bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processing and properties of poly(p‐phenylene benzobisthiazole)/nylon fibers
Authors: Wickliffe Susan M. , Malone Michael F. , Farris Richard J. 
Published: April 2003

AbstractComposite fibers of poly(p‐phenylene benzobisthiazole) (PBT) with nylons were spun from dilute acid solutions. The effects of wet‐stretching, heat treatment time, tension, and temperature on the tensile properties are reported. Nylon 6,6 and nylon 6 at several molecular weights were studied. Moduli of 40 GPa and tensile strengths of 375 MPa were achieved for 30/70 PBT/nylon composites. Heat treatment of the nylon/PBT fibers at 160–225°C for 12–19 h increased the tensile modulus by 20–50% and the tensile strength by a smaller amount. At the same time, the intrinsic viscosity of the nylons increased as much as 100%, indicating the solid‐state polymerization of the nylon. The largest tensile modulus attained is less than half the theoretical value predicted by a linear “rule of mixtures” as might be expected for an oriented molecular composite. Although differential scanning calorimetry shows a melting transition at temperatures 5–10°C higher than the pure nylons, the composite does not flow at temperatures above this transition. Sulfuric acid dissolves most of the nylon, but does not destroy the mechanical integrity of the fibers; differential scanning calorimetry indicates that the remaining fiber contains little or no nylon. The results are consistent with a microstructure consisting of a microfibrillar network of PBT, surrounded by a separate nylon phase.
A comparative study of the response of cottons to zinc chloride and sodium hydroxide
Authors: Iyer P. Bhama , Sreenivasan S. , Patel G. S. , Iyer K. R. Krishna , Patil N. B. 
Published: April 2003

AbstractDifferent varieties of cotton drawn from various botanical species were subjected to swelling and stretching in 64.5% (w/w) aqueous zinc chloride at 32° ± 1°C for different intervals ranging from 10 to 50 min. Swelling was almost complete in 30 min. Samples stretched to original length after this interval showed tremendous improvement in orientation and strength both at zero and 3 mm gauge lengths. In several cases, the improvement was higher than that obtained with similar treatment in sodium hydroxide of mercerizing concentration at room temperature. Swelling in zinc chloride was found to be independent of the variety of cotton as evidenced by the 50% X‐ray angle for the stretched fibers, which was about 9° for all the six cottons included in this study.
Water‐ethanol separation by pervaporation through plasma graft polymerized membranes
Authors: Hirotsu Toshihiro 
Published: April 2003

AbstractWater‐ethanol permselective membranes were prepared through plasma graft polymerization of acrylic acid, methacrylic acid, and acrylamide onto porous polypropylene film. In these membranes, the functions of permseparation and mechanical properties are shared respectively to the graft polymer layer and the substrate film. Higher permselectivity of water is achieved with the ionization of the acrylic acid and the methacrylic acid‐grafted membranes. Permselectivity is dependent on the degree of grafting, and it is necessary to fill the pores of substrate film with graft polymers. Permseparation of water was investigated with respect to the feed ethanol concentration and also to the temperature dependence.
The effect of moisture on the dielectric behavior of poly(vinyl acetate)–natural rubber blend
Authors: Chuu Michael S. , Meyers Raymond R. 
Published: April 2003

AbstractDynamic dielectric analysis was used to analyze the miscibility of poly(vinyl acetate) and natural rubber and the effect of moisture on the dielectric properties of the polymer blend. Two separate dielectric relaxations were observed within the temperature range studied. The high‐temperature relaxation was a result of the glass transition of poly(vinyl acetate), whereas the low‐temperature relaxation was attributed to that of natural rubber. The peak temperatures of ε″ of the high‐temperature relaxation decreased with increasing aging time, while the magnitudes of the ε″ peaks increased with increasing days of aging. The peak temperatures of ε″ of the low‐temperature relaxation stayed constant, while the magnitudes of the ε″ peaks increased with increasing days of aging. This indicates that both polymers are responsible for the sorption of moisture; however, water is an effective plasticizer only for poly(vinyl acetate). Anomalous increases in the magnitudes of ε″, especially in the low frequency sides, of the Argand diagrams were explained by Maxwell–Wagner–Sillar (MWS) polarization at component interfaces. The oscillator strength, relaxation time, and the two distribution parameters, A and B, calculated from the skewed circular are equation, were affected with days of aging.
On‐line studies of structure development during melt spinning of poly(butylene terephthalate)
Authors: Chen Shida , Yu Weiyan , Spruiell J. E. 
Published: April 2003

