bluuebunny/crossref_metadata_2025 huggingface dataset:
Bonding elastomer layers together by a surface oxidation reaction
Authors: Chang R. J. , Gent A. N. , Hsu C. C. , Sehgal K. C.
Published: April 2003

An experimental study has been carried out of the self‐adhesion of thin layes of three crosslinked elastomers: cis‐polyisoprene (natural rubber) and two polybutadienes. For the polybutadiene materials, the strength of self‐adhesion was found to be strongly dependent upon the time of exposure of the two surfaces to air before they were brought into contact. The strength rose dramatically after the first hour or so of exposure so that in some instances the layers could not be forcibly separated later. When the surfaces were exposed to air for longer periods before joining them, the strength of self‐adhesion fell to low levels again. This remarkable enhancement in self‐adhesion, caused by prior exposure to air for short periods, did not take place on exposure to nitrogen or for samples of cis‐polyisoprene, and it was reduced or delayed in samples containing antioxidant. It is therefore attributed to surface oxidation reactions that can lead to the formation of interfacial covalent bonds with polybutadiene but not with polyisoprene. Some possible reaction schemes are discussed.
A VSE equation of state for liquids. VI. Polymethylene 450–650 K
Authors: Doolittle Arthur K.
Published: April 2003

This is the sixth and final paper in the series under the above title. In prior papers, a VSE equation of state was proposed and applied to a variety of liquids at ambient pressure, but over broad ranges of temperature. Comparisons of thermodynamic quantities calculated from the equation were made with published measured values. In the present paper v, α, s, γ, cv, and cp are calculated for polymethylene from our equations between 450 and 650 K, but extensive corresponding values have not been measured on polymethylene at these temperatures. One approximate value of cp and one value of γ, measured on high‐density polyethylene, show that our predicted values for polymethylene must be of the correct order of magnitude. Several characteristics of the liquid state, observed during the progress of this study (1954–1979), are listed and discussed.
Effect of nitrogen‐donor ligands on the stability of the photolysis products of Mn2(CO)10
Authors: Busetto C. , Mattucci A. M. , Cernia E.
Published: April 2003

The photolysis of Mn2(CO)10 in the presence of nitrogen donor ligands has been investigated in various solvents. The disproportionation reaction has been found to be strongly dependent on the solvent and on the temperature. The substitution of CO with the nitrogen donor ligand takes place on the anion Mn(CO)−5. The polymeric ligand poly(4‐vinylpyridine) manifests a stabilizing effect on the substitution product.
Fire‐retarding polypropylene with magnesium hydroxide
Authors: Miyata Shigeo , Imahashi Takeshi , Anabuki Hitoshi
Published: April 2003

Four types of magnesium hydroxide with different particle and crystallite sizes and different degrees of agglomeration were added at amounts up to 60% by weight to polypropylene to obtain a series of composites. The burning characteristics, tensile yield strength, flexural modulus, notched Izod impact strength, and melt flow index of the resulting composites were measured. Magnesium hydroxide coated with sodium stearate was found to give an increased melt flow index and impact strength to the composites as compared to values obtained with uncoated magnesium hydroxide. Incorporation of not less than about 57% by weight of magnesium hydroxide made the composite nonflammable, but at the same time considerably reduced its impact, flexural, and tensile yield strengths. As the amount of magnesium hydroxide filler was increased, the tensile yield strength and flexural strength of the composite proportionally decreased while the flexural modulus increased. The impact strength reached a maximum value when the amount of incorporation was 30% by weight. The lower the degree of agglomeration of the magnesium hydroxide filler and the greater the crystallite size within the range to about 2μm, the better were the mechanical properties of the composite.
Polymerization mechanisms and molecular weight distributions. III. Gamma‐radiation‐initiated polymerization of methyl methacrylate
Authors: Braks Jorma G. , Mayer Gunter , Huang Robert Y. M.
Published: April 2003

The termination mechanism in gamma‐radiation‐initiated polymerization of methyl methacrylate was investigated. The termination mechanism and the associated rate constants were determined by comparing the theoretical molecular weight distribution (MWD) and the experimental MWD, which was determined by gel permeation chromatography. Disproportionation occurs 1.2 times as frequently as combination at 30°C and 0.5 times as frequently at 0°C. The activation energy for disproportionation is 5.5 kcal/mole greater than that for combination. The rates of initiation were determined by a new method and were found to compare well with those reported in the literature. It is also suggested that it is necessary for the theoretical MWD to have the same shape as the experimental MWD before a mechanism can be authenticated.
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

