bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractThe 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

AbstractPoly(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

AbstractBlending 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

AbstractComputer‐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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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.
Molecular interactions in polystyrene cosolvent systems
Authors: Parmer Jerome F. , Porter Roger S. 
Published: April 2003

AbstractStudied here are miscible binary cosolvents for polystyrene, for which polystyrene is insoluble in either of the individual solvents. Polymer‐solvent interactions in solutions of atactic polystyrene in acetone/diethyl ether and in methylcyclopentane (MCP)/acetone binary cosolvents have been investigated using nuclear magnetic resonance (NMR) spectroscopy. Polystyrene 13C chemical shifts were measured as a function of miscible binary solvent compositions and temperature. The NMR data were used to calculate “association constants” as a measure of specific interactions of the solvent components with all sites on the polymer. In mixtures of acetone and diethyl ether, 13C‐NMR indicates a weak interaction between the polystyrene phenyl ring and the diethylether solvent component. In the polystyrene/MCP/acetone system, present NMR data reveal no preferential interactions. Additional NMR measurements were performed on polystyrene in mixtures of CCl4/acetone. From these results, it is concluded that although preferential polymer‐solvent interactions are present in some cosolvent systems, they are not a prerequisite for such behavior.
Permeation of carbon dioxide through homogeneous dense and asymmetric cellulose acetate membranes
Authors: Sada E. , Kumazawa H. , Yoshio Y. , Wang S.‐T. , Xu P. 
Published: April 2003

AbstractSorption isotherms for carbon dioxide in a homogeneous dense cellulose acetate membrane were measured by the pressure decay method at three temperatures between 20 and 40°C and gas pressures up to 1.7 MPa. Steady‐state permeation rates for the same system at three temperatures between 24 and 40°C and gas pressures up to 2.2 MPa were measured by the variable volume method. The equilibrium sorption was described well in terms of the dual‐mode sorption model. The pressure dependence of the mean permeability coefficient was interpreted by the total immobilization model, i.e., a limiting case of the dual‐mode mobility model, where the diffusion coefficient for the Henry's law mode is not assumed to be constant but depends upon gas pressure via a modified free‐volume theory. The observed pressure dependence of the mean permeability coefficient through an asymmetric cellulose acetate membrane was very similar to that through a homogeneous dense membrane. The thin skin layer in the asymmetric membrane can be simulated by a homogeneous dense membrane from the point of view of gas sorption and diffusion.
Selective adsorption to cellulose in cadoxen solution
Authors: Huglin Malcolm B. , O'Donohue Stephen J. , Sasia Pedro M. 
Published: April 2003

AbstractRefractive index and density increments at constant composition and also at constant chemical potential have been measured on solutions of cellulose in alkaline aqueous cadoxen. Apparent and true molecular weights of cellulose in this solvent have been determined by light scattering. The findings indicate that [Cd(en)3]2+ ions are preferentially adsorbed to the polymer to the average extent of two ions per three anhydroglucose subunits. Molecular models have shown that this effect is feasible sterically. In cadoxen alone the specific conductance increased with increasing concentration of cadmium and, for a fixed cadmium concentration, the specific conductance was observed to decrease with increasing concentration of dissolved cellulose. This was attributed to reduced overall ionic mobility resulting from selective adsorption of complex cadmium ions to the polymer chain. An analysis has been proposed to quantify this interaction.
The liquid‐crystalline properties of selected cellulose derivatives
Authors: Pawlowski Walter P. , Gilbert Richard D. , Fornes Raymond E. , Purrington Suzanne T. 
Published: April 2003

AbstractThe liquid‐crystalline properties of three cellulose esters, phenylacetoxy cellulose (PAC), 4‐methoxyphenylacetoxy cellulose (4MPAC), and p‐tolylacetoxy cellulose (TAC) and two cellulose silyl ethers, trimethyl silyl cellulose (TMSC) and t‐butyldimethylsilyl cellulose (TBDMSC), are reported.Hot‐stage polarized light microscopy provided evidence regarding the formation of thermotropic mesophases in the PAC, 4MPAC, TAC, and TMSC in bulk form upon heating. The concomitant DSC data showed further evidence of the thermotropic nature of these materials.PAC, 4MPAC, TAC, and TMSC formed lyotropic mesophases at 44, 48, 50, and 27 wt%, respectively in CH2Cl2. The presence of fingerprint patterns in wholly anisotropic solutions in conjunction with optical rotation measurements confirmed the cholesteric nature of these liquid crystalline solutions. TBDMSC formed neither a lyotropic nor a thermotropic liquid‐crystalline phase due to the low degree of substitution (DS 0.68) of this derivative. The hydroxyl substituents of PAC, 4MPAC, TAC, and TMSC may be readily removed under mild conditions to regenerate cellulose.
Adhesive interface interactions between primary aliphatic amine surface conditioners and polyamic ester/polyimide resins
Authors: Linde H. G. 
Published: April 2003