AbstractAn on‐line study of structure development during poly(butylene terephthalate) melt spinning was carried out. Two polymers with different molecular weights (intrinsic viscosities of 0.75 and 1.0 dL/g) were used. The range of take‐up velocities studied was 1500 to 4500 m/min. On‐line measurements included diameter, temperature, birefringence, and tension. The phenomenon of diameter thinning (necking) was observed for both polymers at take‐up velocities of 3500 and 4500 m/min with a mass throughput of 4 g/min. At a constant mass throughput, the distance from the spinneret at which the necking occurred varied with take‐up velocity and molecular weight of the polymer. Increasing the take‐up velocity at constant mass throughput caused an increase in cooling rate and a slight increase in the rate at which the temperature decreased with distance from teh spinneret. A small but detectable change in the rate of temperature decrease was observed at a position near or just beyond the formation of the neck. It is suggested that this effect is due to the increased heat transfer caused by the rapid increase in filament velocity and increased surface to volume ration in the neck. Increased take‐up velocity also caused necking to occur at higher temperature, as did an increase of polymer molecular weight. Birefringence increased with distance from the spinneret and indicated substantial molecular orientation was developed in the filament prior to the necking zone. A sharp increase of birefringence in the necking zone was observed for take‐up velocities of 3500 and 4500 m/min. A discussion of the mechanism of neck formation is presented, and it was concluded that necking is intimately associated with stress‐induced crystallization in PBT. An increase of spinline stress resulting from either an increase of take‐up velocity or an increase of molecular weight can cause stress‐induced crystallization and, hence, necking to occur nearer the spinneret and at higher temperature. For a given polymer this leads to filaments with higher levels of crystallinity, crystalline orientation, and crystalline perfection (greater crystal size). These changes in morphology result in changes in the filament mechanical properties. The effect of molecular weight change on the structure and properties is complicated by the fact that the development of crystallinity seems to be affected by the molecular weight independent of the spinline stress.
The study on die swell, fiber length distribution, and crystallinity of PP composite through extrusion
Authors: Chiu Wen‐Yen , Shyu Goang‐Ding 
Published: April 2003

AbstractDie swell of PP and glass fiber reinforced PP (GFRPP) through an extruder was investigated. It was observed that the die swell decreased as (1) the temperature increased, (2) the fiber content increased, and (3) the screw speed was lowered. Fiber length distribution in GFRPP was measured. The average fiber length would increase as (1) the fiber content decreased, (2) the temperature increased, and (3) the screw speed was around 25 rpm. The crystallinity of extrudate was measured by DSC and found to be independent of the screw speed and the fiber content.
New aspects in cationization of lignocellulose materials. VI. Modification of steam‐exploded aspen wood chips with quarternary ammonium groups
Authors: Šimkovic Ivan , Ebringerová Anna , Antal Miroslav , Micko Michael M. 
Published: April 2003

AbstractHolocellulose prepared from steam‐exploded aspen wood was gradually fractionated with 2.5% NH4OH, 4.5% NaOH, and 17.5% NaOH, respectively. Some residual polysaccharides were extracted from the material in this way, but their yield was only about 5%. Trimethylammonium‐2‐hydroxypropyl (TMAHP)‐derivatives, exploded aspen wood (EXAW), were prepared by the reaction with 3‐chlor‐2‐hydroxypropyl trimethylammoniumchloride (CHMAC) in alkaline medium. The quantity of water and alkali extracted TMAHP–polysaccharides (yield 2.6%) was lower than the yields from modified healthy beech and aspen, as well as rotten aspen. On the other hand, we can obtain more modified cellulose‐rich and lignin‐rich material than from previously mentioned species. The steam‐explosion process is suitable for increasing the accessibility of cellulose component in lignocellulose material for chemical modification.
Synthesis and characterization of poly(vinyl carbazole) complexes with copper(II) chloride in THF solution
Authors: Katime Issa A. , Ochoa Jose R. , Nido Carlos Sieiro Del 
Published: April 2003

