bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic measurements of the elastic moduli of ultradrawn polyoxymethylene
Authors: Leung W. P. , Choy C. L. , Nakagawa K. , Konaka T.
Published: April 2003

We have employed an ultrasonic method to measure from −40 to 60°C the five independent elastic moduli C11, C13, C33, C44, and C66 of polyoxymethylene with draw ratio λ from 1 to 26 prepared by continuous drawing under microwave heating. The elastic moduli are controlled by three major factors: molecular orientation in the crystalline regions, fraction of noncrystalline taut tie molecules, and void content. The steep rise in the axial extensional modulus C33 and axial Young's modulus E0 with increasing draw ratio results from the alignment of chains in the crystalline blocks and an increase in the number of disordered taut tie molecules. Below the γ relaxation (located at 0°C at our measurement frequency of 10 MHz), these two factors also give rise to a slight decrease in the transverse extensional modulus C11, Young's modulus E90 and shear modulus C66. At high temperature where the amorphous regions have very low modulus, the stiffening effect of taut tie molecules becomes dominant, leading to an increase in all moduli as λ increases from 1 to 10. At higher λ the void fraction increases appreciably, causing small decreases in E90, C11, and C66 at all temperatures.
Photoelastic properties of polybutadiene rubbers
Authors: Mohsin M. A. , Treloar L. R. G.
Published: April 2003

Two polybutadiene polymers were used in this investigation, one with 98% cis‐1,4 units and the other with an approximately equibinary mixture of cis and trans units. A range of cross‐linking densities were obtained using dicumyl peroxide as a vulcanizing agent. The experiments involved measurement of both the elastic force and birefringence (using the changes in length at constant temperature) over the temperature range −10−20°C. The force‐extension curves for both rubbers were similar in form. Both showed a strong upward deviation from the Gaussian statistical theory at high extensions, especially at lower temperature in which the extension to break increases. As expected, the experimental data on both polymers showed the stress‐optical coefficient to be substantially independent of the degree of cross‐linking. On the other hand, the values of the stress‐optical coefficient were found to increase slightly with a decrease in temperature. This effect is a result of the temperature dependence of the stress as indicated by the statistical theory.
Effects of initial morphology and molecular weight on the deformability of poly(ethylene terephthalate)
Authors: Ito Masayoshi , Tanaka Koji , Kanamoto Tetsuo
Published: April 2003

Solution‐grown crystal (SGC) mats and solution‐cast (SC) films of poly(ethylene terephthalate) (PET) were drawn by solid‐state coextrusion followed by tensile drawing of the coextrudates. Drawabilities and properties of the drawn films, such as mechanical and thermal properties, were investigated as functions of molecular weight, initial morphology, and drawing conditions. The initial morphology and molecular weight have a marked effect on the drawability and tensile properties of the resultant drawn films. The attainable maximum draw ratio increases with increasing molecular weight, and the highest draw ratio of 11.5 can be achieved by two‐stage drawing of SC films prepared from pellets with an intrinsic viscosity of 1.43 dl/g. Such highly drawn films exhibit a tensile modulus of 17.5 GPa and strength at break of 400 MPa. These values are comparable to those obtained in conventional spinning of standard grade PET. At a given draw ratio, the tensile strength of the drawn films increases with increasing molecular weight, but the molecular weight dependence is not so marked in the tensile modulus as in the tensile strength. At a given molecular weight, the drawability of SGC mats is lower than that for SC films; however, the efficiency of drawing is higher for the former than for the latter. The difference may arise from the difference in crystallinity and/or crystal perfection of predrawn samples.
Proton NMR relaxation and molecular motion of long‐chain cyclic paraffins in the solid state
Authors: Takenaka Masami , Yamanobe Takeshi , Komoto Tadashi , Ando Isao , Sato Hisaya , Sato Kazuo
Published: April 2003

Temperature‐dependent measurements have been made on the proton NMR relaxations and proton linewidths of the cyclic paraffins (c‐C24H48, c‐C28H56, and c‐C128H256) in the solid state. It is found that in c‐C24H48 and c‐C128H256 there exist two transitions, one due to the melting process and the other due to a rapid transition between trans and gauche conformers in a compact structure that consists of two parallel trans zigzag straight chains bridged at both ends in the crystalline state. In c‐C28H56 there exists only the transition due to melting. Proton NMR relaxations have also been measured for c‐C40H80 and c‐C160H320 at room temperature, in addition to those for c‐C24H48, c‐C28H56, and c‐C128H256. It is found that the extent of molecular motion decreases as the chain length increases.
An experimental study of dilute polyelectrolyte solutions in strong flows
Authors: Dunlap P. N. , Wang C.‐H. , Leal L. G.
Published: April 2003

Flow‐induced changes in the conformation of polymer molecules in dilute polyelectrolyte solutions were studied, using birefringence techniques, as a function of molecular weight and added salt concentration in laminar, two‐dimensional extensional flows produced in four‐ and two‐roll mills. Overshoots in the flow birefringence during startup of simple‐shear flow are presented. Of particular interest is the so‐called coil‐stretch transition. It is shown that the electrostatic expansion of the polyelectrolyte has a dramatic effect on the onset shear rate for the coil‐stretch transition and also on the shape of the flow birefringence versus shear rate curves during the stretching process. A reasonable description of the coil‐stretch transition and its dependence on equilibrium configuration is obtained theoretically using a charged dumbbell model with conformation‐dependent bead friction. Being dependent on the longest relaxation time of the polymer, and therefore not too sensitive to intramolecular details, the dumbbell model can be applied in two ways: either using a charge force to expand its rest state or reducingN, the number of Kuhn segments, in proportion to the increase in relaxation time of the expanded polyelectrolyte.
Stability of the interface between two dynamic phases in capillary flow of linear polymer melts
Authors: McLeish T. C. B.
Published: April 2003

