bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of anionic/cationic sequential IPNs. II. Studies of swelling, modulus, and alternate phase staining with CsF and LiI
Authors: Hargest S. C. , Manson J. A. , Sperling L. H. 
Published: April 2003

AbstractAnionic/cationic interpenetrating polymer networks (IPNs) were synthesized by sequential polymerization from crosslinked polystyrene, PS, as polymer I and crosslinked poly(4‐vinyl pyridine), P(4‐VP), as polymer II. Ionomeric substitution of the two networks was based on sulfonation and quaternization of the phenyl and pyridine rings, respectively. The swelling, morphological, and dynamic mechanical behavior of ionomeric and unsubstituted IPNs was explored as a function of overall IPN composition. A theoretical analysis of the unsubstituted IPNs via the Thiele–Cohen equation showed that essentially no additional physical or chemical crosslinks were developed in the swollen state. Modulus studies showed that network I tends to dominate the mechanical properties in the bulk state. Swelling studies on the ionomeric IPNs as a function of pH demonstrated a complex change in behavior with the addition of NaCl, possibly due to an ionic screening effect. Electron microscopy involved alternate staining of the anionic and cationic phases using CsF and Lil and showed a two‐phase structure, with the possibility of additional phases within phases due to separation of the ionomeric components. Comparison of the two staining techniques yielded strong evidence of a positive/negative–negative/positive phase contrast, depending on the phase being stained. In each case, domains were less than 100 nm (1000 Å), with the domain size decreasing as the P(4‐VP) content increased. Also, a phase inversion appeared to occur between 50 and 80% P(4‐VP). The dynamic mechanical studies supported the two‐phase morphology and gave evidence of significant molecular mixing between the phases.
Dynamic compression mechanical properties of fiber masses with a rheovibron viscoelastometer
Authors: Murayama Takayuki 
Published: April 2003

AbstractThe Rheovibron viscoelastometer is useful for obtaining dynamic tensile, shear, and bending mechanical properties of films and fibers over a wide teḿperature range. In recent years a modification that makes measurement on materials in a liquid or gas medium possible has been reported. A new compression grip and procedure were used for measuring dynamic mechanical properties of a fiber mass in the compression mode using the Rheovibron instrument. The dynamic compression properties on nylon, polyester, and acrylic fibers are presented.
Crystallinity in silk fibers: Partial acid hydrolysis and related studies
Authors: Bhat N. V. , Nadiger G. S. 
Published: April 2003

AbstractFour Indian varieties of silk viz., Mulberry, Tasar, Eri, and Muga, have been investigated by x‐ray diffraction and infrared spectroscopy. The hydrolysis for Mulberry was carried out using 6N HCI at 40°C, whereas the other wild varieties of silk were hydrolyzed partially using 8N HCI at 40°C. The x‐ray order factor, IR crystallinity index, and crystallite size have been determined for control, 48‐hr hydrolysates, and (48 + 48)‐hr hydrolysates. The lateral order improvement need not be associated with selective dissolution of amorphous region. This was further varified by short duration hydrolysis. A sort of recrystallization process could be attributed to order improvement. The results are discussed to understand the fine structure of the crystalline region of the fibroin.
Investigation of the crosslinking efficiency of some additional curing polyimides
Authors: Dynes P. J. , Panos R. M. , Hamermesh C. L. 
Published: April 2003

AbstractThe thermal properties of a PMR (polymerization of monomer reactants) polyimide resin chain terminated with various reactive monomers has been studied. Vinyl groups appear as efficient as ethynyl in providing crosslinks that are more thermally stable than those resulting from nadic ester endcapping. Terminal nitrile groups were found to be unreactive. Evidence for the curing mechanism of these resins is presented from infrared, thermogravimetric, and liquid chromatographic analyses.
Halogenated polyethylenes as electron‐sensitive resists
Authors: Sikorski Ryszard T. , Gabryś Ryszard 
Published: April 2003