Anionic/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

The 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

Four 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

The 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

Irradiation 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

Two 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

Studies 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

Poly(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

The 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

The 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

The 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

The 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

Nonlinear 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

Equilibrium 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

In 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

The 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

Polyamide 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

Poly(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

This 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

The 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

The 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

The 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.
Linear polythioesters. IV. The effect of hydrogen chloride acceptor on interfacial polycondensation of 4,4′‐di(mercaptomethyl) benzophenone with isomeric phthaloyl chlorides
Authors: Podkoscjelny Wawrzyniec , Kultys Anna
Published: April 2003

New polythioesters of better physicochemical and mechanical properties have been obtained by interfacial polycondensation of 4,4′‐di(mercaptomethyl)benzophenone with terephthaloyl, isophthaloyl, and phthaloyl chlorides with the use of sodium hydroxide excess as a hydrogen chloride acceptor. According to preliminary experiments, the best yield and the highest reduced viscosity are reached when the polycondensation at a 1:l ratio of the aqueous to the organic phase is carried out at a temperature of 5–7°C with a little excess of acid chloride with addition time of 0.5–2 min in the presence of 100% excess of NaOH as hydrogen chloride acceptor. The structure of the polythioesters was determined from elemental analysis and infrared spectra. Thermal properties of all polythioesters were determined. Mechanical and electrical properties of only the most interesting polythioesters obtained from isophthaloyl chloride were determined.
The functional role of molybdenum trioxide as a smoke retarder additive in rigid poly(vinyl chloride)
Authors: Lattimer Robert P. , Kroenke William J.
Published: April 2003

The most effective smoke retarders for poly(vinyl chloride) are compounds of transition metals, such as molybdenum trioxide. MoO3 when added to a rigid PVC compound shows three general effects. First, smoke formation is reduced dramatically as measured either by the NBS smoke chamber test or Goodrich smoke–char test. Second, volatile aromatic pyrolyzate formation is also reduced dramatically. The “pure” conjugated aromatic compounds (particularly benzene and naphthalene) are reduced more than the “mixed” aliphatic–aromatic compounds (such as toluene). Third, char formation is effectively promoted. Based on results from studying MoO3 (and other metal‐;based additives) in regular, perdeuterated, and syndiotactic PVC, we propose a “reductive coupling” scheme as the dominant mechanism to explain the smoke retarder action. In this mechanism the MoO3 acts in the condensed phase to promote extensive crosslinking of the PVC polymer chains very early in the thermal degradation process. Specifically, the metal additive forms a redox catalyst system which promotes intermolecular crosslinking of polymer chains to form char, rather than the conventional degradation process which gives rise to aromatics and smoke.
Numerical simulation of a tubular polymerization reactor
Authors: Lynch D. , Kiparissides C.
Published: April 2003

A mathematical model for a tubular emulsion polymerization reactor is developed. The partial differential equations describing the mass balances on initiator, monomer, and number of polymer particles are numerically solved using an implicit–explicit scheme based on the Crank–Nicholson method. The model adequately simulates experimental results reported by Rollin and co‐workers and sufficiently explains the unusual behavior of the reactor when operating at relatively low emulsifier concentrations.
Conduction in polydiacetylene bilayers
Authors: Day David R. , Lando Jerome B.
Published: April 2003

Surface active diacetylene monolayers were polymerized at the gas–water interface and bilayers formed from these layers were deposited onto lock‐and‐key devices. Samples exhibited intial conductivities on the order of 10−7 Ω−1 cm−1, which decayed at varying rates depending on sample composition to 10−11 Ω−1 cm−1. This initial space charge current was found to be strongly dependent on the presence of small amounts of water. A current increase was observed of over three orders of magnitude in some samples upon doping with iodine. Current flow decreased, however, back to original values after removal of the iodine. Polydiacetylene bilayers were also found to exhibit photo conductive current increases of over an order of magnitude.
Morphological changes in twisted nylon monofilament
Authors: Kurokawa Masataka , Nohara Nobuo , Konishi Takashi
Published: April 2003

