bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen permeation through Teflon–PFA tubing into flowing helium
Authors: Giacobbe F. W. 
Published: April 2003

AbstractThe permeability coefficient for oxygen diffusing through a sample of Teflon‐PFA tubing has been determined experimentally. The source of the diffusing oxygen was ambient air surrounding a 1.835 m length of PFA tubing. Pressurized high purity helium was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing pressurized helium was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent helium were determined as a function of varying helium flow rates, at helium gas pressures of 1.92 and 4.40 atm (absolute), within the tubing bore. All measurements were carried out at ambient temperatures of 23.5 ± 1.3°C. In addition, a theoretically related graphical method of evaluating the experimental data was employed to actually determine the oxygen permeability coefficient for this system.
Hydrocarbon‐soluble alkylaniline/formaldehyde oligomers as corrosion inhibitors
Authors: Bacskai R. , Schroeder A. H. , Young D. C. 
Published: April 2003

AbstractHydrocarbon‐soluble oligomers were prepared by the acid‐catalyzed condensation of alkylanilines with formaldehyde. Highest molecular weight oligomers (MW ∼ 6000) were obtained from alkylanilines prepared by the Friedel‐Crafts alkylation of aniline with α‐olefins. By NMR, it was shown that the oligomers contain structures corresponding to methylene‐linked aromatic rings and methylene linked to both an aromatic ring and a nitrogen atom. The oligomers exhibit very good initial inhibition of metal corrosion in aqueous environment; and the inhibition is more persistent than that observed with monomeric analogs.
Sorption of CO2/CH4 mixtures in poly(phenylene oxide) and a carboxylated derivative
Authors: Story Brooks J. , Koros W. J. 
Published: April 2003

AbstractThe sorption of CO2 and CH4 and their binary mixtures in poly(phenlene oxide) (PPO) and its carboxylated derivative (CPPO) is reported. All mixed gas data are accurately described by the dual model sorption model, which predicts mixed gas sorption on the basis of pure gas sorption parameters. The present paper extends the mixed gas sorption data base to include polymers having a wide range of permeabilities and chemical structures. The confirmed accuracy of the model for these systems provides strong support for applying the mixed gas dual mode sorption model to any gas/polymer system. A numerical simulation of the mixed gas sorption experiment is also presented which greatly simplifies the experimental procedures used to maintain the partial pressure of one of the gas components at a constant value over the course of a sorption isotherm measurement. By establishing the appropriate amounts of each gas component which are added to the polymer sample chamber of the sorption cell, the mixed gas apparatus simulator (MIGAS) can be used to maintain the partial pressure of one of the components to within 1% of the desired value.
A DSC study of curative interactions. III. The interaction of TMTM with ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractThe interaction among various combinations of sulfur, tetramethylthiuram monosulphide (TMTM), ZnO, and stearic acid were studied by differential scanning calorimetry in the absence of rubber. Sulfur and TMTM reacted to form tetramethylthiuram disulphide, and the ternary eutectic mixture melted at about 80°C. The absence of the Sγ → Sμ transition in sulfur/TMTM mixes was related to a sulfur/TMTM interaction, wherein the eightmembered sulfur rings were opened at temperatures well below 170°C. The interaction of stearic acid with TMTM led to the decomposition of TMTM, but the reaction was largely suppressed when both ZnO and sulfur were present in the mixture. No evidence was found for the formation of a zinc‐accelerator complex of the type normally attributed a role in the accelerated sulfur vulcanization.
Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. II. Distribution of higher‐order structures
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo 
Published: April 2003