AbstractSeveral polymer‐metal complexes were prepared by reacting poly(vinyl carbazole) (PNVC) with copper(II) chloride, CuCl2.2H2O, in refluxing tetrahydrofurane (THF) for mole ratios of CuCl2.2H2O to monomeric unit (Cu:PNVC ratio) ranging between 0.086 and 4.98. Complexes were characterized by infrared (IR) and elemental analysis. Thermal behavior of complexes was studied by differential thermal analysis (DTA). It appears that THF behaves as a specific solvent for complexation of PNVC with copper(II) chloride.
Determination of the structure and composition of clinically important polyurethanes by mass spectrometric techniques
Authors: Richards Joseph M. , McClennen William H. , Meuzelaar Henk L. C. , Shockcor John P. , Lattimer Robert P. 
Published: April 2003

AbstractCurie‐point pyrolysis mass spectrometry (Py‐MS) and direct probe pyrolysis high resolution mass spectrometry (Py‐HRMS) were used to identify the components and additives used in the synthesis and compounding of Biomer, Lycra Spandex, Tecoflex, and Pellethane. Two types of Biomer were identified (P and Q, our notation) which are composed of poly(tetramethylene glycol) (PTMG) capped with 4,4′‐methylenebis(phenylisocyanate) (MDI) and chain‐extended with ethylenediamine (EDA). Both forms contain 4,4′‐butylidene‐bis‐(6‐t‐butyl‐m‐cresol) antioxidant, and Biomer Q also contains an additive which appears to be a quaternary ammonium chloride salt. Lycra Spandex was found to be identical to Biomer Q, with the exception that a low molecular weight polydimethylsiloxane oil is also present. This silicone oil can be removed by solvent extraction. Tecoflex (type SG80A) is composed of PTMG capped with 4,4′‐diisocyanatodicyclohexylmethane and extended with 1,4‐butanediol (BD). An industrial grade and a medical grade of Pellethane were analyzed. Both were composed of PTMG capped with MDI and extended with 1,4‐butanediol. the industrial grade also contains an antioxidant, possibly butylated diphenylamine.
Characterization of cured polysulfide polymers by thermal degradation: Pyrolysis‐GC and thermogravimetric studies
Authors: Radhakrishnan T. S. , Rao M. Rama 
Published: April 2003

AbstractPolymers prepared by curing thiol‐terminated liquid polysulfide polymer [HS(RS2)nRSH, R = CH2CH2OCH2OCH2CH2] with p‐quinonedioxime, PbO2, and MnO2 were studied by pyrolysis‐GC and thermogravimetry. Characteristic differences were observed in the composition of the pyrolyzates under flash pyrolysis at 420 and 470°C. The concentration of the cyclic monomer, 1,3‐dioxa‐6,7‐dithionane, in the pyrolyzates was found to vary considerably from polymer to polymer. The change in mechanism with the extent of degradation and the corresponding overall activation energies were evaluated by thermogravimetry. The pyrolysis‐GC and thermogravimetric data were shown to provide partial characterization of the substrates. Mn appears to be in a coordinated complex in the MnO2‐cured polymer.
Polysulfone‐bonded polyvinylpyridinium membranes
Authors: Montoneri E. , Orlandoni A. M. , Modica G. , Maffi S. , Pappalardo G. C. 
Published: April 2003

AbstractPolydivinylbenzene‐4‐vinyl‐N‐methylpyridinium iodide (MeVP+‐DVBI−) membranes are obtained by solvent evaporation from dispersions of copolymer powder in polysulfone dichloroethane solutions. The membranes' macroporosity increases from 2.5 to 46.4% and the pore size distribution concentrates in the 103–105 Å range upon varying the concentration of polypyridinium polymer from 0 to 67% w/w. Similarly, the specific conductivity increases from 10−11 to 10−4 ohm−1 cm−1 and the mechanical strength decreases from 500 to 8.8 kg/cm2. The ion selectivity is maximum at 40–50% MeVP+‐DVBI− and lower above or below this concentration range. The properties are discussed in relation to the membrane chemical and physical parameters.
Plasma‐polymerized membranes and gas permeability III
Authors: Sakata Jiro , Hirai Masana , Yamamoto Minoru 
Published: April 2003

