bluuebunny/crossref_metadata_2025_split huggingface dataset:
Swelling behavior of hyaluronic acid gels
Authors: Shah Chirag B. , Barnett Stanley M. 
Published: April 2003

AbstractHyaluronic acid is a naturally occurring mucopolysaccharide. It is an important component of the intercellular matrix. It controls the permeability of tissues by means of the highly entangled network which can be formed because of its high molecular weight. To be able to use hyaluronic acid for several biomedical applications it is necessary to have an understanding of its swelling properties. Equilibrium swelling properties of hyaluronic acid gels were investigated by varying the temperature, pH, ionic strength, and composition of the surrounding solution. Swelling was found to depend on pH and ionic strength and to be reversible. The gel was highly swollen at high pH, but it shrank continuously as the pH was lowered to 10% of its maximum volume. The gel was comparatively insensitive to temperature. Drying affected the swelling capacity of the gel significantly. Gel swelling was also affected by a high concentration of acetone or propyl alcohol in the aqueous swelling solutions.
Study of curative interactions in cis‐1,4‐polyisoprene (IR). VII. The cis‐1,4‐polyisoprene–tetramethylthiuram disulfide–ZnO system
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractA detailed account of the mechanism of crosslinking in the cis‐1,4‐polyisoprene (IR)‐tetramethylthluram disulfide (TMTD)–ZnO system is given. Many experimental observations were harmonized in terms of a radical mechanism, rather than an ionic mechanism. Electron spin resonance (ESR) spectra on the IR–TMTD–ZnO system, recorded at 120°C, inter alia revealed resonance lines in the vicinity of g = 2.02. These were related to the rapid formation of thiuram persulphenyl radicals XS, on the homolytic splitting of tetramethylthiuram polysulfides. The Moore–Trego efficiency E dropped from 11.5 (at 140.0°C) to 3.5 (at 146.9°C), indicating that a substantial part of the sulfur atoms was initially to be associated with pendent groups. The formation of these pendent groups could be viewed as an irreversible, concerted reaction without the formation of a true alkenyl radical intermediate. Crosslinks would form by either a disproportionation reaction between two α‐methylic or α‐methylenic pendent groups RSxX or a reaction between a pendent groups RSxX (R = polyisoprenyl, x ≥ 2, X = Me2NC(S)) and the unsaturated polymer chain. The latter crosslink formation reactions were regarded as rate determining in the vulcanization sequence. A mechanism is proposed that does not require the participation of ZnO in the formation of the active sulfurating agent.
Coconut husk lignin. I. Extraction and characterization
Authors: Váquez‐Torres H. , Canché‐Escamilla G. , Cruz‐Ramos C. A. 
Published: April 2003

AbstractRecently lignin has been the object of a renewed interest because of the need to use raw materials from renewable resources. One such resource is coconut husk, a material usually discarded during the copra extraction process. Due to its high lignin content, coconut husk has been recognized as having a variety of applications. Therefore, it is important to know the approximate structure of coconut husk lignin and those variations introduced by different isolation methods. This work reports a general characterization of coconut husk lignin. Results are given of the contents of hydroxyl and noncondensed guaiacyl units, the extractability of the lignin in alkaline and “organosolv” media along with thermal properties of the extracted lignins. The extraction system of NaOH–anthraquinone at 150°C was most conveniently based on the relatively low amount of condensed lignin generated.
The molecular weight distribution and oligomers of sodium hydroxide hydrolyzed poly(ethylene terephthalate)
Authors: Collins M. J. , Zeronian S. H. 
Published: April 2003

AbstractMethanolic sodium hydroxide reacted more quickly than aqueous sodium hydroxide with poly(ethylene terephthalate) (PET). Larger amounts of low molecular weight deposits were formed at the product surface after the former treatment, also indicating the severity of this attack. The molecular weight distribution, obtained by gel permeation chromatography for the product of methanolic NaOH hydrolysis, had a population with 2400 peak molecular weight, which was not present on the chromatograph of the aqueous sodium hydroxide hydrolyzed product. This population is hypothesized to have been crystalline material. Extraction and analysis by high performance liquid chromatography of the low molecular weight products on the surface and in the bulk of the hydrolyzed PET samples, in comparison to controls, revealed the presence of more oligomeric species after hydrolysis. Also, more oligomeric species were present in the bulk extract of the methanolic sodium hydroxide hydrolyzed sample than in the aqueous NaOH hydrolyzed product.
On the mechanism of the formation of porous structure in filled polyethylene film by thermomechanical deformation
Authors: Islam M. A. , Dimov A. 
Published: April 2003

