bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sorption and transport of CO2 above and below the glass transition of poly(ethylene terephthalate)
Authors: Koros W. J. , Paul D. R. 
Published: December 2004

AbstractAt temperatures at least 30°C above the glass transition (Tg) the sorption and transport of carbon dioxide in poly(ethylene terephthalate) (PET) can be described conveniently using Henry's law and Fick's law with a constant diffusion coefficient. Below Tg Fick's law with a concentration‐ dependent diffusion coefficient, coupled with a sorption isotherm which is concave toward the pressure axis adequately describes the observed sorption and transport data. Physical interpretations of the quantitative deviations from Henry's law and the form of the concentration dependence of the diffusion coefficient is provided by a model which hypothesizes dual modes of sorption and separate non zero mobilities of two populations of sorbed species in local equilibrium. The implications of the observed temperature variations of the phenomenological model parameters are discussed. Dilatometric parameters for PET, polycarbonate, and poly(acrylonitrile) (PAN) are shown to correlate well with a simple. relationship developed to explain the existence of the “extra” mode of sorption responsible for deviations from Henry's law for CO in glassy polymers. In the temperature range from Tg to + 20°C, deviations from Fickian behavior are also apparent. These effects are consistent with a transition in the nature of the polymer from an elastic solid below Tg to a viscous liquid above Tg In the narrow temperature range slightly above T the time scale for chain rearrangements apparently approaches that for the diffusion process. The polymer's viscoelastic response to the probing molecule, therefore, causes deviations from the classical time lag predictions. These deviations disappear 30°C above Tg.
Flow‐induced crystallization of polymer melts in convergent flow regimes and imposed temperature gradient to form ultra‐oriented fiber structures
Authors: Crater Davis H. , Cuculo John A. , Boudreaux Edwin 
Published: December 2004

AbstractFlow crystallization experiments which utilized the Instron rheometer in conjunction with convergent dies were conducted for the purpose of producing high‐modulus poly(ethylene terephthalate) filaments directly from the melt. A temperature gradient was imposed on the lower extremity of the dies in an attempt to control the site of the fluid‐solid phase transformation, and “freeze in” any orientation derived from the elongational flow regime. Comparative studies were made using dies with included angles of 20, 30, and 40°, and extrusion temperatures ranging from 255 to 270°C. Die angle influenced the pressure at which maximum die swell and the onset of extrudate distortion occurred; however, barrel temperature showed little effect on this pressure. The minimum temperature produced by the temperature gradient was the over‐riding factor involved with cessation of flow. In each experiment, the fluid‐solid phase transformation produced by the temperature was always accompanied by extrudate distortion. Thus, only minimal comparative studies of the extrudates could be performed. In view of the above, it appears that utilizing a temperature gradient, by itself, to “freeze in” preferred orientation within the confines of the die presents difficulties. A modification which combines a temperature gradient with external tension and a rapid after‐quench outside the die, now holds appeal for continuing studies.
Temperature‐induced pressure gradient in the clearance between screw flight and barrel of a single screw extruder
Authors: Winter Horst Henning 
Published: December 2004

AbstractThe effect of temperature‐induced pressure gradients occurring in drag flow in a narrow gap between parallel walls, when a viscosity gradient in flow direction is present is described and analyzed. The effect dominates the technologically important clearance flow problem, where the viscosity gradient originates from temperature changes. The polymer layer in the clearance between screw flight and barrel of a single screw extruder supposedly has to separate the metallic surfaces from each other. In certain operating conditions this bearing function breaks down and dry friction between metallic surfaces occurs. This failure, which has not yet been explained, is reasoned to be caused by the temperature‐induced pressure flow in the clearance.
Fracture mechanics of adhesive joints
Authors: Sih G. C. 
Published: December 2004

AbstractThe load carrying capacity of adhesive joints is analyzed by applying the principle of fracture mechanics in which failure is assumed to initiate from sites of initial imperfections such as bubbles, cracks or unbonded portions of the interface. The cohesive and adhesive modes of failure are investigated for a butt joint under angle loading. Based on the prediction of the strain energy density criterion, the lowest failure stress for the adhesive joint occurred when the load is applied at an angle with respect to the crack plane. This is in contrast to the homogeneous material solution where the lowest failure stress corresponds to normal loading. Numerical examples are provided for a joint made of DER 332‐TEPA epoxy with aluminum as the adherends. Discussed in detail are the dependencies of the strength of the joint with reference to the material properties of the constituents, geometries of the components, and direction of loading.
Photoresist development by plasma
Authors: Hughes H. G. , Goodner W. R. , Wood T. E. , Smith J. N. , Keller J. V. 
Published: December 2004