AbstractIrradiation of a layer of halogenated polyethylene with an electron beam at 10‐kV accelerating potential brings about crosslinking of brominated and chlorobrominated polyethylenes, but the chlorinated polyethylenes undergo either crosslinking or degradation, depending on the electron charge delivered. The limiting charge value which separates these two effects was found to be ca. 1 × 10−3C/cm2. The minimum useful dose was found to increase in the order brominated, chlorobrominated, chlorinated polyethylene.
Estimation of diffusion coefficients for trace amounts of solvents in glassy and molten polymers
Authors: Vrentas J. S. , Liu H. T. , Duda J. L. 
Published: April 2003

AbstractTwo methods based on the free‐volume theory of transport are developed for the estimation of diffusion coefficients for trace amounts of solvents in amorphous polymers. The first method uses diffusivity data for a polymer–solvent system above the glass transition temperature to estimate the temperature dependence of the mutual diffusion coefficient below this temperature. In the second method, mutual diffusion coefficients are estimated for a particular polymer–solvent system both above and below the glass transition temperature using no diffusivity data for the system. The predictions of the proposed theory are compared with diffusivity data for the n‐pentane–polystyrene and ethylbenzene–polystyrene systems.
Melt spinning of high‐impact polystyrene: Rubber morphology variations, orientation development, and mechanical properties
Authors: Omotoso M. A. A. , White James L. , Fellers John F. 
Published: April 2003

AbstractStudies of melt‐spun, high‐impact polystyrene filaments indicate that rubber globules are fragmented to smaller sizes with increasing drawdown ratio and spinline stress. The melt‐spun fibers are highly birefringent and obey the same relationship between birefringence and stress as pure polystyrene despite the presence of the rubber globules. These results are interpreted in terms of the stress distribution across the filament cross section. Room temperature tensil force–elongation curves were obtained on the filaments, and mechanical property phenomena were interpreted in terms of the above morphology changes and orientation of polystyrene chains.
Liquid crystal polymers. III. Preparation and properties of poly(ester amides) from p‐aminobenzoic acid and poly(ethylene terephthalate)
Authors: Jackson W. J. , Kuhfuss H. F. 
Published: April 2003

AbstractPoly(ester amides) with physical properties similar to those of liquid crystalline polyesters were prepared by acidolysis of poly(ethylene terephthalate) with p‐acetamidobenzoic acid and then polycondensation through the acetamido and carboxyl groups. The ester amide polymers had a random sequence distribution, contained some branching, and at low frequencies had relaxation times appreciably longer than those of poly(ethylene terephthalate). Because of the extended chain orientation of the polymer segments that contained p‐aminobenzoic acid (PAB) units, the mechanical properties of injection‐molded polymers containing 20–30 mole % PAB were anisotropic. The liquid crystalline characteristics and mechanical properties were further increased by incorporating p‐hydroxybenzoic acid units into the polymers.
Effect of nonionic surfactant and heat on selected properties of polyester
Authors: Needles Howard L. , Berns Roy S. , Lu Wen‐Chu , Alger Kenneth , Varma D. S. 
Published: April 2003

AbstractThe effect of heat treatment in the presence and absence of a nonionic surfactant (Triton X‐100) on selected properties of polyester fabric was studied over the temperature range 180–220°C. Although significant heat‐induced area shrinkage was evident (4.9–9.5%) in the treated polyester fabrics, stiffness, wrinkle recovery, tensile properties, moisture regain, and density of the fabrics showed only slight changes. The moisture‐related properties of surfactant/heat‐treated polyester were greatly improved compared to untreated control polyester or polyester subjected to heat treatment alone. Oligomer formation on the surface of surfactant‐treated polyester was altered as a result of the presence of surfactant on heating compared to polyester heated alone at 180–220°C. Polyester heat treated in the presence and absence of surfactant showed increased dye uptake and more depth of color with 1,4‐substituted anthraquinone dyes than untreated polyester, and these effects increased with increasing treatment temperature.
Dielectric loss microwave degradation of polymers: Cellulose
Authors: Allan G. Graham , Krieger Barbara B. , Work Donald W. 
Published: April 2003

