bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel epoxy resins based on cyclohexanone‐aldehyde condensation products
Authors: Renner Alfred , Cotting Jacques‐Alain 
Published: April 2003

AbstractSolid ketone‐formaldehyde resins are used in certain coating formulations in order to improve hardness, gloss, and light stability. They are soluble, thermoplastic by nature, and contain limited amounts of hydroxyl groups. We found that their primary hydroxyls can be etherified with epichlorohydrin (ECH) either by a two‐step ECH‐addition/dehydrohalogenation procedure or by a one‐step phase‐transfer process. An intermediate of particular usefulness is the crystalline 2,2,6,6‐tetramethylol‐cyclohexanol (TMCH) made from cyclohexanone and 5 mol formaldehyde, yielding low colored epoxy resins with epoxy values up to 7.5 eq/kg. Depending upon the nature of the curing agent, high Tg solids as well as tough and flexible coatings with good outdoor stability can be made. Upon decreasing the formaldehyde–cyclohexanone ratio, solid condensation polymers melting up to 150°C can be obtained. Phase‐transfer glycidylation yielded solid thermoset glycidyl ether resins with M̄n up to 1600, M̄ω up to 13,000, epoxy values up to 3.6 eq/kg, and softening points between 80 and 160°C. Powder coatings formulated with carboxyterminated polyesters are hard, glossy, solvent‐resistant but somewhat brittle. In order to overcome this drawback, polycycloacetals have been produced from TMCH and glutardialdehyde, which are terminated by pairs of methylol groups. Powder coatings of the corresponding glycidylethers with carboxyl‐terminated polyesters exhibited excellent flexibility and impact strength.
Swelling of poly(methyl methacrylate) thin films in low molecular weight alcohols
Authors: Papanu J. S. , Hess D. W. , Soane (Soong) D. S. , Bell A. T. 
Published: April 2003

AbstractThe effects of solvent size, temperature, and polymer molecular weight on the swelling of poly(methyl methacrylate) (PMMA) thin films in low molecular weight alcohols were investigated using an in situ ellipsometer. Apparent activation energies were indicative of non‐Fickian diffusion, although optical data showed substantial Fickian character for swelling in methanol and moderate Fickian character in ethanol. Penetration rates were strongly dependent on the solvent molar volume for methanol, ethanol, and isopropanol, but 1‐butanol and 2‐pentanol had rates similar to isopropanol. The effective cross sections of these longer molecules are similar to isopropanol, and this apparently explains the similar penetration rates. The effect of polymer molecular weight (MW) on methanol penetration rates (21–27°C) was investigated with monodisperse PMMA (Mn = 6.4–40.0 × 104 g/mol). A minimum at intermediate MW was observed. Isopropanol swelling rates (45–52°C) were insensitive to MW. The swelling data were also used to determine parameters for transport models that describe the swelling of thin polymer films.
Limitation and evaluation of the two‐broad standard (TBS) method of calibration of aqueous SEC
Authors: Omorodion S. N. E. , Hamielec A. E. 
Published: April 2003

AbstractFew years ago, the two broad standard method of molecular weight (MW) calibration was proposed1 and the presence of negative σ2 (peak dispersion coefficient) was found to be somewhat disturbing. The limitation of the method was not specified. Since large negative values of σ2 cannot be tolerated, herein is reported another type of instrumental spreading function for which the method may seem to apply, and an evaluation of this method. In its evaluation, plots of loge (intercept of a linear molecular weight calibration curve), that is, loge(D1) vs. the corresponding slope of the molecular weight calibration curve, D2, which were found to be linear, were used. The systems employed were Dextran/Corning controlled porous glass (CPG‐10) packing in well‐chosen mobile phase.
Antifogging effect of cellulose films by chemical modification of the surface using nonionic fluorocarbon surfactant
Authors: Ueno M. , Ugajin Y. , Horie K. , Nishimura T. 
Published: April 2003

