bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure‐property relationships in short‐fiber‐reinforced composites
Authors: Termonia Yves 
Published: April 2003

AbstractA computer model is presented for the study of the effects of fiber characteristics on the mechanical properties of short‐fiber‐reinforced composites. Our model results indicate a very weak effect of fiber orientation on the modulus and tensile strength of the composite. Very high levels of orientation are required before a true reinforcement of the composite by the fiber can occur. For randomly dispersed fibers, our results point to the presence of an optimum fiber aspect ratio for effective reinforcement. They also indicate a microfailure mechanism which originates at the fiber ends and propagates along the fiber‐matrix interface, with no fiber breaking being involved. Our model results are compared with predictions from other theories and available experimental data. © 1994 John Wiley & Sons, Inc.
Hydrodynamic screening of ring copolymer solutions
Authors: Benmouna Mustapha , Borsali Redouane 
Published: April 2003

AbstractThe relaxation frequency of the dynamic correlation function for a diblock cyclic copolymer in solution in the zero average condition is calculated in the presence of hydrodynamic interaction. The latter is introduced through the screened Oseen tensor where the hydrodynamic screening length is used as a parameter to determine the range of screening. Substantial differences with the case of linear homopolymer are found, especially in the low q range where the dynamics are much faster and correspond to nondiffusive processes as usually is the case for copolymer systems. As the screening length decreases the dynamics approach the Rouse behavior and the minimum of the relaxation frequency shifts to lower values. The proportionality constant of the relaxation frequency in the intermediate q range Γ(q) → q3/(kBTη0) is also investigated as a function of the screening length. © 1994 John Wiley & Sons, Inc.
Characterization and gas permeability of a three‐component polyimide series
Authors: Chun Byong‐Wa , Ishizu Chieko , Itatani Hiroshi , Haraya Kenji , Shindo Yuji 
Published: April 2003

AbstractPacking density and gas permeability of a three‐component copolymide series is presented. The three‐component polyimides are prepared a via “stepwise” synthesis procedure that goes through the acid anhydride terminated pre‐polymer. The procedure ensures the statistical distribution of segments of the polymers. The polyimide series is composed of contrasting segments: a bulky and rigid hexafluoroisopropylidene‐2,2‐bis(phthalic acid anhydride)/9,9,‐bis(4‐aminophenyl)fluorene and a flexible hexafluoroisopropylidene‐2‐2‐bis(phthalic acid anhydride)/2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane, with varying segment ratio. Generation of additional free volume by compolymerizing two segments is observed. The permeability of six pure gases—He, H2, N2, O2, CH4, and CO2—to the polymides showed positive deviation from the simple additivity rule of segment weight ratio reflecting the generation of free volume. However, a conflicting result between free volume fraction and gas permeability is observed, which may be due to a difference of the nature of free volume of each segment. © 1994 John Wiley & Sons, Inc.
Phase behavior in copolymer blends of poly (p‐chlorostyrene‐co‐o‐chlorostyrene) and phenylsulfonylated poly (2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Vuković Radivoje , Bogdanić Grozdana , Kurešević Vjera , Tomašković Milivoj , Karasz Frank E. , MacKnight William J. 
Published: April 2003

AbstractThe miscibility of random copolymers of o‐chlorostyrene and p‐chlorostyrene [P (oClSt‐co‐pClSt)] with partially phenylsulfonylated poly (2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) copolymers has been studied, using differential scanning calorimetry (DSC) to establish Tg behavior. It already has been established that the isomeric effect of the chlorine substitution on miscibility is large. Thus the para‐chloro‐substituted styrenic homopolymer is miscible with all SPPOs containing more than ∼ 5 mol % phenylsulfonylation, whereas the ortho‐chloro‐substituted homopolymer is immiscible with the entire range of SPPO copolymer compositions (and also with the respective homopolymers). As a result of this asymmetric behavior of the homopolymers, the width of the window of miscibility in blends now investigated containing copolymers with high pClSt content and SPPO is much greater than in the corresponding blends containing copolymers with large mole fraction of oClSt. These differences are reflected in the corresponding χ parameters calculated from analysis of the data. It was also found that the miscibility is temperature dependent and that the regime in the copolymer‐copolymer composition plane shrank as the equilibrium temperature increased, results indicative of LCST behavior. © 1994 John Wiley & Sons, Inc.
Cellulose‐based fibers from liquid crystalline solutions. IV. Effects of lithium chloride on acetate/butyrate esters
Authors: Davé Vipul , Wang John Z. , Glasser Wolfgang G. , Dillard David A. 
Published: April 2003

