bluuebunny/crossref_metadata_2025_split huggingface dataset:
A generalized correlation for the viscosity of dextrans in aqueous solutions as a function of temperature, concentration, and molecular weight at low shear rates
Authors: Carrasco F. , Chornet E. , Overend R. P. , Costa J. 
Published: April 2003

AbstractAn expression relating the viscosity of dextran solutions to polymer concentration (c), molecular weight (M), and temperature (T) has been derived from experimental data in the following ranges: 5 < c < 25% (wt/wt), 298.2 < T < 363.2 K, and 71,500 < M < 531,000 g/mol. The experimental work was based on capillary viscosimeters. Thermodynamic data (entropy and energy of activation for the viscous flow of a Newtonian fluid) are also presented as a function of polymer concentration for the three molecular weights studied. This thermodynamic analysis suggests that dextrans in aqueous solutions behave as flexible polymers. Application of our expression to existing viscosity data for ethylene/vinylacetate copolymers in paraffin has resulted in improved goodness of fit with respect to established correlations.
Effects of acceptor level on chemically synthesized polypyrrole‐halogen complexes
Authors: Neoh K. G. , Kang E. T. , Tan T. C. 
Published: April 2003

AbstractElectrically conductive polypyrrole (PPY)‐halogen complexes have been synthesized by simultaneous chemical polymerization and oxidation of pyrrole. The ratio of pyrrole monomer to halogen (chlorine, bromine, or iodine) used in the synthesis was varied and the physicochemical and electrical properties of the resulting complexes were studied in detail. With all three halogens, the yield of the complex is affected by the initial amount of halogen used, with the properties of the polypyrrole‐bromine complex showing the strongest dependence on the acceptor level. For this complex, both the percentage of bromine incorporated and the ratio of covalent to ionic bromide increase upon increasing the initial bromine concentration, while the electrical conductivity shows a maximum. Experimental evidence suggests that some halogen substitution at the pyrrole ring must have occurred in the PPY–Br2 and PPY–Cl2 complexes, but not in the PPY–I2 complex.
Gelatin with hydrophilic/hydrophobic grafts and glutaraldehyde crosslinks
Authors: Chatterji Prabha R. 
Published: April 2003

AbstractAcrylic monomers were graft copolymerized onto gelatin chains using potassium persulfate in aqueous medium. The graft copolymers were then treated with glutaraldehyde to establish crosslinks between gelatin macromolecules. This yielded a rigid water insoluble protein network sporting grafted chains at random. The chemistry of the acrylic monomer decided the hydrophilic/hydrophobic properties of the ultimate product. This paper describes the preparation and properties of such grafted, crosslinked gelatins.
Simplified hydrolysis of cellulose and substituted cellulose: Observations on trifluoroacetic acid hydrolyses
Authors: Rowland Stanley P. , Howley Phyllis S. 
Published: April 2003

AbstractHydrolyses of selected soluble polysaccharides (e.g., polyoses) and disordered and crystalline celluloses, each bearing 2‐diethylaminoethyl (DEAE) substituents at low degree of substitution (DS < 0.05) were explored in 100% and 2N trifluoroacetic acid (TFA). Analyses were evaluated relative to hydrolysis with 72% sulfuric acid. DEAE–polyoses hydrolyzed readily in 100% and 2 N TFA during extended reaction periods with complete liberation of DEAE–glucoses. Hydrolyses of cellulose and DEAE–celluloses in 100% TFA were critically dependent upon cautious incremental dilution of the TFA during stepwise reaction to avoid precipitation of incompletely hydrolyzed products. DEAE–celluloses were partially solubilized and hydrolyzed in heterogeneous reaction in 2N TFA at 121°C. Complete liberation of DEAE‐glucoses in the solubilized components was achieved after supplementary hydrolysis at 121°C. In all hydrolyses, including those with 72% sulfuric acid, extended hydrolyses were essential for complete liberation of the 2‐O‐ and 6‐O‐DEAE–glucoses. Under optimum conditions, results of hydrolyses in 100% TFA were comparable to those in 72% sulfuric acid. Ease of release of DEAE‐glucopyranoses in hydrolyses of DEAE‐cellulose in 2N TFA was in the same order (3‐O‐ > 6‐O‐> 2‐O‐) as in homogeneous hydrolyses in sulfuric acid and in 100% TFA. Differences in release of isomeric DEAE–glucoses were greater in the heterogenous system. Degradation of glucose and DEAE–glucopyranoses occurred in extended periods of reaction in all acidic media. Rates of degradation of glucose and DEAE–glucopyranoses in dilute acid at 100°C were similar for glucose and 6‐O‐DEAE–glucose. The rates were about half as fast for 3‐O‐DEAE–glucose and an order of magnitude lower for 2‐O‐DEAE–glucose.
Modification of atactic polypropylene to prepare emulsions by oxidation in melt
Authors: Yaykin Özden , Savaşçi Ö. Tunç , Baysal Bahatti̇n M. 
Published: April 2003