AbstractFlexural test specimens were injection‐molded from polypropylenes added with 0.5 wt % calcium carbonate, talc, p‐tert‐dibutyl‐benzoic acid monohydroxy aluminum, or p‐dimethyl‐benzylidene sorbitol under cylinder temperatures of 200–320°C. Distributions in the flow direction of higher‐order structures such as a*‐axis‐oriented component fraction [A*] and crystalline orientation functions and distributions in the thickness direction of higher‐order structures such as crystallinity, β‐crystal content, the degree of b‐axis orientation to the thickness direction, [A*], and crystalline orientation functions were studied. These higher‐order structures are inhomogeneous in the flow and thickness directions, which strongly influences the product properties such as mechanical and thermal properties.
Synthesis of a copolymer of tetrafluoroethylene and 1‐fluorosulfonyl–difluoroacetylfluoride
Authors: Kostov G. K. , Ivanov G. D. , Kotov St. V. 
Published: April 2003

AbstractTetrafluoroethylene (TFE) was copolymerized with 1‐fluorosulfonyl‐difluoroacetylfluoride (FSDFAF) in both the bulk and solution by using a free radical initiator at temperature 50°C. The presence of sulfonyl fluoride (SO2F) functional groups in the copolymers was proved by infrared (IR) spectroscopy. The copolymers were subjected to alkaline hydrolysis followed by an acid treatment and the SO2F groups content was found not to exceed 0.40–0.50 meq/g with polymer yield ranging between 1 and 36%. Copolymerization in solution of 1,1,2‐trichloro‐1,2,2‐trifluoroethane (Freon 113) under TFE pressure about 1.0 MPa and TFE/FSDFAF mole ratio 1.5–2.0 was proposed for further investigations. A random distribution of single FSDFAF units along the polymeric chain consisting mainly of TFE fragments was considered to exist. The copolymers had melting temperatures within 10–15°C lower than polytetrafluoroethylene and their thermal stability was 360–380°C.
Sign reversal of piezoelectric polarization of hydrated native collagenous and cellulosic fibers by addition of ions
Authors: Maeda Hideatsu 
Published: April 2003

AbstractComplex piezoelectric constants of native collagenous and cellulosic fibers, which take highly oriented and ordered microfibrilar structures, have been measured at 10 Hz between −150 and 50°C. We have found that piezoelectric polarization of both hydrated fibers, which contain many ions, steeply decrease around −60°C and subsequently exhibit the sign reversal around −40°C. These temperatures are found to agree with that at which bound water between the microfibrils begin to get mobile. The steep decrease and sign reversal of the piezoelectric polarization may be explained by actions of ions that reside in piezoelectric and nonpiezoelectric regions of such ordered structures.
The effect of the side chain of acrylate comonomers on the orientation, pore‐size distribution, and properties of polyacrylonitrile precursor and resulting carbon fiber
Authors: Tsai Jin‐Shy , Lin Chung‐Hua 
Published: April 2003

AbstractThe side‐chain size of acrylate comonomer in polyacrylonitrile (PAN) precursor markedly influences the microstructure of PAN fiber and its resulting carbon fiber. In this paper, we propose that the model of the crystal orientation of PAN precursor and its resulting carbon fiber can explain the effect of the side‐chain size of acrylate comonomer on the orientation of PAN fiber and carbon fiber. When PAN precursor contains a larger side chain of comonomer, PAN precursor has the preferred crystal orientation and higher crystallinity and the orientation of its resulting carbon fiber unexpectedly decreases. This is because the larger the side chain is, the lower is the orientation of the amorphous region of PAN fiber; as a result, the average orientation after carbonization decreases. In the same mole fraction of comonomer, the carbon fiber based on PAN precursor with a smaller side chain of acrylate comonomer has better mechanical properties and higher yield.
Novel polyurethane hydrogels for biomedical applications
Authors: Lai Yu‐Chin , Baccei Louis J. 
Published: April 2003

AbstractPolyurethane hydrogels derived from UV‐curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well‐defined hard segments centered with a polyether‐based soft segment and end‐capped with methacrylate groups. The hydrophilic monomers studied were 2‐hydroxyethyl methacrylate (HEMA), N‐vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris (trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All composition were UV‐cured and formed hydrogels after hydration. The oxygen permeabilities of the hydrogels decreased as the water contents increased and increased as the TRIS content was increased. The tear strengths and moduli decreased as the water contents of the hydrogels increased. Most compositions studied have higher oxygen permeability and tear strength than poly(HEMA) because of the presence of urethane prepolymer in the composition.
The forming properties of high molecular weight polyethylene
Authors: Lee Y. W. 
Published: April 2003