AbstractThe interface reactions of 3‐aminopropyltriethoxysilane treated surfaces, with a polyamic alkyl ester/polyimide resin formed from pyromellitic dianhydride and oxydianiline, were defined by Fourier Transform Infrared (FTIR) analysis on the surface layers of germanium internal reflection plates. Adhesion between these interfacial layers is the result of chemical bonding, which apparently proceeds through initial amide formation between the amino function of the silylated surface and the alkyl ester group present in the polyamic ester. Heating results in diamide formation by a second alkyl, surface‐bound amine displacing the aromatic polymer amine. Heating the more stable dialkyldiamide to 300°C imidizes both the polymer and the interfacial region, producing a strong laminate composite. Polymer scission at the aromatic amide linkages occurs in this adhesion process, bonding surface‐bound alkyl amines to one end of a shortened polymer chain.
Polymer degradation during combustion
Authors: Brauman S. K. 
Published: April 2003

AbstractA novel driven‐rod, radiant pyrolysis technique has been used to study the steady‐state linear regression of vertically mounted poly(methyl methacrylate) and polypropylene rods degrading from the top under high‐flux, nonflaming conditions that simulate those of combustion. With this technique reliable temperature‐depth and oxygen‐depth profiles have been obtained and used to calculate the observed mass loss rates and to elucidate the mode of polymer degradation during combustion, respectively. For poly(methyl methacrylate) burning in this rod configuration, condensed phase oxidation is unimportant and the degradation mechanism is similar to that under more conventional slow‐heating conditions in the absence of air. In contrast, for burning polypropylene condensed phase oxidation occurs; the lack of oxygen incorporation suggests that the polymer degrades by oxygen‐promoted pyrolysis.
Chemiluminescence studies of the thermooxidation of PEEK
Authors: Brauman S. K. , Pronko J. G. 
Published: April 2003

AbstractA highly sensitive microcomputer‐controlled chemiluminescence apparatus capable of spectral resolution of emitted light has been used to study the oxidation of thermoplastic matrix material poly(ether ether ketone), PEEK, at 110°C in oxygen. Even after prolonged exposure and extensive decay in the chemiluminescence signal, the samples show no change in properties or accumulation of oxidation products. Evidence suggests that after oxygen‐assisted initiation, reaction proceeds by radical transfer primarily of polymer phenoxy radicals in a type of radical aromatic substitution reaction on PEEK. Similar substitution‐type biomolecular termination of polymer phenoxy radicals can lead to excited polymer and benzoquinone, emitters that account for much of the oxyluminescence spectrum of PEEK. Under the experimental conditions, the benzoquinone is volatile and the product polymer should be indistinguishable from starting polymer.
Hole transport in polymers of (N‐ethylcarbazol‐3‐yl) methyl acrylate and methacrylate
Authors: Uryu Toishiyuki , Ohkawa Haruki , Oshima Ryuichi 
Published: April 2003

Abstract(N‐Ethylcarbazol‐3‐yl)methyl acrylate and methacrylate were polymerized anionically and radically. Anionically‐polymerized polyacrylate using ethylmagnesium chloride‐benzalacetophenone as catalyst is an isotactic rich polymer with 85% isotactic dyad. All polymers except anionically polymerized polymethacrylate showed good film forming property. Hole drift mobilities measured by the time‐of‐flight method at room temperature and at 5 × 105 V/cm are in the following order: isotactic polyacrylate (1.0 × 10‐5 cm2/V s) > atactic polyacrylate (1.8 × 10‐6 cm2/V s) > atactic polymethacrylate (1.2 × 10‐6 cm2/V s) at 5 × 105 V/cm. These results are discussed in terms of the hopping model between localized sites.
Role of negative ions in the RF plasma deposition of fluoropolymer films from perfluoropropane
Authors: Haque Yasmeen , Ratner Buddy D. 
Published: April 2003