AbstractWettability and antifogging effect on the surface of the transparent thin film of cellulose esters were studied by fixing chemically nonionic fluorocarbon surfactants on the film surface and were compared with the properties of the surface fixed with the corresponding nonionic hydrocarbon surfactants. These antifogging properties on the surfaces covered by the monomolecular layer of fluorocarbon surfactant were found to be more excellent than those of the nonionic hydrocarbon surfactants from the measurement of contact angle for water droplets and also from the data of Zisman's plots. The surface of the thin film setting in the closed chamber filled with water vapor at 60°C were confirmed to be transparent during a long time without fogging. Antifogging effect may be due to so‐called double structure consisting of fluorocarbon and nonionic ethyleneoxide chains in the monomolecular layer.
Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate
Authors: Fernández M. J. , Fernández M. D. , Casinos I. , Guzmán G. M. 
Published: April 2003

AbstractThermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate‐methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate‐methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate‐methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.
Reversible crosslinking in epoxy resins. I. Feasibility studies
Authors: Tesoro G. C. , Sastri V. 
Published: April 2003

AbstractThe objective of the research is to investigate epoxy resins where crosslinks formed in curing reactions can be cleaved and reformed without significant sacrifice in resin properties. In this phase of the investigation, experimental disulfide‐containing crosslinking agents have been studied, including dihydrazides of dithiodicarboxylic acids(aliphatic and aromatic) and dithio‐aromatic diamines. Conditions for curing reactions and for subsequent cleavage of crosslinks by reduction have been determined in model systems and confirmed for a prototype epoxy resin. A preliminary comparative evaluation of cure kinetics and of crosslink density and thermal and mechanical properties has been carried out for this resin cured with aromatic curing agents (4,4′‐dithiodianiline and methylene dianiline) and with aliphatic compounds (3,3′‐dithiopropionic acid dihydrazide and hexamethylene diamine). It has been shown that in a resin fully cured with disulfide‐containing crosslinking agents, crosslinks could be ruptured by reduction, and reestablished by oxidation under mild conditions.
Radiation‐induced graft polymerization of 4‐vinyl pyridine to styrene–butadiene–styrene triblock copolymer
Authors: Yang Jen‐Ming , Hsiue Ging‐Ho 
Published: April 2003

AbstractThe radiation‐induced graft polymerization of 4‐vinyl pyridine to styrene–butadiene–styrene triblock copolymer (SBS) was investigated. Relations between the rate of grafting and the dose rate when SBS was irradiated in 4‐vinyl pyridine–methanol solution, and between the rate of grafting and 4‐vinyl pyridine concentration of 4‐vinyl pyridine–methanol solution have been investigated. An experiment that had been carried out on SBS immersed in various 4‐vinyl pyridine concentration of 4‐vinyl pyridine–methanol solutions showed that the extent of swelling of SBS by the various 4‐vinyl pyridine–methanol solutions increased with increasing 4‐vinyl pyridine concentration. The largest rate was found at 20 vol % 4‐vinyl pyridine–methanol solution. The rate was smaller at the volume percent of 4‐vinyl pyridine higher or lower than 20 vol %. On the assumption that the theory of homogeneous homopolymerization could be applied to this grafting reaction, the value of kp2/kt was obtained, where kp and kt are the propagation and termination constant, respectively. The value of kp2/kt greatly decreased with increasing adsorbed concentration of vinyl pyridine–methanol solution. This decrease of kp2/kt was explained by the fact that 4‐vinyl pyridine and methanol absorbed in SBS acted as a plasticizer which increased the molecular motion of the polymer. The solvent effect on the graft polymerization was also investigated. The result was explained by solubility parameter. When the chosen solvent had better solubility with the polymer, the degree of grafting was smaller. That was connected with the extent of the polymer chain mobility.
Electrical properties of chlorinated atactic polypropylene (CAPP) and PVC–DOP–CAPP system
Authors: Mukherjee A. K. , Patri M. 
Published: April 2003