AbstractThe formabilities of cold‐rolled high molecular weight polyethylene (HMWPE) sheets have been studied by measuring their plastic anisotropy ratio (R value), strain‐hardening exponent (n value), strain distribution, and the forming limit diagram (FLD). The deep drawability of the polymer is improved by rolling. After 40% or more reduction in thickness by cold rolling, the HMWPE sheet could be deep‐drawn into a cylindrical cup. The results of R value measurement indicate that the R value is responsible for improved drawability. Cold rolling also increases the n value but decreases the strain gradient. Stretch forming tests have also been carried out, and the results show that cold working could also improve the stretchability of this polymer. The results of the FLD are in agreement with the other properties studied. The mechanical properties, environmental stress cracking resistance, and shape, size, and property stability of the deep‐drawn HMWPE cups have also been investigated.
Analysis of filling, packing, and cooling stages in injection molding of disk cavities
Authors: Chiu Wen‐Yen , Chen Leo‐Wang , Wang Chi , Wang Ding‐Chang 
Published: April 2003

AbstractThis research tried to simulate three stages of injection molding cycles (filling, packing, and cooling) for polypropylene. The cavity used was a center‐grated disk‐shaped mold. During the filling stage, we assumed the polymer fluid obeyed the CEF equation and flowed nonisothermally. The packing stage was represented by isothermal flow of Newtonian fluid, and, during cooling stage, we took into account the effect of pressure drop on the energy balance. By finite difference method, we could solve the partial differential equations numerically. The results showed. (1) Elastic effect was not significant at the filling stage. (2) Pressure buildup in the cavity was very quick at the packing stage. (3) At the cooling stage, temperatures predicted by taking into account pressure drop were lower than those without considering pressure drop. In addition, the influences of mold temperature, flow rate, and inlet melt temperature on the three stages of injection molding process were discussed.
Effect of water absorption and temperature gradients on polycarbonate injection moldings
Authors: Qayyum M. M. , White J. R. 
Published: April 2003

AbstractPolycarbonate injection moldings have been conditioned for various times in (i) hot water (40, 60, 80, and 100°C) or (ii) in a temperature gradient (with hot surface/cold surface temperatures 80/25, 100/25, 120/35, and 140/60°C). Water absorption occurred in hot water and caused the formation of disc‐shaped flaws, which were located at all depths within the bars and at all orientations. The presence of the flaws caused severe embrittlement and cracks were nucleated by them during uniaxial tensile testing. Residual stress levels were found to be diminished by hot water conditioning more than those in bars conditioned at the same temperatures in air. The sense of the residual stresses reversed in a bar that was allowed to cool slowly in the water bath, an observation attributed to desorption. It was generally found that the flaws near the surface healed on allowing the bars to stand in air at room temperature. Temperature gradient conditioning caused reversal of the sense of the residual stresses near to the hot surface at the two higher temperatures used and significant reduction in magnitude at the lower temperatures. Fracture nucleated at this surface during uniaxial tensile testing.
Property stabilization in filled, drawn polyethylene
Authors: Malik T. M. , Carreau P. J. , Schreiber H. P. , Rudin A. , Kale L. , Tchir W. 
Published: April 2003

