bluuebunny/crossref_metadata_2025_split huggingface dataset:
Swelling and sorption in polymer–CO2 mixtures at elevated pressures
Authors: Wissinger R. G. , Paulaitis M. E. 
Published: April 2003

AbstractExperimental 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

AbstractDynamic 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

AbstractCompatibility 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

AbstractDilation 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

AbstractThe 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

AbstractLoss 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

AbstractThe 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

AbstractSurface 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractMiscible 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractLack 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

AbstractA 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

AbstractThe 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

AbstractComblike 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

AbstractElectron 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

AbstractPermeation 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

AbstractEquilibrium 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.