AbstractCellulose acetate butyrate (CAB) fibers were prepared by spinning from liquid crystalline (LC) solutions containing lithium chloride (LiCl). Ionic interactions were observed between carbonyl oxygen and lithium cation by 13C nuclear magnetic resonance (NMR) spectroscopy. Isotropization of the anisotropic phase by LiCl was found to cause a dramatic rise in the viscosity of LC solutions. The mechanosorptive creep behavior described earlier decreased in the presence of residual LiCl salt, possibly due to the formation of electrostatic interactions between Li+ and CAB backbone. © 1994 John Wiley & Sons, Inc.
Co‐crystallization of solvents with polymers: The x‐ray diffraction behavior of solvent‐containing and solvent‐free polyacrylonitrile
Authors: Bashir Z. 
Published: April 2003

AbstractDifferences in the x‐ray diffraction pattern of polyacrylonitrile (PAN) have been observed, both here, as well as in the work reported in the literature. Various workers have cited grossly differing unit cells for PAN and this has never been explained. In this work, it is shown that in dry samples, the diffraction pattern contains only two equatorial peaks, d1 ≈ 5.3 Å and d2 ≈ 3.0 Å. This is consistent with a hexagonal packing of rod‐like chains of PAN with no chain‐axis order. However, in solvent‐plasticized films, the diffraction pattern is altered. It is proposed that certain solvents cause a hexagonal to orthohombic transition. However, the orthorhombic polymorph appears to be a solvated form, where the solvent has co‐crystallized with the polymer. After removal of solvent, the structure reverts to hexagonal packing. Hence, it is suggested that the discrepancy in cell parameters cited in the literature, particularly when large cell dimensions are quoted, may be due to the inadvertent presence of solvent which could have been introduced during sample preparation. Similarities with solvated crystls in other polymeric systems are also briefly discussed. © 1994 John Wiley & Sons, Inc.
NMR Study of the propagation center in the cationic polymerization of N‐benzoyl‐8‐octanelactam. II. Investigation of the propagation center
Authors: Kr̂íẑ J. , Puffer R. 
Published: April 2003

AbstractThe nature of the propagation center in the cationic polymerization of N‐benzoyl‐8‐octanelactam initiated by octanoylium hexachlcroantimonate, SbCl5, and Ph3CAsF6 in perdeuterated tetrachloroethane or its mixture with o‐dichlorobenzene was studied using 1H, 13C, 19F, 31P, 75As, and 121Sb nuclear magnetic resonance (NMR) of model oligomers and the products of their end‐capping with triphenylphosphine. In all cases, the nature of the propagation center has been found to be of an acylium ion pair with an SbCl6− or AsF6− counterion coordinated with the nearest benzoylamide group and cosolvated by the solvent. © 1994 John Wiley & Sons, Inc.
Physical properties and phase separation structure of Antheraea pernyi/Bombyx mori silk fibroin blend films
Authors: Tsukada Masuhiro , Freddi Giuliano , Kasai Nobutami 
Published: April 2003

AbstractThe physical structure and compatibility of solution‐cast Antheraea pernyi/Bombyx mori silk fibroin blend films were stuided by differential scanning calorimetry (DSC), thermomechanical (TMA) and thermogravimetric (TGA) analysis, dynamic viscoelastic measurement, infrared spectroscopy, and x‐ray diffractometry. The DSC curves of the blend films showed independent endotherms at 280 and 358°C, corresponding to the thermal decomposition of B. mori and A. pernyi silk fibroins with random coil conformation. The intensity was roughly proportionate to the amount of each component in the blend. The thermal behavior corresponding to the conformational transitions induced by heating on A. pernyi and B. mori silk fibroins overlapped in the temperature range 190–230°C. Thermal expansion and contraction properties, as well as weight retention behavior of the blend films were intermediate between the pure components, as shown by the TMA and TGA curves. The onset temperature of the storage modulus curve decreased markedly, approaching that of B. mori silk fibroin film when the amount of this component in the blend increased. The loss modulus curve of the blend films showed two peaks at ca. 190 and 210°C, the former corresponding to B. mori, and the latter to A. pernyi silk fibroin. Infrared spectra of the blends exhibited absorption bands characteristic of the pure components overlapping in the spectral region 2000–400 cm−1. The x‐ray diffraction peaks at 23 and 21.5°, attributed to the crystalline spacings of A. pernyi and B. mori fibroins, respectively, overlapped in the diffraction curves of the blends, while the peak at 11.4°, of A. pernyi, increased as the content of this fibroin in the blend increased. The degree of crystallinity, calculated from the x‐ray diffraction curves, diminished as the amount of B. mori silk fibroin decreased. A low degree of compatibility exists between the two fibroins when they are cast from aqueous solution in the experimental conditions adopted in this work. © 1994 John Wiley & Sons, Inc.
Effect of copolymer composition and conversion on the glass transition of methyl acrylate–methyl methacrylate copolymers
Authors: Fernandez‐Garcia M. , Lopez‐Gonzalez M. M. C. , Barrales‐Rienda J. M. , Madruga E. L. , Arias C. 
Published: April 2003

