bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conductivity study of stretch‐oriented new polyacetylene
Authors: Płocharski Janusz , Pukacki Wojciech , Roth Siegmar 
Published: April 2003

AbstractOriented polyacetylene samples were synthetized and doped with iodine and FeCl3. Their electric conductivity and anisotropy were measured within the temperature range 4‐300 K. The results were described using the Ping Sheng model. It is concluded that the factors limiting the conductivity parallel and perpendicular to the stretching direction are the same and thus no interfibrillar conduction occurs. Some processes related to the mechanical stretching are discussed. © 1994 John Wiley & Sons, Inc.
Polymer friction‐transfer layers as orienting substrates
Authors: Motamedi Farshad , Ihn Kyo Jin , Fenwick David , Wittmann Jean‐Claude , Smith Paul 
Published: April 2003

AbstractA variety of polymers were investigated as candidates for the formation of oriented layers by friction transfer. Only polyethylene, the liquid‐crystalline Vectrá and fluorinated ethylene‐propylene copolymer were found to yield oriented transfer layers. These layers, in turn, were found to induce the oriented growth a variety of species deposited onto them from the melt, solution or vapor phase. The present orientation‐inducing friction‐transfer layers, however, were found to be inferior to those of poly(tetrafluoroethylene) [PTFE], described previously. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical properties of sulfonated polystyrene/alumina composites
Authors: Cousin P. , Smith P. 
Published: April 2003

AbstractAmino units were grafted onto the surface of small particle size alumina by reaction with 3‐aminopropyltriethoxysilane. Atactic polystyrene (PS) was sulfonated (1‐14 mol% sulfonation) and mixed with both modified and unmodified alumina at filler loadings varying from 30 to 80 wt %. The resulting composites were characterized by differential scanning calorimetry, Fourier transform infra‐red spectroscopy, and dynamic mechanical spectroscopy in the glass transition region at a frequency of 1 Hz. Whereas mixtures of unsulfonated PS with either filler showed essentially no change in Tg with filler content, sulfonated PS saw its Tg increase as a function of filler loading at a rate which was greater following modification of the alumina. At a fixed filler loading of 30 wt%, the composite rubbery plateau modulus was found to increase with copolymer sulfonic acid content, while the loss tangent maximum corresponding to the glass transition broadened and decreased. These observations were interpreted as a manifestation of the decrease in polymer mobility brought upon by the formation of noncovalent crosslinks resulting from the proton transfer from the sulfonic acid units on the polymer to hydroxyl and/or amino units at the surface of the filler. © 1994 John Wiley & Sons, Inc.
An infrared spectroscopic study of changes in unsaturation resulting from irradiation of isotropic and uniaxially oriented polyethylene films in the presence of acetylene
Authors: Jones R. A. , Salmon G. A. , Ward I. M. 
Published: April 2003

AbstractInterchain bridges of unsaturated double bonds have been proposed to form in amorphous regions, when polyethylene is irradiated in the presence of acetylene. We have corroborated the formation of these bridges by infrared spectroscopic studies. The double bonds are composed mainly of trans‐olefin and vinyl end groups, formed as a result of competing radical‐radical termination and hydrogen atom abstraction reactions. The hydrogen atom abstraction reaction becomes insignificant in uniaxially oriented high‐density polyethylene having a draw ratio of 7.5, because of the alignment and positioning of the initiating radical pairs. During in vacuo irradiation and annealing only in‐chain trans‐olefins are usually formed. © 1994 John Wiley & Sons, Inc.
Toluene diffusion in butyl rubber
Authors: Schneider Nathaniel S. , Moseman James A. , Sung Nak‐Ho 
Published: April 2003

AbstractThe sorption isotherm and the polymer mass‐fixed diffusion coefficients, D, for toluene in butyl rubber have been measured by the incremental sorption method to concentrations of 130%, corresponding to a solvent volume fraction of 0.578. The increase in D with concentration is strongly exponential to a concentration of 30% and then begins to level out. Since the nature of the dimensional change occurring in vapor sorption was not known, the values of D were converted to solvent self‐diffusion coefficients, D1, assuming both swelling in the thickness direction (1D) and isotropically (3D). The free volume (FV) theory of Fujita was fitted to the resulting D1 with the zero concentration diffusion coefficient and the self‐diffusion coefficient of toluene as limiting values leaving only a single arbitrary parameter. In this form the FV theory was able to describe the trend of the experimental D1 for the 1D and 3D cases equally well. Values of D were back‐calculated from the FV relations for the 1D and 3D cases for comparison with the experimental results and with the diffusion coefficient determined by immersion in toluene. These comparisons favor the assumption that swelling is isotropic. It appears that the simple free volume relation is capable of providing a satisfactory representation of the experimental data with only a single fitting parameter, although there are moderate quantitative discrepancies. © 1994 John Wiley & Sons, Inc.
Equibiaxial deformation of poly(4‐methyl‐1‐pentene) by a forging process
Authors: Osawa Satoshi , Porter Roger S. 
Published: April 2003

