bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation, structure, and properties of copolyester‐ether elastic filaments
Authors: Richeson G. C. , Spruiell J. E. 
Published: April 2003

AbstractElastic filaments have been produced by melt spinning poly(tetramethylene terephthalate)/poly(tetramethylene ether glycol)‐terephthalate (PTMT/PTMEG‐T) copolymers of various hard segment contents (HSC). Some of these copolymers are difficult to spin because of their elastic nature and sluggish crystallization kinetics. Differential scanning calorimetry studies show that both the crystallization rate and temperature decrease as HSC decreases. When spinning into air, the filaments low in HSC do not crystallize on‐line and are too tacky and soft to be taken up with a conventional constant tension winder. The elastic nature of these filaments prevents them from being taken up at speeds high enough for “stress‐induced crystallization” to cause appreciable crystallization on‐line. Spinning into a water bath allows the filaments to be taken up without a “sticking” problem. The microstructure and mechanical properties of the water‐quenched filaments were found to be strongly dependent on composition and processing conditions. Small‐angle and wide‐angle x‐ray techniques (SAXS and WAXD) indicate that the hard segment domains are lamellar‐like crystallites which become preferentially oriented perpendicular to the fiber axis at high spin‐draw ratios. As HSC decreases, the lamellae become more widely spaced. High levels of crystalline orientation can be produced using the water quench technique without creating appreciable levels of amorphous orientation. These are desirable features for obtaining high elastic recovery. Birefringence results indicate that these filaments continue to crystallize for up to 10 minutes after spinning. The relative degree of phase separation (DPS) decreases as HSC increases, but the actual level of crystallinity exhibits a maximum with respect to composition. Not coincidentally, the filaments that reach the highest crystallinity are the easiest to spin. The modulus of these filaments depends primarily on HSC and DPS, while the tenacity and ultimate elongation depend more on the degree of orientation developed during spinning. Elastic recovery increases as HSC decreases and as crystalline orientation increases.
Fluorine‐containing photoreactive polyimide. II. Preparation and properties of self‐sensitized polyimide precursors
Authors: Omote Toshihiko , Guo‐jin  , Koseki Ken'ichi , Yamaoka Tsuguo 
Published: April 2003

AbstractTwo series of polyimide precursors that have benzophenone(BP) segments in addition to methacryloyl groups and perfluoromethyl groups in the main chain are described. These fluorinated polyimide precursors offered remarkable improvement in solubility in common organic solvents and self‐sensitivity at 365‐nm light (i‐line). It was also found that the sensitivity is extremely enhanced by the aid of a small amount of photoinitiators, and the effective initiators for sensitivity enhancement were different for each series of the precursors. These self‐sensitized polyimide precursors offered high resolution with good pattern profile of aspect ratio over 1.5. The temperatures for 10% weight loss of the imidized films were nearly 500°C from thermogravimetry analysis (TGA), indicating high thermal stability.
Melt transesterification of diphenyl carbonate with bisphenol a in a batch reactor
Authors: Hersh S. N. , Choi K. Y. 
Published: April 2003

AbstractThe kinetics of the melt transesterification of diphenyl carbonate with 4,4‐dihydroxydiphenyl‐2,2‐propane has been studied in a batch reactor with LiOH · H2O as a catalyst in the temperature range of 150–180°C. The third‐order forward and backward rate constants were determined experimentally and a linear dependence of the transesterification rate on the catalyst concentration was observed. The product oligomer concentration distribution has also been measured experimentally and estimated by the molecular species model which describes the progress of the melt transesterification.
Oxygen permeation in SBS‐g‐VP membrane and effect of facilitated oxygen carrier
Authors: Yang Jen‐ming , Hsiue Ging‐ho 
Published: April 2003

AbstractThe grafting of 4‐vinyl pyridine to styrene‐butadiene‐styrene triblock copolymer by radiationinduced graft copolymerization was studied. The membranes of various degrees of grafting were prepared by the solution casting method. The effect of grafting degree and operating temperature on membrane gas permeability were investigated. The effect of (N,N′‐disalicylideneethylenediamine)cobalt(II) [CoS] on oxygen permeation through the SBS‐g‐VP membrane containing 10 wt % CoS was also studied.
Investigations concerning dissolution and swelling of polymethacrylonitrile in organic liquids
Authors: Schlegel Leo , Schnabel Wolfram 
Published: April 2003