AbstractRF plasma‐deposited fluoropolymer films prepared from perfluoropropane were examined on a variety of metallic, glass, and polymeric substrates using electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared spectroscopy (FTIR). The F1s ESCA spectra of thin (< 100 Å) depositions on some substrates exhibited a peak suggestive of ionic fluoride species. FTIR studies demonstrated the presence of bifluoride ion in some films. Angular‐dependent ESCA studies indicated that these ionic species were not located at the outermost surface of the deposition but rather near the fluoropolymer‐substrate interface. By depositing these fluoropolymer films on a large number of different metallic substrates, and comparing the results of thermal stability studies and solubility studies with literature descriptions of the properties of each of the respective fluoride salts, additional support for the identification of ionic fluoride species at the fluoropolymer‐substrate interface was generated. The implications of this interfacial ionic zone for the adhesion of plasma‐deposited fluoropolymer films to substrates are considered.
Synthesis and characterization of ring polybutadienes
Authors: Roovers J. , Toporowski P. M. 
Published: April 2003

AbstractIt has been shown that butadiene initiated with potassium naphthalene in the mixture THF‐n‐hexane polymerizes conveniently rapidly. The active center is sufficiently stable below 0°C to produce narrow molecular weight linear polybutadiene. The two‐ended living polymer has also served to prepare ring polybutadienes. The analysis of the ring polymers by a high‐resolution set of SEC columns proved superior to the conventional method for the determination of the linear content in rings and in synthetic mixtures of rings and linear polymers. Dilute solution characterization of the linear and ring polymers shows that gr′ = [η]/r[η]l is less than 0.66 in a good solvent.
Sorption and transport properties of MY720/DDS epoxy reacted with blocking reagents
Authors: Kelly B. K. , Gilbert R. D. , Fornes R. E. , Stannett V. T. 
Published: April 2003

AbstractThin films of the epoxy formed by the reaction of tetraglycidyl 4,4'‐diamino‐diphenylmethane and 4,4'‐diaminodiphenyl sulfone (73:27 w/w) were reacted with acrylonitrile (ACN) and isocyanates as blocking reagents for hydroxyl, amine, and epoxy groups. The water uptake at 30, 45, 55, and 70°C of the epoxy resin was monitored gravimetrically. At each temperature the epoxy exhibited case I or Fickian behavior. The diffusion coefficient D increased from 30 to 55°C, but decreased at 70°C because of the reaction of water with residual oxirane groups. Diffusion of ACN is accompanied by both reaction and polymerization, so equilibrium could not be reached. Sorption of the isocyanates essentially follows case I or Fickian behavior. Equilibrium moisture absorptions showed a correspondence between the reduction of moisture absorption and the number of blocked functional groups, irrespective of the nature of the blocking groups. Moisture absorption reductions as high as 68% were obtained. Moisture diffusion of the films after blocking with the various reactants exhibits case I or Fickian behavior. At 30°C, D values are significantly higher for reacted films. At 70°C, the value of D is unchanged as compared with the 30°C value for films reacted with ACN, but D values are significantly lower for films reacted with isocyanate blocking reagents as compared with the epoxy resin.
Mechanical instability of amorphous polymeric networks: Asymmetric deformation under symmetric biaxial tension
Authors: Erman Burak 
Published: April 2003

AbstractAsymmetric deformation of a symmetrically loaded rubber sheet was observed, many years ago, by Treloar in his experiments on natural rubber. The problem has recently been studied by Kearsley, and the possibility of asymmetric deformations in an equi‐biaxial state of force is predicted by the use of phenomenological constitutive relations. In the present study, the problem is analyzed in relation to the molecular constitution of rubber networks. It is shown that mechanical instability in symmetrically loaded networks may be possible only for limited choices of molecular parameters such as junction functionality, degree of crosslinking, and the degree of swelling during crosslinking and during deformation. Stability of multiple valued deformations is discussed by thermodynamic considerations of the elastic potential.
Computer simulation of polymeric materials. I. Stress‐strain behavior
Authors: Cook Robert 
Published: April 2003

AbstractA model of polymeric materials has been developed that includes many of the features of condensed‐phase polymer chain dynamics, central among them chain relaxation via conformational motion. The model consists of a number of chains of particles that are connected by bonds with multiwelled potentials to approximate the energetics of conformational motion. Interactions between particles on adjacent chains are modeled by short range repulsive potentials. We have examined the stress‐strain behavior of the model using molecular dynamics simulations and find qualitative agreement with the observed experimental behavior of polymeric materials.