bluuebunny/crossref_metadata_2025_split huggingface dataset:
A cubic equation of state for high‐pressure phase equilibria of mixtures containing polymers and volatile fluids
Authors: Sako Takeshi , Wu Albert H. , Prausnitz John M. 
Published: April 2003

AbstractGeneralized van der Waals theory is used to obtain a three‐parameter cubic equation of state which is applicable to fluids containing small or large molecules, including polymers. The necessary parameters are obtained from a minimum of experimental information. Upon extension to mixtures, the equation of state is used to calculate high‐pressure phase equilibria for the ethylene–polyethylene system. The relatively simple equation may be useful for engineering‐design calculations for fluid mixtures containg polymers, especially when very few experimental data are available.
Model approach to dielectric‐thermal analysis of wood modified with polymer
Authors: Hoffmann Grzegorz , Poliszko Stefan , Hilczer Tadeusz 
Published: April 2003

AbstractThe modeling of dielectric properties of wood–polymer composite, considered as a multicomponent layered system, was performed. The obtained solutions were used to determine temperature dependences of real and imaginary parts of complex dielectric permittivity characterizing the wood component in the natural and polystyrene‐modified wood in the directions parallel and perpendicular to the fibers. The analysis of the calculated dependences proved that the structural changes of wood depended on the applied method of modification. The main effect attributed to the styrene polymerization occurring in wood placed in a hydrophilic heating medium was an increase in the ordering degree of the mesomorphous regions of cellulose. As a consequence, a part of the polar, functional groups distinguished by particularly high activation energies (i.e., low probability of a dipole jump to an adjacent site) was eliminated from participation in the relaxation processes. The application of a hydrophobic heating medium during modification procedure resulted in a permanent swelling effect of the wood component of the composite. Within the applied investigation method it was found that the changes in increment of dielectric permittivity referring to the β‐relaxation process in wood substance can be the specific criterion of structural changes in wood modified with polystyrene. The distribution functions of relaxation times for natural and modified wood substance were determined.
Melt rheology of plasticized poly(vinyl chloride)/epoxidized natural rubber miscible blends
Authors: Varughese K. T. 
Published: April 2003

AbstractA study of the melt rheological behavior of miscible blends of plasticized poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) was carried out with a capillary rheometer. Melt viscosity and melt elasticity behavior was determined and surface characteristics of the extrudate was examined by using a scanning electron microscope. Melt viscosity of plasticized PVC increased with ENR content at higher processing temperatures. The melt elasticity parameters such as die swell ratio, principal normal stress difference, and recoverable shear strain at a particular shear stress increased with temperature up to a 50 wt % composition of ENR in blends. For high ENR blends the die swell ratio and recoverable shear strain decreased with temperature, and the principal normal stress difference and elastic shear modulus remained independent of temperature for all values of shear stress. It was noted that the nature of deformation in the surface layer was linear for a smooth extrudate and nonlinear for a distorted extrudate. Moreover, recoverable shear strain was found to have a correlation with the extrudate distortion of the melts.
Application of the percolation model to gelation of an epoxy resin
Authors: Serrano Daniel , Peyrelasse Jean , Boned Christian , Harran Daniel , Monge Philippe 
Published: April 2003

AbstractThe percolation model has been applied to the study of gelation of the TGDDM‐DDS system (tetraglycidyldiaminodiphenylmethane–diaminodiphenylsulfone) at a mass concentration of 100–30. For each temperature the experimental viscosity curves are satisfactorily described by a percolation law. Using the degree of chemical reactions, X, as a variable, a very clear change in the reaction mechanism with temperature can be shown. Then a rate of advancement of effective reactions, Y, is defined. This value only takes intermolecular‐type reactions into account, and is probably the only variable on which viscosity depends in a percolation law: η = B(1 − Y/Yc)−p. We obtain Yc= 0.45 and p= 2.0. Comparing Xc and Yc at the gel point, we obtain information on the proportion of intramolecular reactions with temperature. It is also demonstrated that the critical percolation threshold agrees closely with the gel point determined experimentally on log G″= f(t) curves.
Synthesis of new polymers containing tannin
Authors: Kim Min , Saito Kyoichi , Furusaki Shintaro , Sugo Takanobu , Okamoto Jiro 
Published: April 2003