AbstractThe interaction of various liquids with polymethacrylonitrile (PMCN) was investigated with respect to their ability of acting as solvent or soaking agent. The extent of interaction with the polymer solvents were classified on the basis of the following characteristics—Category A liquids: UA, the rate of dissolution, is determined by Vrept, the rate of reptation. A swollen surface layer is formed during dissolution of polymer films. VA increases with decreasing Mw, the weight average molecular weight. Category B liquids: VA is determined by Vsolv, the rate of solvation. A swollen surface layer is not formed during dissolution of polymer films. VA is independent of Mw. Category C liquids: They are incapable of dissolving but capable of soaking PMCN. Penetration of polymer films is characterized by features typical of CASE II sorption—a sharp step‐wise penetrant profile proceeding with constant velocity Vsorp. Dissolution and soaking tests with X‐ray irradiated PMCN films carried out in category B or C liquids, respectively, revealed the importance of morphological properties regarding the rate of dissolution and sorption, respectively. The observed increase in VA and Vsorp with increasing exposure dose was concluded to be due to the radiation‐induced increase in free volume rather than to the decrease in Mw.
Analytical solution of reversible step growth polymerization in semibatch reactors
Authors: Kumar Anil , Khanna Ashok 
Published: April 2003

AbstractWe have developed an analytical solution of reversible step growth polymerization in semibatch reactor with condensation product flashing. We have shown that the MWD of the polymer formed has Flory distribution, unaffected by flashing of condensation product, if the feed to the reactor is either pure monomer or has most probable MWD. We have determined analytical expression for the time when the evaporation of condensation product starts. Assuming the vapor liquid equilibrium (VLE) is given by Raoult's law (as well as the Flory–Huggins relation) we have determined the number and weight average chain lengths. We have subsequently analyzed the polycondensation step of the formation of polyethylene terephthalate and determined the effect of temperature and pressure on the course of polymerization.
Structural features of cellulosic change in alkali‐treated jute stick: An infrared absorption study
Authors: Reddy S. S. 
Published: April 2003

AbstractThe cellulosic change has been discussed in terms of absorption ratio of certain infrared bands. It is shown that the absorption of O—H and C—H stretching frequencies decreases up to 25% alkali treatment and the absorption of β‐glucosidic band increases with increasing alkali strength in swelling. The anomalous behavior in the absorption of these bands at 18% alkali treatment might be due to partial mercerization. A new type of hydrogen bonding is proposed where C6 hydroxyl groups are involved in a bifurcated six‐membered hydrogen bonding system giving more crystalline nature to mixed lattice of cellulose. The O2 hydroxyl proton forms hydrogen bond with O3 of the same unit and with O'2H of its antiparallel chain. It is also noted that the presence of lignin has no significant effect on cellulosic transition.
An infrared spectroscopic study of molecular orientation in heat‐set poly(ethylene terephthalate) yarn using attenuated total reflection technique
Authors: Jain A. K. , Gupta V. B. 
Published: April 2003

AbstractThe attenuated total reflection (ATR) technique has been used to obtain infrared spectra of heat‐set poly(ethylene terephthalate) (PET) fibers. The trans and gauche content have been estimated from the absorbances of the trans band at 1342 cm−1, the gauche band at 1370 cm−1, and the internal standard band at 1410 cm−1. The trans orientation, as calculated from the dichroic ratios of the absorption bands at 1342, 972 and 846 cm−1, shows a decreasing trend with an increase in heat‐setting temperature. The overall molecular orientation, as calculated from the absorption bands at 1410 and 875 cm−1, also decreases slightly with an increase in heat‐setting temperature. The infrared data, in combination with X‐ray data, have been used to calculate the amorphous orientation factor. The ATR technique is shown to give quite representative values of the amorphous orientation factor.
Dissolution rates of poly(methyl methacrylate) in mixtures of nonsolvents
Authors: Groele R. J. , Krasicky P. D. , Chun S.‐W. , Sullivan J. , Rodriguez F. 
Published: April 2003

