bluuebunny/crossref_metadata_2025_split huggingface dataset:
Buffer effects on aqueous swelling kinetics of polyelectrolyte gels
Authors: Chou Loretta Y. , Blanch Harvey W. , Prausnitz John M. , Siegel Ronald A. 
Published: April 2003

AbstractElectrolytes are often added to a gel‐swelling medium under the assumption that the important conditions which characterize swelling rates are the solution pH and ionic strength, with little emphasis on the nature of the electrolyte. Previous research by Siegel et al. has indicated that the presence of the un‐ionized acidic form of an electrolyte buffer is a primary rate determinant for swelling of a polybase gel. A systematic swelling study on two separate gels, 2‐hydroxyethyl methacrylate copolymerized with methacrylic acid (HEMA/MAA) and N,N‐dimethylaminoethyl methacrylate (HEMA/DMA), has been performed to investigate the influence of the concentration of the un‐ionized buffer by three principal factors: (1) total buffer concentration, (2) solution pH, and (3) buffer pKa. Swelling and deswelling kinetics were obtained. In the presence of an electrolyte buffer, a dramatic swelling rate increase is observed for the HEMA gels, with substantial gains in rate obtained as total buffer concentration rises. Results also emphasize that to enhance swelling kinetics, the pH must be such that the buffer is essentially un‐ionized.
Structure of microporous polypropylene sheets containing CaCO3 filler
Authors: Nagō Satoshi , Nakamura Shunichi , Mizutani Yukio 
Published: April 2003

AbstractThe microporous polypropylene sheets were prepared by biaxially stretching polypropylene sheets containing CaCO3 filler (particle size, 0.08–3.0 μm), when the CaCO3 filler content was 59% by weight and the stretching ratio was 2.8 × 1.8. The microstructure of the sheets were investigated in relation to the CaCO3 particle size by a N2 gas permeation method. (1) Effective porosity increases with decreasing mean particle size of filler. (2) The tortuosity factor of the pore is in the range of 25–40 and becomes relatively smaller with decreasing mean particle size of filler. (3) The equivalent pore size becomes relatively smaller with decreasing mean particle size of filler.
A new process for fabricating nonwoven fibrous‐reinforced elastomer composites
Authors: Epstein M. , Shishoo R. L. 
Published: April 2003

AbstractA new type of mold was developed and tested for structural reaction injection molding (SRIM) of elastomer composites having polymer matrices made from a mixture of two components. These mixtures had short pot lives and relatively high viscosity. Channel systems for polymer feeding and vacuum application were investigated. The mold cavity was provided with up to 24 polymer feeding holes and 38 vacuuming holes. The cavity and channels were made from transparent materials that allowed easy observation and video recording of the polymer matrix flow. In addition, some design parameters were studied such as channel layout. Investigations were carried out on the mechanism of polymer matrix flow and fiber breakage during the formation of fiber‐reinforced composites made of non‐woven fiber reinforcement structures with considerably longer fiber lengths than reported earlier. Other studies included determination of the effects of fiber type, fiber dimensions, and fiber/matrix v/v ratio on the matrix flow during impregnation. © 1992 John Wiley & Sons, Inc.
Preparation and properties of negatively charged ultrafiltration membrane: Photografted sodium styrene sulfonate onto brominated polyacrylonitrile membrane
Authors: Kobayashi Takaomi , Fujii Nobuyuki 
Published: April 2003

AbstractCharged ultrafiltration membranes were prepared by photografting sodium styrene sulfonate onto photosensitive polyacrylonitrile membrane containing bromine atoms. The degree of the photografting was characterized by contact angles of air or n‐octane in water and FTIR spectra for the negatively charged membrane. Permeations of dextran and dextransulfate through the negatively charged membranes were studied by ultrafiltration in the aqueous solutions of both solutes. With an increase of photoirradiation, the permeability of the solutes decreased. Also, an electrostatic repulsion of the solute and the membrane was confirmed by direct comparison between the permeability of the solutes, dextran, and dextransulfate, each having similar molecular size.
Preparation of conducting polyacrylonitrile/polypyrrole composite films by electrochemical synthesis and their electrical properties
Authors: Park Yun Heum , Han Myeong Hee 
Published: April 2003