AbstractThe glass transition of methyl methacrylate methyl acrylate copolymers over a wide range of conversion and sequence distribution have been analyzed with the only purpose of predicting the change in the glass transition in copolymers as a function of conversion and consequently of comonomer sequence distribution. © 1994 John Wiley & Sons, Inc.
FTIR analysis of hydrogen bonding in amorphous linear aromatic polyurethanes. II. Influence of styrene solvent
Authors: Wang Fu Cai , Feve Michel , Lam Thanh My , Pascault Jean‐Pierre 
Published: April 2003

AbstractFourier‐transform infrared (FTIR) spectral studies were carried out on a polyurethane in styrene solutions at styrene concentrations from 30 to 90% (w/w). NH vibrations were studied in the stretching and bending regions. The results demonstrated that the NH groups of the polyurethane can hydrogen bond not only with the CO groups but also with other groups in this system. The investigation of the vibrations of the monosubstituted aromatic rings confirms that some aromatic rings of the styrene are hydrogen bonded with the NH groups of the polyurethane. With the results of Part 1 of this series, the mole fractions of “free” NH groups and of NH groups H‐bonded to CO groups and to the π orbitals of the aromatic rings were obtained. These results are useful in elucidating why a physical gel appears in this system. © 1994 John Wiley & Sons, Inc.
Ternary blends of phenoxy/SAN/poly(‐ε‐caprolactone)
Authors: Jo Won Ho , Kim Joo Yong , Lee Moo Sung 
Published: April 2003

AbstractThe compatibilizing effect of poly(ε‐caprolactone) (PCL) on the blends of two immiscible polymers, poly(hydroxy ether of bisphenol A) (phenoxy) and poly(styrene‐co‐acrylonitrile) (SAN) has been investigated. The phase behavior of the ternary blends was affected by the AN content in the SAN copolymers and a maximum miscible region was observed at 19.5 wt % of AN. The effect of AN content on the phase behavior of the ternary blends was interpreted in terms of the relative magnitude of the segmental interaction energy densities, which were obtained by combining a melting point depression and an extended binary interaction model. When a small amount of PCL was added to the phenoxy/SAN blends, the phase morphology showed a finer phase dispersion, indicating that the interfacial tension between the phenoxy and SAN is considerably reduced. However, the improvement in tensile properties was limited despite the morphological change with the PCL content. From the results of the DSC measurements, SEM, and tensile testing, it was understood that the PCL acted as a compatibilizer for the immiscible phenoxy/SAN blends. © 1994 John Wiley & Sons, Inc.
Secondary retardation modes in diglycidyl ether of bisphenol A–diamino diphenyl methane networks
Authors: Boye J. , Demont P. , Lacabanne C. 
Published: April 2003

AbstractThermally stimulated creep (TSCr) has been used to follow the viscoelastic behavior of some amine‐cured epoxy networks below the glass transition. The investigation of the ‐180/+40°C temperature range has revealed two essential retardation modes characterizing localized motion of chain segments: the γ mode centered at −155°C in all samples, and the well‐known β mode observed around −40°C in the stoichiometric network. The magnitude of the β mode was seen to decrease unexpectedly with the cross‐link density, whereas its peak temperature and glass transition temperature both decreased. This evolution was confirmed by thermally stimulated currents (TSC) measurements and discussed on the basis of the antiplasticization concept. Water desorption under vacuum yielded additional information on the nature of the β mode and TSCr fractional loading experiments brought evidence that two types of relaxing units participate in β motions and furnished activation enthalpy data. © 1994 John Wiley & Sons, Inc.
Investigation of molecular motions of crosslinked polyepichlorohydrin by nuclear magnetic resonance spectroscopy
Authors: Zhang Xiaoqing , Shimoda Masahiko , Toyoda Akinobu 
Published: April 2003