AbstractThe electrical properties, such as dielectric properties and volume resistivity, of chlorinated atactic polypropylene(CAPP), obtained by thermal chlorination of APP, have been studied. The results show that dielectric constant, loss tangent, and volume resistivity of the chlorinated samples increase with the increase in degree of chlorination. The effect of CAPP as secondary plasticizer in the PVC–DOP system has also been studied. Dielectric study of PVC compounds shows a single relaxation peak, indicating no phase separation. In the case of PVC compounds, it has been observed that with the increase in CAPP content in PVC compounds dielectric constant and loss tangent decrease whereas volume resistivity increases. The increase in volume resistivity was further supported by the increase in activation energy value, obtained from volume resistivity vs. 1/T plot.
Modification of natural rubber latex. II. Natural rubber poly(methyl methacrylate) composite latexes synthesized using an amine‐activated hydroperoxide
Authors: Hourston D. J. , Romaine J. 
Published: April 2003

AbstractComposite latex particles based on natural rubber latex have been synthesized to yield materials which may be formally regarded as interpenetrating polymer networks and semiinterpenetrating polymer networks. Methyl methacrylate was added to a carefully stabilized natural rubber latex and polymerized in situ using an amine‐activated initiator, tert‐butyl hydroperoxide. The resulting materials were cast to yield solid sheets. The morphology of the materials was determined both by transmission electron microscopy and by dynamic mechanical analysis. In addition the stress–strain behavior was studied.
Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and piperazine‐aromatic polyamides
Authors: Kajiyama Mikio , Kakimoto Masa‐Aki , Imai Yoshio 
Published: April 2003

AbstractPolydimethylsiloxane (PDMS)–polyamide multiblock copolymers were synthesized by three different methods, i.e., two‐step low‐temperature solution polycondensation, one‐step solution polycondensation, and interfacial polycondensation. In the two‐step method, α,ω‐diacid chlorideterminated polyamide oligomers were prepared from trans‐2,5‐dimethylpiperazine (DMP) and terepthaloyl chloride (TPC) or isophthaloyl chloride (IPC) in chloroform in the presence of triethylamine, which in turn were subjected to reaction with α,ω‐bis (3‐aminopropyl) polydimethylsiloxane (PDMS–diamine) in the same solvent to from multiblock copolymers. In the one‐step method, the reaction components, DMP, TPC (or IPC), and PDMS–diamine, were reacted altogether in chloroform in the presence of triethylamine. In the interfacial method, the reaction components were also reacted altogether in an aqueous sodium hydroxide–chloroform two‐phase system. These polycondensations afforded the multiblock copolymers having inherent viscosities of 0.1–1.3 dL g−1 in m‐cresol. The PDMS–polyamide multiblock copolymers dissolved in formic acid and 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP), and transparent, ductile, and elastomeric films were obtained by casting from the HFIP solutions. The films of the multiblock copolymers prepared by three different methods exhibited similar properties by means of thermal analysis and tensile measurements. In the multiblock copolymers, the tensile strength and modulus of the films decreased with increasing the PDMS content, whereas the elongation at break increased.
Micellar behavior of neodymium soaps in methanol
Authors: Mehrotra K. N. , Shukla R. K. , Chauhan Mithlesh 
Published: April 2003

AbstractNeodymium butyrate, valerate, and caproate behave as simple electrolytes in dilute solutions and the CMC was found to decrease with increasing chain length of fatty acid constituent of the soap molecule. The CMC, degree of dissociation, and dissociation constant of neodymium soaps in methanol have been determined by conductometric measurements. The viscosity results have been explained on the basis of the equations proposed by Einstein, Vand, Moulik, and Jones and Dole. The values of the molar volume calculated by Einstein's and Vand's equations are in agreement with each other.
The structure of the effective separating layer of asymmetric hollow fiber membranes with graded density skins
Authors: Fritzsche A. K. , Armbruster B. L. , Fraundorf P. B. , Pellegrin C. J. 
Published: April 2003

AbstractThe structure of the effective separating layer of an asymmetric polysulfone hollow fiber membrane with a graded density skin was studied by SEM, TEM, and osmium tetroxide vapor adsorption and compared to that of a bilayer asymmetric hollow fiber membrane prepared from a solvent/nonsolvent mixture. The studies revealed the presence of micropores which transverse the effective separating layer of the membrane with graded density skin. The structural units which constituted the effective separating layer of this membrane are less tightly packed and distorted than are the entities forming the effective separating layer of its congener prepared from the traditional solvent/nonsolvent mixture. These results indicate that the enhanced free volume in an asymmetric hollow fiber membrane with a graded density skin exists in the effective separating layer as well as in the membrane interior.
Preparation of superabsorbents by gamma‐ray radiation
Authors: Iyer V. , Varadarajan P. V. , Sawakhande K. H. , Nachane N. D. 
Published: April 2003