AbstractElectrically conducting polyacrylonitrile (PAN)/polypyrrole (PPy) composite films were prepared by electrochemical polymerization of pyrrole in an insulating PAN matrix under various polymerization conditions and their electrical properties were studied. The conductivities of PAN/PPy composite films peeled off from the platinum electrode he lie in the range of 10−2–10−3 s/cm, depending on the preparation conditions: The conductivity increased with the concentrations of the electrolyte and the monomer, but it decreased with the polymerization temperature of pyrrole and the applied potential.
Studies on the mechanism of the instability of polymers in tensile testing
Authors: Cao Jinan 
Published: April 2003

AbstractThis study deals with the mechanism of the instability of tensile force occurring in tensile testing for polymer materials. It was found that through a proper transformation of inertia coordinates, a tensile test can be described in the same governing differential equations with the same boundary conditions as those employed in melt spinning. This fact suggests that the nature of the instability is simply due to draw resonance rather than any other cause. The effects of extension rate in tensile testing and the specimen dependence on the instability of tensile force were experimentally investigated by using specimens with various molecular orientations. The results are interpreted by applying the principles of draw resonance in melt spinning.
Mechanical properties and morphology of high‐density polyethylene/linear low‐density polyethylene blend
Authors: Gupta A. K. , Rana S. K. , Deopura B. L. 
Published: April 2003

AbstractThe binary blend of high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE) in the range of composition from 100% HDPE to 100% LLDPE has been investigated for tensile and flexural properties and the morphology in the deformed state on tensile fracture. Tensile properties (initial modulus, yield stress, and elongation‐at‐yield, ultimate tensile strength and elongation‐at‐break, and work of yield and work of rupture) and flexural properties (flexural modulus and flexural yield stress) are studied as a function of blend composition. Behavior, in terms of these properties, is distinguishable in three zones of blend composition, viz. (i) HDPE‐rich blend, (ii) LLDPE‐rich blend, and (iii) the middle zone. In zones (i) and (ii), the variations of these properties are more or less linear, whereas in the middle region [i.e., zone (iii)], there is a reversal of trends in variation or sometimes a behavior opposite to the expected one. The results are explained on the basis of the effects of cocrystallization and the presence of octene‐containing segments in the amorphous phase. Scanning electron micrographs of the tensile fracture surfaces are presented to illustrate the occurrence of transverse bands interconnecting the fibrils.
Thermal and mechanical characterization of partially miscible blends of poly(ether ether ketone) and polyethersulfone
Authors: Malik Tariq M. 
Published: April 2003

AbstractThe miscibility behavior of poly(ether ether ketone) (PEEK) and polyethersulfone was studied by differential scanning calorimetry (glass transition temperature) and tensile properties: Young's modulus and ultimate tensile strength. A single glass transition temperature was observed over the entire composition range. The glass transition temperature of blends, however, did not follow any of the theoretical equations. Utracki and Jukes equation was used with K = 11 to fit the experimental data that indicate partial miscibility. Up to 30 wt % PEEK, the blends showed amorphous behavior with the glass transition temperature very close to that of polyethersulfone. Because of partial miscibility, blends showed mechanical compatibility. Both the modulus and strength increased significantly with an increasing concentration of PEEK in the blends, reaching a maximum around 40%. Electron microscopic results revealed phase separation but strong adhesion between the phases.
Unsaturated polyester containing myrcene–maleic anhydride Diels–Alder adduct
Authors: Abate Diane Wolfer , Stevens Malcolm P. 
Published: April 2003

AbstractMyrcene–maleic anhydride Diels–Alder adduct and the corresponding diacid were used as monomers for unsaturated polyesters. The polyesters exhibited air‐drying properties on cross‐linking with styrene.
Transport of small molecules in polyolefins. I. Diffusion of irganox 1010 in polyethylene
Authors: Földes Enikõ , Turcsányi Béla 
Published: April 2003

