bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion–adsorption problems in macromolecular systems: New techniques for parameter estimation
Authors: Ravetkar D. D. , Ambeskar V. D. , Mashelkar R. A. 
Published: April 2003

AbstractIt has been shown that the techniques used for estimation of diffusion–adsorption parameters in the past have certain basic flaws. New and efficient techniques for parameter estimation have been proposed. These have many advantages such as using the full concentration‐time profile (rather than part of it), time saving, etc. The validity of these techniques has been demonstrated by the analysis of the data generated in our laboratory on adsorption of polyacrylamide and also the data on adsorption of dyes on chitin reported in the literature.
Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters. II. Presence of quaternary ammonium salt in the alkali‐bath
Authors: Datye Keshav V. , Palan Bharat H. 
Published: April 2003

AbstractInfluence of alkyl (C12–C14)‐dimethyl‐benzyl ammonium chloride in the solution of sodium hydroxide on the hydrolysis of poly(ethylene terephthalate) (PET), anionically modified poly(ethylene terephthalate) copolyster (CDP), and block polymer of poly(ethylene terephthalate)‐poly(ethylene glycol) (EDP), has been studied under a variety of proportions, concentrations, time and temperature of reaction, M : L ratio, etc. Mechanical properties of treated polymeric materials are evaluated. Hydrolysis of two polymers in the same bath is compared with that in separate baths.
Suspension polymerization of styrene with circular loop reactor
Authors: Tanaka Masato , Hosogai Kazuhiko 
Published: April 2003

AbstractA circular loop reactor was devised and applied to the suspension polymerization of styrene. The transient droplet diameter distribution and the final particle size distribution are measured by changing widely the impeller speed, the dispersed phase volume fraction, and the stabilizer concentration. The effects of these conditions on the size distribution and mean size of the final polymer particle are investigated. An expression correlating the mean particle size with the operating conditions is derived. The circular loop reactor is found to be superior to the production of the polymer particle of uniform size.
Influence of silica reinforcement upon the glass transition behavior of acrylic polymers
Authors: Reid Charles G. , Greenberg Alan R. 
Published: April 2003

AbstractThe glass transition temperatures (Tg) of poly(acrylic acid), poly(methyl acrylate), and poly(ethyl acrylate) filled with submicron particulate silicas and silicates have been measured by dynamic mechanical spectroscopy and differential scanning calorimetry. The peak temperatures of the damping factor (tan δ) and the dynamic shear loss modulus (G″) were shifted by an amount which depended upon the quantity and type of filler added to each polymer. The temperatures corresponding to the step discontinuity of specific heat also shifted, but to a lesser extent than those measured mechanically. The degree of Tg shift per unit of volumetric filler addition increased with polymer pendant group polarity for both measurement methods. Utilizing a Tg‐crosslinking analogue, a model was developed that related positive Tg shifts to polymeric segmental adsorption onto filler surfaces. This model also incorporated negative contributions to the Tg shift from energy storage mechanisms arising from particle–particle interactions, as well as corrections due to effective surface area available for polymer adsorption.
Radiation‐initiated graft copolymerization of individual monomer and comonomer onto polyethylene and polytetrafluoroethylene films
Authors: Hegazy El‐Sayed A. , Taher N. H. , Ebaid A. R. , Rabie Abdel‐Gawad , Kamal H. 
Published: April 2003

AbstractPreparation and some properties of the graft copolymers obtained by radiation‐induced graft polymerization of methacrylic acid (MAA) and (acrylonitrile/MAA) comonomer onto polyethylene and polytetrafluoroethylene films, were investigated. The effect of reaction conditions, solvent, monomer, and inhibitor concentration, comonomer composition, and comonomer concentration, on the graft copolymerization process was studied. The grafting process was enhanced in the presence of comonomer (AN/MAA) as compared with individual grafting of MAA or acrylonitrile (AN). The optimum comonomer composition, at which the highest grafting yield was obtained, was found to be (80/20) wt % of (AN/MAA) comonomer. The graft copolymerization of (AN/MAA) comonomer was enhanced in presence of AN due to its higher polarity strength. The electrical and swelling properties of the graft copolymers were greatly affected by the contents of PAN and PMAA graft chains. Mechanical properties of the graft copolymers were significantly changed with the grafting yield.
Preparation of microporous membranes from cation exchange membranes prepared by the paste method
Authors: Mizutani Yukio , Kusumoto Koshi , Nishimura Masakatsu , Nishimura Toshihiko , Asada Eiji 
Published: April 2003

