap as evaluated from absorption coefficient spectra is 2.86 eV.
A scaling analysis of the fracture mechanisms in glassy polymers
Authors: Evans K. E. 
Published: April 2003

AbstractRecent experimental work on craze growth in polymers has shown that the reptation model for polymer motion may be successfully applied, in certain cases, to the behavior of glassy polymers in the solid phase. In this paper, a simple scaling analysis is presented to show how the primitive path model for reptation may be applied to the behavior of glassy polymers before and during slow crack growth. Different dynamic regimes are identified and related to the relaxation times of the polymer chain. The dependence on polymer chain length for each mechanism is described. Estimates for the fracture energy of each process are presented.
Miscibility and volume changes of mixing in the polystyrene/poly(2‐chlorostyrene) blend system
Authors: Tsujita Yoshiharu , Iwakiri Keiko , Kinoshita Takatoshi , Takizawa Akira , MacKnight William J. 
Published: April 2003

AbstractThe specific volume‐temperature relationships of polystyrene, poly(2‐chlorostyrene), and their polymer blends as well as the volume change of mixing Δvm of the blends were obtained in the liquid state by dilatometry. The equation of state parameter and the molecular parameter of each homopolymer and blends were determined according to the lattice fluid theory of Sanchez and Lacombe. The experimental Δvm obtained agreed quite well with that predicted from theory, and the enthalpy of mixing ΔHm was also predicted using the pair molecular parameter. These two values were negative, indicative of miscibility of polystyrene and poly(2‐chlorostyrene) in the liquid state. The absolute values of Δvm and ΔHm were about twice those for polystyrene and poly(phenylene oxide) blend, suggesting a specific interaction between the two polymers.
Small‐angle neutron scattering of a model crystallizable polymer: Crystallization and size‐mismatch effects
Authors: Crist B. , Tanzer J. D. , Graessley W. W. 
Published: April 2003

AbstractSmall‐angle neutron scattering (SANS) experiments have been conducted on mixtures of nearly monodisperse hydrogenated polybutadiene (HPB) and its deuterated counterpart (DPB) in molten and semicrystalline states. A direct comparison of scattering patterns from molten and quench‐crystallized samples shows unambiguously that chain conformation is unchanged by crystallization over large and intermediate size scales. The HPB's are shown to have slightly larger coil dimensions than linear polyethylenes of the same molecular weight. The scattering law for mixtures of different chain lengths was also investigated. Mismatched mixtures of monodisperse components give rise to scattering with an angle dependence well described by the Debye function for a Gaussian chain, even in the 50/50 composition range. This permits evaluation of SANS parameters [apparent radius gyration (Rg)e and apparent degree of polymerization Ne] by analysis of the full scattering curve, removing the restrictions that the Guinier condition (qRg < 1) be satisfied. The values of (Rg)e and Ne obtained from experiment are in good agreement with predictions of the scattering law for ideal mixtures.
Macromolecular order in spin‐oriented nylon 6 (polycaproamide) fibers
Authors: Salem D. R. , Moore R. A. F. , Weigmann H.‐D. 
Published: April 2003

AbstractWide‐angle x‐ray scattering (WAXS) has been used to characterize the ordered phases of spin‐oriented nylon 6 fibers wound at speeds ranging from 5000 to 8000 m/min. Quantitative analysis of the radial diffractometer scans by a computerized curve‐fitting procedure reveals that the unit‐cell geometry of both the α and γ crystalline morphologies are highly dependent on winding speed and on annealing conditions. At 800° m/min, there is a particularly large reduction in the intermolecular distance along the van der Waals forces of the α unit cell, which is accompanied by substantial crystal growth in the hydrogen‐bond direction. Similar increases in the width and perfection of the α crystals result from water annealing and steam treatment. The perfection of the γ crystals increases with winding speed and after annealing in water, but steam treatment increases the intermolecular distance along the hydrogen bonds while reducing it along the van der Waals forces. Using bulk density measurements and the experimentally determined crystalline density pc for each sample, the volume‐fraction crystallinity (VFC) is shown to pass through a maximum at ca. 6500 m/min. This maximum arises from a decrease in α crystallinity with increasing winding speed together with an increase in γ crystallinity, which levels off above ca. 7000 m/min. It is demonstrated that the determination of VFC assuming constants pc would lead to large errors. The orientation of the α crystals is found to be much less than that of the γ crystals, but it increases quite rapidly with winding speed. Water and steam treatments cause increases in α orientation and decreases in γ orientation.
Temperature and pressure dependence of the viscosities of perfluoropolyether fluids
Authors: Cantow M. J. R. , Barrall E. M. , Wolf B. A. , Geerissen H. 
Published: April 2003

AbstractThe viscosities of two structurally different perfluoropolyether fluids were determined at a series of temperatures and pressures, from 25 to 100°C and from 1 to 1000 bars. Flow activation energies and volumes as well as their temperature and pressure coefficients were derived. An attempt was made to relate measured and derived quantities to the compound structures.
Observation of single‐chain scattering from homopolymer blended with a triblock copolymer
Authors: Quan X. , Gancarz I. , Koberstein J. T. , Wignall G. D. 
Published: April 2003

AbstractA small‐angle neutron scattering method has been developed to determine the chain conformation of homopolymer chains dispersed in a block copolymer matrix. Two contrast matching techniques are used to achieve this result and are demonstrated for a system based on a styrene‐hydrogenated butadiene‐styrene triblock copolymer and a hydrogenated butadiene homo‐polymer. Composition matching uses a blend of labeled and unlabeled molecules to match the scattering density of another component. Phase matching requires a block copolymer which has been synthesized such that the scattering densities of the blocks are equal. This polymer provides a transparent matrix in which a composition‐matched blend of homopolymer can be dispersed to isolate the single‐chain scattering function of the homopolymer chains.