AbstractThe pyrolysis of organic waste polymers to produce fuels and chemicals is of interest to augment petroleum‐based processes. The wide variety of pyrolysis products of low yield and the uncertain role that heat transfer rate plays in determining these have been deterrents to utilization in the past. A possible approach to increased selectivity for products is to heat them rapidly and homogeneously with the aim of narrowing the product distribution. A very rapid means of homogeneous heat transfer throughout the substrate is microwave heating. A laboratory study has been done to determine what effect high‐intensity microwave energy has on the thermal degradative pathways of cellulose. The product distribution found when cellulose is pyrolyzed in the absence of a microwave discharge is similar to that found in conventional furnace pyrolysis. The major products are levoglucosan (27%), carbon dioxide (2–5%), water, and charred residue. However, the total heat‐up and reaction times for even large pellets are reduced to less than 2–3 min when high‐intensity microwave irradiation is employed. Effects of pressure and microwave power are reported. Low external gas temperature also prevents secondary reactions.
Effect of temperature on creep fracture of polypropylene fibers
Authors: Takaku Akira 
Published: April 2003

AbstractThe tensile strength and ultimate strain of polypropylene fibers were measured by the creep fracture method at various temperatures. The tensile strength against time‐to‐break curves at various temperatures, which were plotted on log–log scales, were superposed by shifting the curves along the logarithmic time‐to‐break axis, and the composite curve of the tensile strength as a function of a reduced time to break was obtained. On the other hand, to construct the composite curve of ultimate strain from the ultimate strain against time‐to‐break curves at various temperatures, shifting the curves along the logarithmic ultimate strain axis was required in combination with shifting along the logarithmic time‐to‐break axis. The temperature dependence of the shift factor aT followed an equation of the Williams–Landel–Ferry (WLF) form. The volume fraction of free volume at the glass transition temperature and the coefficient of thermal volume expansion, which were calculated from the WLF coefficients determined for the polypropylene fibers, are almost the same as those known as “universal values” for amorphous polymers.
Novel polymer alloy membranes composed of poly(4‐vinyl pyridine) and cellulose acetate. I. Asymmetric membranes
Authors: Aptel Philippe , Cabasso Israel 
Published: April 2003

AbstractThe preparation of a novel asymmetric membrane cast from a homogeneous mixture of poly(4‐vinyl pyridine) and cellulose acetate is described. The two polymers were found to be compatible in the presence of Lewis acids, yielding hydrophilic homogeneous alloys when properly prepared. Asymmetric membranes were cast from a six‐component dope mixture containing chloroform, methanol, acetone, and formamide. The as‐cast solution, when coagulated in water at ambient temperature, yields a highly plasticized anisotropic matrix which solidifies into a glassy state as the chloroform slowly diffuses into the water. The membranes, following this stage, exhibit a semipermeable dense skin that produces high fluxes and salt rejections when tested in a high‐pressure reverse osmosis mode (no annealing is required). The anisotropic morphology was confirmed by scanning electron microscopy studies which revealed a dense skin resting on a highly porous, open‐celled foamlike structure. This structure does not collapse upon drying and retains its original wet dimensions. Brief attempts to quaternize the matrix are also reported.
Interpretive nonlinear viscoelasticity: Dynamic properties of nylon 6, nylon 66, and nylon 12 fibers
Authors: Prevorsek D. C. , Kwon Y. D. , Sharma R. K. 
Published: April 2003

AbstractNonlinear response of nylon 6, nylon 66, and nylon 12 fibers to sinusoidal straining under relatively large strain amplitude is analyzed in terms of the changes in properties during the straining, i.e., the change in modulus, change in internal friction and change in structure which involves energy release or absorption in straining. Modulus generally increases with strain but it decreases with increase of strain amplitude, the effect of strain amplitude being largest with nylon 6 and smallest with nylon 66. Mechanical loss increase with the increase of strain amplitudes in nonlinear manner, and the magnitude of change is largest with nylon 66 and smallest with nylon 6. During the extension phase, structural change occurring in nylon 6 is predominantly an increase in order or orientation while that with nylon 66 is crack opening or cavitation. Various aspects of the experiments and analysis of the data are described in detail.
Temperature dependence and energetics of the equilibrium sorption of water vapor in glassy polyacrylonitrile
Authors: Ranade G. , Stannett V. , Koros W. J. 
Published: April 2003