The changes in structure of oriented nylon monofilaments due to an applied twisting action was investigated using wide angle x‐ray scattering analysis and microscopy. The surface layer of the twisted filaments changes to a single texture after being repeatedly twisted in one direction at high temperature. Simultaneously, kink bands were produced on their surface. Characteristic features of kink bands are observed on the surface layer of the filaments first twisted in one direction and then twisted in the opposite direction at high temperature. X‐ray diffraction patterns of the surface layer also changed remarkably. These changes in surface layers are related to the twist direction, the repeated number of twists, and the temperature of untwist. At lower temperatures, kink bands are not formed and a structural change to a single texture does not occur spontaneously.
Cation exchange resin from sulfonated N‐vinylcarbazole and divinylbenzene copolymer
Authors: Biswas Mukul , Mishra Girish Chandra
Published: April 2003

A copolymer of N‐vinylcarbazole and divinylbenzene has been sulfonated to yield a cation exchange resin of improved thermal properties compared to other vinylcarbazole‐based resins. The resin has been characterized by measuring its total and salt‐spliting capacities, pH metric titration, and thermal stability characteristics.
Enhancement of adhesive joint strength by surface texturing
Authors: Chang W. V. , Wang J. S.
Published: April 2003

Proper substrate preparation is an indispensible step for achieving strong adhesive joints. One consequence of such surface treatment is the enhancement of degree of mechanical interlocking between polymers and substrates, which, according to the literature, seems to increase the strength of the joint. A novel method based on photolithography is developed to texture aluminum oxide surface by controlling the pit size and its spatial distribution. Surface profile, surface physical chemical properties of this sample, and the lap shear strength of epoxy adhesive joints are compared with those of the phosphoric acid anodized (PAA) sample. It is shown that the lap shear strength of the textured sample is superior to that of the PAA sample. Surface profile data and mathematical analysis suggest that the inferiority of the PAA sample is probably due to the trapped air in the large pit in the surface resisting the penetration of adhesives. It also concludes that the high surface area provided by the multitude small pits in PAA sample is far from being fully utilized. This study opens up a new avenue to rationally improve the strength of adhesive joint by controlling the surface profile, the surface chemical properties, and the pressure during bond formation.
Influence of drawing speed on some properties of acrylic fibers
Authors: Stoyanov A. I. , Krustev V. P.
Published: April 2003

The effect of drawing speed on several properties of acrylic fibers has been examined. The acrylic fibers were prepared by the wet‐spinning process. The coagulation bath contained 30–70% DMF and was held at a temperature varying from 10–45°C. From x‐ray diffraction measurement, the orientation of finished fibers increased with an increase in drawing speed, and became constant when the drawing speed exceeded 40–50 m/min. The tenacity and stability to repetitive deformation also increased to a drawing speed of 40–50 m/min, but then decreased. The spinning conditions (spin‐bath composition and temperature) influenced the most attainable properties of the finished fibers. The results are discussed from the point of view of structural changes in fibers during drawing.
Application of a constitutive equation to polymer melts
Authors: Shroff Ramesh N. , Shida Mitsuzo
Published: April 2003

Yamamoto's integral constitutive equation in which the memory function is dependent on the second invariant of the rate of deformation tensor at past times has been found to be successful in predicting many of the nonlinear viscoelastic functions from the linear viscoelastic data for melts of linear polyethylenes, polypropylenes, and polystryene but not for those of branched polyethylenes with high level of long‐chain branching. A specific functional form for the rate‐dependent relaxation spectrum is used and is based on the physical meaning resulting from the molecular entanglement theory of Graessley on steady shearing flow. No arbitrary constant is involved in such an interconversion scheme. The data examined are dynamic storage modulus and loss modulus, steady flow viscosity, first normal stress difference, and parallel superimposed small oscillations on steady shear flow. The theory predicts that in such parallel superimposed experiments, storage modulus G′(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) divided by the square of frequency shows a maximum under finite shear and that G′(ω,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \dot \gamma } $\end{document}) would itself become negative at a frequency whose value is about one third the superimposed rate of shear. The experiments are in line with such predictions. Possible reasons for the failure of the theory for branched polyethylenes are considered, and a possible approach is suggested so that the interconversion scheme may be successful for such resins.
Adhesive properties of systems of partially neutralized carboxyl‐terminated liquid rubber–anhydride–bisepoxide
Authors: Matsuda Hideaki , Dohi Hidemi
Published: April 2003