Results of previous work1 on a theoretical explanation of the “spurt effect” in polymer melt flow are extended. A modified Doi—Edwards liquid is shown to support axisymmetric traveling waves on an interface between high and low shear‐rate phases in capillary flow. The stability of these perturbations is found to be governed by normal stress effects and may be related to certain types of melt fracture. Observed effects of varying the capillary length are explained qualitatively.
Gas sorption and transport in miscible blends of tetramethyl bisphenol‐A polycarbonate and polystyrene
Authors: Muruganandam N. , Paul D. R.
Published: April 2003

The permeability coefficients for He, O2, N2, CH4, and CO2 in miscible blends of polystyrene (PS) and tetramethyl bisphenol‐A polycarbonate (TMPC) at 35°C and 1 atm driving pressure are reported. Sorption isotherms for CO2 and CH4 are also presented. The isotherms were fitted to the dual sorption model. The Langmuir capacity factor was found to follow an earlier correlation based on unrelaxed volume. For each gas, the permeability was found to go through a minimum when plotted against blend composition. This behavior is primarily the result of the volume change on mixing observed for this system. The attractive interaction between TMPC and PS is relatively strong as indicated by density and solubility data. The value of the binary interaction parameter was found to be of the same magnitude as that for poly(phenylene oxide) (PPO)‐polystyrene (PS) blends. Considering the similarity of structure between PPO and TMPC, it is concluded that similar phenyl‐phenyl interactions and conformational changes on blending may prevail in TMPC/PS blends.
Properties of poly(ethylene terephthalate) extrudate prepared by hyperbolic convergent flow and high pressure
Authors: Ihm Dae Woo , Cuculo John A.
Published: April 2003

The structure and properties of poly(ethylene terephthalate) segments prepared by high‐pressure extrusion in a pseudohyperbolic die were examined. The translucent segments showed relatively high levels of orientation, crystallinity, and modulus. Higher melting point, larger crystal size, and higher loss modulus peak temperature (Tg) were observed for these segments as compared with those prepared earlier in our laboratory using the conventional 90° conical die. This seems to indicate that a hyperbolic profile is very effective in producing and maintaining a highly aligned chain network in a flowing melt.
Heat capacities and entropies of liquid polyfluoroethylenes and polychloroethylenes
Authors: Loufakis Kyriakos , Wunderlich Bernhard
Published: April 2003

Through new measurements and from literature data, the heat capacity of all liquid polyfluoroethylenes could be established as:

above 480 k, and as

below 480 K in J/(K mol), where NF is the mole fraction of F atoms. In connection with previously established heat capacities of the solid polymers, enthalpies, entropies, and residual entropies of the glassy state at 0 K were computed. Data for liquid polychloroethylenes are much less complete, and the thermodynamic functions could only be established for liquid poly(vinyl chloride) and compared with the data for solid poly(vinyl chloride), poly(vinylidene chloride), and polychlorotrifluoroethylene.
Spherulitic morphology in polyethylene and isotactic polystyrene: Influence of diffusion of segregated species
Authors: Keith H. D. , Padden F. J.
Published: April 2003

Morphological consequences of a localized diffusion of segregated species at crystal growth fronts have been studied in two specific contexts: (1) variation of texture in spherulites grown in unfractionated polyethylene over a range of crystallization temperatures mostly in regime II, and (2) development of elongated lamellar habits in spherulites of a polymer (isotactic polystyrene) whose native crystal habit is regularly polygonal. In relation to (1) it is shown that, as crystallization temperature is varied, there is a correlation between mean thickness of stacks of lamellae and an averaged diffusion range of segregated molecules of lower molecular weight. It is noted that lamellar organization appears to be significantly different in polyethylene fractions. In relation to (2) it is shown that principal contributors to the evolution of spherulitic texture from hedritic precursors are fragmentation of lamellae by screw dislocations and radially biased growth under the influence of concentration gradients of segregated species.
A study of spontaneous rubber/metal adhesion. I. The rolling cylinder test
Authors: Zaghzi N. , Carre A. , Shanahan M. E. R. , Papirer E. , Schultz J.
Published: April 2003

The spontaneous adhesion of vulcanized filled elastomers to steel has been studied using a rolling cylinder test. Owing to the relatively high degree of crosslinking, heavy cylinders are required to ensure good contact with the hard rubber track. This in turn invokes compression within the bulk of the rubber. A consequence is that hysteresis losses are associated not only with the adhesion phenomenon but also with the compression deformation of the system. Theoretical and experimental analyses have led to the conclusion that the two effects may be treated as additive. Both hysteresis losses can be related to the WLF superposition principle.
Molecular orientation in liquid fibers of nematic polymers
Authors: Capasso R. , Roviello A. , Sirigu A. , Iannelli P.
Published: April 2003