AbstractThe pore‐formation mechanism in filled polyethylene film during the process of thermomechanical deformation has been studied. The film material consists of a high density polyethylene and SiO2. The rate of deformation as well as the initial thickness of the polyethylene film play a vital role in the formation of the porous structure. With an increase in the deformation rate, the contribution of crazes in the film decreases. Keeping all the parameters constant, with the increase in the initial film thickness, the porosity of the membranes decreases. The mechanism of pore formation is observed by scanning electron microscopy. It is established that the formation of crazes in the deformation process starts from the zones with lower adhesion of the filler with polymer and in the course of the process propagates throughout the mass. The final pore‐size distributions as well as the permeability data provide additional indirect evidence in favor of the observed mechanism.
Structure formation in stretched sheets of poly(butylene terephthalate)
Authors: Kaito A. , Nakayama K. , Zubaidi  
Published: April 2003

AbstractCrystalline and amorphous sheets of poly(butylene terephthalate) (PBT) were drawn in the temperature range of 20–150°C. The molecular orientation and the relative amount of α‐ and β‐form crystals in the stretched sheets were studied by wide‐angle X‐ray diffraction (WAXD) and density measurements. When crystalline PBT sheets are drawn at lower temperatures, α‐form crystals are partially transformed into β‐form crystals. Both α‐ and β‐form crystals are formed by drawing amorphous PBT sheets. The relative amount of α‐ and β‐form crystals is much more sensitive to drawing temperature than to draw ratio. The α‐form crystallinity is higher at higher drawing temperature and increases slightly with increasing draw ratio. The second moments of orientation functions of α‐ and β‐form crystals increase with increasing draw ratio, and the increase of the orientation function is suppressed at higher draw ratio. The orientation function of α‐form crystals is higher than that of β‐form crystals in a same sample.
Following of the relaxations in a polymer's behavior part I: “Correlation diagram” and creep at linearly increasing temperature
Authors: Genevaux J. M. , Guerrin G. M. 
Published: April 2003

AbstractThe correlation diagram is introduced here in order to follow the different relaxations of polymers. Two examples will be presented: PMMA and wood at several moisture contents between 20 and 100°C. For the two materials, an experiment of creep at linearly increasing temperature is proposed, so as to point out the relaxations of the different components for low frequencies. In this experiment, a relaxation induces a maximum of creep kinetic. The movement of the temperatures of relaxation with the moisture content will be observed. For wood at high moisture content (near the fiber saturation point), the cellulose's relaxation of the reinforcements will be observed at high temperature.
Physical aging deep in the glassy state of a fully cured polyimide
Authors: Venditti R. A. , Gillham J. K. 
Published: April 2003

AbstractPhysical aging of a fully cured polyimide/glass fiber specimen has been investigated deep in the glassy state using a freely oscillating torsion pendulum (TBA). A single specimen, the physical aging effects of which could be erased by heating to above Tg = 304°C (0.8 Hz), could be used for all experiments. Data were obtained during isothermal aging at different aging temperatures, Tα, (from 10°C to Tg) and during subsequent temperature scans (Tα to 5 to 315°C). The aging rate depended upon the value of Tα relative to both Tg and the β‐relaxation temperature, Tβ = 139°C (1.3 Hz). Changes in thermomechanical behavior due to aging were localized about Tα. This suggests that only an intermediate portion of the relaxation spectrum participates in, and is affected by, isothermal physical aging. It follows, and is observed, that the intensity of the β‐relaxation mechanical loss peak is perturbed most significantly by aging at Tα near Tβ. The effect of isothermal aging deep in the glassy state could be essentially eliminated by heating to below Tg. © 1992 John Wiley & Sons, Inc.
Synthesis of chiral polymers containing the acetoxybornyl group and their applications on the asymmetric induction
Authors: Liu Jui‐Hsiang , Kuo Jue‐Cheng , Fang Mau‐Ching 
Published: April 2003

