bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental degradation of an epoxy resin matrix
Authors: Luoma G. A. , Rowland R. D. 
Published: April 2003

AbstractWith the increased use of graphite‐reinforced composites as replacements for metals has come concerns about durability under harsh environmental conditions. Degradation is expected to begin on the surface and progress toward the center of the resin as a function of time, and reflectance infrared techniques are ideal for monitoring structural changes on surfaces. The present paper describes the application of Fourier transform infrared spectroscopy using internal reflectance elements to the determination of the degree of environmental aging of Hercules 3501−6 resin. The results indicate that degradation occurs via hydrolysis, oxidation, and dehydration reactions at specific locations in the polymer chain. Of special interest is the unique reaction of the tertiary amine of the epoxy portion of the molecule.
Thermal and crystallization behavior of alloys of polyphenylene sulfide and high‐density polyethylene
Authors: Nadkarni V. M. , Jog J. P. 
Published: April 2003

AbstractThe thermal and crystallization behavior of alloys of two semicrystalline thermoplastics, namely, polyphenylene sulfide (PPS) and high‐density polyethylene (HDPE) were studied by differential scanning calorimetry (DSC). The presence of a second component in the alloy was found to influence the nonisothermal crystallization process of both the component polymers. The crystallization temperature of PPS in the DSC cooling scan is significantly affected, whereas there is little variation in case of HDPE in the composition range studied. The morphological changes observed in both PPS and HDPE are similar. These include larger crystallite size, a narrower crystallite size distribution, and a lower degree of crystallinity in the alloys as compared to the homopolymers. The isothermal crystallization of the component polymers in the alloys is significantly different from that of the homopolymer. The composition dependence of the overall rate of isothermal crystallization is explained in terms of the competing processes of nucleation and crystal growth. The results show that blending of a high melting polymer with a low melting polymer accelerates the crystallization of the high melting polymer, even at low levels of about 10% of the lower melting component.
Compatibility studies on blends of poly(ethylene ortho‐phthalate) and poly(vinyl acetate)
Authors: Vazquez‐Torres H. , Cruz‐Ramos C. A. 
Published: April 2003

AbstractBlends of poly(ethylene ortho‐phthalate) (PEOP), and poly(vinyl acetate) (PVAc), appear to be compatible at all compositions, from visual examination at room temperature and differential scanning calorimetry tests. Both low‐ (PEOP‐1) and high‐molecular weight (PEOP‐2) alloys with PVAc show a single composition‐dependent glass transition temperature (Tg). Some blends show Tg values that are below the Tg for either of the pure polymers. Couchman's equation, with a slight modification, can be used to model Tg behavior. All PEOP‐2 blends with PVAc, phase separate at high temperatures, whereas PEOP‐1–PVAc blends remain miscible under the same conditions. The composition dependence of the blends refractive index shows a deviation from simple additivity rules, and a similar trend is observed in density measurements. When comparing Flory's characteristic parameters for the polymers, compatibility is predicted for PVAc–PEOP blends. In contrast, blends of PEOP and poly(methyl methacrylate) (PMMA), which has a similar chemical structure to that of PVAc are predicted to be incompatible, in agreement with experimental evidence. It is suggested that compatibility is produced because of possible specific interactions between the aromatic group of PEOP and the ester carbonyl on PVAc, which is not sterically hindered as is the corresponding moiety on PMMA.
Drag reduction characteristics of graft copolymers of xanthangum and polyacrylamide
Authors: Deshmukh S. R. , Singh R. P. 
Published: April 2003

AbstractGraft copolymers of xanthangum and polyacrylamide have been prepared by grafting acrylamide onto xanthangum using ceric‐ion‐initiated solution polymerization technique. These graft copolymers have been tested for their drag reduction effectiveness, shear stability, and biodegradability. It has been shown that the grafting enhances the drag reduction effectiveness and biodegradation resistance of xanthangum considerably.
Characterization of epoxy coatings on steel by reflection/absorption fourier transform infrared spectroscopy. I. Effects of film thickness and angle of incidence
Authors: Nguyen T. , Byrd E. , Tsao A. 
Published: April 2003

