bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible plasticization of nylons 6 and 11 with anhydrous ammonia and their deformation by solid‐state coextrusion
Authors: Zachariades Anagnostis E. , Porter Roger S. 
Published: April 2003

AbstractReversible plasticization of nylons with anhydrous ammonia is a new concept. In the present studies, nylons 6 and 11 have been plasticized with anhydrous ammonia and subsequently were solid‐state coextruded below the melting point. The plasticization is attained by a temporary disruption of the strong hydrogen bonding between amide groups of adjacent nylon chains. Thermogravimetric and infrared analysis show that for the nylons 6 and 11 the amount of ammonia absorbed is 18% and 10% of the weight of the dry samples, respectively. The ammonia incorporation to preformed nylon ribbons prior to extrusion alleviated significantly the processing difficulties encountered with untreated nylons and aided the rapid extrusion of highly oriented states (EDR 12). The extent of orientation is documented by the high total birefringence values (8.25 × 10−2 for nylon 6 and 5.8 × 10−2 for nylon 11), by the significant increase in crystallinity (23.5%–53% for nylon 6 and 25.7%–40% for nylon 11), and by the enhanced tensile moduli (13 GPa for nylon 6 and 4 GPa for nylon 11).
Block copolymers obtained by free‐radical mechanism. I. Methyl methacrylate and styrene
Authors: Piirma Irja , Chou Lee‐Pei H. 
Published: April 2003

AbstractBlock copolymers were synthesized using styrene and methyl methacrylate as the monomers and a multifunctional initiator, di‐t‐butyl 4,4′‐azobis(4‐cyanoperoxyvalerate). The unique feature of this sequential initiator is the fact that the formation of the free radicals can be achieved thermally and/or by a redox system at different stages. The polymerizations for the formation of the block copolymer were carried out in two stages. First, a polymeric initiator was synthesized, which was then used in the second stage to initiate the polymerization of the second monomer. Styrene and methyl methacrylate were used as the comonomers. Selective solvent fractionation was used for the separation of the block from the homopolymers. The separation technique was found to be efficient, giving pure block copolymers which could subsequently be characterized by GPC, NMR, IR, and EM techniques.
Release rate characteristics of microencapsulated 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine
Authors: Noren G. K. , Korpi G. K. , England G. J. 
Published: April 2003

AbstractThe rate at which 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine (TMP) is released from a microcapsular controlled delivery device was determined using aqueous methanol as an extraction medium. The microcapsules were prepared by in situ polymerization of a urea–formaldehyde resin. Release rate studies demonstrated that the amount of 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine released is proportional to t−1/2 and the solubility of 2,3,5,6‐tetrachloro‐4‐methylsulfonylpyridine in the extraction medium. These relationships are characteristic of a porous, monolithic delivery system.
Copolyester studies. V. Preparation and characterization of tetramethylene terephthalate–poly(tetramethylene oxide) random block copolymers
Authors: Boussias C. M. , Peters R. H. , Still R. H. 
Published: April 2003

AbstractRandom block copolymers of tetramethylene terephthalate and polytetrahydrofuran (PTHF) were prepared by melt polycondensation. Five different molecular weights of PTHF were used in the polymerizations with up to 30% by weight incorporation. The copolymers so obtained were characterized in terms of their molecular weight by means of endgroup analysis and solution viscometry. Compositions were established by nuclear magnetic resonance spectroscopy. Thermal properties were studied by differential scanning calorimetry and dynamic mechanical methods. Melting and glass transition temperatures are discussed in terms of the structural differences, particularly the effect of polyether composition and block size on chain flexibility.
Stabilization of poly(vinyl chloride). V. Synergism between metal soaps and polyols upon stabilization of poly(vinyl chloride)
Authors: Iida Takeo , Gotō Kunio 
Published: April 2003