AbstractEquilibrium sorption isotherms for water vapor in commercial polyacrylonitrile film are presented. The data are discussed in terms of hte dual‐mode sorption model at low vapor activities with cluster formation occuring at higher activities. The film samples were treated by a two‐stage extraction process to remove a tenaciously held solvent present from the manufacturing process. Extraction of the residual had a minor effect on the equilibrium sorption of water in the film. The temperature dependence of the various sorption parameters is presented and discussed in detailed.
Simulated autohydrolysis of aspen milled wood lignin in the presence of aromatic additives: Structural modifications
Authors: Wayman Morris , Lora Jairo H. 
Published: April 2003

AbstractIn a previous article the authors have described changes in molecular weight which occur when aspen milled wood lignin is subjecte to autocatalyzed hydrolysis (autohydrolysis) in the presence of three aromatic additives: 2‐naphthol, resorcinol, and p‐hydroxybenzoic acid. In the present work, the reactions of these additives have been studied from the viewpoint of their effect on the structure of the lignin. The use of milled wood lignin instead of aspen wood served to distinguish those reactions between the additives and the lignin, without involving the other wood components. The reaction products have been charactrized by elemental analysis and UV and IR spectroscopy. It was concluded that keto groups, generated on the lignin side‐chain during autohydrolysis, condense with the additives, which become incorporated into the lignin. This occurs most probably through an aromatic eletrophilic substitution reaction. While 2‐naphthol condensed primarily with the β‐keto carbonyl groups, resorcinol attacked also the α‐keto carbonyl groups. When p‐hydroxybenzoic acid was the additive, its incorporation was accompanied by an increase in lignin carboxylic acid groups.
Polymerization of butadiene in toluene with nickel (II) stearate‐diethyl aluminum chloride catalyst. I. Catalytic behaviors
Authors: Lee Dong‐Ho , Hsu C. C. 
Published: April 2003

AbstractThe polymerization of butadiene with nickel (II) stearate–Et2AlCl catalyst has been studied in a batch reactor. The rate of polymerization is first order with respect to monomer and increases with the addition of water. In this system, no appreciable termination reaction has been found and the chain transfer to monomer dictates the molecular weight distribution of the polymer products. Molecular weight increases with conversion and water content. The cis‐1,4 content was found to be a function of the extent of polymerization.
Photochemical rupture of microcapsules: A model system
Authors: Mathiowitz E. , Raziel A. , Cohen M. D. , Fischer E. 
Published: April 2003

AbstractPolyamide microcapsules containing solutions of azo‐bis‐isobutyronitrile (AIBN) were prepared and characterized as regards diameter and wall thickness. Under UV irradiation the AIBN eliminates nitrogen, and this, under suitable conditions, leads to rupture of the capsules. The influence of capsular diameter and wall thickness of the crosslinking agent silane, of AIBN concentration, and of light intensity on the photoelimination and rupture were studied by determining rates of nitrogen release and by microscopic examination. The results are interpreted in terms of release of nitrogen in the core followed by diffusion of nitrogen or of core solution through the walls, or rupture of the microcapsules. The application to controlled photochemical release of contents is considered.
Poly(methyl methacrylate)–cellulose nitrate copolymers. I. Preparation
Authors: Badran B. M. , Sherif Sayed , Abu‐Sedira A. A. 
Published: April 2003

AbstractPoly(methyl methacrylate)–cellulose nitrate copolymers were prepared in the form of rods and sheets by bulk polymerization using benzoyl peroxide as initiator. Suspension polymerization did not succeed in preparing poly(methyl methacrylate)–cellulose nitrate copolymers, especially when cellulose nitrate of 11.4% nitrogen content was used. The parameters such as cellulose nitrate concentration, nitrogen content of cellulose nitrate, the amount of initiator and the reaction time, and the temperature are discussed. The prepared copolymers were irradiated for specified periods of up to 11.83 Mrad. It was found that poly(methyl methacrylate)–cellulose nitrate copolymers did not dissolve in any conventional solvent, but they swelled. Swelling decreases with increasing cellulose nitrate concentrations, nitrogen content of cellulose nitrate, and irradiation dose, indicating the crosslinked structure of the prepared copolymers.
Microbial attack of nitrocellulose
Authors: Brodman Bruce W. , Devine Michael P. 
Published: April 2003