AbstractOptically active 2‐endo‐actoxy‐5‐endo‐bornyl methacrylate (ABMA) was prepared from (+)‐camphor. The homopolymerization of ABMA and copolymerization of ABMA with achiral methyl methacrylate (MMA) or styrene (St) were carried out with 2,2′‐azobisisobutyronitrile (AIBN) in benzene. Effects of temperature, solvents, and reaction time on the copolymerization were discussed. The monomer reactivity ratios(r1, r2) for poly(ABMA‐co‐MMA) and poly(ABMA‐co‐St) and Q and e values for the chiral ABMA in the copolymerization systems were evaluated by the Fineman—Ross method. The absolute value of the specific rotation of poly(ABMA‐co‐MMA) increased with increasing ABMA unit content. A small deviation from linearity was observed, which suggests that asymmetry is not introduced into the copolymer main chain. Temperature and solvent effects on the specific rotation of the chiral homopolymer and copolymers were investigated. The results suggest that the chiral polymers synthesized in this investigation did not show a strong preference for a particular helical conformation. Applications of the chiral polymers on the asymmetric addition of n‐butyllithium to aldehydes were also discussed.
Chlorination and bromination of epoxidized natural rubber (ENR)
Authors: Cataldo Franco 
Published: April 2003

AbstractEpoxidized natural rubber (ENR) with a 25 mol % epoxide content has been chlorinated or brominated in halogenated solvents. The structures of the resulting polymers have been studied by infrared spectrophotometry, and their thermal behavior, by TGA and DSC, and compared with that of chlorinated and brominated natural rubber. For halogenated ENR, a structure of halogenated blocks separated by furanized blocks and products of ring‐opening epoxide groups has been proposed. © 1992 John Wiley & Sons, Inc.
Miscibility of polymethyl methacrylate with poly(hydroxy ether) of bisphenol A
Authors: Soh Young Soo 
Published: April 2003

AbstractThe miscibility of polymethyl methacrylate (PMMA) with the poly(hydroxy ether) of bisphenol A (phenoxy resin) was studied and PMMA has been found to be miscible with phenoxy resin. PMMA/phenoxy blends were found to be clear and showed a single, composition‐dependent glass transition temperature. The k parameter of the Gordon‐Taylor equation can be taken as a measure of the strength of the specific interaction between the two polymers, and a low value of k = 0.3 is found for the PMMA/Phenoxy blends. Fourier transform infrared (FTIR) showed the presence and nature of intermolecular interactions between the two polymers.
Shape memorizing properties of a hydrogel of poly(vinyl alcohol)
Authors: Hirai Toshihiro , Maruyama Hidetoshi , Suzuki Takashi , Hayashi Sadao 
Published: April 2003

AbstractHydrogel prepared by repetitive freezing and thawing of poly(vinyl alcohol) aqueous solution was chemically crosslinked with glutaraldehyde. The chemically crosslinked hydrogel hardly changed its physical appearance, and showed good elasticity and strength as original gel. However, after treating in boiling water, it swelled a little, depending on the condition of the chemical treatment. The melted gel thus obtained showed shape memorizing property, that is, it could firmly hold nearly 200% of strain, keeping its original high elasticity. The strain could be released very quickly (< 1 s) in boiling water, and the gel was suggested to be applied to a new type of gel actuator. X‐ray diffraction study revealed that the melted gel does not necessarily reform the physical crosslinks in exactly the same manner as the original gel in the process of shape restoring, but the distribution of the physical crosslinks can be restored as they were. It was suggested that the chemical crosslinks which remember the distribution of the physical crosslinks plays a critical roll in the shape restoring process.
Radiation‐induced sol–gel transition of protein: Effects of metal ions on flow and melting properties
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractSolid protein was irradiated with 60Co gamma rays, and the effects of metal ions (Cu2+ and Fe2+) on irradiated protein molecules were studied by measuring the viscosity of the protein hydrosol and the melting point of the protein hydrogel at different radiation doses and different concentrations of the metal ions. The effects of metal ions on the flow and thermal properties of irradiated protein molecules were discussed.
A mathematical model for a continuous esterification process with recycle between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro 
Published: April 2003