The degree of macroscopic orientation of molten fibrous samples of nematic semiflexible polymers has been investigated by x‐ray diffraction. Melting of highly oriented fibers is followed by a partial loss of macroscopic orientation but does not produce collapse of the fiber. The residual orientational order remains unaltered for a considerable time. The degree of orientational order depends on the temperature and undergoes odd‐even fluctuations according to the parity of the number of carbon atoms contained in the flexible part of the monomer unit. Extrapolation of the order parameter to the isotropization temperature leads to a value of about 0.63 for even‐type polymers and to about 0.47 for odd‐type polymers. An intermediate value is found for a copolymer containing equal amounts of even and odd monomer units along the polymer chain.
Thermotropic rigid‐chain copolymers: X‐ray investigations of the structure
Authors: Sauer T. H. , Wendorff J. H. , Zimmermann H. J.
Published: April 2003

The structure of a rigid rodlike random copolyester, consisting mainly of p‐hydroxybenzoic acid, hydroquinone, and carbonyl units, was investigated by means of wide‐angle x‐ray scattering. The lateral order of the chain molecules was found to be short‐range in the nematic melt, in close agreement with the spatial order in the melt of flexible chain molecules. The packing density was found to be surprisingly large in the anisotropic melt. The low‐temperature solid state consists of two phases, namely a frozen‐in nematic and a three‐dimensionally ordered crystal phase. Quenched samples were found to have a degree of crystallinity of about 25%, whereas well‐annealed samples may display a degree of crystallinity of up to 70%. The ordered phase apparently displays an orthorhombic unit cell. Its dimensions indicate that a cocrystallization of the comonomers has taken place. On the basis of the observations that the lattice dimensions change continuously as a function of annealing parameters and taking into account the fact that the transition enthalpy, entropy, and volume are smaller by at least one order of magnitude in comparison to those found for crystals of flexible chains, we arrived at the conclusion that the polymer displays a rotationally disordered crystalline state.
Swelling and sorption in polymer–CO2 mixtures at elevated pressures
Authors: Wissinger R. G. , Paulaitis M. E.
Published: April 2003

Experimental data on gas sorption and polymer swelling in glassy polymer—gas systems at elevated pressures are presented for CO2 with polycarbonate, poly(methyl methacrylate), and polystyrene over a range of temperatures from 33 to 65°C and pressures up to 100 atm. The swelling and sorption behavior were found to depend on the occurrence of a glass transition for the polymer induced by the sorption of CO2. Two distinct types of swelling and sorption isotherms were measured. One isotherm is characterized by swelling and sorption that reach limiting values at elevated pressures. The other isotherm is characterized by swelling and sorption that continue to increase with pressure and a pressure effect on swelling that is somewhat greater than the effect of pressure on sorption. Glass transition pressures estimated from the experimental results for polystyrene with CO2 are used to obtain the relationship between CO2 solubility and the glass transition temperature for the polymer. This relationship is in very good agreement with a theoretical corresponding‐states correlation for glass transition temperatures of polystyrene‐liquid diluent mixtures.
Entanglement, friction, and free volume between dissimilar chains in compatible polymer blends
Authors: Wu Souheng
Published: April 2003

Dynamic oscillation, shear creep, and time‐temperature superposition are used to study the entanglement, friction, and free volume between dissimilar chains in compatible polymer blends: PMMA/PEO, PMMA/PVF2, PMMA/SAN, and PS/PPO. It is found that interchain specific interactions, responsible for the compatibility, tend to reduce the entanglement but increase the friction between dissimilar chains. The former appears to arise from local reduction of chain convolution due to segmental alignment and the latter from increased interchain attraction. The entanglement probability and the friction coefficient between dissimilar chains correlate with the strength of specific interactions. On the other hand, the free volume tends to be linearly additive but may deviate either positively or negatively, apparently influenced by segmental conformation and packing rather than specific interactions. The reduced entanglement and the free volume additivity tend to reduced the melt viscosity, while the increased friction tends to increase it. The former two effects are often stronger than the latter, resulting in a net reduction of melt viscosity in many cases.
Development and characterization of thermosetting‐thermoplastic polymer blends for applications in damage‐tolerant composites
Authors: Raghava R. S.
Published: April 2003

Compatibility or miscibility of polyethersulfones (ICI: Victrex 100P and 300P) and a tetrafunctional epoxy (Ciba‐Geigy: MY‐720), cured with an aromatic anhydride, has been studied using scanning electron microscopy, x‐ray microanalysis, and dynamic mechanical spectroscopy. Fracture toughness of epoxy and blends of an epoxy and polyethersulfones has been measured using three‐point bend tests (ASTM: E‐399–81), and the energy release rate (GIC) for the three materials has been compared as a function of test temperature. Fracture surfaces were examined by x‐ray microanalysis for detecting concentration of sulfur, present in polyethersulfones, in the matrix and precipitated phase. The influence of morphology of epoxy/polyethersulfone blends on its fracture toughness and toughening mechanism has been studied. A toughening criterion is proposed.
Sorptive dilation of polysulfone and poly(ethylene terephthalate) films by high‐pressure carbon dioxide
Authors: Kamiya Yoshinori , Hirose Takuji , Naito Yasutoshi , Mizoguchi Keishin
Published: April 2003