AbstractThe marked discolorations observed on aged poly(vinyl chloride) (PVC) containing synergetic metal soaps, in the early heating stage, were due to the excessive coloration of π complex of metal chloride and double bonds in the polyene chain. These excessive colorations were inhibited by masking the excessive metal chloride with some masking agents, thereby slowing down the abrupt discoloration of PVC. In this paper, the masking effect of various alcohols such as 1,2‐butanediol, 1,3‐butanediol, 1,4‐butanediol, 2,3‐butanediol, hexylene glycol, glycerol, 1,2,4‐butanetriol, trimethylolethane, trimethylolpropane, meso‐erythritol, pentaerythritol, sorbitol, and dipentaerythritol is investigated. The polyhydric alcohols, except dihydric alcohols, showed superior masking effect and markedly improved the thermal stabilization effects of synergetic metal soaps. The mechanism for the synergetic effects between polyols and metal soaps should be based on the masking effect of polyols, owing to the formation of the colorless complex of polyols with excess metal chlorides obtained from the metal soap.
Hydrophilic behavior of HSPAN/PVA membrane
Authors: Turner John E. , Shen Mitchel , Lin Chen‐Chong 
Published: April 2003

AbstractThe hydrophilic behavior including water absorption, swelling, and dielectric spectrum of pure HSPAN as well as HSPAN/PVA blends are investigated. The HSPAN/PVA membranes still absorb a considerable amount of water. The effect of water upon mechanical properties is also investigated for these membranes. Formalization of membrane enhances mechanical properties and reduces weight losses during swelling with much loss in the water absorption ability of PVA. This kind of blend shows promise as material for hydrophilic membranes.
Characterization of a new composite material: Fe2O3‐impregnated poly(tetrafluorethylene). Particle size determination and photoacoustic spectroscopy
Authors: Galembeck F. , Ghizoni C. C. , Ribeiro C. A. , Vargas H. , Miranda L. C. M. 
Published: April 2003

AbstractIron carbonyl sorption in PTFE, followed by in situ oxidation, gives the composite material, iron oxide–PTFE. Oxide particle size determination was performed by electron microscopy. The particles were found to be nearly spherical and very small, having diameters in the 30–40 Å range on average. Optical absorption spectra were obtained by photoacoustic spectroscopy, and their intensities show a complex dependence on iron oxide concentration in the samples.
Study on the graft copolymerization of lignosulfonate and acrylic monomers
Authors: Chen R. , Kokta B. V. , Valade J. L. 
Published: April 2003

AbstractGraftings of acrylonitrile and methyl methacrylate onto lignosulfonate were studied, respectively, with and without the lignosulfonate ozonized. Copolymerization was redox‐initiated by peroxideferrous ions. Monomer conversion and grafting efficiency depended essentially on reaction medium and the maount of peroxide charged. Among the media employed, the magnitude of the medium effect on conversion was found to be in the following order: water, dioxane, and methanol. The conversions in water of acrylonitrile and methyl methacrylate were 55 and 90%, respectively, when using 3% hydrogen peroxide. Beyond this 3 % charge, both the grafting efficiency and the degree of lignosulfonate grafted approached certain limits. Ozonization appeared to be capable of stimulating the active centers in lignin macromolecules, whereon acrylic monomers could be grafted. Better grafting efficiency was obtained with the ozonized lignosulfonate.
Metal acetylacetonates as latent accelerators for anhydridehyphen;cured epoxy resins
Authors: Smith J. D. B. 
Published: April 2003

AbstractTwenty‐two metal acetylacetonate compounds have been evaluated as possible latent accelerators for epoxy‐anhydride solventless resins. Experimental data have revealed that titanium (IV) oxyacetylacetonate, chromium (III), zirconium (IV), cobalt (III), and cobalt (II) acetylacetonates are particularly effective with anhydride cured epoxy resins. When added to the resin at a level of 0.05–0.10% (w/w), they provide very fast gel times at 150–175°C combined with very good storage stabilities (> six months) at room temperature. The power factor values of cured resin samples, containing these preferred metal acetylacetonates, have been found to be between 2.0 and 2.5% at 150°C and 60 Hz. Correlation between the catalytic effectiveness of these metal acetylacetonates, as latent accelerators for epoxy‐anhydride resins, and their thermal stabilities suggest that decomposition products may be the active species responsible for initiating polymerization in epoxyanhydride resin systems.
Prediction of rheological behavior of branched polyethylene from molecular structure
Authors: Bersted B. H. , Slee J. D. , Richter C. A. 
Published: April 2003