Systems of partially neutralized carboxyl‐terminated liquid rubber (PNCTLR)‐anhydride–bisepoxide were evaluated for adhesive properties. The PNCTLRs were prepared by the partial neutralization with MgO and CaO from a polymer of butadiene (BD) (Hycar CTB 2000X162) and copolymers of BD–acrylonitrile (Hycar CTBN 1300X8 and CTBNX 1300X9). As the bisepoxide, bisphenol A diglycidyl ether was used, and hexahydrophthalic anhydride was the anhydride used. The adhesive properties of the metal‐containing systems were superior to those of the reference systems not containing metal, owing to the polarity effect of the metal carboxylate groups. Further, the CTBN‐ and CTBNX‐series systems showed higher tensile shear and peel strengths than the CTB‐series systems, owing to the enhanced polarity effect of the nitrile groups.
A study on hydroxyl groups in polyethylene
Authors: Sato Yukihiko , Hoshino Mitsutoshi , Ebisawa Fumihiro
Published: April 2003

The possibility of the presence of hydroxyl groups in polyethylene molecular chains has been investigated in observations of infrared spectra of OH and CO stretching vibrations in olefinic molecular chains. n‐Paraffins and fresh medium‐pressure process polyethylenes containing the primary alcohols were used as a model of polyethylene containing hydroxyl groups in the molecular chains. The characteristic wavenumber of the hydroxyl groups slightly contained in the polyethylene in the region 3600–3200 cm−1 becomes constant over about 10 of carbon‐atom number of the alcohols, approximately 3336 cm−1. The wavenumber does not agree with ∼3370 cm−1, which has been hitherto assigned to hydroxyl groups in polyethylene molecular chains. Although the absorption due to the hydroxyl groups must appear in the region of CO stretching band in the vicinity of 1050 cm−1 if the absorption around 3370 cm−1 is due to the hydroxyl groups, the absorption has not been observed. Changes in infrared spectra of polyethylene absorbing water as much as 10 ppm corresponding to the water absorbing capacity are not observed in comparison with those of extremely dried polyethylene. It is concluded that the absorption at 3370 cm−1 in polyethylene is not due to the hydroxyl groups and that the groups are not contained at least in fresh polyethylene.
Grafting of acrylate monomers onto chlorinated rubber
Authors: Kaleem K. , Reddy C. R. , Rajadurai S.
Published: April 2003

Grafting of chlorinated rubber with ethylacrylate and butyl methacrylate in xylene solution has been studied using benzoyl peroxide as the initiator. It is observed that the grafting reaction follows conventional kinetic behavior under the present experimental conditions. The energies of activation obtained for both monomers were 10.8 and 10.95 K.cals, respectively. The grafting efficiency and percent grafting were calculated. Additional proof for grafting onto chlorinated rubber was also obtained by characterization of the graft copolymer by gel permeation chromatography.
Ultradrawing of polystyrene by solid‐state coextrusion: Shear‐induced crystallization in isotactic polystyrene
Authors: Appelt Bernd , Porter Roger S.
Published: April 2003

Polystyrene with a 60% isotactic dyad content (iPS) was subjected to two‐stage solid‐state coextrusion at 124 and 160°C. It was shown that only shear‐induced crystallization occurred with the amount of crystallinity strongly dependent on draw ratio. The steep increase in crystallinity from 0 to 29% is accompanied by a marked increase in the absolute total birefringence from 0 to 30 × 10−3 and the tensile properties, from 2.5 GPa to 4.5 GPa, giving strong evidence for the necessity of a crystalline phase to achieve higher tensile moduli. Wide‐angle X‐ray scattering showed a higher crystal orientation for the extrudate produced at 124°C than for the one produced at 160°C. Thermal shrinkage experiments support a partial dissipation of orientation after extrusion at 160°C and on reextrusion in general. Electron microscopy revealed a fibrous nature for the solid‐state coextrudates produced at both temperatures.
Novel ion‐containing reverse osmosis membranes. II. Reverse osmosis properties
Authors: Bittencourt E. , Stannett V. , Hopfenberg H. B. , Williams J. L.
Published: April 2003