Dilation of polysulfone (PSUL) and crystalline poly(ethylene terephthalate) (PET) films accompanying sorption of carbon dioxide is measured by a cathetometer under high pressure up to 50 atm over the temperature range of 35–65°C. Sorptive dilation isotherms of PSUL are concave and convex to the pressure and concentration axes, respectively, and both isotherms exhibit hysteresis. Each dilation isotherm plotted versus pressure and concentration for the CO2‐PET system shows an inflection point, i.e., a glass transition point, at which the isotherm changes from a nonlinear curve to a straight line. Dilation isotherms of PET below the glass transition point are similar to those of the CO2‐PSUL system, whereas the isotherms above the glass transition point are linear and exhibit no hysteresis. Partial molar volumes of CO2 in these polymers are determined from data of sorptive dilation. On the basis of the extended dual‐mode sorption model and the current data, primitive equations for gas‐sorptive dilation of glassy polymers are proposed.
Extrusion, fiber formation, and characterization of thermotropic copolyesters
Authors: Cuculo John A. , Chen Gao‐Yuan
Published: April 2003

The flow behavior and the effect of the spinning conditions on the fiber properties and structure of poly(ethylene terephthalate) modified with 60 mol% p‐hydroxybenzoic acid (PET/60PHB) were investigated. PET and its copolyesters with 28 and 80 mol% PHB were used as control samples. The melt of PET/60PHB at temperatures above 265°C exhibited extremely low viscosity and low flow activation energy. High birefringence, indicating the presence of a mesophase, was observed between 265 and 300°C on a hot‐stage polarizing light microscope. The maximum tensile strength and initial modulus, 438 MPa and 37 GPa, respectively, were obtained at 275°C for a 0.69 IV polymer. The fiber strength and modulus were significantly lowered when extrusion was conducted at temperatures below 265°C. The fiber properties could also be improved when a high extrusion rate and/or a high draw down ratio was used. Scanning electron microscopy revealed that the fibers spun at temperatures above 265°C had a well‐developed, highly oriented fibrillar structure. The fibers spun at lower temperatures, however, were poorly oriented and nonfibrillar in character. The high orientation and superior mechanical performance achieved at high temperatures were attributed to the presence of the nematic mesophase in the polymer melt.
Dynamic rheological measurements on hydroxypropylcellulose solutions
Authors: Ernst B. , Navard P. , Haudin J. M.
Published: April 2003

Loss and storage moduli were measured by eccentric disk rheometry for isotropic and anisotropic hydroxypropylcellulose solutions. Two rheological regimes exist for the anisotropic solution, one at low deformation ratios (less than 80%) and one at high deformation ratios (more than 100%). For the high‐deformation regime, the comparison between dynamic and steady‐state parameters is consistent with what is known from the literature. The data on the low‐deformation regime are new and are characterized by loss and storage moduli two orders of magnitude larger than those in the high‐deformation regime. This difference is not due to a cholesteric to nematic transition nor to an elastic to viscoelastic transition (yield stress). It is postulated that a network of defects stabilized by chain molecules could give such a low deformation behavior.
On the fractionation of homopolymers during crystallization from the pure melt
Authors: Glaser Raymond H. , Mandelkern Leo
Published: April 2003

The question as to whether fractionation occurs during the crystallization of homopolymers from the pure melt has been addressed by studying linear polyethylene mixtures. Two methods were used. In one procedure, mixtures of well‐defined fractions were crystallized under controlled conditions and the subsequent fusion process was analyzed. In the other procedure, a selective extraction was carried out on an isothermally crystallized polydisperse whole polymer, and the residue was analyzed by gel permeation chromatography. Both methods lead to the same conclusion, namely that during isothermal crystallization only the very low molecular weight species crystallize separately. An extreme upper limit to fractionation corresponds to M = 7000. More likely, fractionation in linear polyethylene during bulk crystallization is restricted to molecular weights of 5000 or less.
Effects of ionizing radiation on epoxy, graphite fiber and epoxy/graphite fiber composites. Part I: Surface energy changes
Authors: Seo K. S. , Fornes R. E. , Gilbert R. D. , Memory J. D.
Published: April 2003

Surface energy changes of an epoxy based on tetraglycidyl diaminodiphenyl methane (TGDDM)/diaminodiphenyl sulfone (DDS), T‐300 graphite fiber, and T‐300/5208 (graphite fiber/epoxy) composites have been investigated after irradiation with 0.5 MeV electrons. The surface energy of TGDDM‐DDS epoxy increases monotonically with radiation doses up to 1,000 Mrad mainly due to increased concentration of polar groups. IR and ESCA spectral evidence indicates that carbonyl groups are formed, probably from the tertiary hydrogen at the carbon where the OH group is attached in the cured epoxy. The polarity of the graphite fiber and the graphite fiber/epoxy interface also increases with radiation dose. These results and the roles of oxygen are discussed in connection with mechanical properties of epoxy/graphite fiber composites exposed to ionizing radiation.
The pressure‐volume‐temperature relationship and the heat of fusion of polyoxymethylene
Authors: Starkweather Howard W. , Jones Glover A. , Zoller Paul
Published: April 2003