AbstractA microporous membrane is prepared by treating the cation exchange membrane (Fe+++ form) with an H2O2 aqueous solution. The cation exchange membrane is prepared by the paste method: the base membrane is prepared beforehand and then sulfonated. The preparative conditions of the base membrane were studied in connection with the characteristics of the resultant microporous membrane. Furthermore, the availability of the microporous membrane for ultrafiltration was studied by using an aqueous solution of a bovine hemoglobin.
Physical aging in poly(methyl methacrylate) / poly(styrene‐co‐acrylonitrile) blends. I. Stress relaxation
Authors: Mijovic Jovan , Devine Steven T. , Ho Tai 
Published: April 2003

AbstractAn investigation was carried out on the effect of physical aging on viscoelastic properties of compatible polymer blends. Poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were chosen for this study. Blends of six different ratios of PMMA and SAN were physically aged at different times and temperatures and then subjected to stress–relaxation tests at small strains. It was found that the shape of the stress‐relaxation curve does not change with a change in blend composition, aging temperature, or aging time. A single “master curve” is presented, to which all data may be fit using 0.408 for the exponential parameter of the Williams‐Watts equation. In creating the master curve, all data are shifted horizontally in time only. For a given set of experimental conditions, the relaxation time τ may be expressed in terms of blend composition, aging temperature, and aging time.
The effect of physical aging on long‐term properties of poly‐ether‐ketone (PEEK) and PEEK‐based composites
Authors: D'Amore A. , Cocchini F. , Pompo A. , Apicella A. , Nicolais L. 
Published: April 2003

AbstractThe viscoelastic properties of the amorphous and semicrystalline PEEK and of a PEEK‐based composite (APC2) have been analyzed as a function of the aging time and related free volume relaxation, at temperatures close to the glass transition temperature. The effect of thermal treatments (physical aging) on the polymer amorphous phase of the three systems is presented. Creep tests approaching the “zero stress” were performed on samples subjected to different thermal histories. The presence of a second phase, namely crystallites and fibers, determines a loss of the mobility of the polymeric amorphous chains and consequently a decrease of the rate of free volume relaxation.
Influence of the pressure profile inside a dense membrane on the rate of permeation
Authors: Van der Waal M. J. 
Published: April 2003

AbstractLee1 showed that molecular transport in all isothermal membrane processes, based on dense layers, can be described with one single general equation, including only measurable conditions from outside of the membrane. Following arguments given by Paul2 for homogeneous rubber membranes, Lee assumed the pressure everywhere inside the membrane to be equal to the feed side pressure. In this paper the question is stated whether this assumption always holds for very thin and/or nonhomogeneous membranes like asymmetric membranes made of semicrystalline polymers. A study based on less stringent assumptions of the pressure profile inside the membrane is performed. The results show that in most cases this pressure profile does not play a major role in the permeation process.
Characterization of methacrylonitrile‐grafted silk fibers
Authors: Tsukada Masuhiro , Shiozaki Hideki 
Published: April 2003

AbstractThe structure and physical properties of silk fibroin fibers graft‐polymerized with methacrylonitrile (MAN) were analyzed in relation to the weight gain on the basis of the results of tensile properties as well as of thermal analysis and X‐ray diffractometry. The solubility of the specimen in NaOH solution and the moisture absorption decreased slightly with the duration of the MAN treatment. However, the polymerizing treatment with MAN did not affect significantly the tensile properties, i.e., strength and elongation at break of the original fibers. The position of the endothermic peak attributed to the thermal decomposition of the silk fibroin shifted to higher temperatures when the weight gain exceeded 25%, and a constant value at 328°C was obtained above a weight gain of 40%. Wide‐range X‐ray diffraction diagram of silk fibers with a weight gain of 10% showed diffraction maxima at the equator corresponding to the molecule oriented crystal structure of the silk fiber, in addition to the spots on a series of hyperbolic arcs arranged symmetrically at about the equator, which are associated with the crystalline form of the MAN polymer copolymerized in the specimen. Crystalline structure of the silk fiber remained unchanged essentially regardless of MAN treatment.
Optimization of a batch polymerization reactor at the final stage of conversion. II. Molecular weight constraint
Authors: O'Driscoll K. F. , Ponnuswamy S. R. 
Published: April 2003