AbstractA novel method for preparation of immobilized tannin on polyethylene has been suggested. A tannin‐containing polymer was prepared by radiation‐induced graft polymerization of glycidyl methacrylate onto porous polyethylene, followed by coupling tannin with the produced epoxide group. Reaction conditions for preparing immobilized tannin, such as the reaction temperature, pH, and the molar ratio of tannin to the epoxide group were investigated. The tannin content of the tannin‐containing porous polyethylene was 20%, which is approximately equivalent to that of the conventional cellulose‐based immobilized tannin. The adsorption isotherm for immobilized tannin and ferrous ion was determined.
Diffusion‐controlled kinetics for the solution copolymerization of 2‐ethylhexyl acrylate with vinyl chloroacetate in a CSTR
Authors: Das Siddhartha , Rodriguez Ferdinand 
Published: April 2003

AbstractThe solution copolymerization of the comonomer pair 2‐ethylhexyl acrylate–vinyl chloroacetate (in ethyl acetate) has been studied in a continuous stirred tank reactor (CSTR). The initiator used in this study, 2,2′‐azobis‐2,4‐dimethyl valeronitrile was selected on the basis of its high decomposition rate constant. Measurements included the rate of copolymerization, the copolymer composition by infrared spectrophotometric analysis, the molecular weight distribution by gel permeation chromatography, and the viscosity of the reaction mixture by capillary viscometry. The reactivity ratios for the EHA–VCLAC pair were markedly different so that both propagating chains preferentially add EHA. Both the ϕ factor and the penultimate effect models were inadequate for describing the termination reaction. By defining an appropriate expression, based on physicochemical considerations, for the overall termination rate constant, it was possible to model the steady state rates by the diffusion model of Atherton and North. An attempt to model the transient behavior of the reactor by using the ϕ value as an adaptable correction factor was unsuccessful due to the rapid composition drift during approach to steady state. The measured conversions were lower than the model predictions for all feed ratios.
Studies of selective adsorption resins. XXVI. Removal of calcium and magnesium ions in a salt solution with chelating resin containing aminomethylphosphonic acid groups
Authors: Maeda Hironori , Egawa Hiroaki 
Published: April 2003

AbstractRemoval of calcium and magnesium ions in a salt solution with the macroreticular chelating resin containing aminomethylphosphonic acid groups was investigated. The resin (RMT‐P) exhibited high affinity for calcium and magnesium ions in a salt solution containing 200 g/dm3 of sodium chloride. In the column method, calcium and magnesium ions in a salt solution were preferentially absorbed on the RMT‐P, when the salt solution containing 100 mg/dm3 of calcium or magnesium ion was passed through the RMT‐P column at a space velocity of 15 h−1. The calcium and magnesium ions adsorbed were eluted by allowing 1 mol/dm3 hydrochloric acid to pass through the column. The recycle of adsorption and elution was found to be satisfactory.
Catalytic dehydrochlorination of the solid poly(vinyl chloride) in the presence of aluminium chloride (friedel‐crafts) catalyst: Studies of the structure by spectroscopical methods
Authors: Rabek Jan F. , Lucki Julia , Kereszti Henryk , Hjertberg Tomas , Jun Qu Bao 
Published: April 2003

AbstractCatalytic dehydrochlorination (100%) of solid poly(vinyl chloride) (PVC) in the presence of AlCl3 at 200°C gives a product which has a similar structure to the product of catalytic dehydrochlorination of 1,2‐dichloroethane in the presence of AlCl3 at 60°C. Both products have brown‐black color, are completely insoluble, thermally resistant up to more than 400°C, and exhibit conductivities in the range 10−6 S cm−1 (after doping with FeCl3 or I2 conductivities: 10−5 S cm−1). Different spectroscopical methods such as UV/VIS, IR, Raman, ESCA, and 13C‐NMR were employed to the structure study of both products, which are crosslinked polyenes with a number of aromatic rings.
Thioether glycidyl resins. VII. Products of condensation of bis(4‐mercaptophenyl)sulfide and bis(4‐mercaptophenyl)sulfone with epichlorohydrin
Authors: Charmas Władysław , Podkościelny Wawrzyniec , Rudź Wiestaw 
Published: April 2003