The pressure‐volume‐temperature relation of polyoxymethylene was measured at pressures from 100 to 2000 kg/cm2 and from room temperature to 200°C. The dependence of the melting and crystallation temperatures on pressure was also determined. The unit cell parameters were measured up to 170°C by x‐ray diffraction. These data were combined through the use of the Clapeyron equation to compute a heat of fusion of 92.9 cal/g. This value is considerably higher than those previously reported. The weight fraction crystallinity of an injection molded sample was 48% by calorimetry and 66% by interpolation between the specific volumes of the crystal and the amorphous phase. It is suggested that a simple two‐phase model is inadequate to describe this polymer.
A model for x‐ray‐induced solid‐state polymerization
Authors: Kuzyk Mark G. , Sohn John E. , Garito Anthony F.
Published: April 2003

A model for x‐ray‐induced solid‐state polymerization based on experimental results obtained with the disubstituted diacetylene, 10,12‐pentacosadiynoic acid, is presented.
EXAFS analysis of plasticized zinc‐neutralized sulfonated polystyrene ionomers
Authors: Ding Y. S. , Register R. A. , Nagarajan M. R. , Pan H. K. , Cooper S. L.
Published: April 2003

The interaction of several plasticizers with the zinc cation in zinc‐neutralized sulfonated polystyrene was examined with extended x‐ray absorption fine structure (EXAFS) spectroscopy. Glycerol and water were found to interact strongly with the zinc cation, plasticizing the ionic aggregates. At full solvation by glycerol, the zinc atom was found to be coordinated by three glycerol molecules. Dioctylphthalate, acetonitrile, and toluene, which are unable to coordinate to the zinc cation, were found to have a minimal effect on the cation's local structure.
Miscible polybenzimidazole blends with a benzophenone‐based polyimide
Authors: Guerra Gaetano , Williams David J. , Karasz Frank E. , MacKnight William J.
Published: April 2003

Miscible blends of the aromatic polybenzimidazole, poly(2,2(m‐phenylene)‐5,5′‐benzimidazole) (PBI), and the aromatic polyimide formed from 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride and 3,3′‐diaminobenzophenone (LaRC TPI) have been prepared. Blends with PBI were prepared in N,N‐dimethylacetamide solution starting with either the polyamic acid or a 95% imidized form of LaRC TPI; the blend was then precipitated into water or cast as films. The mixture was then imidized thermally to obtain PBI/LaRC TPI blends. Evidence for miscibility was obtained in the form of single composition dependent Tg's intermediate between those of the component polymers and single tan δ dynamic mechanical relaxation peaks. The IR spectra displayed shifts in the NH stretching band, thereby providing evidence for specific interactions related to the miscibility of these two polymers.
NMR approach to the kinetics of polymer crystallization. 1. Cis‐1,4‐polybutadiene
Authors: Feio G. , Cohen‐Addad J. P.
Published: April 2003

The isothermal crystallization kinetics of cis‐1,4‐polybutadiene (PB) in bulk, was studied over the temperature range 193 to 235 K, using 1H pulsed high‐resolution FT‐NMR. Analysis of the spectral line area and width, corresponding to the resonance of protons bonded to noncrystalline chain segments, yields two major results:

The line area variations are associated with the overall progression of crystallization in the sample, which is shown to obey on Avrami law. The time exponent n and rate constant k were determined for each isotherm; their temperature dependence reflects the nucleation and crystal growth mechanisms and provides an estimate of relevant thermodynamic parameters.

The line‐width is assumed to be closely related to a statistical network with the average mesh size determined by a random distribution of crystallites. Finally, concomitant spin‐lattice relaxation time (T1) measurements show an increase of this parameter which parallels the development of the crystalline fraction.
Mobility of spin probes having a primary, secondary, tertiary, or quaternary amino group in drawn and undrawn nylon 6 film
Authors: Hamada Kunihiro , Iijima Toshiro , McGregor Ralph
Published: April 2003

The mobility of spin probes having a secondary, tertiary, or quaternary amino group in dried nylon films was investigated by means of electron spin resonance (ESR) measurements and compared with the behavior of previously investigated spin probes having a primary amino group, a carboxylate group, or a sulfate group. The spin probes having a primary or secondary amino group showed effects of drawing on the mobility, while the other probe molecules did not. This result could be interpreted by considering the interactions between the spin probes and the nylon chains. In the undrawn nylon film, the mobilities of the nonionic spin probes were almost the same, and smaller than those of the charged spin probes, suggesting that the location in the nylon film is different for the uncharged and charged spin probes. These results are discussed in detail using separation of extrema of the ESR spectra, rotational correlation times, and anisotropy parameters.
Piezoelectricity in uniaxially stretched and plasticized nylon 11 films
Authors: Mathur S. C. , Newman B. A. , Scheinbeim J. I.
Published: April 2003

The combined effect of uniaxial stretching and plasticization of nylon 11 films on the resulting piezoelectric response was studied. Three different kinds of samples were studied for nylon 11 α′‐form films: (1) uniaxially stretched at 150°C, (2) samples uniaxially stretched at 150°C and then plasticized by immersion in 2‐ethyl 1,3‐hexanediol, and (3) samples plasticized and then uniaxially stretched. The largest piezoelectric response was obtained from the samples which were plasticized prior to uniaxial stretching under identical poling conditions. For the case of nylon 11 δ′‐form films, two different kinds of experiments were performed: (1) samples uniaxially stretched at room temperature were subsequently plasticized by immersion in the plasticizer and a comparison of their piezoelectric response made with that of the unplasticized samples as a function of poling field; (2) the plasticizer content dependence of the piezoelectric response from these samples was studied. In both cases, d31 was observed to be higher for the plasticized films compared with the unplasticized films. The piezoelectric stress constant e31 showed a small decrease with plasticization. X‐ray diffraction studies indicated a small conversion of δ′‐phase to α′‐phase with plasticization. No significant changes were observed in the x‐ray diffraction scans taken before and after poling.
Viscoelastic Behavior of Amorphous Polymers near the Glass Temperature
Authors: Plazek Donald J. , Rosner Mark J. , Plazek Daniel L.
Published: April 2003