AbstractA new mathematical model for a continuous recycle esterification process has been derived by basically the same procedure as the continuous process of a cascade type, reported earlier, which includes material and heat balances. Such a model can give extensive information about the optimum design of a new plant through the predictions of oligomer characteristics (concentrations of carboxyl and hydroxyl end groups, number average molecular weight, number average degree of polymerization, esterification and saponification degree, DEG content, melting point of oligomer, etc.), distillate properties (concentrations of EG and water in the vapor phase), heat transfer area, mass flow rate of heating medium, amount of heat supplied by heating medium, enthalpy moving with recycle, and amount of heat removed from each reactor. © 1992 John Wiley & Sons, Inc.
The structure and morphology of the skin of polyethersulfone ultrafiltration membranes: A comparative atomic force microscope and scanning electron microscope study
Authors: Fritzsche A. K. , Arevalo A. R. , Connolly A. F. , Moore M. D. , Elings V. , Wu C. M. 
Published: April 2003

AbstractAtomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to investigate the surface structure and morphology of 10,000, 30,000, and 100,000 dalton molecular weight cutoff (MWCO) polyethersulfone (PES) ultrafiltration membranes, and the results are compared. Although both approaches reveal the pore structure in the 30,000 and 100,000 MWCO membranes, the pore diameters derived from SEM are smaller than those measured by AFM. This discrepancy is a result of the diminution in pore dimensions during the sample preparation for SEM, that is, the solvent exchange procedure needed to remove the water from the membrane prior to the high vacuum gold coating deposition step. In contrast to SEM, which requires a high vacuum both during heavy metal coating and during examination, AFM can be performed on wet ultrafiltration membranes. Consequently, the potential of altering the membranes' pore structures during sample preparation is eliminated. Therefore, the pore diameters obtained from AFM are more accurate than those derived from SEM.
Water‐superabsorbent polymers through gamma radiation‐induced graft‐copolymerization of acrylonitrile on guargum
Authors: Lokhande H. T. , Varadarajan P. V. , Iyer Vatsala 
Published: April 2003

AbstractSuperabsorbent polymers based on guargum have been prepared through a graft‐copolymerization reaction using acrylonitrile as the monomer by a gamma ray‐induced irradiation technique. Various grafting parameters have been studied. The grafted products have been characterized using infrared spectroscopy, thermogravimetric, and differential thermal analysis. The thermograms reveal the superior thermal stability of the grafted product over the control at all stages of its degradative cycle. The maximum absorbency obtained of the superabsorbent product was around 300 g/g.
Surface behavior of blends of siloxane and siloxane‐containing copolymers in poly(vinyl chloride)
Authors: Gorelova M. M. , Pertsin A. J. , Levin V. Yu. , Makarova L. I. , Filimonova L. V. 
Published: April 2003

AbstractX‐ray photoelectron spectroscopy is used to reveal surface/bulk compositional relationships in blends of polydimethylsiloxane (PDMS) and PDMS/polycarbonate block copolymers in poly(vinyl chloride) (PVC). It is shown that the surface of PVC can be enriched in siloxane up to 60 at. % PDMS without visible indications of phase separation.
Separation of carbon dioxide by asymmetric hollow fiber membrane of cellulose triacetate
Authors: Sada E. , Kumazawa H. , Wang J.‐S. , Koizumi M. 
Published: April 2003

AbstractPermeation behavior of pure CO2, O2, and N2 and separation characteristics of CO2–air mixtures were examined using hollow fiber modules of asymmetric cellulose triacetate membrane at 30°C. The ideal separation factor for CO2 relative to N2 ranged from 21 to 24. Permeation behavior for pure CO2 was interpreted in terms of the total immobilization model, i.e., a limiting case of the dual‐mode mobility model for glassy polymer, where the diffusion coefficient for Henry's law mode is not assumed to be constant and depends on gas pressure via a modified free‐volume model. Based on pure gas permeabilities to CO2, O2, and N2, simulation for the separation of CO2–air mixtures was made using a counter‐current plug flow model, and the result fitted the corresponding experimental data fairly well. Membrane plasticization induced by CO2 had negligible effect on permeation to mixture of CO2 and air in the range of CO2 composition up to 50% and upstream total pressure up to 1.5 MPa.
Aqueous dispersions of polyurethane anionomers: Effects of countercation
Authors: Chen Yun , Chen Yueh‐Liang 
Published: April 2003