AbstractTransport properties of antioxidants in polymers have a very important role in their effectiveness. Lifetime of a product is strongly influenced by the physical loss of the stabilizer. The diffusion coefficient (D) and solubility (S) of Irganox 1010 in low‐density polyethylene (LDPE) were studied at 45 and 80°C, changing the physical state of the antioxidant in the additive source. Irganox 1010 is a polymorphous material; its actual morphology depends on the thermal history. It was proved that the morphology of the additive has a determining effect on the measured D and S values. Contradictions in the literature data can be explained by the differences in the experimental conditions, i.e., in the physical state of the penetrant in the additive source and the crystallinity and orientation of the polymer.
Gas permeability studies on poly(vinyl chloride) based polymer blends intended for medical applications
Authors: Pal S. N. , Ramani A. V. , Subramanian N. 
Published: April 2003

AbstractPlasticized PVC finds applications in a wide range of medical products. However, plasticizer leaching, known to take place from these conventional materials, is not desirable. A number of approaches to overcome this problem are mentioned in the literature. We suggest pursuing the polyblend approach. Plasticized PVC containing different amounts of plasticizer, binary polyblends of plasticized PVC (PPVC) with acrylonitrile–butadiene rubber (NBR1), and compounded graft polymer of vinyl chloride and ethylene–vinyl acetate copolymer (EVAPVC), and ternary blends of PPVC, NBR1, and EVAPVC, were formulated. In this article, we report our results of studies on water vapor, O2, CO2, and N2 permeabilities. Increased plasticization for PVC was found to increase permeability for water vapor, O2, CO2, and N2. Rise in temperature increased the permeability for water vapor and the change became faster as the materials crossed the region of Tg. A simple model suggested for permeability worked satisfactorily. The binary and ternary blends, based on PPVC, had lower O2, CO2, and N2 permeability. This improvement in property is of great practical significance and interest and the results indicate that PVC‐based polyblends can be investigated further for potential applications in medicine
A mechanical model for the deformational behavior of the polymeric membranes operating in pressure‐driven processes
Authors: Islam M. A. 
Published: April 2003

AbstractA mechanical model consisting of three elements (elastic, viscoelastic, and plastic) is proposed to describe the deformational behavior of a polymeric membrane operating in a pressure‐driven process. The changes in the membrane thickness are proposed to be calculated from the experimentally obtained flux data. The advantages of a mechanical model over the conventional method of hysteresis area measurement as the mechanical stability of the polymeric membranes are discussed. © 1992 John Wiley & Sons, Inc.
Empirical estimation method of intrinsic loss spectra in transparent amorphous polymers for plastic optical fibers
Authors: Takezawa Yoshitaka , Taketani Noriaki , Tanno Seikichi , Ohara Shuichi 
Published: April 2003

AbstractWe have developed a novel simulation to estimate the intrinsic loss spectrum of a plastic optical fiber (POF) having a transparent amorphous polymer as its core. Loss for POF is divided into four elements, that is, αe, αv, αR, and αj Here, αe means the electronic transition absorption loss, αv the absorption loss due to harmonics of molecular vibrations, and αR Rayleigh scattering loss. These three losses cause attenuation loss intrinsically and determine the lower limit of loss in the POF. The αi is the extrinsic loss due to fabrication process and contaminating dust, etc., and as such can be decreased to a negligible amount. We clarified the relationship between the chemical structure of polymer repeating unit and the three intrinsic losses and derived empirical equations to estimate the losses. The spectra estimated by this simulation agreed well with experimental ones. © 1992 John Wiley & Sons, Inc.
Characterization of water vapor plasma‐modified polyimide
Authors: Goldblatt R. D. , Ferreiro L. M. , Nunes S. L. , Thomas R. R. , Chou N. J. , Buchwalter L. P. , Heidenreich J. E. , Chao T. H. 
Published: April 2003

AbstractTo enhance polyimide‐to‐polyimide adhesion, we have investigated the effect of surface modification in water vapor plasma. The use of a water vapor plasma to treat a fully cured polyimide (PMDA–ODA) surface before subsequent layers of polyimide are applied results in dramatically enhanced interfacial adhesion. The polyimide‐to‐polyimide interfacial adhesion strength attained following water vapor plasma treatment exceeds the cohesive strength of the applied polyimide layer. The effect of surface modification in water vapor plasma on metal‐to‐polyimide adhesion has also been investigated. The use of a water vapor plasma to treat a fully cured polyimide (PMDA–ODA) surface prior to metallization results in increased metal‐to‐polymer interfacial adhesion. A study of both electroless and vacuum‐deposited metal was conducted. The use of contact‐angle measurements, peel tests, Fourier transform infrared spectroscopy, optical emission spectroscopy, nuclear forward scattering, and X‐ray photoelectron spectroscopy has led us to a preliminary understanding of the resulting surface modification and the subsequent effect of adhesion promotion. © 1992 John Wiley & Sons, Inc.
Coconut husk lignin. III. Reactivity of alkaline extracts with formaldehyde
Authors: Vázquez‐Torres H. , Canché‐Escamilla G. , Cruz‐Ramos C. A. 
Published: April 2003