AbstractPoly(4‐methyl‐1‐pentene) (PMP) has been uniaxially compressed by a forging (equibiaxial) process. The rheology of the process has been examined for this semicrystalline polyolefin, melting point about 235°C. The yield energy, area under the compressive stress‐strain curve up to the yield point, as a function of temperature was found to consist of two linear components of different slope. These two linear relations arise from the glassy and crystalline phases of PMP. The intercept temperature (Ti) at zero yield energy for the glassy phase has been evaluated. The attainable maximum compression ratio without sample rupture (CRmax) increased steadily on increasing forging temperature above Ti, and below Tm. In this range, the crystalline relaxation temperature (Tc), evaluated from an Arrhenius plot of yield stress was 160°C. Above Tc, a CRmax of 240 was reached. This value is five times higher than that attained for isotactic polypropylene (i‐PP). However, the draw efficiency evaluated by elastic recovery in the plane direction of PMP (0.76) is lower than for i‐PP (0.97). Differential scanning calorimetry analyses showed that the melting peak became a complex doublet on increasing compression ratio ( > 100). The drawing and stress‐strain behavior of PMP are compared with i‐PP. © 1994 John Wiley & Sons, Inc.
Spectroscopic analysis and in situ monitoring of impregnation and extraction of polymer films and powders using supercritical fluids
Authors: Howdle S. M. , Ramsay J. M. , Cooper A. I. 
Published: April 2003

AbstractA range of vibrational spectroscopic techniques are used to monitor supercritical fluid extraction and impregnation of polymers. Impregnation processes of this type show potential as alternative apporaches to the synthesis of polymer based catalysts and new materials. Methods have been devised using conventional Fourier transform infrared spectroscopy for real time monitoring of the extraction and impregnation of polyethylene films using an organometallic complex, CpMn(CO)3 (Cp = η5 − C5 H5) as a spectroscopic probe. Both low and high density powdered polyethylene may be impregnated using supercritical carbon dioxide. The resulting materials are analysed using FTIR photoacoustic spectroscopy, diffuse reflectance infrared spectroscopy and FT Raman spectroscopy to probe both the impregnated bulk of the polymer and surface‐coated material. © 1994 John Wiley & Sons, Inc.
Solid polymers doped with rare earth metal compounds. III. Formation and stability of macromolecular complexes comprising neodymium nitrate and dipivaloylmethane in poly(ethylene oxide)
Authors: Twomey Conor J. , Chen Shaw H. , Blanton Thomas N. , Schmid Ansgar , Marshall Kenneth L. 
Published: April 2003

AbstractThe solubility, complexation, and morphology in the Nd(NO3)3‐PEO and Nd(Dpm)3‐PEO systems were investigated using the FTIR, DSC, TGA, WAXD, and SAXS techniques. In both systems, dissolution was verified by the absence of features characteristic of the bulk‐phase dopants detectable with WAXD and DSC, and complexation was evident from the FTIR spectral shifts involving the stretching motions of the EO unit. The extent of the Nd3+‐EO interaction was found to be much stronger with Nd(NO3)3 than Nd(Dpm)3. As a consequence, a Tg elevation from 222K in pure PEO to 335K at an EO/Nd3+ ratio (defined as n) of between 4.0 and 5.6 was observed in the Nd(NO3)3‐PEO system. Moreover, completely dry and amorphous complexes were obtained at n ≥ 5.6, while residual moisture accompanying complexes at n ≤ 4 was found to persist upon prolonged vacuum drying. Being intrinsically hygroscopic at all doping levels, the Nd(NO3)3‐PEO system was found to absorb moisture from the atmosphere resulting in wet amorphous complexes, although precipitation of Nd(NO3)3)·6H2O was observed at n ≤ 4. It was proposed that moisture present in the Nd(NO3)3‐PEO system be classified into two categories. One is tightly bound to Nd3+ to satisfy its coordination requirement, which was determined to be 11. The other is loosely bound, which is capable of being removed by heating and returning upon exposure to the atmosphere. It is the latter that can be readily quantified by the TGA technique and that lowers Tg via plasticization. In addition to the observed minor FTIR spectral shifts, a relatively weak Nd3+‐EO interaction in the Nd(Dpm)3‐PEO system resulted in a lack of the Tg elevation for PEO, persistence of the crystalline portion of PEO at all doping levels, and the formation of new crystalline phases as revealed by the WAXD patterns and the DSC thermograms. The short‐range order in PEO does not appear to be perturbed, but the SAXS data suggest that the long range‐order is disrupted by the presence of Nd(Dpm)3 at an extremely low doping level (i.e., n ≥ 60). © 1994 John Wiley & Sons, Inc.
Optical and SAXS characterization of poly(phenylene sulfide) (PPS) oligomers
Authors: Sass C. S. , Fagerburg D. R. 
Published: April 2003