AbstractSuperabsorbent polymers were prepared using acrylonitrile grafted to corn starch employing low levels of gamma ray radiation as initiator. Various grafting parameters have been studied at these low dosages. Absorbency values for the final products are reported. Use of the above superabsorbent as a desiccant has been evaluated. The product will find application where dispersions of low viscosity and high water absorbencies are desired.
Preparation and characterization of silk fibroin powder and its application to enzyme immobilization
Authors: Yoshimizu Hiroaki , Asakura Tetsuo 
Published: April 2003

AbstractThe powders of Bombyx mori silk fibroin were prepared from aqueous solutions of silk fibroin by several kinds of the insolubilization methods, some of which used methanol. The insolubilization appeared to be effected by the conformational transition of silk fibroin from the random coil to antiparallel β‐sheet form, which was monitored with IR spectroscopy. In order to characterize the structure of the power in the swollen state in water, a spin‐labeled silk fibroin powder was prepared and the ESR spectra were observed, as well as 13C‐NMR. The heterogeneous structure was analyzed quantitatively in terms of the fraction of fast, slow, and very slow components in the ESR spectra. Finally, an enzyme, invertase, was immobilized with the silk fibroin powder. The thermal stability of the enzyme was much improved by the immobilization.
Rate studies on polyaniline films preparation in static cells and in fluidized bed electrode reactors
Authors: Segelke S. , Mahalingam R. , Subramanian R. V. 
Published: April 2003

AbstractAniline was polymerized using a static electrochemical cell and a fluidized bed electrode reactor (both static and fluidized beds) to form thin films, respectively, on plate and particulate substrates. Parameters such as reaction time, applied voltage, anolyte flowrate, and monomer concentration on the rate of polymerization were studied and correlated with polymer film thickness and surface morphology, as observed on a scanning electron microscope.
Latex preparation and stabilization by hydrophobically modified hydroxyethyl celluloses
Authors: Puterman Moshe , Fitch Robert M. 
Published: April 2003

AbstractHydrophobically modified hydroxyethyl celluloses (HMHEC) are derivatives of water‐soluble hydroxyethyl‐ethers of cellulose. Because these amphiphilic molecules are known to adsorb strongly on water–oil interfaces, they were tested as nonionic surfactants and stabilizers in emulsion polymerization. Styrene and methyl acrylate were used as water‐insoluble and slightly water‐soluble monomers, respectively. In situ nucleation, seed latex polymerization, and postpolymerization addition of HMHEC were examined. The main difficulty with the HMHEC materials is their bridging effect, which enhances aggregation. However, these nonionic materials impart pronounced stability to latices against electrolytes. This property can be achieved also by postaddition of the HMHEC to a performed emulsion.
Polymerization of acrylamide using mandelic acid/permanganate redox system in acidic medium
Authors: Bajpai U. D. N. , Ahi Anita 
Published: April 2003

AbstractA combined system of potassium permanganate and mandelic acid was found to initiate vinyl polymerization, specifically acrylamide. A study of the reaction kinetics of this system showed that free radicals are formed. The energy of activation was found to be 3.54 kcal/° mol in the temperature range 27–40°C, in nitrogen atmosphere.
Effects of coating treatments on the mechanical behavior of wood‐fiber‐filled polystyrene composites. I. Use of polyethylene and isocyanate as coating components
Authors: Maldas D. , Kokta B. V. 
Published: April 2003