AbstractFilms of amine‐cured epoxy coating of varying thicknesses from 100 Å to 2.5 μm on steel have been studied by reflection/absorption Fourier transform infrared spectroscopy (FTIR‐RA). The shape and frequency of several strongly absorbed bands of epoxy have been examined as a function of film thickness and angle of incidence. Compared to transmission spectra, reflection/absorption spectra of epoxy coating on steel show band shifts and distortions of the bands at 1510, 1247, and 1040 cm−1. These effects are more pronounced at increased thickness and at grazing angles. For thin films ( < 100 nm), RA spectral intensity increases with increasing angle of incidence. For thicker films, the relationship is quite complex. The relationship between film thickness and FTIR‐RA spectral peak height of an amine‐cured epoxy coating on steel has also been established.
Microcrystalline chitosan. I. Preparation and properties of microcrystalline chitosan
Authors: Struszczyk Henryk 
Published: April 2003

AbstractA new type of microcrystalline polymer prepared by aggregation has been discussed. The effect of the parameters of the preparation process on the properties of microcrystalline chitosan in hydrogel and solid forms has been studied using also microscopy and spectroscopy. The product obtained according to the method discussed shows the average molecular weight within a range 2.2–5.0 X 105, WRVs ≈ 260–520%, WRVg ≈ 700–1000%, and CrI up to 95%.
Synthesis, characterization, properties, and derivatives of poly(starch‐g‐(1‐amidoethylene)). II. Measurement of molecular weights by ultracentrifugation
Authors: Meister John J. , Sha Mu Lan , Richards E. Glen 
Published: April 2003

AbstractWeight‐average molecular weights of samples of poly(starch‐g‐(1‐amidoethylene)) determined by ultracentrifugation range from 0.19 to 3.7 × 106. These data show the copolymer to be a partially permeable coil in aqueous solution and to be formed at significantly higher molecular weights as the mole ratio of cerium(+ IV) to 2‐propenamide in the reaction mixture decreases. Sedimentation coefficients show no indications of distribution broadening from aggregation of copolymer molecules. Buoyancy factor and partial specific volume of the copolymers bracket the values of these variables for the backbone and sidechain.
On the long‐term strength of specimens made of phenol‐formaldehyde press powders
Authors: Natov M. , Vasileva S. , Kotsev G. 
Published: April 2003

AbstractThe study of the long‐term strength (LTS) of polyethylene, poly(vinyl chloride), and polyoximethylene shows that the In τ–σ relation for specimens, undergoing tension, is S‐shaped. Structure changes during the process of deformation may occur in these polymers. However, the structure of spatial‐grid polymers (solidifying phenol–formaldehyde resins, for instance) does not prove to be stress‐sensitive and experiments show that the In τ–σ relation can be described with sufficient accuracy by employing an equation of the form τ = τ0 exp[(U − γσ)/(RT + ασn)].
New aspects in cationization of lignocellulose materials. V. Modification of rotten aspen wood meal with quarternary ammonium groups
Authors: Šimkovic Ivan , Ebringerová Anna , Antal Miroslav , Micko Michael M. 
Published: April 2003

AbstractHolocelluloses prepared from clear and rotten aspen wood were gradually fractionated with 2.5% NH4OH, 4.5% NaOH, and 17.5% NaOH, respectively. A higher yield of polysaccharides (24.4%) was obtained from the rotten sample in comparison with clear wood (20.9%). Trimethyl ammonium‐2‐hydroxypropyl (TMAHP) derivatives of rotten aspen were prepared by the reaction of wood with 3‐chlor‐2‐hydroxypropyltrimethylammoniumchloride (CHMAC) in alkaline medium. The quantity of TMAHP—hemicelluloses (yield 14.1%) is only slightly lower in comparison with TMAHP—hemicelluloses (yield 15.8%) obtained by modification and subsequent extraction from clear aspen wood meal. The hemicelluloses isolated from the rotten aspen wood meal are contaminated with low molecular cellulose fraction, the degradation products of cellulose attacked by fungi. The lignin component of rotten wood is less intensively attacked by fungi than the polysaccharidic one.
Reaction kinetics of vinyl acetate emulsion polymerization
Authors: Chern Chorng‐Shyan , Poehlein Gary W. 
Published: April 2003

AbstractTransport of free radicals out of latex particles into the aqueous phase plays an important role in the emulsion polymerization of vinyl acetate. This so‐called “desorption” process involves chain transfer to monomer which generates a mobile and rather stable monomer‐unit free radical followed by the diffusion of this free radical out of the latex particle. A kinetic model is developed based on the reaction mechanisms of such an emulsion system. The experimental data available in the literature are used to test the model under various polymerization conditions. Reasonable agreement between the model predictions and experimental data is observed.
Polymer degradation in porous media flow
Authors: Farinato Raymond S. , Yen Wei S. 
Published: April 2003

