bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic mechanical properties of epoxy resin/epoxidized rubber blends: Effect of phase separated rubber
Authors: Bussi Philippe , Ishida Hatsuo 
Published: April 2003

AbstractThe dynamic mechanical properties of blends of diglycidyl ether of bisphenol‐A‐based epoxy resin and internally epoxidized polybutadiene rubber have been studied. It is shown that the influence of the composition of the continuous phase and of the dispersed phase can be studied not only from the variations of the glass transition temperature but also from the changes in the apparent enthalpy of activation associated with this transition. As the initial rubber content increases, the composition of the dispersed phase remains practically constant while more rubber is able to dissolve in the continuous phase. Analysis of the rubbery plateau region reveals that the shear modulus of the blends is not much affected by the presence of dissolved rubber in the continuous phase but strongly depends on the volume fraction of dispersed phase. This volume fraction can be obtained from the relative drop in shear modulus after modeling the results with the Kerner equation. The results compares well with independent measurements by scanning electron microscopy. © 1994 John Wiley & Sons, Inc.
Molecular orientation and microstructure of roller‐drawn sheets of poly(ether ether ketone)
Authors: Kaito A. , Nakayama K. 
Published: April 2003

AbstractThe rolling and roller‐drawing of poly(ether ether ketone) (PEEK) sheets were carried out in the roller temperature range of 165‐262°C. The crystal orientation functions of the PEEK sheets were determined from the azimuthal intensity distribution of wide‐angle x‐ray diffraction, and the orientation behavior in the amorphous region was characterized by the measurements of sonic modulus and polarized fluorescence. The orientation functions increase monotonically with increasing draw ratio. The orientation function in the amorphous region is close to that of crystal orientation function of the same sample. The long period evaluated by small‐angle x‐ray scattering is almost constant over the draw ratio range studied, whereas the crystallite size along the 001 plane, D001 tends to increase with increasing draw ratio. The value of the crystallite size exceeds the product of the crystallinity and the long period. The result suggests the formation of the crystalline linkages that penetrate the periodic layers. © 1994 John Wiley & Sons, Inc.
The influence of alkylene spacers on conformational and thermal properties of poly (aryl methacrylates)
Authors: Chen Yuan‐Ju , Mays Jimmy W. , Hadjichristidis Nikos 
Published: April 2003

AbstractThe effect of introducing alkylene spacers on the thermal and conformational properties of poly(aryl methacrylates) has been studied. Poly(2‐phenylethyl‐1‐methacrylate) (PPEMA) and poly(4‐phenylbutyl‐1‐methacrylate) (PPBMA) samples of narrow poly‐dispersities and covering a very broad range of molecular weights were produced by free radical solution polymerization, followed by fractionation. These materials were studied by a combination of differential scanning calorimetry, light scattering, and viscometry measurements to allow evaluation of their glass transition temperatures (Tg) and characteristic ratios (C∞). These results are compared with literature data available for poly(phenyl methacrylate) (PPMA), which has no alkylene spacer, and poly(benzylmethacrylate) (PBMA), which has a methylene spacer. A progressive decrease in Tg is observed as the length of the alkylene spacer is increased, reflecting the enhancement of side group (local) flexibility. C∞ decreases substantially on going from PPMA to PBMA but then increases on going to PPEMA and PPBMA. This behavior is attributed to the fact that while side group flexibility increases for the materials with longer alkylene spacers, and this would be expected to decrease C∞, the side group size is progressively increasing. Larger side groups generally increase C∞ of polymethacrylates. Thus the observed C∞ behavior for these polymers reflects both the size and flexibility of the substituents. © 1994 John Wiley & Sons, Inc.
Dynamic relaxation behavior of solvent‐crystallized poly(ether ether ketone)
Authors: Kalika D. S. , Nickell J. C. , Krishnaswamy R. K. , Barton B. F. 
Published: April 2003

