bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yielding of commercial poly(vinyl chloride) pipe material
Authors: Ragab A. R. , Mahmoud M. A. , Khorshied S. A. 
Published: August 2002

AbstractTubular test specimens of commercial poly(vinyl chloride) pipe material were tested in biaxial stress systems covering the four quadrants of the plane–stress space. The test rig provided yield stresses at a constant temperature and controlled strain rate tension, compression, internal pressure, external pressure, and torsion combined loading. The experimental yield points fit the von Mises yield criterion. This result was confirmed by the ratio of compressive to tensile yield stresses; being unity, the density remaining constant with the applied hydrostatic stress, and, finally, the normality of the strain vector to the yield locus at the corresponding stressing point. Subsequent yielding loci of previously deformed specimens deviated largely from the von Mises locus. This deviation may have been caused by craze–void interaction. Finally, the viscous behavior, the dependence of yield stresses on the strain rate and temperature, is represented with a generalized phenomenological model based on an Eyring–Ward‐type expression. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 991–999, 2001
Kinetic crystallization of polypropylene in ternary composites based on fiber‐reinforced PP‐EPDM blends
Authors: López Manchado Miguel A. , Torre Luigi , Kenny José M. 
Published: August 2002

AbstractThe crystallization of isotactic polypropylene (iPP) in its blends with ethylene–propylene–diene terpolymer (EPDM), reinforced with different fibers, is described in this work. In particular, the effects of both the fibers and the EPDM on the crystallization kinetics and morphology of iPP are analyzed. The study was performed using differential scanning calorimetry (DSC) in dynamic and isothermal conditions and optical microscopy. It was found that all the fibers act as effective nucleant agents on iPP crystallization independently of the blend composition. The results obtained highlight the accelerating effect of the fibers and of the EPDM on the PP crystallization up to a certain EPDM percentage. The halftime of crystallization, τ1/2, and the overall crystallization rate, Kn, increase in the presence of all the fibers analyzed, showed the aramidic ones the most effective. The isothermal crystallization kinetics of ternary composites based on PP–EPDM blend matrices reinforced with different types of fibers can be modeled using the Avrami equation. On the other hand, the kinetic curves obtained under nonisothermal conditions provide a further confirmation of the nucleating action of the fibers on the PP crystallization. Optical polarizing microscopy was also used to investigate the effect of EPDM on the spherulite growth and the transcrystallinity phenomenon on the surface of the fibers. The results of such analysis showed that the transcrystallinity phenomenon is hindered at high rubber percentages. As in the case of the rate of crystallization, the highest proportion of transcrystallinity was observed in the presence of the aramidic fibers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1063–1074, 2001
Synthesis and swelling characteristics of acid‐containing poly(vinyl alcohol) hydrogels
Authors: Ruiz J. , Mantecón A. , Cádiz V. 
Published: August 2002

AbstractPoly(vinyl alcohol) (PVA) was modified with phthalic and succinic anhydrides to produce vinyl alcohol‐vinyl ester copolymers that contain free carboxylic acid or carboxylate groups. These half‐esters were then crosslinked using the diglycidylether of 1,4‐butanediol. Low crosslinker/carboxylic acid ratios were used to obtain low degrees of crosslinking, so that the capacity to absorb water of the resulting hydrogel was high. Water absorption was determined gravimetrically as a function of time at room temperature. The swelling behavior was significantly different in both ionic and nonionic polymers. The water uptake of the former was high enough for products to be considered superabsorbents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1444–1450, 2001
Synthesis and swelling properties of 2‐hydroxyethyl methacrylate‐co‐1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine hydrogels
Authors: Lee Wen‐Fu , Chen Ying‐Jou 
Published: August 2002