AbstractThe hydrodynamic degradation of high molecular weight poly(acrylamide‐co‐Na acrylate) in 1M NaCl in porous media flow was studied as a function of polymer concentration in the dilute and semidilute concentration ranges. Porous media rheometry was used to monitor molecular weight changes due to chain scission. At equivalent superficial velocities of flow through a glass bead pack, polymers at dilute concentrations showed greater loss of molecular weight than polymers at semidilute concentrations.
Correlation of the solubility of volatile liquids in molten polymers
Authors: Han Chang Dae 
Published: April 2003

AbstractThe solubility of volatile liquids at infinite dilution (i.e., in the Henry's law region) in poly(vinyl acetate) (PVAc) and polystyrene (PS) at elevated temperatures has been correlated by plotting ln(1/Kp) against (Tc/T)2, where Tc is the critical temperature of the solute and Kp is Henry's constant at temperature T and a total pressure of approximately at 1 atm, defined as P1 = KpV10, where P1 is the partial pressure of the solute in the vapor phase and V10 is the solubility (cm3 solute per g polymer at 273.2 K and 1 atm). For this correlation, we have used experimental data available in the literature for 16 solutes covering 81 data points for PVAc and 17 solutes covering 82 data points for PS. We have calculated values of 1/Kp from the literature data reported in terms of the retention volume Vg0, weight‐fraction Henry's constant H1, and activity coefficient at infinite dilution Ω1∞. We have made the following observations: (1) for PVAc, ln(1/Kp) = −1.564 + B(Tc/T)2; and (2) for PS, ln(1/Kp) = −2.028 + B(Tc/T)2. In both cases, we found that values of B, the slope in the ln(1/Kp) versus (Tc/T)2 plots, vary with the acentric factor ω of the solutes. It has been found that, in both PVAc and PS at the same value of ω, values of B for slightly polar aromatic solutes are larger than those for nonpolar aliphatic solutes. Further, in PS at the same value of ω, values of B are smaller for strongly polar solutes than for slightly polar solutes, whereas in PVAc the opposite trend holds. This observation may be interpreted as that the solubility of strongly polar solutes in a polar polymer (e.g., PVAc) is greater than that of slightly polar and nonpolar solutes, whereas the solubility of strongly polar solutes in a nonpolar polymer (e.g., PS) is less than that of slightly polar solutes but greater than that of nonpolar solutes. The dependence of B on ω, observed in this investigation, is at variance with the correlations reported by Tseng, Lloyd, and Ward for PVAc and by Stiel and Harnish for PS.
Synthesis and characterization of castor oil urethane triamine networks
Authors: Saikumar C. , Rajadurai S. 
Published: April 2003

AbstractCastor oil was polymerized with diisocyanate and crosslinked with primary triamine (Jeffamine T‐403) to form networks. The effect of triamine as a crosslinking agent on rubbery castor oil urethane elastomer was determined by measuring network parameters such as average molecular weight between crosslinks (MC) number of polymer chains per unit volume (N), tensile strength, and modulus of the networks. The crosslinking density was varied by varying the ratio of NCO : NH2 from 0.60 to 0.95. The results indicated the formation of highly crosslinked elastomers at all NCO : NH2 ratios employed. The tensile stregth and modulus increased with increasing crosslink density up to a value of NCO : NH2 0.85 and after this there was no significant change, indicating the maximum limit of improvement attainble in terms of network characteristics.
Polymerization of olefins through heterogeneous catalysis. VII. Particle ignition and extinction phenomena
Authors: Hutchinson R. A. , Ray W. H. 
Published: April 2003

AbstractThe possibility of multiple steady states for a polymer particle is examined for propylene and ethylene, liquid and gas phase polymerizations. It is shown that multiple steady states should not occur in conventional diluent slurry polymerizations, but are always a possibility for gas phase and bulk propylene slurry reactions. Simulations to determine particle temperatures as a function of particle diameter show that polymer melting is predicted immediately upon catalyst injection for many cases in a gas phase reactor and for some cases in bulk polymerization. The practical implications of this result are discussed.
Photolysis of segmented polyurethanes. The role of hard‐segment content and hydrogen bonding
Authors: Hoyle Charles E. , Kim Kyu‐Jun , No Y. G. , Nelson G. L. 
Published: April 2003