AbstractOver the past several years the semiconductor industry has placed major efforts into replacing wet processes with dry processes in fabricating electronic devices. Plasma photoresist stripping, plasma cleaning, and other dry etching techniques have replaced wet methods in many product lines. One area that has received little mention but which is vital toward achieving a totally dry manufacturing process is the dry development of photoresist. One production applicable plasma developable photoresist (PDF) process, using a proprietary resist formulation, is reported. Plasma process characterization, such as end point detection, development latitude, and mechanism are discussed. Included also are development temperature, batch film uniformity, and resolution currently obtainable with the PDF process.
Retention of a foaming agent in poly(vinyl chloride) (PVC) and chlorinated PVC
Authors: Khanna Y. P. , Turi E. A. , Sibilia J. P. 
Published: December 2004

AbstractPoly(vinyl chloride) and chlorinated poly(vinyl chloride) films were saturated at 100°C with fluorotrichloromethane (Genetron‐11, a foaming agent) and then allowed to desorb at RT and 65°C. The desorption data for a three month period was fitted into a mathematical relationship which could be used for long term predictions of the G‐11 retention in the films. Using thermoanalytical techniques, plots of glass transition temperature vs G‐11 concentration were made for the polymers under study. These plots were used to demonstrate the effect of stabilizer, polymer type and temperature on the desorption of the G‐11.
The effect of strain rate on the toughening mechanisms of rubber‐modified plastics
Authors: Maxwell M. A. , Yee A. F. 
Published: December 2004

AbstractThe impact modification mechanisms of polycarbonate (PC) blended with polyethylene (PE) and blends of polyxylenol ether (PXE)/high impact polystyrene (HIPS), were studied using a volume dilation technique. With two extensometers, measurements of volume change during tensile deformation were made on the plastics. Strain rates of 2 × 10−5 s−1 to 4 s−1 were achieved with a MTS servo‐hydraulic testing machine. Analysis of both systems were supported with scanning and transmission electron microscopy. Results on the PC/PE system indicate that the impact modification mechanism is one of voiding and shear banding. The mechanism appeared to be rate sensitive: the amount of voiding increased with rate. The toughening mechanism in the PXE/HIPS blends is identified as a combination of crazing and shear banding. The amount of shear banding that occurs is proportional to the amount of PXE in the blends. The point of craze initiation was found to be delayed by increasing strain rate. The stress for craze initiation appears to be greater than for shear banding.
The development of C‐10 phthalocyanine for composite matrix applications
Authors: Ting R. Y. , Nash H. C. 
Published: December 2004

AbstractThermomechanical analysis was carried out for various phthalocyanine resins. The polymer based on the C‐10 diamide resin was then chosen for evaluation as a potential composite matrix material. Prepregs with Thornel 300 graphite reinforcements were successfully prepared using a hot‐melt technique. The processability of this material was studied by employing instrumental techniques including differential scanning calorimetry, thermal gravimetric analysis and dynamic dielectric analysis. A cure cycle was developed for the fabrication of angle‐ply laminate using the conventional vacuum‐bag technique in a hydraulic press. Laminate mechanical properties both in tension and in flexure were determined. The results for the C‐10/T‐300 samples were shown to be similar to those of an epoxy/graphite and a polyimide/graphite composite system.
The physical aging of isotactic polypropylene
Authors: Agarwal M. K. , Schultz J. M. 
Published: December 2004

AbstractThe microstructural changes in isotactic polypropylene (PP), subsequent to quench from the melt to around Tg were studied using dynamic mechanical loss, volume dilatometry, small and wide angle X‐ray scattering, infrared and NMR spectroscopy. The β‐transition loss tangent and the specific volume decreased linearly with logarithm of aging time. Dynamic mechanical loss and NMR spectroscopy results established that amorphous chain mobility reduced during aging. X‐ray and IR techniques showed that the crystallinity, the crystalline density, and the average chain conformation do not change during aging. Tensile tests indicated that diffusion of air or moisture into the polymer is not a competitive mechanism for the aging phenomenon. A simple free‐volume model is quantitatively consistent with these observations. The fraction of the material which cannot age increased as the quench temperature decreased. Further, at lower temperatures a portion of the nonageable fraction is shown to reside in the amorphous fraction.
Residual stresses in polymers. II. Their effect on mechanical behavior
Authors: Siegmann A. , Buchman A. , Kenig S. 
Published: December 2004