AbstractThe molecular motion of crosslinked polyepichlorohydrin (PECH) is studied qualitatively by NMR techniques. The results of temperature dependence of 1H T2 and T1 indicate that the crosslinking (crosslink density < 3%) restricts molecular motions of the polymer even far above its Tg. The 1H T1 minimum, corresponding to the large‐scale chain‐motion of crosslinked PECH, shifts to higher temperatures with increasing crosslink density. 1H T2 data also show that the crosslinking hinders free chain motions of the polymer above its Tg. The 13C T1 relaxation time is sensitive to such motional changes as well. 13C linewidths of crosslinked PECHs vary with the crosslink density in both the swollen state and the solid state. The mechanism of 13C linewidth broadening of crosslinked polymers is discussed in detail. In the case of PECH, the linewidth broadening is caused by changing molecular environment due to crosslinking (such as presence of various chemical shift structures and freezing effects in conformational environment as chain mobility decreases), rather than increasing correlation times, which shorten the relaxation time (T2) of polymer chains. © 1994 John Wiley & Sons, Inc.
Concurrent crystallization in polypropylene/nylon‐6 blends using maleic anhydride grafted polypropylene as a compatibilizing agent
Authors: Moon Hyuk‐Soo , Ryoo Byung‐Kyu , Park Jung‐Ki 
Published: April 2003

AbstractThis paper describes the nonisothermal crystallization of molten blends of two semicrystalline polymers, polypropylene (PP) and Nylon‐6 (N6). A discussion details the effect of the concentration of the compatibilizing agent, maleic anhydride grafted polypropylene (MAH‐g‐PP), on the crystallization behavior. The crystallization thermograms showed one crystallization peak or two crystallization peaks, which were significantly affected by the presence of MAH‐g‐PP. The crystallization temperature of N6 levels off down as the concentration of MAH‐g‐PP increases, whereas that of PP stays at a roughly constant temperature. These blends containing the compatibilizing agent exhibited concurrent crystallization at the crystallization temperature of PP. The crystallization behavior are also studied by optical microscopy under crossed polarizers. © 1994 John Wiley & Sons, Inc.
Formation of a highly ordered poly (N,N'‐bis‐phenoxyphenylpyromellitimide) powder using a high pressure curing technique
Authors: Jennings Robert M. , Farris Richard J. 
Published: April 2003

AbstractA high‐pressure curing technique was developed to help determine the effects of solvent presence during the thermal curing of the polyimide poly (N,N'‐bis‐phenoxyphenylpyro‐mellitimide) (PMDA‐ODA). A powder form of this aromatic polyimide was produced from a polyamic acid solution using the high‐pressure thermal curing technique. Preliminary characterization of the powder indicates a high degree of crystallinity with a measured density of 1.46 ± 0.01 g/cm3 and a distinct melting point of 594°C. The addition of chemical curing agents to the polyamic acid solution prior to thermal treatment reduced the amount of crystallinity observed in the cured material. Molecular weight measurements of the polyamic acid precursor and powder suggest that the high degree of order observed in the powder is a result of degradation during cure. © 1994 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America
A FTIR study of PVDF irradiated by means of swift heavy ions
Authors: Betz N. , Le Moël A. , Balanzat E. , Ramillon J. M. , Lamotte J. , Gallas J. P. , Jaskierowicz G. 
Published: April 2003

AbstractPoly(vinylidene difluoride) (PVDF) films were irradiated by means of heavy ions (in the electronic stopping‐power range) and electrons. Both types of ionizing radiation induce in the polymer film ionizations and excitations, but swift heavy ions induce a huge density of excitations and ionizations along the ion path. Dose‐range goes from 0.3 to 40 MGy. Irradiations were performed with Kr ions in the presence of helium, hydrogen, deuterium, and oxygen. Fourier transform infrared (FTIR) transmission measurements show differences in the nature of the created defects. Triple bonds are characteristic of the Kr ion irradiation. Double bonds, isolated and conjugated, exist for both kinds of radiation, but concentrations are higher with the Kr radiation. The presence of oxygen during irradiation produces oxidization defects. Typical bands of hydroxyls and carbonyls can be seen, respectively, in the 3800‐3000 cm−1 zone and ca. 1850–1730 cm−1. The formation of conjugated double bonds is enhanced when the Kr irradiation is performed under an O2 atmosphere. © 1994 John Wiley & Sons, Inc.
Solid‐state 13C NMR characterization of molecular orientation of hot drawn nylon 6
Authors: Tzou D. L. , Spiess H. W. , Curran S. 
Published: April 2003