AbstractThe photodegradation of segmented polyurethanes based on methylene 4, 4′‐diphenyldiisocyanate (MDI) is shown to be dependent on the physical structure of the polymer. As the hard segment content of the polyurethane is increased, the photodegradation efficiency is lowered. In particular, the extent of the photolytic decomposition is inversely dependent on the degree of hydrogen bonding in the aryl carbamate groups in the polyurethane backbone. Utilizing appropriate model compounds for comparison, the formation of the ortho photo‐Fries rearrangement product, as detected by fluorescene spectroscopy, is also shown to be dependent onthe degree of hydrogen bonding. In general, the restrictive mobility imposed by hydrogen bonding is a critical factor which must be considered in the photochemistry of segmented polyurethanes.
Investigation of PVC life at sinusoidal loading
Authors: Natov M. , Vassileva St. , Trifonov P. 
Published: April 2003

AbstractThe durability of polyvinylchloride (PVC) at static and cyclic loads during establishing of tensile and flexural strength is studied. It is found out that bulk static and cyclic durability can be described by a kinetic equation assuming that the tension changes the temperature‐energy factor. During testing of tensile strength it is established that the maximum deformation at break depends upon the tension of loading in an elaborate way with the existance of a peak at 32 MPa.
Role of reinforcing material in ion exchange membranes prepared by the paste method
Authors: Mizutani Yukio , Ikeda Katsuhiro 
Published: April 2003

AbstractIon exchange membranes prepared by the paste method contain polyvinylchloide cloth as a reinforcing material, which is necessarily used to endow the membranes well‐balanced properties: electrochemical and mechanical properties. The role of the reinforcing material was studied in terms of the membrane structure.
Photosensitized grafting of acrylamide and hydroxyethyl methacrylate onto cellulose
Authors: Silva M. Alves Da , Gil M. Helena , Lapa Elisa , Guthrie J. T. 
Published: April 2003

AbstractThe photoinitiated copolymerization of acrylamide and hydroxyethyl methacrylate onto cellulose substrates, from acetone/water solutions, was studied using isopropyl thioxanthone as the photoinitiator. The graft copolymerization was carried out over a range of monomer and photoinitiator concentrations. Grafting is shown to be dependent on the nature of the monomer and the concentration of monomer and photoinitiator. In the case of acrylamide, it was found that there is an optimum concentration of the photoinitiator for grafting to occur effectively. The kinetics of graft copolymerization were studied in some detail and the results are considered.
A critical evaluation of the single‐point determination of intrinsic viscosity
Authors: Chee K. K. 
Published: April 2003

AbstractThe general validity of four single‐point methods for intrinsic viscosity ([η]) determination is verified to be unacceptable even for dilute polymer solutions. Also, a direct method based on a truncated version of Huggins equation is shown to be less practical in that it involves advanced experimentation and is valid only at sufficiently low concentrations. In view of the shortcoming and sophistication of the above procedures, an effective approach is introduced to resolve these problems. This novel computation expresses the Huggins coefficient in terms of [η], and the associated equations are calibrated against the polymer system of interest. This procedure is tested using various polymer solutions with results compatible with those acquired by other means. The advantage of the proposed technique is discussed.
Permselectivity of cellulose acetate membranes; separation of H2/CO mixtures and the effect of added transition metals
Authors: Feldman Julian , Shim Il Wun , Orchin Milton 
Published: April 2003

AbstractCellulose acetate membranes permit permeation of H2 and CO2 but are relatively impervious to CO and N2. Permselectivity was demonstrated by effective separation of H2 from its mixtures with CO. The presence of RuCl3 in the membrane does not result in any appreciable change in permselectivity. The exposure of RuCl3‐ and RhCl3‐modified membranes to H2/CO mixtures results in the formation of RuCl2(CO)x and [RhCl(CO)2]2, respectively. However, these complexes are not covalently anchored to the cellulose acetate matrix and apparently function only as additives that block access to the press and channels in the cellulose acetate membrane.
Homo‐ and copolymerization of ethylene with highly active catalysts based on TiCl4 and grignard compounds
Authors: Muñoz‐Escalona A. , García H. , Albornoz A. 
Published: April 2003

AbstractIn this paper, the synthesis of different catalytic systems based on the reduction of TiCl4 by Grignard compounds has been systematically studied. The catalysts exhibited the highest activities when used in the copolymerization of ethylene with n‐hexene. The profile of the kinetic curves also changed when the comonomer was present during polymerization. By thermal analysis and scanning electron microscopy techniques, it could be found that the incorporation of the comonomer to the polymer chain brings about a decrease in the polymer crystallinities and an increase in the porosities of the growing particles. Due to that, the diffusion of the monomer to the catalytic active centers takes place more easily, consequently increasing the polymerization rate. In addition, catalysts control better the morphology (size and shape) of the nascent polymer particles when used for copolymerization.
Silicone polymerization by glow discharge application
Authors: Hasirci N. 
Published: April 2003

