bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of intramolecular hydroxyls on electron beam polymerization and photopolymerization of acrylate monomers
Authors: Itoh Maki , Shiota Toshiaki
Published: April 2003

The effect of intramolecular hydroxyls on the electron beam polymerization and photopolymerization of monoacrylate monomers has been studied. In both polymerization methods, the rate of polymerization of monoacrylate monomers containing a hydroxyl was several times faster than those without hydroxyls. This can be partly explained by the higher viscosity of the hydroxyl containing monomer, resulting in a decrease in the termination rate constant to increase the polymerization rate. In electron beam polymerization, an increase in initiating species by the generation of radicals from the hydroxyls can also accelerate the polymerization.
Effect of electron beam radiation on the mechanical and thermal properties of poly(4‐methylpentene‐1)
Authors: El‐Naggar A. M. , Lopez L. C. , Wilkes G. L.
Published: April 2003

The changes in the mechanical and thermal properties of electron‐beam‐irradiated PMP of two different molecular weights (〈Mw〉 = 9.2 × 105, 〈Mw〉 = 1.8 × 106) have been studied. Electron beam (EB) irradiation was performed either in a nitrogen or air atmosphere to a maximum dosage of 40 Mrad. Stress–strain behavior of the irradiated materials show that the lower molecular weight polymer is more affected within this dose range than the higher molecular weight material. The modulus of both PMP materials (at 23°C), however, was not affected by EB. Moreover, it was observed that by increasing radiation dose up to 10 Mrad the occurrence of yielding disappeared in the case of the lower molecular weight system but was still found in the high molecular weight material up to 20 Mrad. The elongation at break of both PMP materials was systematically decreased by increasing the dose level. The rate of stress–relaxation of irradiated samples increased as dosage increased. It is believed that oxidative degradation is promoted as a result of irradiation which induces chain scission. This result was confirmed by GPC analysis which showed that, by increasing radiation dose, the molecular weight systematically decreased. DSC measurements used to investigate the changes in thermal properties showed that the melting temperature and heat of fusion decreased as the dose increased. An interesting feature of the DSC studies was the presence of an endothermic doublet in the melting behavior that transformed into a single peak following irradiation.
Surface lubrication of polymer films by photoinduced graft polymerization
Authors: Uyama Y. , Tadokoro H. , Ikada Y.
Published: April 2003

Films of nylon 6, polypropylene, and ethylene–vinyl acetate copolymers were graft polymerized with acrylamide or dimethylacrylamide to render the hydrated surfaces slippery. Following UV irradiation in air, the films were placed in the aqueous monomer solution and then either heated to 50°C after degassing or UV‐irradiated in the presence of a small amount of riboflavin without degassing to effect graft polymerization. The graft polymerization altered the films from the hydrophobic and nonlubricating to the hydrophilic and slippery surfaces. To evaluate the surface lubricity, the coefficient of friction (μ) against a glass plate in water was determined with the help of a tensile testing machine. The μ value for the films surface‐grafted with acrylamide up to 30 μ g cm−2 was reduced to less than 0.05, regardless of the substrate polymers.
A study of the low temperature nitration of cellulose in mixed acids
Authors: Munro H. S. , Short R. D.
Published: April 2003

The low temperature surface and bulk nitration of cellulose has been investigated by electron spectroscopy for chemical analysis (ESCA), 13C‐NMR and X‐ray diffraction. Acid mix composition has been probed at room temperature and at low temperatures (0–20°C) by Raman spectroscopy. This multitechnique approach has been employed to elucidate the behavior of surface degree of substitution (DOS) with acid mix composition over a 40°C temperature range. The data obtained have prompted a reinterpretation of previously reported work. Surface “equilibrium DOS” is shown to be established within 1 s at all temperatures investigated. but, at lower temperatures (> 5°C) the surface DOS as monitored by ESCA is observed to “dip” after immersion times of t < 5 s. This change in DOS is correlated with major structural changes in the fiber as observed by SEM. At low temperatures, e.g., −15°C, nitration is shown to be complete throughout the cellulose fiber after 10 h nitration. Solution state 13C‐NMR is used to compare the nitrate ester substitution distribution in cellulose nitrates prepared from acid mixes of the same composition at different temperatures.
Selective sorption of heavy metal thiocyanate complexes on crown ether resin
Authors: Hayashita Takashi , Noguchi Hiroaki , Oka Hisashi , Igawa Manabu , Takagi Makoto
Published: April 2003