AbstractThe dynamic relaxation behavior of solvent‐crystallized poly(ether ether ketone) (PEEK) has been investigated in the region of the glass‐rubber (α) relaxation using dynamic mechanical and dielectric methods. Amorphous PEEK films were exposed to saturated methylene chloride and acetone vapor, with solvent‐induced crystallization observed for both penetrants. Sample desorption at elevated temperatures (under vacuum) resulted in virtually complete removal of residual penetrant, thus providing for the measurement of relaxation characteristics independent of plasticization. Both dynamic mechanical and dielectric studies indicated a marked positive offset in the isochronal relaxation temperatures of the solvent‐crystallized samples relative to thermally crystallized specimens of comparable bulk crystallinity, and a higher apparent activation energy in the solvent‐crystallized case. These results are consistent with the evolution of a tighter crystalline morphology (i.e., smaller crystal long spacing) in the solvent‐crystallized samples, the crystallites imposing a greater degree of constraint on the long‐range motions of the amorphous chains inherent to the glass‐rubber relaxation. © 1994 John Wiley & Sons, Inc.
Temperature measurements of the gaseous emission during the fracture of polystyrene: A determination of the fracture energy and fracture surface temperature
Authors: Dickinson J. T. , Jensen L. C. , Langford S. C. , Dion R. P. 
Published: April 2003

AbstractThe emission of volatile species accompanying the fracture of polystyrene has been monitored as a function of time by two quadrupole mass spectrometers mounted at different distances from the sample. The resulting time‐of‐arrival signals were numerically modeled to yield an estimate of the energy per unit area dissipated as heat by fracture. Neutral emissions of ethyl benzene molecules (a common volatile impurity) and a noble gas (Arintroduced by exposure) were monitored. Dissipation (fracture) energies determined ranged from 680 to 1480 J/cm2, consistent with the range of energy release rates in the literature. The peak surface temperatures calculated from the measured heat dissipation ranged from 600 to 1300 K. © 1994 John Wiley & Sons, Inc.
Effect of glass fiber‐matrix polymer interaction on fatigue characteristics of short glass fiber‐reinforced poly(butylene terephthalate) based on dynamic viscoelastic measurement during the fatigue process
Authors: Takahara Atsushi , Magome Tateshi , Kajiyama Tisato 
Published: April 2003

AbstractFatigue behaviors of glass fiber‐reinforced poly(butylene terephthalate) (PBT) were studied based on dynamic viscoelastic measurements during the fatigue process. The fatigue strength of glass fiber‐reinforced PBT was greatly improved by strengthening the interfacial adhesion between glass fiber and matrix PBT. The heat generation rate under cyclic fatigue for PBT reinforced with surface‐unmodified short glass fiber was always larger than that reinforced with surface‐modified short glass fiber because of the large net imposed strain amplitude of PBT matrix which occurred due to the interfacial debonding under cyclic fatigue. A fatigue fracture criterion based on the magnitude of hysteresis energy loss being consumed for a structural change was established for the PBT/short glass fiber composites in consideration of glass fiber‐matrix polymer interfacial interaction. © 1994 John Wiley & Sons, Inc.
Sub‐Tg molecular motions in glassy poly(vinyl chloride). Influence of the nucleophilic substitution
Authors: Del Val J. J. , Colmenero J. , Martínez G. , Millán J. L. 
Published: April 2003

AbstractDielectric local molecular motions in the glass transition region of poly(vinyl chloride) (PVC) have been investigated by means of the isothermal depolarization currents technique. Attention is paid to the influence of the modification of the polymer by the substitution of chlorine atoms of PVC chain by the benzenethiolate group. The results are well described by stretched exponential laws. According to the Ngai's coupling model, the coupling between moving units as well as the activation energy responsible for the motions occurring at primitive level have been calculated for each sample at each temperature. All these parameters are noticeably altered by the modification of PVC. © 1994 John Wiley & Sons, Inc.
Phenolic materials via ring‐opening polymerization of benzoxazines: Effect of molecular structure on mechanical and dynamic mechanical properties
Authors: Ning Xin , Ishida Hatsuo 
Published: April 2003

AbstractA series of benzoxazine compounds have been prepared from different bifunctional phenols and primary amines and the molecular compositions of the precursors are characterized by nuclear magnetic resonance, Fourier transform infrared, and size exclusion chromatography. It has been demonstrated that by design of the molecular structures of the benzoxazine precursors, therefore by tailoring of the network molecular architectures, new phenolic materials with superior mechanical and thermal properties, and ease‐of‐processing characteristics can be obtained. The characteristics of dynamic mechanical spectra of the phenolic materials are studied and related to their structural features. © 1994 John Wiley & Sons, Inc.
Structural changes of silk fibroin membranes induced by immersion in methanol aqueous solutions
Authors: Tsukada Masuhiro , Gotoh Yoko , Nagura Masanobu , Minoura Norihiko , Kasai Nobutami , Freddi Giuliano 
Published: April 2003