AbstractPolymerization of hexamethyldisiloxane (HMDS) on aluminum by application of capacitively coupled plasma was carried out under different polymerization conditions. The effect of applied frequency, power, and discharge duration on polymerization rate was investigated. Film adhesion was found to be directly related to applied frequency and power. Polymer deposits were examined with SEM and ATR, and the effect of the coat on wattability was sought by measuring the contact angles. The chemical structure of the coat was affected by the energy density applied during coat preparation.
Interaction of cation‐exchange membrane with polycation I. Poly(N‐methyl‐4‐vinylpyridinium chloride)
Authors: Ohmura Nobuhiko , Kagiyama Yasuhiro , Mizutani Yukio 
Published: April 2003

AbstractWe elucidated the effect of the molecular weight of poly(N‐methyl‐4‐vinylpyridinium chloride) (PMVP) on its adsorbed or ion‐exchanged amount on the cation‐exchange membrane and the preferntial permselectivity of the membrane for sodium ion to calcium ion. The amount of the adsorbed or ion‐exchanged PMVP increases with time and then attains to a definite value at a definite concentration. Also, the ultimate value increases with increasing the concentration of PMVP. When the molecular weight of PMVP is 3090, the ratio of the pyridinium groups of PMVP ion‐exchanged with the sulfonic acid groups on the membrane surface to the total pyridinium groups of the cohered PMVP is in the range of 70–80%. The relative transport number of calcium ions to sodium ions(PNaCa) decreases with increasing the amount of adsorbed or ion‐exchanged PMVP and the numbe rof non‐ion‐exchanged pyridinium groups of PMVP and the number of non‐ion‐exchanged pyridinium groups of PMVP on the membrane surface. The smaller the molecular weight of PMVP, the more the adsorbed or ion‐exchanged amount and the more preferable the permselectivity for sodium ion.
Dilute solution behavior and Mark‐Houwink constants for a non‐linear cationic polyelectrolyte
Authors: McCarthy Kevin J. , Burkhardt Charles W. , Parazak Dennis P. 
Published: April 2003

AbstractMark‐Houwink coefficients and radius of gyration dimensions are presented for six unfractionated cationic polyelectrolytes of the poly(dimethylamine‐epichlorohydrin‐ethylendiamine) type. The copolymer system was studied in .05M, .10M, and 1.0M NaCl, and .12M NaClO4 aqueous solutions. Their solution behavior, as studied by intrinsic viscosity and light‐scattering technique, suggests these polymers adopt a somewhat spherical or star‐like conformation in aqueous salt solutions.
Recovery of uranium from seawater V. Preparation and properties of the macroreticular chelating resins containing amidoxime and other functional groups
Authors: Egawa Hiroaki , Nakayama Morio , Nonaka Takamasa , Yamamoto Hideki , Uemura Keiji 
Published: April 2003

AbstractWe have synthesized macroreticular chelating resins containing amidoxime groups from acrylonitrile (AN)‐divinylbenzene (DVB)‐alkyl acrylate, alkyl methacrylate, or vinylpyridine (VPy) copolymer beads. It was found that the chelating resin (RNMH)‐containing amidoxime groups prepared from AN‐DVB‐methyl acrylate (MA) indicated the highest adsorption ability for uranium in seawater. Hydroxamic acid and carboxylic groups in addition to amidoxime groups were formed during the reaction of the copolymer beads with a methanol solution of hydroxylamine. The adsorption ability for uranium was greatly influenced by the physical pore structure (macropore) and the pore structure formed by the swelling(micropore). RNMH (RNMH10‐10) prepared with 10 mol% of DVB and 10 mol% of MA had the highest adsorption ability and physical stability for uranium. On the other hand, improved adsorption ability for uranium was not observed in the case of the macroporous resins (RNPyH) prepared by the copolymerization of VPy as the basic component. After seawater was passed through the column packed with RNMH10‐10 at a space velocity (SV) of 180 h−1 (up‐flow) for 10 days, the amount of uranium adsorbed on the resin was about 100 mg/dm3‐R and 260 mg/kg‐R.