AbstractPlasma‐polymerized films of hexamethyldisiloxane were deposited onto various porous substrates having different pore sizes, and the gas permeability of these composite membranes was studied. In each membrane, permselectivity between oxygen and nitrogen was found, but the oxygen permeation rate was different with each substance tested. The minimum thickness of the plasma‐polymerized film needed to plug all pores and show permselectivity is about five times the pore radius of the porous substrate. The maximum oxygen permeation rates of the permselective composite membranes are approximately proportional to the effective areas for the gas permeation and inversely proportional to the pore sizes. The composite membranes show high oxygen permeation rates in cases using porous glass hollow fibers which have small pore sizes and large surface porosity as porous substrates. In cases using polysulfone hollow fibers which have high permselectivity, the composite membranes show much higher permeability ratios of oxygen‐to‐nitrogen than do those of the porous glass hollow fibers.
Photosensitive resins containing p‐dimethylaminobenzylidene derivatives and diphenyliodonium salt as photoinitiators
Authors: Ichimura K. , Kameyama A. , Hayashi K. 
Published: April 2003

AbstractA series of p‐dimethylaminobenzylidene derivatives was able to sensitize the photodecomposition of diphenyliodonium salt to afford highly photosensitive negative‐type resins. When a polymer‐bearing methacryloylated group in the side chain was sensitized with a combination of the p‐dimethylaminobenzylidene compounds and the iodonium salt, the polymer demonstrated high sensitivity even to 488 nm light emitted from an Argon laser. The same photoinitiator systems were applicable to insolubilize poly(glycidyl methacrylate) through cationic photopolymerization. The storage stability of these types of photoinitiators depends on the structure of the benzylidene compounds; decreasing the basicity of the amino group enhanced the thermal stability.
Effect of high energy radiation on the stress–relaxation of ultra‐high molecular weight linear polyethylene
Authors: Bhateja S. K. , Andrews E. H. 
Published: April 2003

AbstractStress–relaxation behavior was studied in ultra‐high and normal molecular weight linear polyethylenes (UHMWPE and NMWPE) as a function of radiation dose over the range 0–128 Mrad. Irradiation up to 16 Mrad raises the crystallinity in both types of PE, as demonstrated previously,1 and thus increases the initial modulus. Also, the initial modulus of NMWPE is higher than that of UHMWPE because the former has a higher crystallinity. Consequently, the initial stress at a constant imposed strain of 1% varies greatly between the two materials. To eliminate the effect of this initial difference on relaxed stress, the stress–relaxation data were normalized with respect to the initial stress and plotted as the fraction, retained stress after time t/initial stress. The normalized plots show no significant difference between NMWPE and UHMWPE in their stress–relaxation behavior. For both materials stress retention improves progressively with increasing radiation dose, the percentage improvement being greatest at long times (50% at 50 h and 64 Mrad, compared with 6% at 10−2 h). These results are interpreted to indicate that radiation crosslinking in the amorphous phase is independent of molecular weight and preferentially retards those molecular motions responsible for short relaxation times. The motions in question could involve molecular flow in the amorphous phase or “pull out” of tie molecules from the crystalline lamellae.
Relationship between the mechanical relaxations in the α zone and the calorimetric transitions in low density polyethylene
Authors: Ribes‐Greus Amparo , Diaz‐Calleja Ricardo 
Published: April 2003

AbstractThe α‐relaxation spectra of LDPE, irradiated and unirradiated, has been compared with their calorimetric thermograms. There exists a correlation between the two mechanical relaxations that appear in the α zone and the two fusion peaks observed in the calorimetric thermograms, confirming that the parameter that governs the temperature of the relaxations αI and αII is the most probable crystallite thickness, whereas the height of the α‐relaxation zone, as measured by means of tan δmax, depends on the total crystalline content of the sample.
Aggregation of basic dyes induced by anionic polyelectrolytes
Authors: Neumann Miguel G. , Hioka Noboru 
Published: April 2003

AbstractThe aggregation of basic dyes in aqueous solution in the presence of polyelectrolytes has been studied to determine the nature of the interaction between the dye molecules and the polymer sites. The aggregation induced by carboxymethylcellulose with isolated anionic sites cannot be explained assuming interaction between dye molecules bound to neighbouring sites. Maximum aggregation for various dyes on that polyelectrolyte has been found around P/D = 0.3 whereas for PSS that value is found around 1. Dimerization constants calculated for these systems are in good agreement with the values expected from dimerization in aqueous solutions. A new model is proposed to explain these results.
Photoacoustic monitoring of adhesive curing
Authors: Torres‐Filho A. , Perondi L. F. , Miranda L. C. M. 
Published: April 2003

