bluuebunny/crossref_metadata_2025 huggingface dataset:
Small‐Angle light scattering from an anisotropic sphere: Anisotropy and size effects
Authors: Holoubek J.
Published: April 2003

The recently developed theory of light scattering from an anisotropic sphere (taken as a model for a spherulite) summarizes all information obtainable from such scattering system when the Rayleigh‐Gans‐Debye approximation is appropriate. The commonly used procedure of size determination from the maximum of the Hv intensity is tested for a number of models differing in radius size, inherent anisotropy δn and mean refractive index ¯n. It has been confirmed, that the parameter (¯n ‐ 1)/δn plays the decisive role in the angular dependence of the Hv intensity and the influence of that parameter on the size determination and resulting accuracy is specified. The results differ for positive and negative spherulites and the stabilizing role of increasing spherulite size in accuracy of procedure is demonstrated. It has been shown that the RGD approximation is appropriate especially for the case of homogeneous spherulite texture (thus implying, that the refractive index of the surrounding is close to the average refractive index of a single spherulite). The results extrapolated outside of the RGD approximation display invariable Umax position for isotropic contribution with increasing sphere size in contrast to the oscillatory character of Umax predicted by the LM solution. It is proposed to construct the anisotropic solution under an approximation recently suggested for thin anisotropic shell. © 1994 John Wiley & Sons, Inc.
Effect of shear history on the steady shear flow behavior of a thermotropic liquid‐crystalline polymer
Authors: Kim Seung Su , Han Chang Dae
Published: April 2003

The steady shear stress (σ) and first normal stress difference (N1) of a thermotropic liquid‐crystalline polyester, poly[(phenylsulfonyl)‐p‐phenylene 1,10‐decamethylene‐bis(4‐oxybenzoate)] (PSHQ10), in both the isotropic and nematic regions were measured as a function of shear rate (γ), using a cone‐and‐plate rheometer. For the study, PSHQ10 was synthesized via solution polymerization in our laboratory. The PSHQ10 was found to have (a) the weight‐average molecular weight of 45,000 relative to polystyrene standards and a polydispersity index of 2, (b) a glass transition temperature of 88°C, (c) a melting point of 115°C, and (d) a nematic‐to‐isotropic transition temperature of 175°C. For the measurements of σ and N1 in the nematic region of PSHQ10, its initial conditions for the startup of shear flow was controlled by (a) first heating an as‐cast specimen to 190°C, (b) shearing there at γ = 0.085 s−1 for about 5 min, and then (c) cooling slowly down to a predetermined temperature (130, 140, 150, 160, or 171°C) in the nematic region. For each γ chosen, after start‐up of shear flow, we waited for a sufficiently long time until both the shear stress and first normal stress difference leveled off, giving rise to steady‐state values of σ and N1. Emphasis was placed on investigating the effect of shear history on σ and N1 of PSHQ10 in the nematic region. For this, the following experiments were conducted: (a) a fresh specimen was sheared continuously by increasing the γ stepwise, and (b) a presheared specimen was further sheared continuously by increasing the γ stepwise. We have found that fresh specimens exhibited ‘shear‐thinning’ behavior over the entire range of γ (0.008−0.27 s−1) tested, whereas the presheared specimens exhibited both zero‐shear viscosities and shear‐thinning behavior. When using fresh specimens, we found that N1 was positive over the entire range of γ (0.008–0.27 s−1) tested. However, when using presheared specimens we found that (a) at very low γ, N1 initially was negative and then became positive as shearing continued, and (b) at higher γ, N1 was positive over the entire duration of shearing. © 1994 John Wiley & Sons, Inc.
Toughening of highly crosslinked epoxy resins by reactive blending with bisphenol A polycarbonate. II. Yield and fracture behavior
Authors: Di Liello V. , Martuscelli E. , Musto P. , Ragosta G. , Scarinzi G.
Published: April 2003

The yield and fracture behavior of highly crosslinked epoxy resin modified by a reactive blending process carried out in the presence of bisphenol A polycarbonate has been studied. It was found that the fracture toughness of this blend system increases markedly with increasing PC content in the blend. Scanning electron microscopy of the fractured surfaces indicated a crack blunting mechanism as the main source of energy dissipation in the various investigated blend compositions. No evidence of phase separation of the minor component during the curing and postcuring steps was observed. The yield data were correlated with the fracture toughness data to evaluate the extent of crack‐tip blunting. © 1994 John Wiley & Sons, Inc.
Conductivity study of stretch‐oriented new polyacetylene
Authors: Płocharski Janusz , Pukacki Wojciech , Roth Siegmar
Published: April 2003

Oriented 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

A 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

Amino 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

Interchain 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

The 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

Poly(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

A 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

The 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

Previously 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

Residual 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

The 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

Nylon‐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

Copolymers 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

Laser 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

The 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

The 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

For 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

A 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

The 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.
Structure‐property relationships in short‐fiber‐reinforced composites
Authors: Termonia Yves
Published: April 2003

A 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

The 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

Packing 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

The 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

Cellulose 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

Differences 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

The 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

The 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

The 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

Fourier‐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

The 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

Thermally 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

The 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

This 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

A 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

Poly(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

Two‐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.