AbstractA mathematical model for the free radical batch solution polymerization of methyl methacrylate that takes depropagation into account was developed. This model was then used to derive optimal temperature and initiator concentration policies to reduce residual monomer concentration to desired levels, producing at the same time a polymer with the desired number average molecular weight. An objective function was formulated to take account of the cost of the initiator with respect to the cost of time of reaction. It was observed that when the cost of initiator increased, optimal initiator concentration decreased whereas optimal temperature increased. Finally temperature reached a limiting value above which polymer with desired number average molecular weight could not be produced. These results give insight into the factors that determine the policies that could be employed in optimizing the operation of a reactor.
FT‐IR studies of polymer blends containing an oligo(isophthalate‐co‐fumarate of diethylene glycol) and different epoxy prepolymers
Authors: Suspene L. , Lam T. M. , Pascault J. P. 
Published: April 2003

AbstractMiscibility of one unsaturated polyester (UP) with different epoxy prepolymers have been examined. Thermodynamic interaction parameters have been calculated. Calorimetric and clarity measurements indicate formation of miscible blends. This is in good agreement with the theoretical predictions excepted those with the 3‐dimensional solubility parameter. Fourier transform infrared (FT‐IR) studies are presented. The ability of acid solvent to associate with ester group have been used to determine the shift of the carbonyl stretching frequency. Similar shift has been found in UP/DGEBA blends and is attributed to specific interactions between these two types of oligomers.
Graft polymerization of methyl methacrylate on flavin mononucleotide by tetravalent cerium ion and an application of obtained polymer to dye transfer printing
Authors: Enmanji Koe 
Published: April 2003

AbstractThe polymerization mechanism of methyl methacrylate (MMA) with flavin mononucleotide (FMN) and cerium nitrate was investigated. The effect of the polymer grafted to FMN on the color fastness to light of some dyes were also investigated. Poly(methyl methacrylate) (PMMA) was produced with FMN, cerium nitrate, and MMA in the presence of water above 40°C. The conversion of PMMA is proportional to the reaction time up to 2 h in this system. It is also proportional to the first order of concentration of FMN and Ce(IV). Activation energy of the polymerization reaction was estimated to be 29.3 kJ mol−1 by the investigation of the temperature dependence of conversion. Purified polymer in acetone has the absorption peak at the same wavelength as FMN aqueous solution. The color fastness to light of Methylene Blue and anthraquinone dye were improved in the presence of the obtained polymer. Heat stability of the printed image which is made by transferring anthraquinone dye did not decrease by use of obtained polymer to recording layer of the medium in dye transfer printing system.
Alcoholysis of copolymers of vinyl acetate with itaconic acid
Authors: Kotzeva L. , Mateva R. 
Published: April 2003

AbstractWe studied alcoholysis of vinyl acetate and itaconic acid (up to 8.5 mol %) copolymers. We obtained the copolymers both by single and continuous addition of the second comoner, and carried out the alcoholysis in methanol and methanol‐gasoline medium at temperature 30°C using sodium hydroxide as catalyst. We established that the presence of itaconic sequences in the vinyl acetate polymer chain in an amount of 1.5–2 mol % causes significant reduction in the viscosity of methanol solutions without greatly affecting the molecular weight of the copolymer. The alcoholysis of random copolymers, containing not more than 4 mol % itaconic sequences takes place at a higher rate. The vinyl acetate‐vinyl alcohol copolymer, containing groups of itaconic acid has better surface activity. This is more clearly expressed in the case of random copolymers.
Comparative study of orientation in hot‐drawn poly(ethylene terephthalate) by means of refractive index and microhardness measurements
Authors: Lorenzo V. , Pereña J. M. 
Published: April 2003