AbstractThe influence of counterions on the properties of aqueous dispersions of polyurethane (PU) anionomer have been investigated. The PU anionomers were prepared by polyaddition reaction of 4,4′‐methylenebis(phenylisocyanate) with poly(propylene glycol) (PPG), dimethylolpropionic acid (DMPA), and 1,4‐butanediol, followed by neutralization of pendant COOH groups by various bases. Stable dispersions are obtained for PU anionomers containing 0.8–1.1 wt % COOH groups (17.8–24.4 mmol/100 g polymer) that have been neutralized by ammonia, trimethylamine, triethylamine, LiOH, NaOH, and KOH, respectively. It is found that average particle size is determined mainly by the zeta potential of the dispersions. The number‐average diameter of the dispersions containing metal cations (Li‐, Na‐, and K‐0.9) is between 60–73 nm (zetal potential −65 to −70 mV), while that of the dispersions containing ammonium cations (AMM‐, TMA‐, and TEA‐0.9) is between 104–251 nm (zeta potential −47 to −64 mV). The surface tension of the dispersions decreases with concentration rapidly and levels off at concentrations higher than 20 mmol/L. The decreased decomposition temperature of the PU anionomers, compared to unionized PUs, can be attributed to the disordering of hard domains after ionization or decomposition reaction catalyzed by alkali metal carboxylates. The thermal decomposition proceeds mainly via cyclic elimination.
Surface‐modified polysulfone hollow fibers. IV. Chloromethylated fibers and their derivatives
Authors: Higuchi Akon , Koga Hiroyuki , Nakagawa Tsutomu 
Published: April 2003

AbstractA chloromethylated reaction was performed on the surfaces of polysulfone ultrafiltration hollow fibers and their derivative membranes, i.e., triethylaminated, ethylenediaminated, and acethylated fibers, were prepared. The modified fibers have a 30–60% insoluble region in chloroform, whereas nonmodified fibers can be dissolved in the chloroform. It is suggested that the insoluble parts of the fibers are highly cross‐linked due to the high degree of chloromethylation. The modified fibers showed a 50–98% rejection of polyethylene glycol 6000 at a feed concentration of 0.5 wt %, except for the triethylaminated fibers, which gave a negative rejection from −91 to −96%. It was found that the modified segments significantly influenced the rejection behavior of the solutes. Absorption of bovine serum albumin on the ethylenediaminated fibers at pH 7.1 was estimated from permeation measurements to be less than that of the other modified and nonmodified fibers. This effect is attributed to the hydrophilic surface of the ethylenediaminated fibers.
Poly(ethylene terephthalate) melt spinning via controlled threadline dynamics
Authors: Lin Chon‐Yie , Tucker Paul A. , Cuculo John A. 
Published: April 2003

AbstractFiber melt spinning of poly(ethylene terephthalate) (PET) was studied via modification of threadline dynamics. Several techniques were implemented in the high‐speed spinning process for the judicious control of threadline dynamics. This included a thermal conditioning zone (TCZ) for controlling the threadline temperature profile and a dydraulic drag bath (HDB) for controlling the threadline spinning stress. Through controlled threadline dynamics, key factors affecting the structure development—namely, temperature, tensile stress, and crystallization time—were manipulated to favor formation of a highly oriented and transversely uniform structure in the spun fibers. This carries the implication that optimum or near‐optimum processing conditions are being applied during the structure development period. More specifically, tensile stress in the threadline, independent of temperature, is substantially increased to many orders higher than that ordinarily attained in the normal high‐speed spinning process. Concurrently, the temperature crucial to the structure development is being independently optimized and its duration extended to attain a highly oriented structural order. Properties of the spun fibers were found to be correlated with the threadline parameters including cooling profile, tension profile, and strain rate. PET fibers spun via the one‐step process with the introduction of the TCZ and HDB possess superior mechanical performance. Structural characterization suggests that the spun fibers have a high amorphous orientation factor and a uniform radial structure distribution. Further on‐line studies indicate that structure development in the threadline is completely different from that of the traditional high‐speed spinning process. The attenuation profile of the threadline is observed to be dependent of TCZ temperature, residence time in the HDB, temperature of the HDB, and take‐up speed. It is believed that for the melt spinning process with the TCZ and the HDB, the threadline dynamics is changed from one controlled by inertia and air drag forces to one controlled by the imposed hydraulic drag.