AbstractOxidation of atactic polypropylene (APP) obtained as by product from polypropylene production is studied in melt to obtain polymers which are easily emulsified by commercial emulsifiers. The experiments are done using a sitrred, jacketed glass reactor and the relevant heating, air‐feeding, and sampling attachments. Oxidation is followed by the change of carbonyl absorbance, iodine number, acid number, molecular weight, and melt flow index (MFI) by time. The relevant tests are done by infrared (IR) spectroscopy and gel permeation chromatography (GPC) and standard tests with minor modifications are applied. It is found that as temperature, air flow rate, and mixing speed are increased, higher oxidation rates are obtained. It is also found that initiator types and concentrations used are not as effective as the above parameters. By oxidation as molecular weight reduces, molecular weight distribution narrows. Correlation between MFI, iodine number, and molecular weight of the oxidized APP is also made for easy follow‐up of oxidations. In addition, it is found that for easy and stable emulsions, APP must be modified by oxidation to iodine number and MFI higher than 30 mg/g and 3.5, respectively.
Sorption of organic compounds on strong basic macroporous anion exchangers
Authors: Chitanu Gabriela , Luca Cornelia , Avram Ecaterina , Airinei A. , Petrariu I. , Carpov A. 
Published: April 2003

AbstractThe behavior of various strong basic type II macroporous anion exchangers against the sorption of some organic acid alkaline salts as follows: natrium benzoate, natrium benzenesulfonate, potassium α‐naphthylacetate, natrium β‐naphthalenesulfonate, and natrium anthraquinone‐2‐sulfonate was established. The values of the sorption capacities depend on the morphology of anion exchanger network, the type and the size of organic anion, as well as the type of anion exchanger.
Determination of diffusion coefficient of oxygen into polymers by using electron spin resonance spectroscopy. I. Poly(methyl methacrylate)
Authors: Kaptan Yilmaz , Pekcan Önder , Arca Emin , Güven Olgun 
Published: April 2003

AbstractA simple technique has been proposed for the measurement of the diffusion coefficient of oxygen into polymeric spheres. The technique is based on the scavenging of radicals produced by high energy radiation by oxygen. The diffusion coefficient of oxygen determined for poly(methyl methacrylate) has shown an inverse dependency on the dose received. Diffusion coefficient determined for low doses (D = 3.4 × 10−8 cm2/s) as well as that determined after extrapolation to zero dose (D0 = 3.7 × 10−8 cm2/s) are in excellent agreement with the values reported in the literature.
PVT scaling parameters for polymer melts
Authors: Hartmann Bruce , Simha Robert , Berger Alan E. 
Published: April 2003

AbstractScaling parameters for two PVT equations of state are evaluated for 11 polymer melt systems using a nonlinear least square fitting algorithm that analyzes all of the experimental data simultaneously. Two different criteria are considered in this evaluation. In the first method, the fitting criterion is the difference between the calculated and experimental volume. In the second method, the criterion is the difference between the calculated and experimental pressure. In both cases, the differences between the scaling parameters obtained using the simultaneous fit procedure and those obtained using the earlier consecutive fit procedure are a few percent, which can have a significant effect in some calculations. In addition to being a more consistent method of evaluating scaling parameters, the simultaneous fit procedure leads to much better agreement between calculated and experimental values, in some cases by a factor of 2.
Cure kinetics of neat and graphite‐fiber‐reinforced epoxy formulations
Authors: Mijović Jovan , Wang H. T. 
Published: April 2003

AbstractAn investigation was carried out into the cure kinetics of neat and graphite fiber‐reinforced epoxy formulation, composed of tetraglycidyl 4,4′‐diaminodiphenyl methane (TGDDM) resin and diaminodiphenyl sulfone (DDS) curing agent. Two experimental techniques were employed: isothermal differential scanning calorimetry (IDSC) and dynamic differential scanning calorimetry (DDSC). An autocatalytic mechanism with the overall reaction rate order of 2 was found to describe adequately the cure kinetics, of the neat resin and the composite. All kinetic parameters, including reaction rate constants, activation energies and preexponential factors, were calculated and reported. The presence of graphite fibers in the composite had only a very small initial effect on the kinetics of cure.
Self‐assembly of octadecyltrichlorosilane films on mica
Authors: Carson George , Granick Steve 
Published: April 2003