AbstractA series of 2‐hydroxyethyl methacrylate/1‐vinyl‐3‐(3‐sulfopropyl)imidazolium betaine (HEMA/VSIB) copolymeric gels were prepared from various molar ratios of HEMA and the zwitterionic monomer VSIB. The influence of the amount of VSIB in copolymeric gels on their swelling behavior in water and various saline solutions at different temperatures and the drug‐release behavior, compression strength, and crosslinking density were investigated. Experimental results indicated that the PHEMA hydrogel and the lower VSIB content (3%) in the HEMA/VSIB gel exhibited an overshooting phenomenon in their dynamic swelling behavior, and the overshooting ratio decreased with increase of the temperature. In the equilibrium water content, the value increased with increase of the VSIB content in HEMA/VSIB hydrogels. In the saline solution, the water content for these gels was not affected by the ion concentration when the salt concentration was lower than the minimum salt concentration (MSC) of poly(VSIB). When the salt concentration was higher than the MSC of poly(VSIB), the deswelling behavior of the copolymeric gel was more effectively suppressed as more VSIB was added to the copolymeric gels. However, the swelling behavior of gels in KI, KBr, NaClO4, and NaNO3 solutions at a higher concentration would cause an antipolyelectrolyte phenomenon. Besides, the anion effects were larger than were the cation effects in the presence of a common anion (Cl−) with different cations and a common cation (K+) with different anions for the hydrogel. In drug‐release behavior, the addition of VSIB increased the drug‐release ratio and the release rate. Finally, the addition of VSIB in the hydrogel improved the gel strength and crosslinking density of the gel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2888–2900, 2001
The effect of temperature on physical aging of glassy polymers
Authors: Drozdov Aleksey D. 
Published: August 2002

AbstractConstitutive equations are derived for the linear viscoelastic response of amorphous glassy polymers subjected to physical aging. Stress–strain relations are applied to fit experimental data for poly(methyl methacrylate), poly(styrene‐co‐acronitrile), and poly(vinyl acetate) in tensile relaxation tests and in torsional dynamic tests at various temperatures. Fair agreement is demonstrated between observations and results of numerical simulation. It is revealed that an increase in the annealing temperature results in an increase in the rate of relaxation and a decrease in the apparent rate of structural recovery. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3309–3320, 2001
Morphology and mechanical properties of interpenetrating polymer networks of poly(allyl diglycol carbonate) and rigid polyurethane
Authors: Dadbin Susan , Chaplin R. P. 
Published: August 2002

AbstractNovel simultaneous interpenetrating polymer networks (SINs) of poly(allyl diglycol carbonate) (ADC) and a rigid high modulus polyurethane based on the Conathane UC‐33 prepolymer system (UC) were synthesized. The completion of each component reaction was verified by means of Fourier transform IR spectroscopy. The effects of the composition on the morphology, mechanical properties, and thermal transition behavior of the SINs were studied. At 10% composition, transmission electron microscopy revealed complete phase miscibility. This was also supported by the high optical transparency of the sample. As the UC content increased to 20% a two‐phase morphology was observed in which the UC phase domains were dispersed in the matrix of the ADC phase. At higher UC content the ADC continuous phase was replaced by the UC phase, implying the occurrence of phase inversion. This variation of morphology allowed the SINs to have a property range from the UC‐toughened plastics to the ADC‐reinforced polyurethane. The SINs containing 50% UC showed synergism in the mechanical properties as the elongation was significantly increased to 4 times that of the unmodified UC and ADC homopolymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3361–3370, 2001
The effect of addition of different elastomers upon the crystalline nature of PP
Authors: Da Silva Ana Lúcia N. , Rocha Marisa C. G. , Lopes Léa , Chagas Beatriz S. , Coutinho Fernanda M. B. 
Published: August 2002

AbstractThermal and morphological studies have been performed on polymer blends based on ethylene–octene copolymer (PEE)/PP and ethylene–propylene–diene copolymer (EPDM)/PP. The thermal and morphological behavior of PEE, EPDM, PEE/PP, and EPDM/PP systems were analyzed by differential scanning calorimetry (DSC) and polarizing light microscopy, respectively. It was observed that the behaviors of crystallization kinetics of PEE/PP and EPDM/PP blends were similar. It was also observed that addition up to 10–20% (w/w) of elastomers resulted in increasing of spherulite size. The heat of fusion (ΔHf) and crystallinity degree of PEE/PP and EPDM/PP systems decreased when the elastomer contents were increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3530–3537, 2001
Molecular interactions in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) interpenetrating polymer networks
Authors: Zhang Jing , Peppas Nicholas A. 
Published: August 2002