The sorption behavior of heavy metal thiocyanate complexes was investigated for dibenzo‐18‐crown‐6 (DB18C6) resin and bis[2‐(o‐methoxyphenoxy)ethyl]ether (BMPE) resin. The DB18C6 resin showed a high sorption ability and the degree of zinc sorption increased significantly with thiocyanate concentration. This behavior was not observed for BMPE resin. The sorption behavior was influenced by the countercation species, and the degree of sorption of zinc ions showed the maximum when the potassium thiocyanate was used as a complexing salt. The sorbed species appear to be KZn(SCN)3, K2Zn(SCN)4 in the potassium thiocyanate system, and Zn(SCN)2 in the lithium thiocyanate system, respectively, according to analysis of the sorption equilibrium. Sodium and ammonium thiocyanate systems show an intermediate behavior of the two. The sorption selectivity for DB18C6 resin depended not only on the hydrophobic nature of heavy metal thiocyanate complexes but also on the stabilization of counter cation species with crown ether matrix, and the sorption selectively was found to be effectively controlled by countercation species according to the cation‐chelation mechanism.
A new type of solid‐state crystalline photopolymerization
Authors: Xiaolin Zhang , Youan Mao
Published: April 2003

A new type of solid‐state crystalline photopolymerization is researched in which, different from the topochemical polymerization, vinyl monomers are filmed under the induction of other macromolecular compound, crystallized, and polymerized after photoirradiation. Therefore, it may be also known as induction‐filming polymerization. The crystalline polyacrylamide film with large spherulite structures was obtained from the crystalline acrylamide by this means. Microscopy, differential scanning colorimetry, and infrared measurements were carried out. Mechanism is proposed for the induction‐filming polymerization involved.
An anion‐permeable polymeric coating for the protection of a semiconductor photoelectrode against decomposition
Authors: Bolts J. M. , Mariella R. P.
Published: April 2003

An anion‐permeable polymeric film has been applied to the surfaces of cadmium sulfide photoanodes to decrease the rate of electrode corrosion which is observed during the photoelectro‐chemical oxidation of aqueous species. Although the rate of surface corrosion was reduced, film adhesion problems were observed.
Novel epoxy resins based on cyclohexanone‐aldehyde condensation products
Authors: Renner Alfred , Cotting Jacques‐Alain
Published: April 2003

Solid 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

The 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

Few 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

Wettability 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

Thermal 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

The 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

The 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

The 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

Composite 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

Polydimethylsiloxane (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

Neodymium 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

The 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

Superabsorbent 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

The 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

Aniline 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.
Penetration of oils into polychloroprene rubber
Authors: Lawandy S. N. , Wassef M. T.
Published: April 2003

A number of factors which influence the penetration rate of motor oils in polychloroprene rubber have been investigated. These are relevant to carbon black concentration, carbon black particle size and oil characterization.
Latex preparation and stabilization by hydrophobically modified hydroxyethyl celluloses
Authors: Puterman Moshe , Fitch Robert M.
Published: April 2003

Hydrophobically 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

A 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

The 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

This 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

The 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

Mechanical 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

As 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.
Effect of polyamic acids on interfacial shear strength in carbon fiber/aromatic thermoplastics
Authors: Chuang S. L. , Chu Ning‐Jo , Whang W. T.
Published: April 2003

Carbon fiber surfaces were coated in various thickness with polyamic acids (PAA) prepared from (1) benzophenone tetracarboxylic dianhydride (BTDA) and 4,4'‐diaminodiphenyl ether (ODA), (2) BTDA and 4,4'‐diaminodiphenyl sulfone (DAS), and (3) BTDA and ODA modified with bisaminopropyldisilane, designated as PAA‐1, PAA‐2 and PAA‐3 respectively. The treated carbon fiber, with or without imidization, was embedded in thermoplastic polyetheretherketone (PEEK), polyetherimide (PEI), polyethersulfone (PES), polysulfone (PSF), and polyphenylsulfide (PPS) by the microbond method, and the interfacial shear strength was measured by pulling out the fiber from the embedded resin. Maximum increments in interfacial bonding strength from 24% to 35% were obtained from PAA‐1 in PEEK in PEI, PAA‐2 in PEEK, PEI, PSF, and PPS, and PAA‐3 in PEEK and PES. Imidization of PAA‐1 and PAA‐2 before resin application reduced their bonding capability. A linear relationship between the length of the embedded fiber and debonding load was found in the case of PEEK, PEI, and PSF; scattered results were obtained in the case of PES and PPS. Inadequate specimen annealing was believed to be the cause for PES, Brittle fracture appeared to occur in the case of PPS.
Effects of gamma‐ray irradiation on the change of characteristics of polyurethane
Authors: Shintani Hideharu , Kikuchi Hiroshi , Nakamura Akitada
Published: April 2003