AbstractNew thioether glycidyl resins by condensation of bis(4‐mercaptophenyl)sulfide or bis(4‐mercaptophenyl)sulfone with epichlorohydrin were obtained by heterophase alkaline condensation in aqueous and isopropanol medium using sodium hydroxide. The detailed studies on their structures from elemental analysis and IR and 1H‐NMR spectra, physical and chemical properties, and curing conditions are presented. Thioether glycidyl resins compositions were also prepared using curatives typical for epoxy resins and after curing they were characterized from derivatographic, thermomechanical, and mechanical studies.
Synthesis and properties of hydrophilic copolypeptide membranes containing L‐aspartic acid as one component
Authors: Hayashi Toshio , Iwatsuki Makoto , Oya Masanao 
Published: April 2003

AbstractThree‐component random copolypeptide consisting of N‐hydroxypropyl‐L‐glutamine, L‐aspartic acid, and L‐lysine, related two component random copolypeptides and homopolypeptides, were prepared by carrying out aminolysis reaction with 3‐amino‐1‐propanol, followed by crosslinking reaction with 1,8‐octamethylenediamine on starting polymer membranes consisting of γ‐methyl‐L‐glutamate, L‐aspartic acid, and L‐lysine. The effective crosslink density was shown to be proportional to the content of the crosslinker in the reaction mixture. The tensile properties of these hydrophilic membranes were highly dependent on the degree of swelling in the pseudoextracellular fluid, hydrophobicity of the side chains, and the effective charge density of membranes, and their behavior was typical of an elastomer. A higher rate of water permeability was obtained with charged membranes than noncharged and/or compensated charged membranes with the same order of the degree of swelling in the pseudo‐extracellular fluid. Biodegradation of the samples in vitro by papain indicated that the degradation could be regarded as a bulk rather than a surface phenomenon. The rate of degradation was also highly dependent on the degree of swelling of membranes, as well as on the hydrophobicity and the effective charge density of side chains of sample membranes.
SSIMS analysis of methacrylate copolymers employed in drug delivery
Authors: Wilding Ian R. , Melia Colin D. , Short Robert D. , Davies Martyn C. , Brown Alan 
Published: April 2003

AbstractThis study reports on the use of static secondary ion mass spectroscopy (SSIMS) to chemically characterize complex methacrylate copolymers used in the pharmaceutical industry for controlled drug delivery. Ions diagnostic of the component monomer residues were detected, which could be interpreted using a fragmentation model for alkylmethacrylate homopolymers proposed previously. This model is extended to include the SSIMS analysis of nitrogen‐containing methacrylate copolymer residues.
On the possibilities of immobilization and utilization of some cellulase enzymes
Authors: Simionescu Cristofor I. , Popa Valentin I. , Popa Mariana , Maxim Steliana 
Published: April 2003

AbstractCellulase enzymes produced by the microorganisms Aspergillus niger and Trichoderma viride have been immobilized on Ponilex type ion exchangers, both by ionic and by covalent bonding. Immobilization efficiency has been determined for enzyme preparations obtained, by their activity, as well as by that of the resulted effluent, on using as substrate carboxymethyl cellulose, cellobiose, and filter paper. The catalytic activity of the immobilized products has been tested against solutions of carboxymethyl cellulose and a series of hemicellulose containing alkaline extracts resulted from the alkaline pretreatments of some vegetal materials. The presence of polyphenol compounds in the latter ones determines a series of peculiarities in the behavior of the enzyme preparations, such as the transformation of the hydrolysis products and reduction of thecatalytic activity of the enzyme, after a certain period of reaction.
Effect of additives on the degradation of acrylamide–acrylic acid copolymer in aqueous solution
Authors: Kheradmand Houchang , François Jeanne , Plazanet Veronique 
Published: April 2003