AbstractThe distribution of density and tensile properties in quenched modified poly(phenylene oxide) specimens was investigated. Quenching was carried out from temperature level above Tg to below Tg temperatures. Simultaneous to buildup of residual stresses, profiles of density and tensile properties were observed. The profiles were obtained using the layer removal technique, which was found not to affect the measured properties. Quenching of the material results in a steep density gradient in the surface layers. Correspondingly, the tensile modulus increases significantly from the surface to the inner layers and so are also the ultimate tensile properties. This behavior could be accounted for neither by the conventional packing volume approach nor by superposition of internal and external stresses. However, observations of the fracture surfaces are very supportive and indicate that the fracture initiation sites are influenced by the residual stresses. Hence, the mechanical behavior is strongly affected by both density and residual stresses profile. Density is the controlling factor in determining the elastic properties whereas residual stresses determine the ultimate strength and fracture mechanism.
A dynamic mechanical study of the curing reaction of an unsaturated polyester
Authors: Yap C. Y. , Williams H. Leverne 
Published: December 2004

AbstractThe curing process of an unsaturated polyester was followed by employing the dynamic spring analysis (DSA) technique attached to the Rheovibron viscoelastometer. The storage and loss moduli and the gel times of the resin with various concentrations of initiator (methyl ethyl ketone peroxide) were determined at several temperatures. The activation energy for the curing process studied was about 40 kJ/mol. Temperature effects on films partially cured below the ultimate glassy transition temperature (Tg) were studied similarly using the tensile mode on the Rheovibron from room temperature to 120°C. Two modulus peaks were observed upon heating and these were independent of precure conditions. The lower temperature peak was the result of continued curing and the higher temperature peak was attributed to the glassy relaxation of the cured product. The DSA technique were found to be useful for characterization of the curing process and the results showed good qualitative agreement with those obtained by tensile measurements using cast films when the shapes of the curves were compared.
Unsaturated polyesters from 2,2‐dimethyl‐1,3‐propanediol
Authors: Tong S. N. , Horng H. K. 
Published: December 2004

AbstractA series unsaturated polyesters were made from 2,2‐di‐methyl‐l,3‐propanediol, propylene glycol, fumaric acid, and isophthalic acid by a two‐step fusion process. The effect of catalyst, conversion, composition, unsaturation, and styrene content were studied, and the relationship between composition and properties was established.
Time‐dependent morphologies and viscoelastic properties of block copolymers
Authors: Kelterborn Jeffrey C. , Soong David S. 
Published: December 2004

AbstractDynamic mechanical properties of block copolymers over a wide temperature range have been previously correlated with the phase‐separated microstructure of these systems. In the present work, the morphology of the block copolymer is altered by large tensile deformation at various temperatures. Upon removal of the applied stress, the morphological features of such stretched‐and‐released systems become functions of time, as the nonequilibrium microstructure reverts to a thermodynamically stable state. This reformation process is monitored by dynamic mechanical measurements, with a modified torsion pendulum capable of applying both tensile and torsional deformation. Experimental results are analyzed using a modified Nielsen model to obtain information on the time‐dependent structural state of the samples. These results are then compared with stress‐strain curves to provide further insight into the structure breakdown‐reformation mechanisms. Two competing mechanisms, domain fracture and block pull‐out, are proposed to explain these experimental observations.
Dynamic mechanical spectroscopy of sheet compound as a function of deformation
Authors: Ard K. , Kolman H. J. , Beatty C. L. 
Published: December 2004

AbstractIt has been determined that preload and cyclic amplitude have significant effect on the results of dynamic mechanical measurements of tan δ. To illustrate these effects on composites, a particular type of sheet‐molding compound (SMC‐R50) was used in this study. In addition to the effects of preload and cycle amplitude, the effects of frequency, post‐cure, and creep prior to dynamic mechanical testing were also investigated.
Studies of epoxy resin systems: Part B: Effect of crosslinking on the physical properties of an epoxy resin
Authors: Chang T. D. , Carr S. H. , Brittain J. O. 
Published: December 2004