AbstractRefractive index and microhardness of drawn samples of poly(ethylene terephthalate) were measured by means of an Abbé refractometer and a microindentation hardness equipment. The optical and mechanical anisotropies determined from these measurements were compared with the birefringences obtained by using compensators and fitted to the affine deformation scheme, showing that microhardness anisotropy is a suitable technique for studying the overall orientation in polymers.
Impedance characteristics of parchment supported inorganic precipitate membranes
Authors: Beg M. N. , Altaf I. 
Published: April 2003

AbstractThe impedance characteristics of parchment‐supported inorganic precipitate model membranes have been analyzed in order to understand the mechanism of ionic diffusion through biomembranes. The observed values of membrane capacitance and resistance were found to be dependent on the concentration of bathing electrolyte and applied oscillator frequency. The change in membrane capacitance and resistance values with the change in electrolyte concentration and oscillator frequency has been interpreted in terms of changes produced in the electrical double layer at the membrane–solution interface. The values of interfacial double layer capacitance derived by the equations of Armstrong and Longer were found to be different due to the presence of polarising charge and other structural details of membrane matrix. Different model‐equivalent electrical circuits have been analyzed using the experimental data. The complex impedance spectra have been found to deviate from the theoretical predictions at low frequencies due to nonhomogenous and rough surface of the membrane.
Synthesis of casein‐g‐poly(methyl acrylate). II
Authors: Mohan D. , Radhakrishnan Ganga , Rajadurai S. 
Published: April 2003

AbstractThe synthesis of casein‐g‐poly(methyl acrylate) was studied using the potassium peroxydisulfate–ascorbic acid redox system. The effect of synthetic variables has been investigated in the light of rates of conversion of monomer, graft copolymerization and homopolymerization, percent grafting, and grafting efficiency. The results are compared with the system initiated by pure potassium peroxydisulfate alone.
Processing of polymer latex emulsion: Batch coagulation
Authors: Ghosh Anup K. , Lindt J. Thomas 
Published: April 2003

AbstractA small‐scale batch experiment has been developed to establish processing conditions for latex coagulation in an extruder environment—characterized by the prevailing flow field, temperature, and pressure. Our experiments have shown that the most effective processing means to control the particle size distribution and also the particle morphology is the coagulation temperature. The changes in hydrodynamics, introduced by variations in the channel depth and rotor speed, affect the average particle size to a lesser degree. The morphology of the coagulated particles and their size distribution have been found to play an important role in the latex dewatering process. By coagulating well above the glass transition temperature(s) of the polymer, an order of magnitude drop in the specific surface area of the coagulated particles has been observed.
Linear polythioesters. XV. Products of interfacial polycondensation of 1,4‐dimercapto‐tetramethylbenzene with some aliphatic and aromatic acid dichlorides
Authors: Podkościelny Wawrzyniec , Kowalewska Wanda 
Published: April 2003

AbstractNew polythioesters by interfacial polycondensation of 1,4‐dimercaptomethyl–tetramethylbenzene with oxalyl, succinyl, adipoyl, suberoyl, sebacoyl, and isomeric phthaloyl dichlorides were obtained. To define the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: type of organic phase, concentration of hydrogen chloride acceptor, the quantitative ratio of aqueous to organic phase, molar ratio of reagents rate of acid chloride addition, contribution of benzyltriethylammonium chloride as a catalyst, and the temperature of the reaction. Thorough studies were carried out only for polycondensation of the dithiol with adipoyl, sebacoyl, and isophthaloyl chlorides. The structure of polythioesters obtained under the model conditions was determined by elementary analysis and infrared spectra. Initial decomposition temperature, mass loss in percentage at the same temperature, maximum rate of decomposition, and mass loss percentage at 100–400°C were defined from the curves of thermogravimetric analysis. Chemical resistance of the polythioesters was determined by treatment with some organic solvents, mineral acids (concentrated and 10%) and sodium hydroxide (10% and 50%). The molecular weight was not measured because of the low solubility of the polythioesters.
Grafting. III. Copolymerization of methyl methacrylate and methacrylic acid
Authors: Sankholkar S. , Deb P. C. 
Published: April 2003