AbstractPreviously reported oligomeric PPSs prepared via the melt reaction of sulfur with excess p‐diiodobenzene have been examined by optical microscopy and small‐angle x‐ray scattering (SAXS) techniques. A transition was seen from lamellar crystals for longer chains in the PPS samples of this work to a different type, which probably are extended chain crystals, occurring at about 20 DP. Spherulitic growth was observed optically for 38.8 DP and above. SAXS data established 31.8 DP as the point where a long period peak was first observed. The lamellar thickness of these bulk crystallized samples was established as about 50 Å which corresponds to a DP of 10. Maximum intensity of the SAXS peak increased with oligomer DP indicating increasing crystal perfection. Because of the random nature of the crystallization process, in PPS the average oligomer chain must be longer than three times this lamellar thickness to allow for folding and a spherulitic growth habit. © 1994 John Wiley & Sons, Inc.
Molecular orientation induced by cooling stresses. Birefringence in polycarbonate: III. Constrained quench and injection molding
Authors: Wimberger‐Friedl R. 
Published: April 2003

AbstractResidual stress and birefringence distributions are determined in polycarbonate samples obtained by quenching in a specially designed apparatus and by injection molding. The molecular orientation is distinguished from the thermally and pressure‐induced residual stresses. The birefringence in the quenched samples is found to be positive and almost constant, independent of the quench temperature, but varying strongly with initial quench temperature between 150 and 180°C. The residual stress level, as determined by layer removal and sectioning, is very low. The birefringence distribution is mainly due to a tensile equibiaxial orientation induced by transient cooling stresses built up above Tg. The samples which are injection‐molded with a high injection speed and without packing pressure display the same birefringence distribution as the quenched samples, apart from a local maximum beneath the surface due to the shear flow during filling. Apart from the flow during filling and packing, the frozen‐in molecular orientation in injection‐molded samples is also induced by transient thermal stresses present during vitrification. The birefringence from thermally induced orientation was found to be of comparable magnitude to that from flow‐induced orientation. For a correct prediction of molecular orientation the thermal strains above Tg must therefore be included in simulation programs. Because of the low level of thermal stresses, the application of a packing pressure will lead to tensile stresses at the surface in general. © 1994 John Wiley & Sons, Inc.
Miscibility behavior of di(ethyl‐2 hexyl) phthalate in binary and ternary chlorinated polymer blends
Authors: Champagne Michel F. , Prud'homme Robert E. 
Published: April 2003

AbstractThe miscibility behavior of ternary blends made by the addition of di(ethyl‐2 hexyl) phthalate (DOP) to a mixture of chlorinated polymers was investigated by differential scanning calorimetry. Two chlorinated polymer mixtures were selected: polyvinyl chloride (PVC) with a chlorinated polyethylene containing 48 wt% Cl (CPE48), and PVC with a chlorinated PVC containing 67 wt% Cl (CPVC67). Each binary DOP/chlorinated polymer pair is miscible whereas PVC/CPE48 and PVC/CPVC67 blends are immiscible. DOP/CPE48/PVC and DOP/PVC/CPVC67 ternary blends containing, respectively, more than 55 and 20% DOP exhibit a single glass transition temperature (Tg). The spinodal between the one‐Tg zone and the two‐Tg zone is symmetrical in the two cases. At high DOP concentrations, a quantitative analysis of the results leads to the conclusion of the presence of a true ternary phase. At low DOP concentrations where two Tgs are observed, the DOP is distributed equally between the two chlorinated polymers forming, in the DOP/CPE48/PVC case for instance, two binary DOP/CPE48 and DOP/PVC phases. The broad immiscibility zone observed in the DOP/CPE48/PVC ternary blend as compared to the DOP/PVC/CPVC67 blend appears to be mainly caused by the high molecular weight of CPE48, as compared with PVC and CPVC67. © 1994 John Wiley & Sons. Inc.
Fine structure of nylon–6–clay hybrid
Authors: Kojima Yoshitsugu , Usuki Arimitsu , Kawasumi Masaya , Okada Akane , Kurauchi Toshio , Kamigaito Osami , Kaji Keisuke 
Published: April 2003