AbstractMechanical properties of high density polyethylene (HDPE) extended to draw ratios in the 20–40 range have been determined and compared with corresponding properties of the polymers containing particulates including rutile, carbon black, iron oxide, and mica. Shrinkage of drawn structures was studied to temperatures near the fusion of the polymer host. The degree of interaction at polymer/additive interfaces was varied by surface coating certain of the solids with standard coupling agents. Solids were found to increase tensile moduli and to decrease shrinkage, particularly at higher exposure temperatures. The magnitude of changes due to the presence of solids was shown to depend on the apparent interaction at contacts between host and additive. In a dispersion–force matrix, like HDPE, benefits were optimized when the particulates were amphoteric or neutral, rather than having pronounced acid or base interaction potentials.
Structural characteristics of silk fibers treated with epoxides
Authors: Tsukada Masuhiro , Nagura Masanobu , Ishikawa Hiroshi , Shiozaki Hideki 
Published: April 2003

AbstractStructural characteristics of the silk fibroin fiber‐modified with epoxide treatment were elucidated by refractive index measurement, differential scanning calorimetry, and thermomechanical analysis and on the basis of strength–elongation measurements. The four epoxides used were glycidol (G), ethylene glycol diglycidyl ether (E), tolyl glycidyl ether (T), and resorcinol diglycidyl ether (R). The values of the isotropic refractive index of the silk fiber increased by the action of T or R. The position of the endothermic peak attributed to the thermal decomposition and the position of the onset of the contraction of each of the samples treated with epoxides shifted to higher temperature, suggesting the more thermal stability. However, the values of the molecular orientation and the crystallinity of the specimen evaluated from X‐ray diffraction analysis remained unchanged regardless of the epoxide treatment. These experimental results have been interpreted in terms of the cross‐links between the adjacent silk fibroin molecules and of the hydrogen bonds between the hydroxyl groups of the epoxide molecules attached to the side chains of the silk fibroin.
Mathematical modeling of weather‐induced degradation of polymer properties
Authors: Hamid S. H. , Prichard W. H. 
Published: April 2003

AbstractWeather‐induced degradation of polymer properties is caused by all the factors of weather, which include solar radiation, temperature, humidity, wind, rain, environmental pollutants, thermal cycling (cold night and hot days), and sand abrasion. Linear low‐density polyethylene (LLDPE) is exposed to natural weather, and degradation is monitored by the mechanical properties testing system, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Three mathematical models were developed with weather parameters as independent parameters and mechanical property (tensile strength), chemical change (carbonyl growth), and thermal property (percent crystallinity) as dependent parameters. The mechanical property was found to be more dependent on the ultraviolet (UV) portion of the total solar radiation, chemical change was found to be synergestically effected by UV and total solar radiation, and change in thermal property was because of UV, total solar radiation, and temperature. Humidity and other weather parameters were found to play a less significant role in the weather‐induced degradation of LLDPE properties.
Effect of structure on the thermal stability of photocurable urethane acrylate formulations
Authors: Shama Sami A. , Tortorello Anthony J. 
Published: April 2003

AbstractThe effect of structural segments on the thermal stability of photocurable urethane acrylates was studied. A series of model compounds, where one segment of the molecular structure was varied at a time while keeping the remainder of the molecule unchanged, was tested for thermal stability. The results from this study indicate a prominent equivalent weight effect: Increasing the equivalent weight decreases the thermal stability within a given series of model compounds. Polyol‐based urethanes were found to be more stable than their amine counterparts. Of the hydroxy‐terminated starting materials, polycaprolactones were found to produce the greatest thermal stability, whereas polyethers resulted in the least stable photocurable materials. The diisocyanate segment exhibits a marked effect on the thermal stability of the cured material also. Surprisingly, the dicycloaliphatic diisocyanates resulted in greater stability than the aromatic diisocyanates, while the monocycloaliphatic diisocyanates yielded the least stable materials in the model compound series tested.
Modified avrami expression for polymer crystallization kinetics
Authors: Pérez‐Ćardenas Fernando C. , Castillo L. Felipe Del , Vera‐Graziano Ricardo 
Published: April 2003