AbstractThe method of graft copolymerization of methyl methacrylate on halogen‐containing polymer has been utilized for grafting of methyl methacrylate–methacrylic acid monomer pair onto poly(vinyl chloride) and chlorinated rubber. Substantial grafting could be obtained by using the method reported earlier. However, the compositions of the grafted chains are found to deviate appreciably from the compositions calculated from r1 and r2 values reported in literature. The reactivity ratios for this pair of monomers have been therefore evaluated using azobisisobutyronitrile and n‐butane thiol–dimethyl sulfoxide as initiators. The anomalies of the grafted chain compositions have been discussed and an explanation presented on preferential solvation.
Annealing effects on the viscoelastic anomaly between the β and γ processes for as‐polymerized polytetrafluoroethylene
Authors: Takenaga Mitsuru , Yamagata Kyozo , Kasai Akinari , Ariyama Takashi 
Published: April 2003

AbstractThe viscoelastic anomaly found at 208 K for as‐polymerized polytetrafluoroethylene (PTFE) is investigated on the basis of thermal treatment dependence of mechanical spectra. The loss intensity and relaxation strength of the anomaly tend to decrease at annealing temperatures much lower than the melting point. The structural region relevant to the anomaly can be rearranged in more ordered states on annealing; accordingly, the loss peak of the crystalline dispersion is intesified, although that of the amorphous γ‐relaxation remains nearly unchanged. The anomaly originates from the intermediate or paracrystalline regions, many of which are included in the virgin samples; segmental motions like local mode relaxation are considered.
Pressure effects in polymer melt rheology
Authors: Driscoll Paul D. , Bogue Donald C. 
Published: April 2003

AbstractWide ranges of pressure and temperature are encountered in polymer processing operations, as, for example, in injection molding. While the temperature dependence of viscosity has been widely studied, the pressure dependence has not. The present work focuses on the measurement of the melt viscosity of polystyrene at high pressures (up to 124 MPa or 18,000 psi) and high shear rates (1–100 s−1) at 180°C. The apparatus was a capillary rheometer with the downstream chamber being held at a high back pressure by means of a needle valve. The data so obtained were combined with zero shear viscosity data from the literature; and then correlated with a shear‐dependent rheological model of the authors, using a shift factor suggested by Utracki (based on the Simha–Somcynsky equation of state). The final correlation calls for making both the elastic modulus and the time constant dependent on pressure, with the modulus being the dominant factor at high shear rates.
Photomodification of polymer surface by utilizing photoinitiated amino‐groups formation–effects of comonomers on the dyeing of irradiated polymer surface
Authors: Song Kyoung‐Hun , Iwamoto Akiko , Tsunooka Masahiro , Tanaka Makoto 
Published: April 2003

AbstractPhotomodifications of polymer surface are investigated from the viewpoint of dyeing of the irradiated polymer surface. For this purpose, several kinds of acryloyl acetophenone oxime (AAPO) copolymers are prepared. As the other monomer components, methyl methacrylate (MMA), styrene (St), 2,3‐epoxypropyl methacrylate (EPMA), 2‐hydroxyethyl methacrylate (HEMA), N‐vinyl pyrroridone (NVP), and n‐butyl methacrylate (BMA) are used. In the photolysis of acyloxyimino (AOI) groups in AAPO copolymers, alkylimino groups can be introduced very effectively, which can be easily transformed to ammonium groups by hydrolysis in an aqueous solution of HCI. The surface of AAPO copolymers becomes dyeable with an acid dye (Congo Red) by the irradiation followed by HCI treatment and the degree of dyeing of the surface depends on not only the contents of ammonium groups but also the physical properties of the other monomer components. Although the hydrophilic or polar monomer such as NVP, HEMA, and MMA are cooperative for dyeing, the hydrophobic monomer such as St decreases the function of ammonium groups for dyeing. Although the undecomposed AAPO components in AAPO–MMA do not affect the degree of dyeing up to 24.5 mol % of AAPO contents in AAPO–MMA copolymers, they show the inhibition effect for dyeing of AAPO(38.8)–MMA at an earlier stage in irradiation. Aromatic moieties in AAPO are thought to inhibit the dyeing.