AbstractThis paper presents the results of a systematic study of the effect of different additives on the degradation of acrylamide–acrylic acid copolymers at high temperature. Under conditions of current applications in enhanced oil recovery (without oxygen and in the presence of ferrous ions), the effects of sodium azide, sequestrant DTPA, and isobutanol have been separately tested. It is shown that DTPA enhances degradation when ferrous ions are present. A new process of stabilization which may be efficient in most of the conditions is proposed.
Polysulfone hollow fiber membranes spun from lewis acid: Base complexes. II. The effect of lewis acid to base ratio on membrane structure
Authors: Fritzsche A. K. , Cruse C. A. , Kesting R. E. , Murphy M. K. 
Published: April 2003

AbstractOxygen plasma ablation has been used to define the structure of polysulfone hollow fiber membranes spun from Lewis acid:base complex solvents in which the molar ratio of propionic acid to N‐methylpyrrolidone was varied. It was found that the helium/nitrogen separation factor of the unetched samples increases with increasing PA/NMP molar ratios. This increase implies a decrease in surface porosity of the resultant hollow fiber as larger fractions of the total NMP in the solvent are complexed with propionic acid. The results also suggest that the differences between the outer separating layer and the supporting matrix increase with increases in the PA/NMP molar ratios. Therefore, a more rapid transition from the separating layer to the porous supporting matrix exists in hollow fiber membranes spun from the higher PA/NMP ratios.
Study of the factors affecting the electrical conductivity of zinc–polycarboxylate cement
Authors: Sawaby A. , Moharam M. A. , Tahon Kh. 
Published: April 2003

AbstractThe behavior of the electrical conductivity of polycarboxylate cement with temperature was studied from room temperature up to 160°C. The effects of powder/liquid ratio, mixing temperature, percentage of MgO in the powder, and aging on this behavior were also investigated. The results obtained revealed that the electrical conductivity decreases with increasing the powder/liquid ratio and with decreasing mixing temperature and the amount of MgO in the powder. The reason for the changes of the conductivity due to the mentioned factors were discussed.
Studies on irradiation of agar–agar in the solid state: On the changes of X‐ray diffraction of agar–agar film produced by irradiation
Authors: Nisizawa M. , Hirano T. 
Published: April 2003

AbstractSolid agar–agar was irradiated with 60Co gamma‐rays, dissolved in aqueous solutions, molded and made a thin film. Effects of radiation on the ordered conformation of agar–agar molecule were studied by measuring the X‐ray diffraction intensity at different radiation doses, elapsed times after irradiation, and concentrations of added substances (sugar and starch). Empirical equations in changes of X‐ray diffraction were obtained.
Gas transport in lanthanide‐polymer membranes
Authors: Dong Jian‐Hua , Huang Xiao , Huang Chang‐Kai , Jiang Ying‐Yan 
Published: April 2003

AbstractPermeation properties of O2, N2, and CO2 were investigated by using copolymer membranes having the pyridine‐lanthanids complexed group. The membranes of poly(4‐vinylpyridine‐co‐n‐butylmethacrylate) and its complexes with lanthanide were prepared. Complexation with lanthanide can be used to tailoring selectivity of CO2/O2. The CO2 permeability for lanthanide‐polymer, which is oppsite to most polymers. the upstream pressure dependent of grass in lanthanide‐polymer varies with temperature. A tentative explanation is given for the results according to the free colume model.
The physical mechanism for the production of hydrophilic polymer microparticles from aqueous suspensions
Authors: Scranton Alec B. , Mikos Antonios G. , Scranton Lisa C. , Peppas Nikolaos A. 
Published: April 2003

AbstractA previously reported method of producing spherical, hydrophilic microparticles by aqueous suspension polymerization is experimentally investigated. The phase separation is the result of a salting‐out phenomenon. Characteristics of the salting‐out effect between the monomer and suspending phase of aqueous NaCl solution are studied. The size and shape of the produced particles are characterized. It is concluded that the mechanism of polymerization is actually a combination of suspension and solution polymerization, and that the water content in the monomer phase is low enough to produce structurally homogeneous particles.
Novel poly(n‐butyl methacrylate)/titanium oxide alloys produced by te sol–gel process for titanium alkoxides
Authors: Mauritz K. A. , Jones C. K. 
Published: April 2003