AbstractNylon‐6–clay hybrid (NCH) is a molecular composite of Nylon‐6 and uniformly dispersed silicate monolayers of montmorillonite. In this study, orientation of montmorillonite and Nylon‐6 crystallites in the NCH film was measured by x‐ray diffraction and transmission electron micrography (TEM), which revealed that, the silicate layers and the Nylon‐6 crystallites (γ‐form) have planar orientation, independent of montmorillonite content. Based on the crystal structure model proposed by Bradbury et al., it seems that hydrogen bonded sheet plane {020} or zigzag plane of molecular backbone {110} is parallel to the film surface. In contrast, crystallites in pure Nylon‐6 film are randomly oriented. The degree of orientation of Nylon‐6 crystallites increases with content of montmorillonite. © 1994 John Wiley & Sons, Inc.
Isomorphism in the poly(3,3‐bis‐hydroxymethyloxetane) family and copolymers: Poly (3,3‐bis‐hydroxymethyloxetane‐co‐3‐methyl‐3‐hydroxymethyloxetane)
Authors: Parris J. M. , Marchessault R. H. , Vandenberg E. J. , Mullis J. C. 
Published: April 2003

AbstractCopolymers of 3,3‐bis‐hydroxymethyloxetane, BHMO, 3‐metyl‐3‐hydroxymethyloxetane, MHMO, or with 3‐ethyl‐3‐hydroxymethyloxetane, EHMO, monomer units were characterized by x‐ray fiber diffraction, differential scanning calorimetry and 13C solid‐state nuclear magnetic resonance (NMR). The copolymers are statistically random and crystalline throughout the range of compositions. Both P(BHMO) and P(MHMO) appear to crystallize in the same crystal form. The fiber repeat indicates a planar zigzag backbone conformation, c(fiber axis) = 4.77 ± 0.03 Å. Similarities in the x‐ray fiber diagrams as well as a linear dependence of Tm with composition of copolymer with no change in fiber diagrams indicates isomorphism, a phenomenon in which the random substitution of MHMO monomeric units into the crystalline lattice of P(BHMO) occurs without hindering crystallization of the resulting copolymer. © 1994 John Wiley & Sons, Inc.
Laser light‐scattering characterization of gelatin in formamide
Authors: Wu Chi 
Published: April 2003

AbstractLaser light scattering (LLS) including angular dependence of absolute integrated scattered intensity (static LLS) and of the spectral distribution (dynamic LLS) has been used successfully to characterize gelatin in formamide at room temperature. In static LLS, the use of formamide as a single solvent instead of an aqueous salt solution avoids the well‐known problem of preferential sorption of salts in the domain of gelatin molecules. Therefore the true weight‐average molecular weight Mw, the z‐average radius of gyration, and the second virial coefficient have been determined. In dynamic LLS, precise measurements of the intensity‐intensity time correlation function permit a Laplace inversion to obtain an estimate of the normalized characteristic linewidth distribution which could be reduced to a translational diffusion coefficient distribution, G(D). This report shows that the calibration between D and M can be established from Mw and G(D) by using only two broadly distributed gelatins instead of a set of narrowly distributed gelatin standards. After establishing a calibration between D and M, we were able to estimate the molecular weight distribution of gelatin from G(D). © 1994 John Wiley & Sons, Inc.
Electron beam crosslinking of poly(vinylmethyl ether)
Authors: Liu Xiaodu , Briber Robert M. , Bauer Barry J. 
Published: April 2003