AbstractThe influence of different grades of polyethylenes and poly[methylene(polyphenyl isocyanate)] (used to precoat the fiber) on the mechanical properties of polystyrene (PS 201 and PS 525) and chemithermomechanical pulp composites have been investigated. Mechanical properties, including impact strengtth of PS 201 based composites, improved when polyethylene was used along with isocyanate, whereas PS 525 based composites performed less well in this respect. Polystyrene itself seems a better partner for isocyanate as a coating component.
Determination of the influence of structure and thermal history on the dynamic mechanical properties of high density polyethylenes
Authors: Rego J. M. , Orozco J. A. Gonzalez , Katime Issa 
Published: April 2003

AbstractThis work is aimed at determining the influence of molecular weight distribution, branch content, and thermal history on the dynamic mechanical properties of four high density polyethylenes. Molecular segregation as a function of crystallization conditions has been measured by means of differential thermal analysis, whereas infrared spectroscopy allowed us to relate the structural changes introduced by the use of different crystallization conditions with both molecular segregation and dynamic mechanical properties. The α‐relaxation is the most affected transition by thermal treatments. Molecular segregation plays an important role in the mechanical behavior when the amount of segregated material is big enough as to shield the effect due to the isothermally thickened crystals. The presence of a high degree of segregation brings about asymmetry in the α‐relaxation peak as well as detectable changes in the reorganization factor (which defines the degree of order within the system) obtained by infrared spectroscopy. The supermolecular structure is found not to affect the dynamic mechanical properties. The β‐relaxation depends on the branch content, whereas the λ‐relaxation remains constant regardless of structural characteristics and thermal conditions.
In vitro drug release profile of bioerodable citric acid–glycerol copolymer
Authors: Pramanick D. , Ray T. T. 
Published: April 2003

AbstractThe incorporation and release of sulfadiazine, paracetamol, diazepam, quinine hydrochloride, and doxycycline hydrochloride in and from rectangular slabs of highly crosslinked citric acidglycerol copolymer matrix have been described. The release of the drugs in phosphate buffer of pH 7.4 and at 37°C was followed spectrophotometrically. After an initial burst, the first three drugs were released up to 4 days and the last two drugs up to 7 days at almost constant rates. The erosion profile of the drug‐free matrix and the release characteristics of the drug‐loaded slabs under physiological conditions indicate hydrolytic erosion of the slab from the surface as well as from the bulk. It has been suggested that the zero‐order release of the drugs was possible due to a balance between the decreasing release rate by diffusion through the matrix and the increasing release rate because of increasing polymer permeability resulting from gradual crosslink cleavage.
Interfacial interactions and mechanical properties of filled polymers
Authors: Boluk M. Y. , Schreiber H. P. 
Published: April 2003

AbstractMechanical properties, notably the ductility of rutile‐filled low‐density polyethylene (LDPE) and chlorinated polyethylene (CPE), were studied to determine the influence of filler dispersion and of matrix‐filler interactions. Potential interactions between polymer and filler were obtained from inverse gas chromatography, in the form of acid/base interaction parameters. The strength of filler aggregates was obtained from flow properties of the dry powders. Dispersion quality in molded specimens was identified from X‐ray contact micrographs. The ductility of filled, nonpolar LDPE was found to be independent of acid/base considerations, but strong correlations have been drawn between the strength of filler aggregates and the quality of dispersion attained by controlled mixing methods. Inherent filler agglomeration thus also affects the mechanical properties of the nonpolar matrix. Coated, nonagglomerated fillers dispersed well, leading to ductilities at low filler load that exceeded that of the unfilled host polymer. In contrast, acid/base interactions were found to exert dominant influence on rutile dispertion in CPE. Similarly, the mechanical properties of this polymer varied with the acid/base forces acting at matrix/filler contacts.
Some studies of annular extrudate swell phenomena
Authors: Seo Yongsok 
Published: April 2003

AbstractAs a part of continuous study, annular extrudate swell phenomena was investigated using a finite element method. For a Newtonian fluid, gravitational force and surface tension effects are considered. For non‐Newtonian fluids, power‐law fluid and second‐order fluid were considered. Some interesting results were found for non‐Newtonian fluids. For highly shear thinning fluid, thickness was contracted instead of swelling. For second‐order fluid, the analysis was confined only to weak elastic fluid. Explanations are presented for high Weisenberg number problems.