Lack of thermorheological simplicity and possible effects of the molecular weight distribution in the softening dispersion of linear amorphous polymers are demonstrated with viscoelastic data on polymethylacrylate PMA and polyvinylacetate PVAc. Superposition of the short time portion of the softening transitions of the retardation spectra of PMA, PVAc, polystyrene, and amorphous polypropylene APP indicates that the local molecular mobility is a constant at Tg within experimental uncertainty. The general features of the retardation spectra of linear amorphous polymers are discussed.
Water insoluble polyacrylamide part VI: Dilute solution properties of poly(N‐acryloyl‐m‐aminobenzoic acid)
Authors: Desai Trushar , Shah Praful , Suthar Bhikhu
Published: April 2003

A high molecular weight poly(N‐acryloyl‐m‐aminobenzoic acid) (PMAB) was synthesized in a mixed solvent medium by radical polymerization. The polymer was separated into different fractions by fractional precipitation. All those eight fractions were characterized by viscometry, vapor pressure osmometry and gel permeation chromatography. Mark‐Houwink‐Kuhn‐Sakurada relationships were established for three different solvents at 30°C. Unperturbed dimensions were estimated from the viscosity‐molecular weight data using graphical methods based on approximate theories of Stockmayer and Fixman, and of Kurata, Stockmayer, and Roig, and on a first‐order perturbation treatment of the excluded volume effect. The results indicate that the PMAB chain is of intermediate stiffness.
Effect of plasticization by amines on the physical properties of an acidic styrene copolymer
Authors: Smith Pierre , Eisenberg Adi
Published: April 2003

The dynamic mechanical properties of partly sulfonated (8.1 mole%) polystyrene were investigated at a frequency of ca. 1 Hz, following neutralization with various low molecular weight flexible and rigid amines. IR spectroscopic evidence suggested that the protonated amine units were possibly H‐bonded to the sulfonate anion. Neutralization with flexible amines was found to result in a decrease in the glass transition temperature Tg by an amount proportional to the number of carbon atoms in the amine, while neutralization with rigid amines was found to result in an increase in Tg. It was also observed that the amines were more miscible with the sulfonated material than with polystyrene. It was concluded that the changes in properties observed upon neutralization are similar to those expected from a graft.
Salt effects on cloud points and viscosities of polymethacrylates with pendant oligo‐oxyethylene chains
Authors: Nwankwo Ifeoma , Xia Du Wei , Smid Johannes
Published: April 2003

Comblike polymethacrylates with oligo‐oxyethylene side chains were synthesized from the commercially available monomers CH2  C (CH3) COO (CH2CH2O)nCH 3, the average n being 4, 8, and 22. The three polymers exhibited lower critical solution temperatures in aqueous media. Cloud points were determined as a function of the nature and concentration of salt. For salts that destabilize the polymer solutions, the cloud points decrease linearly with salt concentration, the extent of the decrease being strongly anion dependent. Salt effects on the viscosity of the polymers were measured in water, methanol, and acetonitrile. In water the viscosity decreases on adding salt, but in methanol and acetonitrile the neutral polymers are converted to polycations as cations form stable adducts with the oligo‐oxyethylene side chains. The increase in viscosity is both cation and anion dependent. The general behavior of the comblike polymers resembles that reported for aqueous or methanolic salt solutions of poly (ethylene oxide) and nonionic surfactants.
Electron energy loss spectroscopy: Application to synthetic organic polymers
Authors: Briber Robert M. , Khoury F.
Published: April 2003

Electron energy loss spectroscopy has been examined as a possible tool for measuring the atomic composition of polymers on a local scale in the transmission electron microscope. Thin films of nylon 6,6 and single crystal lamellae of poly(chlorotrifluorethylene) were investigated as model systems. Spectra were obtained using an 100 kV electron beam. Results for nylon 6,6 gave fairly good quantitative agreement between the measured relative atomic contents of carbon, nitrogen, and oxygen (77, 9, and 14%, ± 5%, respectively) and the calculated values (75, 12.5, and 12.5%, respectively). Spectra obtained for poly(chlorotrifluoroethylene) single crystals revealed significant mass loss of chlorine as a function of electron dose. The amount of chlorine decayed exponentially with a characteristic dose D* of 96 C/m2. Supporting the poly(chlorotrifluoroethylene) crystals on a continuous carbon film, a holey carbon film, or sandwiched between two carbon films did not effect the mass loss decay constant significantly but did effect the amount of chlorine remaining in the irradiated area at large electron doses. The poly(chlorotrifluorethylene) crystals sandwiched between two carbon films retained more chlorine at large doses, possibly due to the carbon film on both sides of the crystals, inhibiting surface diffusion of the chlorine. Analysis of the spectrum from a portion of a trilayer PCTFE crystal suspended over a hole in the support film gave the relative contents of C, Cl, and F (extrapolated to zero dose) as being 38, 15, and 47%, respectively. The calculated values are 33, 17, and 50%, respectively.
Gas transport in polymers based on bisphenol‐A
Authors: Barbari T. A. , Koros W. J. , Paul D. R.
Published: April 2003