AbstractSelf‐assembled films of Octadecyltrichlorosilane (OTS) have been deposited on freshly cleaved mica. A combination of argon plasma pretreatment, long adsorption times in solution, and a posttreatment at a moderate temperature (60°C) were required to form homogeneous OTS layers exhibiting good adherence to the mica. This process is more complex than the procedure required to form similar layers on glass. Advancing contact angles of water droplets ranged from 113 to 116°, with receding angles of 107 to 110°.
Morphological studies of blends containing liquid crystalline polymers with poly(ethylene terephthalate)
Authors: Ko C. U. , Wilkes G. L. , Wong C. P. 
Published: April 2003

AbstractThe investigation involved the structure–property behavior of extruded cast films prepared from blends of thermotropic liquid crystalline copolyesters with poly(ethylene terephthalate) (PET). Data were obtained which showed not only the temperature dependence of the moduli and stress–strain behavior but also the orientation effects that must be prevalent in order to explain the differences between the moduli measured parallel and perpendicular to the extrusion direction. Only at high liquid crystal polymer (LCP) composition is the modulus particularly increased. The modulus enhancement with lower LCP content and utilization of process variables are discussed with respect to the induced morphological textures and nature of the process equipment. Specifically, the process variable extruder gear pump speed did not enhance Young's modulus at the same LCP content as extensively as did the process variable of extruder screw speed.
Thermal behavior and fiber studies of certain azoaromatic polyamides
Authors: Rajendran V. , Nanjan M. J. 
Published: April 2003

AbstractTwo aromatic polyamides containing azo linkage in the main chain were synthesized and characterized by TGA, DTA, and pyrolysis–GC–chemical ionization mass spectra. Fibers were also spun using a laboratory scale wet spinning unit and their mechanical and morphological properties studied. The results were correlated with structure and spinning conditions.
Structure and viscoelastic properties of epoxy resins prepared from four‐nuclei novolacs
Authors: Hasegawa Kiichi , Fukuda Akinori , Tonogai Saburo 
Published: April 2003

AbstractThe relation between the structure and the viscoelastic properties of seven kinds of epoxy resins was studied. Seven tetraglycidylethers were synthesized from four‐nuclei novolacs in which the positions of methylene linkage or number of kind of substituents were different. These epoxy compounds were cured with diaminodiphenylmethane as a hardener. From the viscoelastic properties of the fully cured resins with the hardener, characteristic properties such as glass transition temperature (Tg), average molecular weight between crosslinking points (M̄c), and front factor (ϕ) were obtained. It was concluded that higher linearity in the main chain of epoxy resins gave a cured resin with a higher Tg, a smaller M̄c, and a larger ϕ.
Swelling of porous ethylvinylbenzene–divinylbenzene copolymers and the stability of the pore structure
Authors: Jun Yan , Rongnan Xu , Juntan Yan 
Published: April 2003

AbstractA series of porous ethylvinylbenzene–divinylbenzene (EVB–DVB) copolymers with DVB contents ranging from 22.0 to 98.4% were prepared using various amounts of toluene as the inert diluent, and studies were made on the copolymers as to their swelling properties, the stability of their pore structure, and the relationship between swelling in nonsolvents and variations in their pore structure. The swelling experiments showed that the ethanol regains of the copolymers were closely related to the course of phase separation, and the increases in both the DVB content and the volume fraction of monomers in the organic phase resulted in enhanced capacity of the highly crosslinked copolymers to keep swelling in solvents having extremely small affinity for these copolymers. The variations in pore structure, sometimes quite considerable, for copolymers pretreated with different solvents were observed even at DVB content up to 98.4% and further studies showed that a consistent relationship existed between pore volume variation and volume swelling ratio in ethanol for toluene modified copolymers.
Copolymerization of styrene with fumaronitrile initiated by L‐ascorbic acid
Authors: Kuramoto Noriyuki , Sakoh Kenji , Nagai Katsutoshi 
Published: April 2003

AbstractCopolymerization of styrene (ST) with fumaronitrile (FN) initiated by L‐Ascorbic acid (L‐Asc) was investigated in dioxane containing a small amount of methanol in the presence of atmospheric oxygen. L‐Asc was found to initiate the alternating copolymerization of ST with FN at mild conditions. The copolymerization rate Rp was found to increase with increasing L‐Asc concentration and was found to depend on [L‐Asc]0.6 [(ST) + (FN)]2.7. The overall energy of activation as calculated from Arrhenius plot was found to be 10.9 kcal/mol−1 within the temperature range of 25–40°C.
Hydrolysis of cationic polyacrylamides
Authors: Aksberg Rein , Wågberg Lars 
Published: April 2003