AbstractIn this article we report results of the evaluation of the reactivity of polyphenolic extracts of coconut husk with formaldehyde in both acidic and alkaline media. The objective of this evaluation was to determine if the extracts could be used in the preparation of phenol–formaldehyde‐type resins. Extracts were obtained using aqueous solutions of NaOH (with and without anthraquinone) and NH4OH. Because of their low Stiasny's Number values, these extracts are not suitable for phenol–formaldehyde resin preparation in acidic conditions unless they are mixed with phenol or phenolic derivatives. Nevertheless, extracts obtained with NaOH, especially at 100 and 120°C, showed sufficient reactivity with form‐aldehyde in basic conditions and may therefore be considered suitable for resin preparation in an alkaline medium. The resins were characterized using infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). A transition temperature prior to decomposition was not detected; their thermal stability was similar to phenol–formaldehyde‐type resins. © 1993 John Wiley & Sons, Inc.
Physical aging in the glassy state of a thermosetting system vs. extent of cure
Authors: Wang Xiaorong , Gillham John K. 
Published: April 2003

AbstractThe physical aging behavior of a high‐Tg amine/epoxy thermosetting system has been investigated vs. change of chemical structure induced by cure and vs. aging temperature (Ta) using the Torsional Braid Analysis (TBA) technique. The chemical structure was changed systematically from monomer to highly crosslinked polymer by curing in the equilibrilium state (T > Tg). The aging temperatures ranged from just below the glass transition temperature to deep in the glassy state (Ta > Tg). In the absence of chemical reaction, the physical aging rate at a given temperature, Ta, passes through a minimum with increasing chemical conversion (i.e., change of chemical structure). Analysis of this behavior is simplified by using Tg as an index of measurement of extent of cure. There is a superposition principle for normalizing the physical aging behavior of the thermosetting glasses, which involves a shift of Tg–Ta and a shift of C(Ta) (a function of aging temperature), regardless of chemical structure. Analysis reveals that: (1) this behavior is the consequence of the Tg and Tβ transitions, (2) the segmental mobility (1/τ) is a function of the deviation from equilibrium (as measured by Tg–Tg and the aging time), (3) the segmental mobility, which is involved in the physical aging process in the glassy state, is insensitive to the extreme changes of chemical structure (from monomer, to sol/gel polymer, and to highly crosslinked polymer), and (4) physical aging deep in the glassy state affects both segmental mobility and cohesive energy density. © 1993 John Wiley & Sons, Inc.
Efficiency of metal activators of accelerated sulfur vulcanization
Authors: Ducháček Vratislav , Kuta Antonín , Pr̆ibyl Pavel 
Published: April 2003

AbstractThe effects of copper, mercury, nickel, zinc, cadmium, indium, magnesium, and calcium stearates on the course of N‐cyclohexyl‐2‐benzthiazylsulphenamide‐accelerated sulfur vulcanization of natural rubber have been investigated on the basis of curemeter measurements at 145°C. The differences in the efficiencies of these metal activators of accelerated sulfur vulcanization have been discussed from the points of view of the electron configurations of the metals and their affinities to sulfur. We attempted to determine why zinc oxide is generally accepted as the best metal vulcanization activator. © 1993 John Wiley & Sons, Inc.
Lignocellulose–polymer composite. III
Authors: Mansour Olfat Y. 
Published: April 2003