Investigations have been carried out on gamma‐ray irradiated thermoplastic polyurethane (PU). The change of molecular weight as a result of irradiation and the change of absorbance of samples eluted daily by methanol extraction were determined. GPC patterns, tensile strength, and residual amount of radicals based on chemiluminescence were also measured. PU chain‐extended with 1,4‐butanediol (BU) showed degradation, while PU without chain‐extended with BU (linear PU) showed mainly crosslinking by gamma‐ray irradiation. G values were 1.1 (degradation) and 0.2 (crosslinking). A linear relationship between the irradiation dose and the residual radical amount was found. There was no significant difference in molecular weight as determined immediately following irradiation with analysis 6 months after irradiation. The influence of the amount of residual radical on the changes in the characteristics of PU was not significant. The elution of PU oligomers (n = 1–10) was confirmed from the GPC pattern of methanol extract. The changes in tensile strength correlated well with the changes in molecular weight. Sequential daily methanol extract analysis showed that elution occurred semilogarithmically. Methanol extract at an early stage is more toxic due to abundant elution of lower molecular weight compound.
Fibers from flexible liquid crystal main‐chain polymers. I. Polymers based on 4,4′‐dihydroxy‐2,2′‐dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides
Authors: Blumstein A. , Lin C. H. , Mithal A. K. , Tayebi A.
Published: April 2003

The anisotropic properties of thermotropic liquid crystalline polymers are paramount to the development of highly oriented and extended polymer chains in a fiber spinning process. Fibers from liquid crystalline polymers were spun above the mesophase transition temperature. Linear thermotropic liquid crystalline polymers based on 4,4′‐dihydroxy‐2,2′‐dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides have been previously studied by different techniques and their conformational properties are well established. In this work the mechanical properties of fibers based on such polymers were studied. High values of tenacity and tensile moduli were obtained. These values increase with molecular mass, but decrease with the length of the flexible spacer moiety. The spinning temperature is also an important parameter.
Effect of cooling rate and shear‐induced crystallization on the pressure–specific volume–temperature diagram of isotactic polypropylene
Authors: Fleischmann E. , Koppelmann J.
Published: April 2003

Rectangular plates were injection molded with isotactic polypropylene. At a pressure of 1300 bar the mold was sealed mechanically in the gate. After the injection and compression phase the internal pressure decay has been calculated using the pressure–specific volume–temperature diagram and compared with measurements. The calculation method is described. The pvT diagram determined on stationary melt at a low cooling rate yields no good approximations of the measured values. It is shown which modifications of the pvT diagram are necessary to obtain a better description of the melt behavior under injection molding conditions. At the end of the cooling phase, the calculated pressure differs from the measured pressure. The reason is the volume change of the mold caused by the high internal pressure.
Epoxy resins based on aromatic glycidylamines. I. Analysis of N,N‐diglycidylaniline by GPC and HPLC
Authors: Podzimek S̆. , Dobás̆ I. , S̆vestka S̆. , Horálek J. , Tkaczyk M. , Kubín M.
Published: April 2003

N,N‐bis(2,3‐epoxypropyl) aniline (N,N‐diglycidylaniline, DGA) and an intermediate of its synthesis, N,N‐bis(2‐hydroxy‐3‐chloropropyl) aniline (N,N‐dichlorohydrin of aniline, DCHA), were analyzed by GPC and HPLC. The main impurities were isolated by semipreparative HPLC and their structure was identified by mass, IR, and NMR spectroscopy. Attention was also paid to the mechanism underlying the formation of these impurities.
The use of RuO4 in studies of polymer blends by scanning electron microscopy
Authors: Ohlsson Bertil , Törnell Bertil
Published: April 2003