AbstractThe alkaline hydrolysis of two acrylamide‐based polyelectrolytes has been investigated. The experiments were carried out in buffered aqueous solutions in the pH range of 3.5–8.5 and in the temperature range of 22–50°C. 13C‐NMR analysis of the hydrolysis product showed that choline chloride was the substance released upon hydrolysis. The decrease in charge density of the copolymer due to the hydrolysis was studied by polyelectrolyte titration and nitrogen analysis. The results show that the rate of hydrolysis increased with increasing pH or increasing temperature. In the hydrolysis of C‐PAM 1 at 22°C and pH 6, the half‐life of the cationic groups was 10 days. At pH 7 the half‐life was shorter, 24 h, and at pH 8.5 the reaction was very fast with a half‐life of about 0.25 h. The charged groups on C‐PAM 2, the polymer with the higher charge density of the two polymers studied, have somewhat longer half lives than those on C‐PAM 1. This can be explained by the structure of the polymers.
Preparation of ion‐exchange celluloses. I. Anion exchange celluloses
Authors: Khalil M. I. , Wally A. , Kantouch A. , Abo‐Shosha M. H. 
Published: April 2003

AbstractCellulose–poly(glycidyl methacrylate) graft copolymer (CPGMA) was treated with ammonia (AH), ethylamine (EA), diethylamine (DEA), and triethylamine (TEA). Factors affecting the reaction, such as reaction duration, temperature, liquor ratio, pH, and aminating agent/epoxide molar ratio were studied. A mechanism of the reaction was suggested. The anion exchange celluloses were characterized by studying its capacity, potentiometric titration, and durability to use. Potentiometric titration of the produced anion exchangers has been studied and pKb values were found to be 6.1, 7.6, and 8.9 for DEA–CPGMA, EA–CPGMA, and AH–CPGMA, respectively.
Dynamic mechanical analysis of fibers. I. Effect of experimental variables and material type
Authors: Khanna Y. P. , Wenner W. M. , Kumar R. , Kavesh S. 
Published: April 2003

AbstractDepending upon the fiber material, some of the experimental variables can have a profound effect on the dynamic tensile modulus vs. temperature data. With the use of an experimental fiber (25°C < Tg < 75°C; Tm > 220°C; hot stretched), the effect of several variables, e.g., moisture/volatiles, annealing/relaxation, frequency (strain rate), pretension, and % strain on the modulus retention term [(E100°C/E25°C) × 100] have been studied. Of these variables, pretension and especially % strain dramatically increase the modulus retention and this effect is attributed to the elastic orientation under force (EOF), i.e., it exists only in the presence of tensile forces and is reversible. Such an effect was insignificant for Kevlar (Tg − 375°C) and absent for steel wire. Dynamic modulus measurements at 25°C using sonic techniques also support the EOF phenomenon in polyethylene yarns (Tg ∼ −30°C) but not in Kevlar polymide yarns (Tg ∼ 375°C).
Structural interpretation of plasma‐polymerized propargyl alcohol
Authors: Yoshimura K. , Kitade T. , Kitamura K. , Hozumi K. 
Published: April 2003

AbstractVapor of propargyl alcohol under reduced pressure was glow‐discharged for plasma polymerization by which hydrophilic polymer film could be deposited onto a solid substrate. The hydrophilic property was more enhanced with use of the same monomer containing water. An interpretation of chemical structures of the polymer molecules was therefore attempted to discover the reason of the hydrophilic property. The polymer materials were subjected to IR spectroscopy, 13C‐NMR and 1H‐NMR spectroscopies, elemental analysis, number average molecular weight determination, mass spectrometry, and other wet chemical analysis for . The IR spectra of the polymers showed the presence of OH, CO, and CC groups with a disappearance of CC group of the monomer. It was also found that the molecular formula of a solvent extract of the polymer derived from the plain monomer was C26H36O9 ≒ 490, involving four hydroxyl, one carbonyl, and two to three olefinic unsaturation groups within a unit molecule. On the other hand, the polymer from 60% water‐containing monomer showed its molecular formula as C44H66O18 ≒ 890, containing seven to eight hydroxyl, two carbonyl, and one to two olefinic unsaturation groups. This information was used to establish the symbolic chemical structures of the polymer molecules. It has been found that both polymers were not as much crosslinked as other plasma polymers because of having side chains with fewer branching. The oxygen atoms were retained in the polymer not only as the forms of OH and CO but also as a member of the principal frame of the polymers.
Activation parameters and the catalytic effects of poly(3‐alkyl‐1‐vinylimidazolium) salts on the hydrolysis of neutral phenyl esters
Authors: Papathomas K. I. , Israel S. C. , Salamone J. C. 
Published: April 2003