AbstractTwo‐dimensional cross polarization (CP), magic angle spinning (MAS) rotor synchronization NMR spectroscopy has been used to determine quantitatively the molecular orientational distribution function on hot‐drawn Nylon 6. Both films and fibers are studied that had been thermally deformed at temperature above Tg, from 60 to 175°C at draw ratios in the range of 1‐5.5. In the two‐dimensional NMR spectrum, the sidebands that intrinsically originate from the chemical shift anisotropy reveal the degree of molecular orientational order. No preferential orientational order is detected for the sample without thermal deformation, and the highest degree of order is observed for samples which have been hot drawn above Tg at ratios ca. 5. Based on the aggregate model the maximum achievable order parameters are determined. © 1994 John Wiley & Sons, Inc.
Polyurethane cationomers with pendant trialkylammonium groups: Effects of ion content, alkyl group, and neutralizing anion
Authors: Goddard R. J. , Cooper S. L. 
Published: April 2003

AbstractDiphenylmethane‐4,4′‐diisocyanate based polyether polyurethane cationomers were synthesized using 3‐trialkylammonium‐(1,2‐propanediol)iodide (TAPI) as the chain extender. The ionic content was varied by substituting up to 100% of 3‐dialkylamino‐1,2‐propanediol (DAP) for TAPI. Cationomers with bromine and chlorine ions were prepared from the iodine‐based polymer via ion exchange. The morphology and properties of the cationomers were studied as a function of alkyl group, ion content, and anion type using small‐angle x‐ray scattering, tensile testing, dynamic mechanical thermal analysis, and differential scanning calorimetry. The bulky side groups of DAP and TAPI prevented crystallization in the hard domains, and consequently little or no phase separation was evident in the unionized materials. Polyurethanes with cationic functionality showed dramatic improvements in phase separation and tensile properties. Results suggest tht while ionic interactions are the primary driving force for phase separation, they produce a morphology not typical of ionomers, but rather akin to that of a conventional polyurethane with semicrystalline hard segments. © 1994 John Wiley & Sons, Inc.
NMR analysis of distribution of chain lengths between crosslinks of polymer networks
Authors: Sandakov G. I. , Smirnov L. P. , Sosikov A. I. , Summanen K. T. , Volkova N. N. 
Published: April 2003

AbstractA novel technique for the analysis of the distribution of chain lengths between crosslink junctions of polymer networks is proposed. The technique is based on the relation between the high‐temperature nuclear magnetic resonance free‐induction decay and the network structure. The distribution functions are determined for a number of networks. In particular, the evolution of structure of a thermally degrading network is studied. © 1994 John Wiley & Sons, Inc.
Influence of intrachain hydrogen bonding on the cyclization of a polystyrene chain
Authors: Farinha J. P. S. , Martinho J. M. G. , Xu H. , Winnik M. A. , Quirk R. P. 
Published: April 2003

AbstractCyclization of a polystyrene chain (Mn = 10,600; Mw/Mn = 1.09) both ends labeled with 4‐(1‐pyrenyl)butanoamide groups was studied in cyclohexane between 25 and 95°C. The amide groups (peptide bonds) at both ends can form an intrachain hydrogen bond between the amide hydrogen at one chain end and the carbonyl oxygen at the other. The presence of two sets of conformers, random coils, and chains cyclized through hydrogen bonding, complicates the data analysis. The pyrene excimer kinetics of this polymer is well described by a model composed of two monomers (hydrogen bonded and nonbonded chains) and one excimer, in equilibrium. The cyclization rate constant for hydrogen‐bonded chains is larger than the one for nonhydrogen‐bonded chains. The pyrene excimer binding energy (ca. 1.6 kcal/mol) is lower than the published value for nonhydrogen‐bonded chains (∼ 9 kcal/mol), suggesting that intrachain hydrogen bonding hinders the stabilization of the excimer. © 1994 John Wiley & Sons, Inc.