AbstractStructural changes of native and regenerated silk fibroin membranes were induced by immersion in water‐methanol solutions and examined as a function of immersion time and methanol concentration. X‐ray diffractometry and infrared spectroscopy data showed that transition from random coil to β‐sheet structure occurred favorably when both native and regenerated silk fibroin membranes were immersed in water‐methanol solutions, regardless of the different immersion time. Only native silk membrane, treated for 2 min with pure methanol, maintained its original amorphous structure, as demonstrated by differential scanning calorimetric (DSC) curves. The degree of displacement, measured by thermomechanical analysis (TMA), was much greater for regenerated than for native silk fibroin membranes. SDS‐PAGE pattern showed that native silk fibroin has a molecular weight of 350, while the regenerated sample is formed by a large number of polypeptides in the range of 200‐50 KD. The amount of acidic and basic amino acids decreased slightly in regenerated silk fibroin. Physical properties of silk membranes treated with water‐methanol solutions are discussed in terms of membrane structure, treatment conditions, and chemical structure of starting material. © 1994 John Wiley & Sons, Inc.
Cyclic polymers swollen in a good solvent dynamic scattering properties
Authors: Benmouna M. , Borsali R. , Rinaudo M. 
Published: April 2003

AbstractA general formalism for the dynamic scattering properties of cyclic polymers in good solvent conditions is presented. Single‐chain dynamics are investigated in the framework of the Oseen tensor model with and without the preaveraging approximation. The chain swelling due to excluded volume interactions is introduced by a renormalization of the internal chain statistics of cyclic polymers. The relaxations of the concentration fluctuations are also described for both ring homopolymers and copolymers. © 1994 John Wiley & Sons, Inc.
Emission of occluded volatiles during deformation of polycarbonate due to strain‐enhanced diffusion
Authors: Dickinson J. T. , Jensen L. C. , Langford S. C. , Dion R. P. 
Published: April 2003

AbstractMeasurements of the emission of purposely entrained volatiles (Ar and D2O) during the loading and unloading of a bisphenol‐A polycarbonate in vacuum are made by quadrupole mass spectrometry. Transient loading events are accompanied by dramatic increases in emission, reflecting a similar rise in the diffusion constant of the measured species. We attribute this change to an increase in size of molecular voids in the polymer network, which accompany the increase in sample volume under load. The results are interpreted in terms of the Dolittle relation in which the diffusion constant depends exponentially upon v*/vf0, the ratio between an activation volume for diffusion and the average size of the relevant voids in the polymer network. Our data suggests that v*/vf0 is unusually low in the D2O‐polycarbonate system, which we attribute to a relatively large value of vf0; this would be consistent with the relatively long distance between flexible links in the polycarbonate structure. © 1994 John Wiley & Sons, Inc.
Depolarization thermocurrent studies in poly(hydroxyethyl acrylate)/water hydrogels
Authors: Kyritsis A. , Pissis P. , Ribelles J. L. Gómez , Pradas M. Monleón 
Published: April 2003

AbstractDetailed investigations on the dielectric relaxation mechanisms in poly(hydroxyethyl acrylate) (PHEA), by means of the thermally stimulated depolarization currents (TSDC) method in the temperature range 77‐300 K are reported. There is particular interest in the dependence of the dielectric relaxation mechanisms on the water content h, h = 0 − 0.5 w/w, in an attempt to contribute to a better understanding of the physical structure of water in the PHEA hydrogels. We employ thermal sampling (TS) and partial heating (PH) techniques to experimentally analyze the observed complex relaxation processes, due to the secondary (βsw) and the main (α) relaxation, into approximately single responses and to determine the spectra of activation energies E(T) at different h values. Measurements with different electrode configurations reveal different aspects of the dynamics of the relaxation mechanisms and allow the distinction between dipolar and conductivity relaxation contributions. It is shown that by means of these techniques we can determine certain temperature characteristics for the α relaxation and investigate their dependence on water content. We discuss the relation of these characteristic temperatures to the calorimetric glass transition temperature Tg. © 1994 John Wiley & Sons, Inc.
Swelling studies of crosslinked poly(p‐phenylene terephthalamide) copolymers in sulfuric acid
Authors: Rigney Jennifer , Little Monica D. , Martin David C. 
Published: April 2003