AbstractThe general description of steady shear melt viscosity as a function of shear rate for polyethylene, containing any level of long chain branching, in terms of molecular structure is reported. A model, developed previously by B. H. Bersted for the prediction of rheological properties from the molecular structure of linear materials, and which has been subsequently modified by Ram and Pedersen for application to highly branched low‐density polyethylene, is extended to describe the flow behavior of branched high‐density polyethylene. The description of the branched high‐density polyethylenes, which characteristically show dramatic viscosity enhancement relative to linear polyethylene, is effected by considering these materials to be blends of branched and linear species. A logarithmic rule of mixtures was found adequate at all shear rates for the description of blends of branched and linear materials.
Effect of concentration and second polymer on elution volumes in gel permeation chromatography
Authors: Narasimhan V. , Huang R. Y. M. , Burns C. M. 
Published: April 2003

AbstractShifts have been observed in the elution volumes of solutions of polystyrene, polybutadiene, and mixtures of the two in gel permeation chromatography using tetrahydrofuran as solvent. Such shifts are examined in terms of the effect on the hydrodynamic volumes of concentration, of molecular weight, and of the presence of an incompatible polymer. Suitable concentration ranges to minimize these shifts have been found.
Push–pull extrusion: A new approach for the solid‐state deformation illustrated with high density polyethylene
Authors: Shimada Toshio , Zachariades Anagnostis E. , Watts Michael P. C. , Porter Roger S. 
Published: April 2003

AbstractThe crystalline state deformation of high density polyethylene has been examined at an extrusion draw ratio of 30 over a range of temperatures and pressures. The experiments involve combined pushing (extrusion) and pulling through a conical die. The pressure dependence of the extrusion rate through conical dies is given by a logarithmic relation and the temperature dependence by an activation energy of ∼95 kcal/mole. An equation established for the total applied force linearly relates the pulling and extrusion pressure components and represents a force balance at the die entrance and exit. Steady‐state extrusion, with or without pulling, was feasible in a pressure range beyond which fractures occurred owing to strain rate and shear or tensile failure. Under some circumstances the extrusion rate was increased by ten times. The mechanical properties and mode of deformation were not affected by pull load and fibers with a tensile modulus of 55 GPa were produced at T < 110°C.
Emulsion polymerization of styrene with ionic comonomer in the presence of methanol
Authors: Chonde Y. , Krieger I. M. 
Published: April 2003

AbstractSoap‐free emulsion polymerization of styrene with sodium vinylbenzyl sulfonate (NaVBS) was studied in the presence of water–methanol mixtures. In the presence of both methanol and NaVBS, the particle size and uniformity increased with methanol content. Increasing the concentration of NaVBS decreased the particle size. Initiator and electrolyte level had similar effects on particle size as in recipes prepared in aqueous medium.
Investigations on nylon 4 membranes: Synthesis and transport properties. II. Transport properties of nylon 4 polymer membranes
Authors: Huang R. Y. M. , Kim U. Y. , Dickson J. M. , Lloyd D. R. , Peng C. Y. 
Published: April 2003

AbstractThe reverse osmosis, ultrafiltration, and dialysis properties of nylon 4 membranes to separations of sodium chloride, urea, a series of ethylene glycols and other compounds in the aqueous phase were investigated. The nylon 4 membranes were prepared from a formic acid solution with and without organic or inorganic additives. The effects of polymer concentration, amount of additives, casting time, and temperature on the membrane performance in terms of salt separation and product rate were investigated. The tensile properties of the nylon 4 membranes in both the dry and wet states were determined. It was found that the highest salt separation of a 0.1% sodium chloride solution did not exceed 53.3%. However, these membranes showed some intersting dialysis properties which were comparable to those of commercial cellophane and cellulose acetate membranes.
Onset of phase separation in segmented urethane polymerization
Authors: Castro J. M. , López‐Serrano F. , Camargo R. E. , Macosko C. W. , Tirrell M. 
Published: April 2003

AbstractThe development of heterogeneous structure during the polymerization of a polyurethane system using a polyether diol of M̄n = 2000 as the soft segment and 4,4′‐diphenylmethane disocyanate extended with 1,4‐butanediol as the hard segment was monitored following the amount of light transmitted by the sample and the increase in viscosity of the reacting mixture. The amount of light transmitted by the reacting sample was observed to decrease sharply at a given point in the reaction. The cloud point was taken as the onset of phase separation in the system and the number average sequence at this point was found to be fairly constant at about 1.3 independent of reaction temperature and system composition. In many cases, the cloud point occurred at quite low conversion, meaning that a significant amount of subsequent polymerization occurs in a heterogeneous medium. It was also found that the viscosity of the material reached very large values at partial conversions of the monomers and presented throughout the reaction values larger than those expected from an increase in molecular weight alone. Viscosity is apparently sensitive to a different aspect of the phase separation process than the light transmission.
Hydrolytic stability of some uncured epoxy resins
Authors: Pearce P. J. , Davidson R. G. , Morris C. E. M. 
Published: April 2003