AbstractA method has been developed to cast novel organic/inorganic hybrid films from multicomponent solutions containing titanium alkoxides, poly(n‐butyl methacrylate), water, and isopropanol of prescribed compositions. The sol–gel reactions and controlled drying procedure yielded materials of mechanical integrity for which the multistep thermal degradation profile of the organic polymer has been significantly modified. A crystallization exotherm, presumably due to anatase formation, is seen for tetraethyl titanate‐derived films beyond the organic degradation temperature. The trend of mechanical tensile parameters with increasing Ti oxide content depicts progressive material strengthening. FT‐IR as well as the thermal and mechanical studies of these films suggest a highly unconnected and heterogeneous Ti oxide phase.
Vitrification and curing studies of a photopolymerizable semi‐interpenetrating polymer network. II
Authors: Fitzgerald J. J. , Landry C. J. T. 
Published: April 2003

AbstractThe photopolymerizable semi‐interpenetrating polymer network‐II being studied consists of a linear copolyester, a crosslinked network of multifunctional acrylate monomers and a very efficient photoinitiator system. Using both Raman and dynamic mechanical spectroscopy (DMS), it has been determined that the polymerizing network vitrifies after a very low level of crosslinking is attained. This results in a sample that has a Tg which is substantially lower than would be expected from knowledge of the values of Tg for the individual components of the blend. The extent of reaction and, therefore, the glass transition temperature can be increased by heating the sample during photopolymerization. In addition, the glass transition temperature of the network can be increased by thermally curing the sample after photopolymerization. It has been found that once the network has been fully cured, the glass transition temperature is much higher than would be predicted. This has been interpreted in terms of synergistic effects; conceivably, the acrylates form a tight matrix around the linear copolyester and effectively reduce the molecular mobility of the components. The results also show that the acrylates and the copolyester are not inherently miscible. However, if a sufficient concentration of acrylates is present, it is possible to prevent the copolyester from phase separating. Dynamic mechanical spectroscopy data do indicate that these semi‐inter‐penetrating polymer networks‐II (semi‐IPN‐II) samples are somewhat heterogeneous; however, there does not seem to be any gross phase separation. Transmission, electron microscopy (TEM) results show that the most fully cured sample has domains on the order of 50–250 Å associated with the copolyester phase.
Effects of resin and curing parameters on the degree of cure of resole phenolic resins and woodflour composites
Authors: So Solomon , Rudin Alfred 
Published: April 2003

AbstractThe degree of cure of various resole phenolic resins was assessed from their resistance to acetone extraction. Cured woodflour composites of resoles were also characterized by dynamic mechanical tests in linear viscoelastic behaviour regions. Acetone extraction is not a sensitive discriminator between highly cross‐linked resins. In addition, residual basic catalyst promotes aldol condensation reactions of acetone to produce materials that are absorbed in the phenolic resin so as to provide negative weight loss data on extraction. Despite its inaccuracies, however, this solvent resistance test is still useful as a go/no‐go specification technique. Dynamic mechanical tests were performed on molded resole/woodflour composites. This is a useful method for characterizing degree of cure and residual reactivity of the phenolic resin. Degree of cure increases with curing time, temperature and resin pH, with pH being the most important variable. Resins cured at pH's near neutral are linked by ether linkages rather than the more stable methylene bridges. The final degree of cure of woodflour composites depends heavily on the curing conditions (pH, time, temperature). It does not appear to be crucial how the initial resoles were made (i.e., catalyst, phenol/formaldehyde mole ratio or duration of the condensation reaction time) so long as the resoles have relatively high molecular weight. Curing should preferably be at temperatures below 180°C to minimize degradation of the polymer.
Influence of water on esterification reaction between terephthalic acid and ethylene glycol
Authors: Yamada Toshiro 
Published: April 2003

AbstractExamples of simulation in the first reactor for the direct continuous esterification were shown to predict the effects of water added into the reactor (δ) on the reactions by a computer. From the simulation results, the followings were confirmed: Although the higher δ gives the worse results, i.e., the main reaction rates become lower, it brings about the better results, i.e., the side reactions of diethylene glycol (DEG) formation is suppressed; the clearing point where solid (undissolved) terephthalic acid begins not to exist in the reaction mixtures, β = 1, is the point of AV = 0.6 eq/kg, which coincides with the point obtained from the experimental observation, independently of reaction conditions.