AbstractThe electron beam induced branching of poly(vinylmethyl ether) (PVME) in bulk and in isopropanol solutions has been studied by gel permeation chromatography. The branching probability of bulk PVME induced by high‐energy electrons can be characterized by gel permeation chromatography and a simple probability constant obtained. In isopropanol solutions this branching probability is not constant as a function of dose and is found to decrease with decreasing concentration. These results indicate the importance of solvent effects on the crosslinking of PVME in isopropanol solution by electron beam radiation. © 1994 John Wiley & Sons, Inc.
Liquid crystalline main chain polymers with a poly(p‐phenylene‐terephthalate) backbone: 7. Thermal expansion of oriented films of the polyester with dodecyloxy side chains
Authors: Buijs J. A. H. M. , Damman S. B. 
Published: April 2003

AbstractThe linear thermal expansion coefficients of oriented films of poly(p‐phenylene‐2,5‐didodecyloxy‐terephthalate) in the three structures B, A, and Lf are reported. The results are interpreted in terms of a molecular laminate model in which the rigid main‐chain layers are separated by the aliphatic side chains. In a film oriented unidirectionally the rigid mainchain layers provide a negative contribution to the thermal expansion coefficient, while the side chains supply a positive contribution. Therefore, the resulting expansion coefficient α depends on the details of the main‐ and side‐chain packing and low‐temperature values between α = +0.3 × 10−5 K−1 (A and Lf and α = −1.2 × 10−5 K−1 (B) are found in highly oriented films. Measurements on undrawn films are in accordance with the molecular laminate model. © 1994 John Wiley & Sons, Inc.
Molecular dimensions and chain conformation in glassy syndiotactic polystyrene
Authors: Stölken S. , Ewen B. , Kobayashi M. , Nakaoki T. 
Published: April 2003

AbstractFor the first time the small‐angle neutron scattering (SANS) from mixtures of protonated and totally deuterated syndiotactic polystyrene (sPS) has been studied. Two amorphous samples with similar molecular weights have been measured at various concentrations of the protonated part. All measurements were performed at room temperature using the scattering equipment of two different laboratories. The molecular weight Mw evaluated from SANS data agreed with those obtained by gel permeation analysis (GPC). In the Kratky representation the scattering contribution due to the contrast scattering shows a plateau behavior up to q = 0.45 Å−1, where q is magnitude of the scattering vector. This observation is in evident contrast to what is expected from the rotational isomeric state (RIS) model. In addition the characteristic ratios C∞, derived either from the plateau height or from radii of gyration of the Zimm regime and being in reasonable agreement with each other, show strong deviations from the predictions of the RIS model. © 1994 John Wiley & Sons, Inc.
A simulation model for long‐chain branching in vinyl acetate polymerization: 2. Continuous polymerization in a stirred tank reactor
Authors: Tobita Hidetaka 
Published: April 2003

AbstractA new simulation model for the kinetics of long‐chain branching formed via chain transfer to polymer and terminal double bond polymerization that was proposed in Part 1 of this series is extended to a continuous stirred tank reactor. The present model is applied to the free radical polymerization of vinyl acetate in a micromixed continuous stirred tank reactor, and various information on branched structure such as the molecular weight distribution, distribution of branch points, and branching density of the largest polymer molecule are calculated. Based on the present simulation model, it was found that the method of moments used successfully to predict various average properties in a batch polymerization cannot be applied to a continuous stirred tank reactor without accounting for the outflow of polymer radicals and the existence of polyradicals. The present model has given an excellent agreement with the experimental results of Chatterjee, Park, and Graessley (1977) for a solution polymerization of vinyl acetate in a continuous stirred tank reactor. © 1994 John Wiley & Sons, Inc.
The diffuse behavior of the ferroelectric transition in poly(vinylidene fluoride‐trifluoroethylene) copolymers
Authors: Moreira R. L. , Lobo R. P. S. M. , Medeiros‐Ribeiro G. , Rodrigues W. N. 
Published: April 2003

AbstractThe ferroelectric‐to‐paraelectric phase transition in poly(vinylidene fluoride‐trifluoroethylene) copolymers has been investigated using calorimetric and dielectric technics. In these materials, as it is well known, the ferro‐ and paraelectric phases coexist at large temperature intervals, which produces a smearing of the physical anomalies within the transition region. Thus, in order to treat our data, we have used an extended Landau‐Devonshire treatment, which has provided a quantitative analysis of the macroscopic behavior of the systems. In particular, the Landau expansion parameters, the sample crystallinities, the spontaneous polarizations, and the coercive electric fields have been estimated for the copolymers with 25, 30, and 40 mol% of trifluoroethylene. © 1994 John Wiley & Sons, Inc.