AbstractAlkaline hydrolyses of p‐nitrophenyl acetate (PNPA) and p‐nitrophenyl laurate (PNPL) were studied in the presence of poly(3‐methyl‐1‐vinylimidazolium iodide) (PVII‐C1), poly(3‐n‐hexadecyl‐1‐vinylimidazolium iodide) (PVIII‐C16) and their monomeric analogs. The polysoap (PVII‐C16) was a completely quaternized polyion, in contrast to other polysoap systems that have been studied. The hydrolysis of PNPA was not affected by these polyions. The hydrolysis of PNPL was instead enhanced by the addition of these cationic polyions. The magnitudes of the enhancement were in the order of PVII‐C16 > PVII‐C1, which is explained in terms of the hydrophobicity of these polyions. Values of k2, the rate constant of the polymer substrate complex, indicated that the esters bound to the polymer were more reactive than the free esters. Binding or association constants (K) obtained also increased in the order PVII‐C16 > PVII‐C1. Inhibitory results were observed for the hydrolysis of PNPL in presence of 3‐n‐hexadecyl‐1‐vinylimidazolium iodide (VII‐C16). The activation parameters for these reactions were also investigated.
Compatibilization of natural rubber–polyolefin thermoplastic elastomeric blends by phase modification
Authors: Choudhury Namita Roy , Bhowmick Anil K. 
Published: April 2003

AbstractNatural rubber–polyolefin (70/30) blends have been studied by incorporation of modified rubber and plastic phases with a view to make the heterogeneous phases compatible. The modified rubbers used were epoxidized natural rubber (ENR) and sulfonated ethylene–propylene diene rubber (S‐EPDM) at a level of 20 parts. Other rubbers such as chlorinated polyethylene (CPE) and ethylene propylene diene rubbers (EPDM) were also used at a level of 20 parts in the natural rubber–polyethylene (NR/PE) systems. The plastic phase was chemically modified with maleic anhydride (MA) in presence of benzoyl peroxide (BPO) and used at a concentration of 10% of PE, i.e., PEm. The tensile properties such as the modulus, elongation at break, tensile strength, and hysteresis were studied. NR/ENR/PEm/PE shows the greatest improvement in tensile strength (45% over control NR/PE). NR/S‐EPDM/PEm/PE also shows similar improvement, although the hysteresis loss decreases. The change in these properties could be related to the adhesive strength. This was found to be improved by the incorporation of modified rubber and modified plastic phases. The best adhesion values have been obtained with NR/ENR/PEm/PE and NR/S‐EPDM/PEm/PE. Thus, a correlation between tensile and adhesive strength was obtained for all the systems. The increase in adhesive strength is due to chemical reactions between the various phases. Probable chemical reactions have been suggested. Morphological observations show that the phases are interpenetrating, and this is consistent with the increased tensile strength. The natural rubber–polypropylene (NR/PP) systems do not offer good strength properties with the modified PP and modified rubbers. The adhesive strength also decreases with the incorporation of the modified system. The hysteresis properties show some improvement.
Characterization of physical aging of poly(methyl methacrylate) powders by a novel high pressure sorption technique
Authors: Stewart M. E. , Hopfenberg H. B. , Koros W. J. 
Published: April 2003

AbstractHigh pressure CO2 sorption isotherms were measured at 35°C in previously dilated PMMA microspheres, which were subsequently aged in vacuum at 35°C. The dilation was induced by preswelling with high activity methanol vapor at 13°C, or alternatively with CO2 at a pressure of 20 atm and a temperature of 5°C. The state of the samples during long‐term aging was probed by rapid and intermittent determination of complete high pressure CO2 isotherms. The dilation increased the sorption levels observed in the sorption experiments compared to those observed in untreated samples and, as the aging time increased, the sorption level progressively decreased. The isotherms under all conditions were well described by the dual mode sorption model. The observed time dependence of the isotherms was successfully described by confining all changes in sorption capacity to a systematic decay of the Langmuir capacity parameter. The equilibrium parameters of the model, however, were essentially unaffected by the preswelling and aging histories.