Flat samples of blends of PP and SEBS were contrasted with ruthenium tetroxide and studied in a scanning electron microscope provided with a detector for back‐scattered electrons. The images showed the SEBS phase as bright areas with dark dots and the PP phase as dark. The dots in the bright SEBS areas corresponded to the unstained EB‐domains of the triblock SEBS polymer. The technique used provided BSE images of high resolution. This is a consequence of the intrinsic electrical conductivity conferred to the sample surface by the ruthenium species deposited there during staining. Treatment with ruthenium tetroxide vapor conferred electrical conductivity to the stained areas, which explains the high resolution obtained with the present technique.
Synthetic sequence effects in polyurethane–poly(n‐butyl methacrylate) mixtures: Grafting and mechanical properties
Authors: Fox R. B. , Armistead J. P. , Roland C. M. , Moonay D. J.
Published: April 2003

Morphology, stress–strain properties, and grafting have been investigated in highly phase‐separated polyurethane (PU)‐poly(n‐butyl methacrylate) (PBMA) mixtures as a function of the sequence of formation of the components, both linear (l) and crosslinked (x), in the presence of each other. In the range of 0.3–0.7 weight fraction of PU, a morphology of PBMA particles in a PU matrix results. Particle size depends on matrix viscosity at the time of PBMA formation, decreasing as viscosity increases. The PBMA (l) particles are spherical; PBMA (x) particles are irregular in shape when formed in a fluid medium but tend to become spherical as the delay time before the onset of their formation is increased. Grafting, decreasing with increasing delay time, is observed between PBMA (l) particles and the PU (x) or PU (l) matrix. The grafting results from transesterification between BMA and the polyol precursors to the PU. Two families of mechanical properties are found, depending generally more on particle shape than size. Systematic trends of property values through a series of samples of constant composition, but increasing delay times, are observed with greater variation in the series with PBMA (x) particles; the trends are explainable in terms of matrix immobilization by the particles.
Melt flow index values and molecular weight distributions of commercial thermoplastics
Authors: Bremner T. , Rudin A. , Cook D. G.
Published: April 2003

The traditional melt index test (ASTM D 1238) is widely used in the plastics industry to characterize polymer processability. The data from this measurement must be interpreted cautiously, however, because polymers are usually processed under conditions that are far removed from those of the melt index test. In this study, melt index (MI) values from a series of polystyrene, polypropylene, linear low‐density polyethylenes (butene and octene copolymers), and high‐density polyethylenes were measured and related to molecular weight distributions of these materials. It was found that a simple relationship between 1/MI versus M̄xw (where x = 3.4–3.7) was followed for the linear polymers with similar polydispersities. For branched polymers, the best correlation was that of ‐ln(MI) versus ln(M̄v). A general relation for shear modifiable polymers like polyethylenes cannot be obtained unless the rheological state of the material can also be defined.
Effect of corona discharge treatment on cellulose prepared from beech wood
Authors: Uehara Tohru , Sakata Isao
Published: April 2003

Cellulose prepared from beech wood (Fagus crenata Blume) was treated in a corona discharge. The chemical changes produced by the treatment were investigated by use of infrared spectrum, Schiff's reaction, adsorption of methylene blue and Orange II, and intrinsic viscosity. Infrared absorption bands at 1382 and 1715 cm−1 were formed. The color reaction with Schiff's reagent indicated that the 1715 cm−1 absorption was due to the aldehyde group and not to the carboxyl group. The intrinsic viscosity was decreased by the air corona treatment, but was not affected by nitrogen corona treatment. The adsorption of methylene blue was not increased by corona treatment, indicating that no acidic groups were formed. Adsorption of Orange II indicated that some basic groups were formed by the nitrogen corona after a long treatment time. Low molecular weight fractions showing the 1382 cm−1 infrared absorption band were formed by corona treatment. These fractions were removed from cellulose by washing with water, and they increased with an increase in the treatment time. The absorption band at 1382 cm−1 was assigned to the symmetric carbon‐hydrogen bending of methyl group.
Bead–spring macromolecules that perturb the solvent
Authors: Grisafi S.
Published: April 2003

A dispersion force based interaction between the solvent and the beads of a bead‐spring model macromolecule is used to couple the motion of the solvent and polymer in dilute solution flows. The polymer exerts a force on the solvent equal and opposite to the force that the solvent exerts on it. The friction coefficient approximation of the Rouse‐Zimm theories is eliminated. Both the solvent and polymer are subject to ensemble averaging over their respective phase space. A constitutive equation for the polymer stress is presented. By appropriate selection of the interaction potential between the solvent and the polymer, any normal stress difference can be predicted.
The effect of biaxial orientation and crystallinity on the long‐term creep behavior of poly(ethylene terephthalate) films below glass transition temperature
Authors: Cakmak M. , Wang Y. D.
Published: April 2003