AbstractThe crosslinking reaction of an epoxy‐based resin has been monitored by observing the time evolution of the thermal diffusivity of the mixture, using photoacoustic spectroscopy. The results are interpreted in terms of the expected thermal properties of liquids, polymers and solids, and a comparison with the reported viscosity behavior in similar systems is also made. The potential of the technique for following the curing process is discussed.
Effect of methylene chloride sorption on the mechanical properties of poly(aryl‐ether‐ether‐ketone) (PEEK)
Authors: Pao Peter S. , Grayson Michael A. , Wolf Clarence J. 
Published: April 2003

AbstractThe effect of sorbed methylene chloride on the tensile strength and fatigue crack growth (FCG) resistance of PEEK were determined. PEEK sorbs up to 23 wt% methylene chloride; the transport process is essentially Case II, that is, the methylene chloride advances as a sharp front. Sorbed methylene chloride significantly reduces the tensile strength of neat PEEK and the strength reduction is linearly proportional to the amount of solvent sorbed. FCG rates in neat PEEK are increased by the methylene chloride sorption. At saturation, the FCG rates are two orders of magnitude higher than in dry PEEK. Methylene chloride plasticizes the resin, thereby reducing its glass transition temperature (Tg), tensile strength, and FCG resistance.
Preparation of aldehydocelluloses from completely allylated methylcellulose, allylated ethylcellulose, and tri‐O‐allylcellulose by ozonization
Authors: Kondo Tetsuo , Ishizu Atsushi , Nakano Junzo 
Published: April 2003

AbstractIn order to prepare aldehydocelluloses which are more stable than periodate‐oxidized cellulose, completely allylated methylcellulose, allylated ethylcellulose, and tri‐O‐allylcellulose were subjected to ozonization followed by reduction with dimethylsulfide. The aldehydocelluloses thus prepared without any degradation showed the presence of many free aldehyde groups by IR and 13C‐NMR spectrometries, as well as the presence of hydroxyl groups which were produced by deallylation. The degree of substitution (DS) by aldehyde group was 0.6 for the products from both completely allylated methylcellulose and tri‐O‐allylcellulose, and 0.02 for that from allylated ethylcellulose.
ESR study and copolymer analysis of acrylamide‐methacrylamide solid solutions
Authors: Ramelow Ulku , Baysal Bahattin M. 
Published: April 2003

AbstractWhen acrylamide‐methacrylamide mixed crystals are irradiated by ultraviolet (UV) rays, a copolymeric sample is obtained containing both monomeric constituents. For identification and quantitative analysis of these copolymers, a modified form of UV spectroscopy was used. The greatest advantage of UV spectroscopy for copolymer analysis lies in its rapid application. A comparison of the spectrum of the unknown compositions with spectra of known systems by using a calibration curve and the shifts in absorption maxima in different concentrations are valuable aids in establishing the composition. Electron spin resonance (ESR) provides a correlation between the obtained copolymer composition and the shape of the signal of the responsible radical. ESR spectra obtained for UV‐irradiated acrylamide‐methacrylamide mixed crystals reveal that during polymerization both radicals are present. As methacrylamide percentage increases in the mixture, the signal becomes similar to the 9‐line spectrum of pure methacrylamide. When there is 90% methacrylamide present in the original mixture, a 5‐line signal is observed, with even‐numbered peaks in the methacrylamide signal appearing now as shoulders. When the methacrylamide percentage is about 16%, a characteristic 3‐line signal of acrylamide is dominant. As the methacrylamide percentage increases in the original mixture of the copolymers, ESR signals indicate a decrease in the rate constant values for second‐order decay at 60°C. The stability of the formed radicals was studied by admitting oxygen to the copolymeric samples as well as to the homopolymeric systems. Since the peroxidic radicals are more active in the hydrogen abstraction process, they decay more rapidly than the macro radical itself by a bimolecular termination reaction. As the methacrylamide percentage increases in the copolymeric mixtures, the peroxide radical formation becomes more difficult. This indicates that polymethacrylamide brings more stability in copolymerization reactions with acrylamide. The polymerization rate of both monomers and their mixed crystals were enhanced by adding chlorine gas before irradiation. Chlorine acts as an agent for slowing down the radical decay as well as accelerating the radical initiation reactions.