Permeation measurements for CO2, CH4, O2, N2, and He were made with three polymers based on bisphenol‐A, namely a polyhydroxyether, a polyetherimide, and a polyarylate. Measurements were also made for CO2 and CH4 in polysulfone. The data for CO2, CH4, and N2 plus previous data for these gases in polycarbonate and polysulfone were combined with equilibrium gas sorption data and analyzed with the dual mode/partial immobilization model and the more recent gas‐polymer‐matrix model. A comparison of the two models was done on the basis of physical interpretations of the resulting parameters. The diffusion coefficient for the Henry's law population was related to the kinetic diameter of the gas. The infinite dilution, Henry's law, and Langmuir diffusion coefficients were related to the free volume of the polymer. The work suggests a means for order‐of‐magnitude estimation of diffusion coefficients from polymer density and molecular structure.
Gas sorption in polymers based on bisphenol‐A
Authors: Barbari T. A. , Koros W. J. , Paul D. R.
Published: April 2003

Equilibrium gas sorption measurements for CO2, CH4, and N2 were made with three polymers based on bisphenol‐A, namely a polyhydroxyether, a polyetherimide, and a polyarylate. These data plus previous results for two other bisphenol‐A polymers, polycarhonate and polysulfone, were analyzed using the dual‐mode sorption model and the more recent gas‐polymer‐matrix model. The models were compared on the basis of physical interpretations of the resulting parameters. The Langmuir capacity from the dual‐model model was related to the unrelaxed volume of the glassy polymer. The Henry's law sorption parameter from the dual‐mode model was related to the internal pressure of the polymer and to its tensile stress at yield. The work suggests a means for estimation of gas sorption levels from thermal and mechanical properties of the polymer.
Dynamic small‐angle scattering system for the study of materials deformation and relaxation
Authors: Suehiro Shoji , Hendricks Robert W. , Lin J. S. , Kyu Thein , Young Ping , Stein Richard S.
Published: April 2003

A dynamic small‐angle x‐ray scattering system (DSAXS) for the study of materials deformation and relaxation has been developed in the National Center for Small‐Angle Scattering Research, Oak Ridge National Laboratory (NCSASR‐ORNL), in collaboration with Polymer Research Institute of the University of Massachusetts. The principles of DSAXS are outlined, including experimental procedures such as π‐sector and Fourier expansion techniques. A few important functions required for studies of crystalline polymers, namely, static and dynamic lamellar orientation, dynamic lamellar separation, dynamic invariant function, etc., are defined. The hardware and software of the DSAXS system are described. Some preliminary results obtained for a spherulitic high‐density polyethylene by π‐sector technique and for a row‐nucleated polybutene‐1 by Fourier expansion techniques are demonstrated to evaluate the performance of the system.
The determination of network structures in anhydride‐cured butanediol diglycidal ether using 13C‐NMR
Authors: Weisenberger L. A. , Koenig J. L.
Published: April 2003

The static and dynamic structures of butanediol diglycidal ether (BDGE) cured with phthalic anhydride are determined using high resolution solid state 13C‐NMR. Crosslink and junction point resonances are identified by varying the cure state and confirmed using chemical shift calculations. As crosslinking increases, the variety of structures creates a broad distribution of chemical shifts and thus a single broad resonance for the crosslink region. The crosslinking also influences the dynamic structures of the network as indiated by the changes in the various relaxation times of the system. Motions in both the megahertz and kilohertz regimes decrease with cure due to the increasing motional restrictions imposed by the crosslinks.
Uniaxial Draw Of Poly(aryl‐ether‐ether‐ketone) by solid‐state extrusion
Authors: Lee Youngchul , Lefebvre Jean‐Marc , Porter Roger S.
Published: April 2003

Poly(aryl‐ether‐ether‐ketone) (PEEK) films and rods have been solid‐state extruded at 154 and 310°C, respectively. The crystal orientation functions, melting behavior, density, and tensile properties of the drawn PEEK films (EDR ≤ 3.7) and rods (EDR ≤ 5.5) have been measured. As extrusion draw ratio (EDR) was increased, the c‐axis orientation function, melting temperature, and tensile modulus and strength increased. Moduli up to 6.5 GPa and the strengths up to 600 MPa, 3 and 6 times the values of undrawn films, respectively, were obtained for the drawn films. The thermal expansivities along (α‖) and perpendicular (α⟂) to the draw direction of PEEK rods were measured from −40 to +10°C. As EDR was increased, α⟂ increased, but α‖ decreased. At EDRs of 3.8 and 5.5, α‖ even exhibited negative values (about −5 × 10−6°C−1), probably due to reversible contraction of elongated tie‐molecules.
Compatibilizer‐aided toughening in polymer blends consisting of brittle polymer particles dispersed in a ductile polymer matrix
Authors: Angola Juan C. , Fujita Yuji , Sakai Tetsuya , Inoue Takashi
Published: April 2003