AbstractThe molecular interactions between the component networks in poly(methacrylic acid)/poly(N‐isopropyl acrylamide) (PMAA/PNIPAAm) interpenetrating polymer networks (IPNs) were investigated using attenuated total reflectance (ATR)‐Fourier transform IR (FTIR) spectroscopy. Hydrogen‐bond formation was noted between the carboxyl groups of PMAA and the amide groups of PNIPAAm. The ATR‐FTIR results showed shifts in the carboxylic and amide groups, indicating the existence of hydrogen bonding between these two individual networks within the IPNs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1077–1082, 2001
Studies on the synthesis and properties of hydroxyl azacrown ether‐grafted chitosan
Authors: Yang Zhikuan , Yuan Yang 
Published: August 2002

AbstractThe chitosan hydroxyl azacrown ether was synthesized by reaction of hydroxyl azacrown ether with epoxy‐activated chitosan. The C2 amino group in chitosan was protected from the reaction between benzaldehyde and chitosan to form N‐benzylidene chitosan. After reaction with epichlorohydrin and azacrown ether, reacting O‐aryl mesocyclic diamine‐N‐benzylidene chitosan and dilute ethanol hydrochloride solution to obtain novel chitosan‐azacrown ether bearing hydroxyl removed the Schiff base. Its structure was confirmed with elemental analysis, FTIR spectra analysis, X‐ray diffraction analysis, and solid‐state 13C NMR analysis. Its static adsorption properties for Ag(I), Cd(II), Pb(II), and Cr(III) were also investigated. The experimental results showed that the hydroxyl azacrown ether grafted chitosan has good adsorption capacity and high selectivity for Ag(I) in the coexistence of Pb(II) and Cd(II), the selectivity coefficients of hydroxyl azacrown ether chitosan were KAg(I)/Pb(II) = 32.34; KAg(I)/Cd(II) = 56.12. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1838–1843, 2001
Study on molecular interaction behavior, and thermal and mechanical properties of polyacrylic acid and lactose blends
Authors: Fan Xiao‐Dong , Hsieh You‐Lo , Krochta John M. , Kurth Mark J. 
Published: August 2002

AbstractPolyacrylic acid (PAA) blending with lactose or polyol, a lactose derivative, is investigated by Fourier transform infrared, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and stress–strain tests. The IR spectra of PAA/lactose blends exist shifting around 1700 cm and 3400 cm−1, implying intermolecular hydrogen‐bonding interaction between two compounds. DSC data show that PAA and lactose are miscible below 17% lactose. At the higher content of lactose, phase separation occurs due to lactose self‐association. Comparing to PAA/lactose blends, PAA/ polyol systems show much weaker hydrogen‐bonding interaction effect. All blending systems studied exhibit extensive reduction in their thermal and mechanical properties. The result suggests that both lactose and polyol cannot be used as effective additives to enhance the physical properties of PAA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1921–1927, 2001
Morphology and mechanical properties of pullulan/poly(vinyl alcohol) blends crosslinked with glyoxal
Authors: Teramoto Naozumi , Saitoh Masahiko , Kuroiwa Johta , Shibata Mitsuhiro , Yosomiya Ryutoku 
Published: August 2002

AbstractWe prepared pullulan/poly(vinyl alcohol) (PVA) blend films by casting the polymer solution in dimethyl sulfoxide. Their morphology and mechanical properties were investigated. Scanning electron micrographs revealed that the pullulan was immiscible with PVA over the entire composition range. The tensile strength and modulus of the blend films were lower than those predicted by the upper bound composite equation. To improve the mechanical properties, we investigated the reaction of the 40/60 blend with glyoxal. The infrared spectral change and the increase in the glass‐transition temperature (corresponding to the PVA component) accompanying the reaction indicated that crosslinking with glyoxal had proceeded. The crosslinked films were homogeneous and had higher tensile strengths and moduli than the simple blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2273–2280, 2001
Phase‐separation prevention and performance improvement of poly(vinyl acetate)/TEOS hybrid using modified sol‐gel process
Authors: Jang Jyongsik , Bae Joonwon , Kang Doohwan 
Published: August 2002