AbstractIn an attempt to improve the mechanical properties of extended chain polymers such as poly(p‐phenylene terephthalamide) (PPTA), a crosslinkable terephthalic acid derivative (XTA) has been developed which can be incorporated into copolymers in various concentrations and activated after polymerization. The crosslinking of PPTA‐co‐XTA copolymer particles was investigated through a series of swelling experiments in concentrated H2SO4. The data show a systematic decrease in equilibrium swelling with increasing XTA content, indicating the XTA units are in fact acting as crosslink sites. Values for crosslink density were calculated from the Flory‐Rehner theory of polymer swelling and compared with previous findings on crosslinked rigid polymer network systems. The effective number of crosslinks per XTA unit (efficiency) predicted by the Flory‐Rehner theory increases and then decreases with % XTA. The decrease in crosslinking efficiency at high XTA concentrations is consistent with differential scanning calorimetry data which show the enthalpy of XTA reaction decreasing slightly with % XTA. The deviations at low % XTA may represent a failure of the Flory‐Rehner theory to properly describe the rubbery elasticity of extended chain polymers. © 1994 John Wiley & Sons, Inc.
Characteristics of charged networks under an electric stimulus
Authors: Kwon Ick Chan , Bae You Han , Kim Sung Wan 
Published: April 2003

AbstractThe electrokinetic phenomena of poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐n‐butylmethacrylate) were examined to investigate physical changes of the gel under an applied electric current. When an electrical stimulus was applied to a piece of the gel, without being in contact with an electrode, reversible gel bending was observed. The bending degree was directly proportional to the intensity of the applied electric stimulus. This was explained by ‘depletion polarization’ of ionic species under the stimulus. The swelling of the gel surface facing the anode increased, due to the decreased ionic strength of the boundary layer upon electric stimulation, while gel shrinking occurred at the cathode. When the gel is in direct contact with electrodes, deswelling of the gel was observed at the anode side, while water seepage occurred at the cathode side. This observation was attributed to the electro‐osmosis inside the gel, combined with local pH changes around the electrodes resulting from electrochemical reactions, particularly water electrolysis. © 1994 John Wiley & Sons, Inc.
Modelling of water transport in ionic hydrophilic polymers
Authors: Hariharan Deepak , Peppas Nikolaos A. 
Published: April 2003

AbstractWater and ion transport in thin sheets of initially dry, ionic, hydrophilic crosslinked polymers was modelled throughout the dynamic swelling process. The water transport was expressed in terms of a non‐Fickian equation with a diffusion term containing a Fujitatype concentration‐dependent diffusion coefficient coupled with a pseudoconvective term arising from the reasonable assumption that the stress in ionic polymers is proportional to the total number of ionized pendant groups in the polymer. Ion transport was expressed in terms of generalized Fickian equations with water concentration‐dependent diffusion coefficients. These equations were solved with appropriate boundary conditions to establish the water uptake as a function of time, pH and ionic strength in a citrate‐phosphate‐borate buffer solution. A new dimensionless number, the Stress Swelling number, A, was defined to quantify the relative importance of stress in the overall swelling process. Water uptake was a strong function of A. © 1994 John Wiley & Sons, Inc.
Block copolyetheramides III. Blends of nylon‐6 and block copolyetheramides
Authors: Chung Lie‐Zen , Kuo Dee‐Lun , Tsai Hong‐Bing 
Published: April 2003

AbstractBlends of Nylon‐6 and block copolyetheramides with hard segments of Nylon‐6 and soft segments of poly(tetramethylene ether) were prepared. The impact strength of the blends was enhanced by the presence of the block copolyetheramides as compared to the Nylon‐6. Different block copolyetheramides exhibited different effects on the impact strength which could be described as the difference in compatibility between the Nylon‐6 and the Nylon‐6 segments of the block copolymers. The difference in compatibility was verified by the investigations of TEM and DSC. As the caprolactam content of the block copolyetheramides increased, the compatibility between the Nylon‐6 and the Nylon‐6 segments of the block copolymers was enhanced and the blends exhibited a higher impact strength in general. The heat deflection temperature of the blends decreased as the polyether content (depending on the type and the content of the block copolyetheramide) of the blends increased. When the polyether content was ≤ or 20 wt %, a small decrease in heat distortion temperature was found. © 1994 John Wiley & Sons, Inc.
Protonation of CIS‐PBO in metanesulfonic acid solutions
Authors: Roitman Daniel B. , McAlister Jan , McAdon Marc , Wessling Ritchie A. 
Published: April 2003