Blending brittle polymer particles in a ductile polymer matrix is a new way to obtain toughened plastics. Although the nylon‐6/poly(acrylonitrile‐co‐styrene) (SAN) system is a ductile/brittle combination, the blend does not result in a toughened plastic. We have investigated the effect of adding a small amount of a third component, poly(styrene‐co‐maleic anhydride) (SMA), to the nylon/SAN system. SMA significantly improves the tensile and impact strength of the blend. Morphological observations indicate a finer dispersion of the SAN particles when SMA is present in the blend. The improved dispersion is attributed to the formation of nylon‐SMA graft copolymer, and infrared analysis supports this supposition. That is, a “compatibilizer” seems to be produced during melt mixing of the ternary system. The role that the compatibilizer plays in improving the stress transfer in the two‐phase system and its potential to induce a brittle‐ductile transition of the glassy SAN particles are considered to explain the toughening mechanism.
An apparatus for measuring polymer thermal conductivities at high pressure and temperature
Authors: Gobbe C. , Bazin M. , Gounot J. , Dehay G.
Published: April 2003

Computer‐sided design of plastic moldings requires knowledge of their thermal properties, e.g., thermal conductivity λ, under specific conditions. For this purpose, we constructed an apparatus that measures λ and functions within the 80–350°C temperature range and up to a pressure of 500 bar. It was used to carry out experiments on three types of polymers (polyamide, polystyrene, and polypropylene). This paper includes a description of the experimental setup and a presentation of the numerical modeling required for simulating the thermal behavior of tested samples whose measurements have been reported herein.
Reversal and activation of physical aging by applied deformations in simple compression and extension
Authors: Smith T. L. , Levita G. , Moonan W. K.
Published: April 2003

The differential (incremental) storage modulus E′ was measured intermittently at 1 Hz during the stress relaxation of cylindrical specimens of polycarbonate subjected to finite static strains in both simple compression and extension. (In measuring E′, the amplitude of the applied sinusoidal strain was 0.2%.) Application of each static strain gave a value of E′/E′0 less than unity, where E′0 is the storage modulus at 1 Hz of the undeformed specimen. This behavior results from an increase in the mobility of short molecular segments; it signifies a partial erasure of the state of physical aging, a change also termed de‐aging or rejuvenation. After a static strain had been applied, E′ increased continuously, a reflection of physical aging that results from a progressive decrease in segmental mobility. Plots of E′/E′0 at an aging time of 100 s against the absolute value of the static strain show that simple extension de‐ages a specimen somewhat more than does a strain of the same magnitude in compression. This difference results from the increase or decrease in volume (or free volume) effected by strains in extension or compression, respectively. The dominant cause of de‐aging, however, is the deviatoric (shear) component of the strain tensor. The increase or decrease in volume produced by an applied strain modifies only slightly the segmental mobility.
Electrochemical synthesis and optical analysis of poly[(2,2′‐dithienyl)‐5,5′‐diylvinylene]
Authors: Martinez Maria , Reynolds John R. , Basak Sanjay , Black Douglas A. , Marynick Dennis S. , Pomerantz Martin
Published: April 2003

The electrochemical synthesis of poly[(2,2′‐dithienyl)‐5,5′‐diylvinylene tetrafluoroborate] (PDTE/BF4) has been accomplished and provides coppery‐black free‐standing films with a room‐temperature four‐probe conductivity as high as 15 (Ω cm)−1. The conductivity and morphology of the films were found to be strongly dependent on synthetic conditions. The oxidized form of PDTE is not air stable, as evidenced by a rapid, three order of magnitude drop in the conductivity. Optoelectrochemical experiments demonstrate that bipolarons are the main charge‐carrying species in conductive PDTE and allow their evolution to be followed as a function of oxidation.
Thermal expansion of polyoxymethylene
Authors: Choy C. L. , Nakafuku C.
Published: April 2003

The thermal expensivities of polyoxymethylene crystals in the direction parallel (α|c) and perpendicular (α‖c) to the chain axis have been measured from 160 to 400 K using wide‐angle x‐ray diffraction. Although polyoxymethylene has a helical chain structure, it exhibits a thermal expansion behavior similar to that of polymer crystals with planar zigzag chains, namely that α‖c is negative while α|c is positive and larger by an order of magnitude. The negative α‖c arises from the shortening along the chain axis caused by the torsional and bending motions of the chain, whereas the large and positive α|c reflects the weak interaction across the chains. Combining the crystal data with dilatometric measurements on semicrystalline samples, the thermal expansivity is found to vary linearly with crystallinity, thus allowing the expansivity of the amorphous phase to be derived by extrapolation. With the thermal expansivities of the crystalline and smorphous phases known, the draw ratio dependence can be calculated in terms of existing models and is found to agree reasonably with experimental data.
Multiple endothermic melting behavior in poly(tetramethylene terephthalate)‐containing polyesters and block copolyether‐esters
Authors: Stevenson Janis Castles , Cooper Stuart L.
Published: April 2003

The multiple endothermic behavior of poly(tetramethylene terephthalate) (PTMT) and its random and block copolymers with poly(tetramethylene isophthalate) (PTMI) and poly(tetramethylene oxide) (PTMO) is described. The differential scanning calorimetry heating scans of these polymers exhibit up to four endotherms. Endotherm I, the lowest‐temperature endotherm, is an annealing peak and is ascribed to a clustering of PTMT sequences. Endotherms II, III, and IV are associated with crystal populations originated during periods of isothermal crystallization, cooling, and heating, respectively. The dependence of the endotherms on sample composition, crystallization and annealing temperatures, crystallization and annealing times, and sample cooling and heating rate is discussed.