AbstractAs predicted by thermodynamic studies of polymer conformation, high molecular weight poly(methyl methacrylate) (PMMA) dissolves cleanly, and at a constant rate, in a 7 : 3 mixture of 1‐butanol and acetonitrile, although neither liquid is a solvent for PMMA by itself. Mixtures of other alcohols with acetonitrile also dissolve PMMA. When mixtures with the same fraction of acetonitrile are compared, methanol dissolves PMMA almost twice as fast, ethanol and hexanol at about the same rate, and 2‐propanol somewhat more slowly than the 1‐butanol mixture with acetonitrile. The measurements of dissolution rate were made using a laser interferometer at 20°C.
Rheology and morphology of polymer blends containing liquid‐crystalline component in melt and solid state
Authors: Kulichikhin V. G. , Vasil'Eva O. V. , Litvinov I. A. , Antipov E. M. , Parsamyan I. L. , Platé N. A. 
Published: April 2003

AbstractThe rheological properties of polymer blends containing polysulfone and LC polyester have been investigated in terms of the morphology and physical‐mechanical characteristics of the extrudates. The peculiarities of rheological behavior are connected with the morphology of stream, the latter being maintained also in solid extrudates. The reinforcement of an isotropic matrix by LC polymers as well as formation of an anisotropic surface layer leads to a specific change in the strength properties of compositions. A maximal increase in the strength and initial modulus was observed for blends containing not more than 10% LC polymer.
Pyridine‐catalyzed depolymerization of cellulose during carbanilation with phenylisocyanate in dimethylsulfoxide
Authors: Evans Robert , Wearne Ross H. , Wallis Adrian F. A. 
Published: April 2003

AbstractCarbanilation reactions of cellulose samples (bleached cotton linters and Avicel) with phenylisocyanate in dimethylsulfoxide (DMSO) were carried out at 60°C in the presence of various pyridine derivatives. The molecular weight distributions of the resulting cellulose tricarbanilates (CTCs) were measured by high‐performance size exclusion chromatography. When pyridine or its derivatives were included in the reactions, the CTCs had reduced degree of polymerization (DP) values compared to those of CTCs prepared without the additives. The cellulose depolymerization was promoted by pyridines with electron‐donating substituents and was not favored by pyridines with electron‐withdrawing substituents nor with groups at positions ortho to the pyridine ring nitrogen atom. For the 3‐, 4‐, and 3,4‐ substituted pyridines, there was a linear relationship between log (weight‐average CTC DP) and the pKa (in water) of the pyridine derivative. For 2‐ and 2,6‐substituted pyridines, the DP–pKa relationships were different, probably because of steric effects of the different substituents ortho to the pyridine nitrogen atom. The optimum DMSO : pyridine solvent ratio for cellulose depolymerization during carbanilation in DMSO : pyridine mixtures was 3 : 1. All three components, phenylisocyanate, pyridine or its derivatives, and DMSO, are required for the depolymerization reaction. It is suggested that the depolymerization may be a consequence of cellulose oxidation by DMSO and/or cleavage of glucosidic bonds of partially carbanilated cellulose by reactions promoted by an enhanced solvent effect of DMSO.
Degradation mechanisms of poly(ethylene terephthalate) tire yarn
Authors: Sawada Shuzo , Kamiyama Kiyosuke , Ohgushi Shinichiro , Yabuki Kazayuki 
Published: April 2003

AbstractIn order to clarify the fatigue mechanism of PET tire cords in rubber focusing on chemical degradation, hydrolysis in saturated steam atmosphere, ammonolysis in ammonia gas, and the degradation of the cords embedded in rubber have been studied at high temperature conditions. It was found that the strength loss of polyester tire cords in rubber has linear correlation with the amount of chemically induced chain scissions mainly caused by hydrolysis catalyzed by amines.
Electron beam effects on polymers: V. Symmetric and asymmetric materials based on the controlled distribution of bis‐GMA into crosslinked nitrile rubber films prior to curing by electron beam radiation
Authors: Kim Ha‐Chul , El‐Naggar Abdel M. , Wilkes Garth L. 
Published: April 2003