AbstractThe formation of covalent bonds between silanols in copolymer and those in silica prevents organic–inorganic phase separation. Two series of hybrid composite materials, poly(vinyl acetate‐co‐vinyl trimethoxysilane)/TEOS and poly[vinyl acetate‐co‐3‐(trimethoxysilyl)propyl methacrylate]/TEOS, were fabricated using a modified sol‐gel process. The hybrids were transparent. Two kinds of silane coupling agents, vinyl trimethoxysilane (VTS) and 3‐(trimethoxysilyl)propyl methacrylate (γ‐MPS), were used to prevent macrophase separation through formation of covalent bonds. Thermal analysis showed that γ‐MPS was more effective than VTS for the formation of covalent bonds. Enhancement of thermal stability of the hybrids was investigated by thermogravimetric analysis. Photomicrographs of scanning electron microscopy and images of atomic force microscopy indicated that inorganic silica particles were homogeneously dispersed in less than 50 nm in organic matrix. The morphological properties of hybrids were strongly dependent on the organic–inorganic composition. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2310–2318, 2001
Chemical, chromatographic, and thermal analysis of rosemary (Rosmarinus officinalis)
Authors: Kaloustian J. , Portugal H. , Pauli A. M. , Pastor J. 
Published: August 2002

AbstractRosemary (Rosmarinus officinalis) is mainly known for its cooking qualities, but it possesses an essential oil with pharmacological properties. Moreover, this plant was the start of forest fires in Provence, France. The presence of biopolymers can contribute to electrical energy production by biomass combustion. The aim of this work was to study a stalk of rosemary during its biological cycle (November 1998 to June 1999). The chemical analysis (water, mineral ashes, cellulose, lignin, holocellulose, and extractives) showed few variations during this period. Leaves and branches differentiated themselves according to their chemical composition. Analyzed by chromatography gas–liquid chromatography/mass spectroscopy (GC‐MS) and gas–liquid chromatography/flam ionization detector (GC‐FID), the essential oil of this rosemary had a high level of camphor (30–45%), which could be used in new therapeutics (cardiac and respiratory analeptic). Finally, the simultaneous thermal analysis (DTA‐TG) was run on the fresh plants and the dried powdered samples. Several kinetic constants of the biopolymers had been computed: activation energies of cellulose and holocellulose. During heating, the rosemary's lignin decomposed more than others plants, thereby increasing the fire risks. The chemical, chromatographic, and thermal analysis run on the rosemary could be applied on other species in the Mediterranean basin. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 747–756, 2002
Simultaneous SAXS and WAXS investigations of changes in native cellulose fiber microstructure on swelling in aqueous sodium hydroxide
Authors: Crawshaw J. , Bras W. , Mant G. R. , Cameron R. E. 
Published: August 2002

AbstractSimultaneous small‐ and wide‐angle X‐ray scattering was used to follow changes in the microstructure of native cellulose (cellulose I) fibers during conversion to sodium cellulose I (Na‐cellulose I) by aqueous sodium hydroxide. Wide‐angle X‐ray scattering was used to monitor the extent of conversion, while small‐angle X‐ray scattering was used to explore what occurs at the higher structural levels of the elementary fibrils, microfibrils, and interfibrillar voids. Native cellulose fibers, swollen in either water or aqueous sodium hydroxide, exhibited an increase in the void volume fraction and a decrease in the void cross‐section size, as the swelling agent separated elementary fibrils, opening up the structure, and creating many small voids. After conversion of swollen native cellulose to sodium cellulose I, the void volume fraction and average void cross‐section dimensions both increased. During conversion from dry cellulose I fibers to swollen Na‐cellulose I fibers, the void cross‐section dimensions went through a minimum, suggesting that the void structure may go via an intermediate similar to the water swollen structure of cellulose I. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1209–1218, 2002
Properties of high‐temperature drilling fluids incorporating disodium itaconate/acrylamide/sodium 2‐acrylamido‐2‐methylpropanesulfonate terpolymers as fluid‐loss reducers
Authors: Wu Y. M. , Sun D. J. , Zhang B. Q. , Zhang Ch. G. 
Published: August 2002

AbstractThe terpolymer of disodium itaconate (DIA), acrylamide (AM) and sodium 2‐acrylamido‐2‐methyl‐1‐propane sulfonate (SAMPS) was synthesized through free‐radical polymerization, and characterized using FTIR and TGA methods. The IR spectra of DIA‐AM‐SAMPS terpolymer confirmed that there was no olefinic band at 1635–1620 cm−1, while the TGA results revealed that the terpolymer was of higher thermal stability than the SAMPS homopolymer. The filtrate volume reduced with increase of the terpolymer concentration before or after the aging test. The rheology properties of both fresh‐water mud and salt‐water mud were improved by DIA‐AM‐SAMPS terpolymer, and apparent viscosity (ηa); plastic viscosity (ηb) and yield point (τ0) of salt‐water mud reached the smallest values at 1.2% of the terpolymer concentration after the aging test. The particle size data demonstrated that only a small change of the clay particle size occurred before and after the aging test at 220°C. This further confirmed the thermal stability of the terpolymer–clay dispersion from another point of view. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3068–3075, 2002; DOI 10.1002/app.2335
Ecoregional planning in marine environments: identifying priority sites for conservation in the northern Gulf of Mexico
Authors: Beck Michael W. , Odaya Mami 
Published: August 2002