The use of thin polymeric films in applications such as flexible circuit boards and dish membrane solar collectors has been gaining popularity. In these and many other applications the films are used under constant loading conditions which subjects them to long‐term creep. In this paper, we present detailed experimental tensile creep results on unoriented films of varying crystallinities and unequal and equal biaxially oriented poly(ethylene terephthalate) (PET) films. The results indicate that the increasc of crystallinity, stretch ratios, and annealing causes reduction in longterm creep strains. Unequal biaxially stretched films exhibited in‐plane anisotropy in their tensile creep behavior. In these films the lowest creep strains are observed in the direction along which the film stretched to the highest stretch ratio.
Heterogeneous polymerization of methyl methacrylate in absence and presence of surface modified cuprous oxide
Authors: Moustafa A. B. , Aboul‐Wafa O. , Radwan F. M. , Emam A.
Published: April 2003

The heterogenous polymerization of methyl methacrylate in the presence of cuprous oxide was studied. Adsorption measurements of stearic acid from benzene solution onto the surface of Cu2O were carried out. The specific surface area of cuprous oxide as obtained from the extrapolation to the concentration of monolayer surface coverage in the adsorption isotherm was compared with that evaluated from the BET‐equation. Sedimentation volume and sedimentation rate of the variably surface modified Cu2O samples were determined. It was found that the surface modification of Cu2O enhances its catalytic effect in the heterogenous polymerization of methyl methacrylate up to monolayer surface coverage. The viscosity average molecular weights M̄v of the respective polymers as well as the apparent activation energy of the polymerization process were correlated with the reaction parameters.
Thermal shock resistance of plastic IC package
Authors: Kojima Yoshitsugu , Ohta Takashi , Matsushita Mitsumasa , Takahara Minoru , Kurauchi Toshio
Published: April 2003

Dual‐in‐line packages (DIPs) were formed from epoxy molding compounds with various physical properties using a transfer molding machine. The compounds were prepared by changing kinds and amounts of additives and addition methods. The thermal shock test was carried out by the following procedures. The plastic package was soaked alternately in liquid nitrogen (−196°C) and in liquid solder (250°C) in the cycle of 140 s. The packages were intermittently subjected to optical microscopic inspection for crack initiation. The median life to crack initiation is defined to be the number of the cycles when half of the specimens exhibited crack initiation. Glass transition temperature, coefficient of linear expansion, and flexural modulus were measured to calculate thermal stress in plastic packages. According to the linear fracture mechanics, the following expression was obtained among the median life N, thermal stress σt and strength σb. N =/σ We found the linear relation between logarithm of Nσ and logarithm of σb/σ t for various packages, and obtained that the value of C and m are estimated as 3 × 104 MPa2 and 5.5, respectively. Therefore, the median life can be predicted from the glass transition temperature, coefficient of linear expansion, flexural modulus, and strength of plastic materials for packages.
Modification of transport properties of ion exchange membrane. XI. Electrodialytic properties of cation exchange membranes having polyethyleneimine layer fixed by acid–amide bonding
Authors: Sata Toshikatsu , Izuo Ryuji
Published: April 2003

For the purpose of preparing the monovalent cation permselective membrane for electrodialysis, the membrane having—SO2Cl groups reacted with the polyethyleneimine to form a cationic polyelectrolyte layer on the membrane surface by using the acid–amide bonding. Reaction conditions, i.e., reaction temperature, concentration of the polyethyleneimine solution and the addition of tertiary amines to the polyethyleneimine solution, were all examined in detail. As a result, all the different kinds of polyethyleneimines were effective in obtaining the monovalent cation permselective membrane if the correct reaction conditions were selected. The durability of the monovalent cation permselectivity was evaluated in a continuous electrodialytic concentration of sea water. The monovalent cation permselectivity decreased gradually during the electrodialysis in the cation exchange membrane with the polyethyleneimine layer. Therefore, the cation exchange membrane with the cationic polyelectrolyte layer was further treated with crosslinking reagents, i.e., form aldehyde–hydrochloric acid, epichlorohydrin, etc. or other alkylating reagents. The monovalent cation permselectivity of the treated membranes was almost constant for two months. The crosslinking reaction of polyethyleneimine was more effective than alkylation in maintaining the high permselectivity constantly.