AbstractTwo systems based on the controlled distribution of the methacrylic acid derivative of the diglycidyl ether of bisphenol‐A (bis‐GMA) into crosslinked acrylonitrile–butadiene co‐polymers, commonly called nitrile rubber (NBR), were prepared utilizing electron beam (EB) radiation. In the system called “symmetric,” the EB crosslinked NBR was swollen to equilibrium in solutions containing different concentrations of bis‐GMA. The swollen NBR film was then EB irradiated to different dosage levels. The other system, called “asymmetric” or “gradient,” was prepared by applying the solutions containing bis‐GMA to one surface of the EB crosslinked NBR film in a controlled time that was less than the time to achieve an equilibrium concentration across the thickness or “swelling” dimension. This asymmetrically swollen NBR film was then immediately EB irradiated using different dose levels. The prepared symmetric and asymmetric NBR systems were investigated by thermal and mechanical, as well as microscopic, analyses. The mechanical responses were shown to be strongly dependent on the bis‐GMA content in the NBR film and the type of preparation history. The dynamic mechanical spectra showed the presence of two transitions, indicating some level of phase separation that was supported by scanning electron microscopy of fracture surfaces for symmetric and asymmetric systems. The asymmetric distribution of the imbided (cured) monomer in the asymmetric system was confirmed by both FT‐IR and optical microscopy analyses.
Crosslinking structure of keratin: III. Rubberlike elasticity originating from non‐uniform structures of the swollen hair and wool fibers
Authors: Arai Kozo , Ma Guanghui , Hirata Taishi 
Published: April 2003

AbstractHair and wool fibers treated with an 11 M LiBr solution containing N‐ethylmaleimide showed typical rubberlike elasticity in a solution composed of equal volumes of 8 M LiBr and diethylene glycol monobutyl ether. Stress–strain relations of the swollen fibers were treated with a two‐phase structural model: a mechanically stable phase of higher crosslinked domains and a rubbery phase with lower crosslink density. Stress–strain curves were analyzed by applying non‐Gaussian chain statistics to the swollen keratin network, including microdomains, which act as reinforcing filler particles in rubber. Swollen hair showed about 2.3 times higher modulus than wool. It has been suggested that: (1) the difference in the modulus between the two keratins is attributable to the difference in the volume fraction of domains, and (2) the crosslink density of rubbery phase in hair is virtually identical to that in wool.
Chemical reactions in crosslinking of copolymers of ethylene and vinyltrimethoxy silane
Authors: Hjertberg T. , Palmlöf M. , Sultan B.‐Å. 
Published: April 2003

AbstractThe crosslinking reactions of a new type of polyethylene, an ethylene vinyltrimethoxy silane (EVS) copolymer, when reacted with water has been studied. Samples of EVS were treated in water at 90°C. The kinetics of the crosslinking was followed by measuring the gel content and by determination of the content of different structures (SiOCH3,SiOH, and SiOSi) using FT‐IR. The observations show that a maximum gel content of 70‐75% is obtained after 25 h treatment in water at 90°C. On the other hand, the absorption index for the crosslinks, SiOSi, continues to increase until about 100 h, i.e., more crosslinks seem to be formed without a simultaneous increase in gel content. Mechanical measurements showed decreased elongation at break even after very long treatments. Thermo‐oxidative degradation is, however, also responsible for the change in mechanical properties. For properly stabilized samples, the decrease in elongation leveled off after about 100 h of treatment. This indicates that the crosslinks formed after 25 h mainly should be within the already existing gel. The observed synergistic effect of crosslinking and thermo‐oxidative degradation emphasizes the importance of a proper stabilizing system.
Crosslinking reactions of ethylene vinyl silane copolymers at processing temperatures
Authors: Palmlöf M. , Hjertberg T. , Sultan B.‐Å. 
Published: April 2003