Abstract1. The overall aim of this work was to identify sites within the northern Gulf of Mexico that, if protected, would fully represent the biological diversity of the nearshore waters of this ecoregion. In this paper, we focus on the eastern subregion, northwest Florida, to illustrate the process of ecoregional planning in marine environments.2. The basic steps in ecoregional planning include: identification of conservation targets, i.e. species and habitats; collection of data on their ecology and distribution; determination of conservation goals for the amount of targets that must be protected; and identification of a set of sites that meets these goals for all targets.3. As a preliminary goal, it was determined that the set of priority sites should contain at least 20% of the current distribution of each target habitat and species.4. Two primary tools were used to choose a set of priority sites: a reserve selection program, SITES, and interviews and a workshop with scientists and managers. The final set of priority sites integrated information from these various sources.5. The goals were exceeded for all conservation targets in the priority sites. On average, 75 and 58% of the distributions of the habitat targets were contained within the priority and high priority sites, respectively. These priority and high priority sites only occupied 29 and 17% of the study area, respectively.6. One of the first steps in the conservation of the bays identified as priority sites is the recognition that they are integrally linked by important processes to the surrounding terrestrial and aquatic environments. Conservation in a part of these estuarine landscapes will benefit biodiversity across environments. Copyright © 2001 John Wiley & Sons, Ltd.
Differential expression of multiple genes during articular chondrocyte redifferentiation
Authors: Haudenschild Dominik R. , McPherson John M. , Tubo Ross , Binette François 
Published: August 2002

AbstractArticular chondrocytes undergo a rapid change in phenotype and gene expression, termed dedifferentiation, when isolated from cartilage tissue and cultured on tissue culture plastic. On the other hand, “redifferentiation” of articular chondrocytes in suspension culture is characterized by decreased cellular proliferation and the reinitiation of synthesis of hyaline articular cartilage extracellular matrix molecules. The molecular triggers for these events have yet to be defined. Subtracted cDNA libraries representing genes involved in the early events of adult human articular chondrocyte redifferentiation were generated from human articular chondrocytes that were first cultured in monolayer, and subsequently transferred to suspension culture at 106 cells/ml for redifferentiation. Differential regulation of genes involved in cellular organization, nuclear structure, cellular growth regulation, and extracellular matrix deposition and remodeling were observed within 48 hr of this transfer. Many of these genes had not been previously identified in the chondrocyte differentiation pathway and a number of the isolated cDNAs did not have homologies to sequences in the public data banks. Genes involved in IL‐6 signal transduction including acute phase response factor (APRF), Mn superoxide dismutase, and IL‐6 itself were up‐regulated in suspension culture. Membrane glycoprotein gp130, a component of the IL‐6 receptor, was down‐regulated. Other genes involved in cell polarity, cell adherence, apoptosis, and possibly TGF‐beta signaling were differentially regulated. The differential regulation of the cytokine connective tissue growth factor (CTGF) during the early stages of articular chondrocyte redifferentiation, decreasing within 48 hours of transfer to suspension culture, was particularly interesting given its reported role in the stimulation of cellular proliferation. CTGF was highly expressed in proliferative monolayer culture, and then greatly reduced by redifferentiation in standard high‐density suspension culture. When articular chondrocytes were seeded in suspension at low‐density (104 cells/ml), however, high levels of CTGF were observed along with increased levels of mature articular cartilage extracellular matrix protein RNAs, such as type II collagen and aggrecan. Although the role of CTGF in articular cartilage biology remains to be elucidated, the results described here demonstrate the potential utility of subtractive hybridization in understanding the process of articular chondrocyte redifferentiation. Anat Rec 263:91–98, 2001. © 2001 Wiley‐Liss, Inc.