The reverse osmosis properties of ion‐containing membranes prepared by60Co mutual irradiation grafting of 2‐vinylpyridine to poly(3,3‐bis(chloromethyl)oxetane) (polyoxetane, Penton) followed by quaternization with methyl bromide are presented. In general, the volumetric fluxes varied linearly with pressures up to 55 atm. Katchalsky's treatment of membrane permeability was used to analyze the data. Membrane constants and diffusion coefficients of water and sodium chloride were determined with membranes containing different volume fractions of water. The diffusion coefficients of water in the membranes were of the same order of magnitude as the self‐diffusion coefficient of water (∼3 × 10−5cm2/s). The diffusion coefficients of sodium chloride in the membrane were of the order of 10−7cm2/s. The diffusion coefficients increased with hydration, and the salt rejections were markedly affected by the external salt concentrations. The apparent energies of activation for the volumetric flux were calculated in distilled water and in 0.5% sodium chloride solution.
Accelerated photo‐oxidation of polyethylene. II. Further evaluation of selected additives
Authors: Taylor Lynn J. , Tobias John W.
Published: April 2003

A number of additives previously observed to promote photo‐oxidative degradation of polyethylene films have been evaluated with respect to their relative photoinitiating effectiveness at wavelengths near 300 nm and their effects on thermal‐oxidative stability of polyethylene. Depending on the nature of the additive, the photo‐oxidation process may display autoretarding or autoaccelerating behavior. Thermomechanical analyses and gel content measurements on UV‐exposed films containing substituted anthraquinones suggest that at short exposure times, photo‐oxidative degradation is accompanied by photochemical crosslinking.
Chromic titanate catalysts for high‐melt‐index polyethylene by the particle‐form process
Authors: Hoff R. E. , Pullukat T. J. , Shida M.
Published: April 2003

A novel thermal activation procedure for ethylene polymerization catalysts made from silica, a chromium compound, and a titanium ester greatly increases the melt index of the polyethylene product under commericla polymerization conditions in comparison with conventional air activation. The novel activation has two steps. The first is heating under a reducing gas atmosphere (N2 + CO). The second step is partial oxidation at a lower temperature for a shorter time. The size of the melt index increase is related to the average oxidation number of the chromium, but oxidized chromium can be reduced and the effect persists with less intensity. Additionally, the magnitude of the effect is dependent upon gas flow rates during activation and prior chemical and thermal history of the chromium–silica combination. Since titanium is required for the two‐step activation to be effective in increasing melt index, titanium atoms have a critical influence on the catalyst active sites. An experiment with tetraethoxysilane added to the catalyst shows that titanium and chromium atoms must be next nearest neighbors (separated by oxygen atoms).
Selective permeability of PVA membranes. I. Radiation‐crosslinked membranes
Authors: Katz Moshe G. , Wydeven Theodore
Published: April 2003

The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution–diffusion model for transport across the membranes, in which pressure‐dependent permeability coefficients are employed.
Initial flux and rejection characteristics of partially permeable ultrafiltration membranes
Authors: Waters A. G. , Fane A. G.
Published: April 2003

Solutions of bovine serum albumin (BSA) were ultrafiltered with and without stirring through membranes partially permeable to the solute, over a range of pH values. At the isoelectric point, flux was a minimum and rejection was a maximum. For all conditions, the flux for stirred ultrafiltration was greater than without stirring, as expected from conventional theory, and in contrast to recently reported “anomalous” behavior measured at the isoelectric point. Some evidence of unusual behavior at the isoelectric point was obtained when the flux of a freshly ultrafiltered solution of BSA was compared to that when the permeate and retentate were recombined, and when the retentate concentration was adjusted to the original concentration. For pH values other than the isoelectric point, the fluxes were similar for each set of experiments. At the isoelectric point, it was also found that flux was insensitive to changes in stirring speed. The unusual behavior at the isoelectric point is attributed to protein aggregation and precipitation causing loss of membrane permeability.
Diffusion coefficient measurements by solvent absorption in concentrated polymer solution
Authors: Hansen Charles M.
Published: April 2003

Diffusion coefficient measurements for solvents in concentrated polymer solutions require consideration of both concentration dependence of the diffusion coefficient and surface resistance to mass transport. Solutions to the diffusion equation have been generated where these effects are explored. A method to account for both concentration dependence and surface (absorption) resistance in the experimental determination of diffusion coefficients is given and demonstrated with an example where a multiplying factor of over 300 is required to adjust the apparent diffusion coefficient to the value sought.