AbstractThe crosslinking reactions of ethylene vinyltrimethoxy silane (EVS) copolymers at processing temperatures have been studied. Samples were heated in inert atmosphere with or without water at 130–350°C. The crosslinking reactions were followed by determination of the gel content and by analyzing the structural changes using FT‐IR. As expected, no gel could be observed in pure EVS after treatment in nitrogen, whereas 30% was obtained if the nitrogen was presaturated with water. Addition of a catalyst, dibutyltindilaurate, increased the reaction rate considerably and a final gel content of 70–75% was obtained above 300°C. In contrast, neither water nor catalyst was needed for the formation of gel in a terpolymer of EVS containing butylacrylate as well. During heat treatment the acrylate units formed carboxylic acid, and blends of EVS and an ethylene acrylic acid (EAA) copolymer were therefore used as a model to study the reactions in detail. Despite absence of water these blends started to form gel at low temperatures, 150–200°C. This could mainly be related to internal production of water due to reaction between carboxylic groups leading to anhydride. Both cyclic and noncyclic anhydrides were detected by FT‐IR analysis. A larger amount of EAA in the EVS–EAA blend increased the rate of gel formation and decreased the onset temperature, but no corresponding change in the formation of noncyclic anhydride was observed. Another kind of crosslink, formed by reaction between carboxylic acid and silanol groups, can possibly be one explanation to this behavior.
Sulfonation of polyethylene membranes
Authors: Dimov A. , Islam M. A. 
Published: April 2003

AbstractThe polyethylene membranes are hydrophilized under the action of chlorosulfonic acid. Such a hydrophilized membrane shows much better water permeability in comparison with the unmodified one. The ion‐exchange capacity of the sulfonated membrane is taken as a measure for the hydrophilicity. The influences of the concentration of the sulfonating agent, temperature, and reaction time, on the ion‐exchange capacity and water permeability, are investigated. It is shown that the increase in the degree of sulfonation does not always lead to an increase in the water permeability of the membrane. A lower concentration of the sulfonating agent and a lower temperature are to be chosen, so that only the surface and the inner walls of the pores are sulfonated. Sulfonation in the bulk leads to the deterioration of mechanical properties of the membrane without having any contribution to the increase in the water permeability of the membrane.
Study on ketalization reaction of poly(vinyl alcohol) by ketones. IV. Reaction between poly(vinyl alcohol) and aliphatic ketones and behavior of polyvinylketal in water
Authors: Nakamura Naofumi 
Published: April 2003

AbstractKetalization reaction of poly(vinyl alcohol) (PVA) by aliphatic ketones, dimethylsulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out and the synthesis of polyvinylketals were successfully performed. The equilibrium constant at 40°C is ca. 0.07 in the case of methyl n‐propyl ketone (nPK) and methyl n‐butyl ketone (nBK), but is ca. 0.05 in the case of methyl i‐propyl ketone (iPK) and ca. 0.01 in the case of methyl i‐butyl ketone (iBK) and methyl t‐butyl ketone (tBK), respectively. Moreover, the ketalization degree of polyvinylketal by iBK and tBK reached to only ca. 35 mol % as the maximum. It seems that these were due to steric hindrance of bulky side chain of ketones. But the heat of reaction is 7.5 kcal/mol in all aliphatic ketones, it seems to proceed the same ketalization reaction mechanism. Films prepared from the polyvinylketals were soaked in water and degree of swelling, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, at first the film swells, and then, as the deketalization reaction proceeds, the film dissolves in water. The dissolution time is controlled by the kind of ketones, ketalization degree, and pH of water which reveals that deketalization reaction proceeds proportional to proton concentration. It is more difficult to dissolve highly ketalized polyvinylketals obtained by propyl ketones and butyl ketones than that by acetone. The hydrolysis of polyvinylketal film proceeds in the order as follows: acetone > MEK > nPK > iPK ≒ nBK > iBK > tBK. This phenomenon seems to be affected by hydrophobicity of the film surface which depends upon the kind of the original ketones.
N‐acryloyl–N′‐phenylpiperazine as curing activator of unsaturated resins
Authors: Tanzi M. Cristina , Levi Marinella , Danusso Ferdinando 
Published: April 2003

AbstractN‐acryloyl–N′‐phenylpiperazine and three of its homopolymers of different molecular weight are tested as low toxicity redox activators in the BPO curing of unsaturated polyester resins. Gel times and other time and temperature parameters drawn from standard exothermal curves are determined with two kinds of resin, at different bath temperatures and amounts of activator. The reciprocal of gel time follows a kinetic equation with average order 0.85 with respect to the activator, and an activation energy of 19 kcal/mol. With polymeric activators it is a simple decreasing exponential function of intrinsic viscosity. Correlations are observed for other parameters relative to the second, faster step of the curing process, in general less sensitive to the mentioned variables. The crosslinked resins show mechanical properties similar to those obtainable with dimethylaniline as activator.