AbstractThe Avrami equation has been widely used to describe polymer crystallization kinetics. However, the equation accurately fits experimental data only during the early stages of the crystallization process, and is unsuccessful in describing the entire process because it does not take into account secondary crystallization. Here we present a modified Avrami expression that describes polymer crystallization kinetics that takes into account both primary and secondary processes. The expression uses a new parameter introduced to indicate the fraction of material that has completed crystallization when the primary crystallization process has terminated. The theoretical results are in good agreement with experimental data.
Kinetics and mechanisms of water sorption in hydrophobic, ionizable copolymer gels
Authors: Firestone B. A. , Siegel R. A. 
Published: April 2003

AbstractThe aqueous kinetic swelling properties of a class of cross‐linked hydrophobic polyamine copolymer gels based on n‐alkyl esters of methacrylic acid (nAMA) and N,N‐dimethylaminoethyl methacrylate (DMA) have been studied as a function of solution ionic composition (pH, ionic strength, and buffer content), gel composition, and temperature. Water uptake and swelling in these gels are driven by ionization of the DMA amine groups, which overcomes the hydrophobic tendency of these gels to exclude water in the unionized state. Sorption kinetics in initially glassy gel disks are generally biphasic, characterized by an initial phase of relatively slow water uptake followed by an accelerated phase during which significant volume expansion of the gel occurs. This sorption/swelling behavior strongly suggests a moving penetrant front mechanism. The initial rate of water sorption increases markedly as (1) solution pH decreases, (2) gel nAMA comonomer content decreases, (3) gel nAMA side‐chain length decreases, and (4) temperature increases. Furthermore, the initial phase of sorption in initially glassy gels is generally non‐Fickian and approaches zero‐order behavior as (1) pH increases, (2) nAMA content increases, and (3) temperature decreases. In direct contrast, sorption in initially dry, rubbery gels is monophasic, but non‐Fickian, and approaches zero‐order behavior as temperature increases. This behavior is contrary to the Fickian sorption behavior normally observed in polymers above their glass transition temperatures. Finally, sorption kinetics critically depend upon the nature of the ions in solution: Kinetics are significantly faster in the presence of weak electrolytes than that of strong electrolytes. We discuss the importance of the rate of ion transport in determining the overall sorption kinetics and how sorption kinetics can be non‐Fickian in rubbery gels. Also, we propose a mechanism for the observed enhanced kinetics in the presence of weak electrolytes.
Selective plasticization of the ionic domains in a segmented thermoplastic ionene cationomer
Authors: Venkateshwaran L. N. , Leir C. E. , Wilkes G. L. 
Published: April 2003

AbstractThe use of zinc stearate as an ionic plasticizer has been demonstrated to function effectively in a segmented ionene cationomer thereby permitting its melt processability. The ionene polymer is prepared by reacting dimethylamino‐terminated polytetramethylene oxide (PTMO) oligomers with various benzyl dihalide compounds, leading to a segmented cationomer. Since the unplasticized ionene polymer undergoes degradation near the softening temperature (ca. 180°C), an ionic plasticizer was incorporated as a means of lowering the softening temperature to prevent degradation and permit melt processability. Zinc stearate was utilized in this study as it has been demonstrated to function well in other ionomers (essentially anionomers) in this capacity. Through the utilization of melt rheological and solid‐state morphological investigations, it has been clearly shown that zinc stearate will function effectively as an ionic plasticizer in these quite different ionomer materials by lowering the softening temperature to ca. 120°C, thereby permitting melt processability. In addition, due to the crystallization of the zinc stearate following cooling, this same species also serves to enhance the mechanical properties in the solid state.
Study on cure behavior of epoxy resin–BF3–MEA system by dynamic torsional vibration method
Authors: Pingsheng He , Chune Li 
Published: April 2003

AbstractA dynamic torsional vibration method has been developed and used to investigate the isothermal cure processes of resin system of epoxy resin–boron trifluoride monoethylamine complexSiO2, optimizing its cure conditions and estimating the apparent dynamic parameters including gel time and rate of cure reaction and discussing the effect of filler on cure. The cure behavior of resin system has been predicted by the nonequilibrium thermodynamic theory. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method.