AbstractA comparative study of the conductivity behavior of methane‐sulfonic acid solutions of poly(p‐phenylene‐cis‐benzobisoxazole) or cis‐PBO and other compounds, including CH3SO3Na (NaMSA), a cis‐PBO model compound, and 6,7‐dimethyl‐2,3‐di(2‐pyridyl) quinoxaline, a molecule containing four protonating sites, was carried out to determine the degree of protonation of PBO and its model compound. The conductivity dependence with increasing cis‐PBO concentration indicates that only two sites per repeat unit are protonated. © 1994 John Wiley & Sons, Inc.
Raman spectral study of solid and dissolved poly(vinyl alcohol) and ethylene‐vinyl alcohol copolymer
Authors: Cooney T. F. , Wang L. , Sharma S. K. , Gauldie R. W. , Montana A. J. 
Published: April 2003

AbstractWe have measured the Raman spectra of ethylene‐vinyl alcohol copolymer (EVOH) and poly(vinyl alcohol) (PVOH). Spectra of 88% hydrolyzed PVOH were examined from the partially crystalline solid, from PVOH dissolved in both H2O and D2O, and from films precipitated from these solutions. The spectrum in H2O differs from that of the starting material by disappearance of sharp bands having Raman shift values of 1146 and 1093 cm−1, strengthening of a band near 915 cm−1, decrease in frequency of bands at 480, 1356, and 1441 cm−1, and increase in frequency of bands at 369, 413, 1023, 1371, and 2910 cm−1. The spectrum of the film shows partial reversal of these trends. With D2O as the solvent, the band shifts are slightly different from those listed above and new bands appear. These changes are indicative of loss of crystallinity, change in stereochemistry, and partial deuteration of hydroxyl during dissolution of this PVOH sample at room temperature. © 1994 John Wiley & Sons, Inc.
Ethanol‐induced crack healing in poly(methyl methacrylate)
Authors: Wang Peng‐Peng , Lee Sanboh , Harmon Julie P. 
Published: April 2003

AbstractThe crack healing induced by ethanol in poly(methyl methacrylate) (PMMA) has been studied at temperatures of 40–60°C. Crack healing occurs because the effective glass transition temperature of PMMA is reduced to below the test temperature by ethanol plasticization. It is found that crack closure rate is constant at a given temperature. The fracture strength of healed PMMA is lower than that of the original samples. By comparing the fracture stress with the morphology of the crack edge on the PMMA surface, we found that a high degree of swelling is responsible for the incomplete recovery of mechanical strength. The fractography of the completely healed sample shows a very different fracture morphology from that of virgin PMMA. The transport of ethanol in PMMA also is studied. At lower temperatures, transport is described by ideal Case II behavior. As the temperature increases, the kinetics shift from ideal Case II to anomalous behavior. The first stage of crack healing is controlled by Case I transport. © 1994 John Wiley & Sons, Inc.
Hydrogen bonds in regioselectively substituted cellulose derivatives
Authors: Kondo Tetsuo 
Published: April 2003

AbstractFormation of hydrogen bonds in various cellulose derivatives, 2,3‐di‐O‐ and 6‐O‐substituted cellulose ethers, were characterized by FTIR and solid‐state CP/MAS13C‐NMR. The polymers were synthesized by regioselective substitution of hydroxyl groups and had a uniform structure. Since their three hydroxyl groups (OH) are selectively blocked, the cellulose derivatives appeared to form specific inter‐ and intramolecular hydrogen bonds. The characteristic OH stretching frequencies in IR spectra and the C‐1 chemical shift in CP/MAS spectra of 6‐O‐substituted cellulose derivatives indicated existence of two equivalent intramolecular hydrogen bonds between ether oxygen and OH groups at 3‐OH‐O5′ and O6‐HO‐2′ [Figure 3(C)]. Influence of the substituents at the C‐6 position on the formation was not significant except trityl group. Behavior of the hydrogen bonds in 6‐O‐tritylcellulose were also discussed. © 1994 John Wiley & Sons, Inc.