AbstractA linear relationship was achieved between the polymer load and the monomer concentration up to 200% when china clay or talc replaced the glass in the initiating system, sodium bisulfite–soda lime glass, for the free‐radical graft polymerization reactions using semichemical pulp of bagasse as substrate. The results showed that china clay is better than talc, which may be contributed to the difference in their network structure. The properties of the composites prepared from the cografted semichemical pulp–polymethyl methacrylate revealed that the china clay leads to composites with high compression strength and hardness. Deformation percent increased with increasing polymer load. However, decreasing or increasing the polymer load affects the properties of the composites up to a limit, where there is a maximum or minimum for both compression strength and hardness at china clay ratio of 2 or 3. Composites were also prepared from poly(methyl methacrylate)‐cografted‐pith of bagasse using the initiating system sodium bisulfite in the absence or presence of soda lime glass. Compression strength, deformation percent, and hardness increased on decreasing the glass ratio from 1 to 0, at nearly the same polymer load. The presence of waxes and resins decreased the compression strength of the composites prepared by impregnation of the lignocellulose in polymer solution. The hardness of these composites increased on removing waxes and resins. Removal of part of hemicellulose by alkali treatment of the lignocellulose has increased the effect on hardness. Alkali treatments of the substrates lead to a high deformation percentage. The compression strength of alkali‐treated lignocellulose are lower than the untreated ones. The change of compression strength to deformation percent and the compressibility due to complete removal of waxes and resins by the extraction with methanol–benzene or partial removal of the waxes, resins, and hemicellulose through alkali treatment followed the change of both the compression strength and percent of deformation. Water uptake of the composites prepared in this work was ranged between 6.8 and 7%. After 48 h the water uptake increased to the range 8.5–14.1%. Impregnation of the composites in water for 72 h increased the water uptake to the range 10.2–18.1%. © 1993 John Wiley & Sons, Inc.
Temperature effect on PI/Cu interface
Authors: Wang Tsung‐Hsiung , Ho Shy‐Ming , Chen Ker‐Ming , Hung Aina 
Published: April 2003

AbstractThe interfacial reaction and peel strength of polyimide with copper foil at various cure schedules have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and peel test to determine the temperature effect on polyimide/copper interface diffusion and adhesion. SEM studies indicate that the polyimide/copper interfaces are fairly smooth for all samples studied in this experiment. The TEM microstructure reveals the existence of a copper‐polyimide interaction zone at the interface when it is cured at a temperature higher than 250°C, which also results in a high peel strength. XPS spectra revealed higher copper and carbonyl carbon contents at the polyimide interface when it is cured at a high‐temperature schedule (350°C). From the results of these interface studies, it is concluded that chemical bonding resulting from the interaction of copper oxide and polyimide carbonyl group provides the binding force for polyimide and copper foil. © 1993 John Wiley & Sons, Inc.
Surface modification of polyethylene by photochemical grafting with 2‐hydroxyethylmethacrylate
Authors: Edge Stephen , Walker Susan , Feast W. James , Pacynko Witold F. 
Published: April 2003

AbstractThe photochemical grafting of 2‐hydroxyethylmethacrylate onto low‐density polyethylene film is described. The grafting technique employed involved irradiating a solution of 2‐hydroxyethylmethacrylate and benzophenone in acetone spread between films of poly(ethylene terephthalate) or glass and low‐density polyethylene. After irradiation for 2 min, the contact angle of the polyethylene films with water fell from 97° to about 50°. The contact angle of the poly(ethylene terephthalate) substrate also fell during grafting. X‐ray photoelectron spectroscopy was consistent with the presence of poly(2‐hydroxethylmethacrylate) at the surface of the polyethylene. The effect of solvent on the photochemical grafting of 2‐hydroxyethylmethacrylate onto low‐density polyethylene is discussed. © 1993 John Wiley & Sons, Inc.
Solution properties of methyl methacrylate–acrylonitrile copolymers
Authors: Asaduzzaman A. K. M. , Rakshit A. K. , Devi Surekha 
Published: April 2003

AbstractCharacterization of methyl methacrylate‐acrylonitrile copolymers is done through viscosity, swelling, and differential refractometric studies. Viscosities of the copolymers and homopolymers were determined at 30, 40, and 50°C. The activation parameters of viscous flow, voluminosity, and shape factor were also calculated. The average shape factor was observed to be 2.5 ± 0.005 for all copolymer systems. Viscosity molecular weights were calculated, and from intramolecular expansion factor (α), it was observed that copolymers are less flexible than are homopolymers. dn/dc values obtained from differential refractometry are in good agreement with those calculated theoretically. © 1993 John Wiley & Sons, Inc.