AbstractThis is a study dealing with the use of a microorganism for partial denitration of the surface of nitrocellulose‐based small arms propellants, in order to gain burning rate control. An organism, Aspergillus fumigatus, was found to grow on pyroxylin suspended in a nitrogen deficient, carbon‐containing nutrient medium. No growth was observed under the same conditions when carbon was absent. This would indicate that the organism utilized nitrogen from nitrocellulose without attacking the carbon backbone. Further, mechanism studies indicated that the organism did not utilize the nitrogen directly from nitrocellulose, but rather relied on a hydrolysis reaction for a source of nitrogen.
Practical and theoretical molecular weights in polyaddition reactions of ethylene and propylene oxide
Authors: Penati Amabile , Maffezzoni Carlo , Moretti Enrico 
Published: April 2003

AbstractThe addition reactions of ethylene oxide and/or propylene oxide catalyzed by KOH and initiated with compounds containing free hydroxyls are followed by secondary reactions which vary the expected molecular weight. By using ethylene oxide, diols are formed and by using propylene oxide, both diols and unsaturated monofunctional compounds are formed. These products are usually characterized by their hydroxyl number. The average molecular weight is found by taking into consideration the starter functionality only. There are often some behavioral differences among similar products owing to the different quantity and chain length of the secondary products contained therein. The secondary products are analyzed and the quantity of the secondary products were determined from the hydroxyl number values and from the unsaturation of reagents and products. In the case of monofunctional adducts using the calculation method, the results have been experimentally confirmed.
Analysis of fatigue behavior of high‐density polyethylene based on dynamic viscoelastic measurements during the fatigue process
Authors: Takahara Atsushi , Yamada Kenji , Kajiyama Tisato , Takayanagi Motowo 
Published: April 2003

AbstractThe fatigue behavior of high‐density polyethylene was studied by measuring the variation in the dynamic viscoelasticity during the fatigue process. Brittle failure was observed under the conditions of small imposed strain amplitude, low ambient temperature, and large heat transfer coefficient to the surroundings. Ductile failure was observed under the conditions of large imposed strain amplitude, high ambient temperature, and small heat transfer coefficient to the surroundings. In the case of brittle failure, absolute value of dynamic complex modulus, ∣E*∣, showed maximum and phase difference, δ, did minimum on approaching the point of failure. In the case of ductile failure, ∣E*∣ decreased and δ increased monotonously from the start of the fatigue testing. The effect of environmental conditions on fatigue behavior was elucidated in terms of the heat transfer coefficient to the surroundings. As both forced convection of air and water enlarge the heat transfer coefficient, temperature rise of the specimen hardly occured and brittle failure took place preferentially. The coefficient, ϰ, was introduced to express the ratio of the actual generated heat to the hysteresis loss. With increase of the magnitude of the strain amplitude, the nonlinear viscoelastic behavior appeared and ϰ became smaller. A positive correlation between ϰ and lifetime was found. As the heat generation rate does not strongly affect lifetime, it was concluded that the hysteresis loss with low efficiency of heat generation would contribute to the fatigue failure. The relationship between average hysteresis loss and lifetime was proposed. The total hysteresis loss up to fatigue failure is constant, being independent of ambient temperature and imposed strain amplitude. The cumulative damage theory of fatigue failure was proposed based on hysteresis loss.
Investigations on nylon 4 membranes. Synthesis and transport properties. I. Synthesis of nylon 4 polymer
Authors: Huang R. Y. M. , Kim U. Y. , Dickson J. M. , Lloyd D. R. , Peng C. Y. 
Published: April 2003

AbstractThe synthesis of nylon 4 (polypyrrolidone) by the anionic polymerization of 2‐pyrrolidone through the use of the CO2/potassium pyrrolidonate catalyst system for use in preparing polymer membranes for separation purposes was investigated in detail. The effects of the quantity of CO2, the potassium pyrrolidonate catalyst, and the reaction temperature on the yield and molecular weights of the nylon 4 were studied. At reaction temperatures of 50°C and a reaction time of 120 hr, a yield of 50.9% with intrinsic viscosity of 4.42 (corresponding to Mn of 108,200 and Mw of 135,850) was obtained. The molecular weight distributions of the nylon 4 were determined by gel permeation chromatography (GPC) using m‐cresol as the eluting solvent and were found to have a relatively narrow distribution.