AbstractThe hydrolytic stability of triglycidyl(4‐aminophenol) (ERL 0500), tetraglycidyl(methylenedianiline) (MY720), and a number of model compounds has been investigated. It has been shown that at 60°C and 96% relative humidity undiluted N‐glycidyl aromatic amine‐based epoxy resins readily undergo hydrolysis followed by homopolymerization. Impurities in the resin may significantly accelerate the rate of reaction. The effect of the consequent loss of epoxide on the performance of an adhesive based on ERL 0500 has been studied. The high‐temperature tensile‐shear strength of Joints was markedly reduced when the adhesive was aged, before cure, for 24 hr at 60°C and 96% relative humidity. Some implications of these findings for aerospace applications of epoxy compounds are discussed.
Structure‐property relationships of an electron beam cured model urethane prepolymer
Authors: Joseph Eugene , Wilkes Garth , Park Kisoon 
Published: April 2003

AbstractA semicrystalline urethane prepolymer derived from polycaprolactone was crosslinked below and above the melt to different levels using electron beam radiation. Studies at room temperature on the systems crosslinked under ambient conditions, which is below the melting temperature, show that changes in mechanical properties which occur as the electron beam dose is increased are due principally to the increase in crosslink density and to the changes in the crosslinking mechanism. Specifically, crosslinking takes place mainly at the acrylate double bonds or may also occur along the polymer backbone. All systems, however, are semicrystalline and possess a spherulitic texture. Mechanical and rheo‐optical testing above the melt on these same systems indicate that at extensions up to 125% classical rubber elasticity theory and photoelasticity theory is obeyed. Isothermal crystallization kinetics measurements show that the rate of crystallization decreases as the electron beam dose is raised. When the systems are crosslinked above the melt again a spherulitic texture results. Mechanical testing above the melting temperature on the prepolymer crosslinked up to 4 Mrad shows that at elongations up to 125% classical rubber elasticity theory is obeyed. At room temperature these latter crosslinked systems exhibited a lower modulus compared to the materials crosslinked below the melt. Polarizing optical microscopy carried out above the melting temperature strongly suggested that no order was present in these systems during crosslinking in contrast to those crosslinked below the melting temperature.
Dry etching durability of positive electron resists
Authors: Harada Katsuhiro 
Published: April 2003

AbstractThe effects of positive electron resist structures and G values for scission on dry etching durability have been studied with regard to plasma etching, reactive sputter etching, and plasma ashing. Polymers of aromatic methacrylates, especially poly(α‐methylstyrene), all of which contain a benzene ring in the side chain, exhibit superior durability for each etching system. On the other hand, polymers of fluorinated and chlorinated methacrylates show low durability compared with the nonsubstituted polymethacrylates. In addition, they vary in durability with respect to the etching gas used. The sputtering effect which is induced by ion bombardment in flat bed‐type reactors produces a significant loss in thickness of positive resists. Rough correlations between dry etching rates and Gs(scission) as the indication of sensitivity were obtained. The large dispersion of the correlations implies the possibility of more useful positive electron resists of high durability and high sensitivity.
Thermal and pulse NMR analysis of water in poly(2‐hydroxyethyl methacrylate)
Authors: Sung Y. K. , Gregonis D. E. , John M. S. , Andrade J. D. 
Published: April 2003

AbstractHydrophilic three‐dimensional methacrylate polymer networks (hydrogels) were prepared from 2‐hydroxyethyl methacrylate (HEMA) monomer and tetraethylene glycol dimethacrylate (TEGDMA) as crosslinker. The nature and states of water in these hydrogels were studied by differential thermal analysis and pulse NMR relaxation spectroscopy. The thermal studies showed no endotherm peak for ice melting in the lower water content (bound water region); there are two endotherms peaks for higher water content hydrogels near 0°C. The amounts of bound water, intermediate water, and bulklike (free) water in the hydrogels were determined from a quantitative analysis of the endotherms of the water melting transitions. The water structure ordering in the hydrogels were discussed in terms of the fusion entropy and enthalpy obtained from the endotherm. Nuclear magnetic relaxation spectroscopy was also used to understand the mobilities of the water protons in the hydrogels and the interaction of water molecules with the gel networks. The measured spin‐lattice relaxation time (T1) values for water protons in the hydrogels are greatly reduced compared to that of liquid water. The measured values of spin–spin relaxation times (T2) of water protons in the hydrogels are approximately 10 times less than that of T1 and are almost constant in the region of bound water content. Beyond the bound water content region in the hydrogels, the T2 values rapidly increase as the water content increases.
Low‐density polyethylene filled with chalk and liquid modifier
Authors: Kaliński R. , Galeski A. , Kryszewski M. 
Published: April 2003

AbstractBased on the concept of introducing a liquid layer between the polymer and filler, a composition containing low‐density polyethylene, chalk, and oligomer of ethylene oxide was proposed. Compositions containing up to 50% chalk modified with ethylene oxide exhibit typical thermoplastic behavior, i.e., neck formation and plastic deformation. They also show high‐impact strength and other good properties. On the basis of mechanical data, the main action of the ethylene oxide oligomer in the system is to inhibit crack generation and propagation.
Three‐stage interaction of dimethyl phthalate, dibutyl phthalate, and poly(vinyl acetate) with poly(methyl methacrylate)
Authors: Olayemi J. Y. , Oniyangi N. A. 
Published: April 2003

AbstractThe interaction of dimethyl phthalate (DMP), n‐dibutyl phthalate (DBP), and poly(vinyl acetate) (PVAc) with poly(methyl methacrylate) (PMMA) was studied. Changes in the tensile strength, elastic modulus, and percentage elongation at break of the PMMA‐additive films produced were followed using the Instron testing machine. The three additives produced (1) an initial plasticization, with a decrease in tensile strength and modulus and a possible increase in elongation; (2) an antiplasticization, with accompanying increase in tensile strength and modulus and an anomalous increase in elongation; and (3) a final plasticization, with a marked decrease in tensile strength and modulus and a definite increase in elongation of PMMA. The three effects were influenced by the molecular weight of the PMMA. A spacer effect by the interposition of the molecules of the additives between those of PMMA is proposed for the initial plasticization, while for the final plasticization, a lubrication action of the plasticizers on PMMA is suggested. Antiplasticization is explained by the formation of secondary bonds between the antiplasticizer and the PMMA molecules.
Photochemical grafting of acrylated azo dyes onto polymeric surfaces. V. Grafting of some acryloxy‐substituted aromatic diazenes as model molecules onto polypropylene, polycaprolactam, and poly(ethylene terephthalate) films
Authors: Calgari S. , Selli E. , Bellobono I. R. 
Published: April 2003

AbstractPhotochemically induced grafting (1) and graft polymerization (2) from N,N‐dimethylformamide solutions of four acryloxy‐substituted aromatic diazenes, chosen as model molecules of acryloxy azo dyes, were investigated kinetically at 25°C onto polypropylene, polycaprolactam, and poly(ethylene terephtalate) films, by polychromatic irradiations. Quantum efficiencies at zero concentration of dyes and lifetimes of excited states for processes (1) and (2) were evaluated from experimental data by Stern–Volmer plots. The surface density of grafted molecules at the end of process (1) was not affected by the concentration of dyes in solution, but varied sensibly with the chemical nature of polymers and dyes. The relevant parameters are discussed on the basis of the proposed mechanism.
Removal of mercuric ions by systems based on cellulose derivatives
Authors: Tashiro Tatsuo , Shimura Yukio 
Published: April 2003

AbstractA few cellulose derivatives were prepared by the reaction of chlorodeoxycellulose (CDC) with ethylenediamine (ED), thiourea, thiosemicarbazide, thioacetamide, and others. These derivatives were found to be able to remove mercuric ions to an extent greater than 99% from a 10 ppm aqueous solution of mercuric chloride. For example, thiocellulose obtained by reacting CDC with thiourea and subsequently hydrolyzing it showed such good removal in the batch and continuous removal tests which involved passing the solution through a column packed with this cellulose derivatives.