AbstractAn epoxy system consisting of diglycidyl ether of butanediol, DGEB, cured with 4‐4′ diaminodiphenyl sulfone, DDS, has been used for a study of the effect of crosslinking density on the properties of the epoxy resin. Because of the low curing rate at room temperature and the low glass‐transition temperature, this system was amenable to a wide range of controlled cross‐linking density. The crosslinking density was monitored by FTIR (Fourier transform infrared spectroscopy), which followed the change in concentration of the epoxy groups during the curing reaction. The bulk density was found to increase linearly with the crosslinking density. The modulus, the upper yield point, the lower yield point, and the degree of retraction of a deformed sample all increased with the degree of crosslinking. The thermally stimulated depolarization (TSD) β‐peak was found to vary with crosslinking density, but the γ‐peak was not changed. The TSD a peak was found to decrease in strength, but increased in temperature as the crosslinking density increased. This observation suggests that TSD measurements arc a good monitor of crosslinking density of epoxy resins, particularly near the final stage of the crosslinking reaction.
Electron transport processes in conductor‐filled polymers
Authors: Sherman R. D. , Middleman L. M. , Jacobs S. M. 
Published: December 2004

AbstractThis article contends that three distinct physical processes control electron transport in conductor‐filled polymer systems. Percolation is required to explain the macroscopic conduction in the disordered medium. Quantum mechanical tunneling (possibly quantum fluctuation augmented) is needed to describe conduction between adjacent conductive particles at the microscopic level. And, thermal expansion is invoked to deduce constituent volume densities and microscopic tunnel lengths. Each of these mechanisms is given a mathematical form. The ansatz is used to predict resistivity vs. temperature and resistivity vs. conductor‐filling fraction functions. Successes and deficiencies of the theory are discussed with respect to experimental data and theoretical considerations.
Prediction of strain recovery during solid‐phase forming of thermoplastics
Authors: Okine R. K. , Suh N. P. 
Published: December 2004

AbstractAn approach to predict the strain recovery behavior of polycarbonate (PC) and high impact polystyrene (HIPS) under isothermal and non‐isothermal conditions in a solid‐phase forming environment is presented in this paper. The constants A and n of a power law relationship of the form ϵ(t) or δ(t) = Atn, fitted to isothermal creep and stress relaxation data, were determined over a wide range of temperatures for both materials. An expression for isothermal recovery was derived and compared to experimental data. Master curves and the resultant shift factors, obtained by superposing the stress relaxation and creep data (both in tension and compression) were used with the time‐temperature super position principle to numerically evaluate uniaxial strain recovery under a specific temperature history. The average temperature history obtained by numerically solving for the temperature distribution in a disc, at an initially high temperature and in contact with a cold metal surface, was used for the non‐isothermal case. The theoretical results were compared with recovery data obtained from non‐isothermal backward extrusion tests with a temperature history similar to the one described above. Reasonably good agreement was obtained.
Notch sensitivity and fractography of polyolefins
Authors: Goolsby R. D. , Chatterjee A. M. 
Published: December 2004

AbstractThe notch sensitivity of high‐density polyethylene (HDPE), polypropylene (PP), and polybutylene (PB) was evaluated using uniaxial tensile deformation and fractographic analysis. Each polyolefin was tested at relatively low and high molecular weights (MW). Only the lower MW HDPE was found to be clearly notch‐sensitive. The lower MW PP exhibited some tendency toward notch sensitivity. The lower and higher MW PB, the higher MW HDPE, and the higher MW PP displayed notch strengthening. Whereas PB showed similar notched tensile performance regardless of molecular weight, both HDPE and PP showed higher susceptibility to notch sensitivity at lower molecular weights (and concomitant higher crystallinity). Tendencies toward notch sensitivity or notch stengthening were evidenced in the failure modes of these materials.
Analytical melting model for extrusion: Stress of fully compacted solid polymers
Authors: Chung K. H. , Chung C. I. 
Published: December 2004

AbstractOur laboratory recently published several analytical equations that can be used to predict the melting rate of fully compacted solid polymers sliding on a heated metal surface, modeling the melting mechanism inside an extruder. These equations were obtained by seeking asymptotic solutions to the differential equations describing the melting mechanism, temperature, and shear‐dependent viscosity of polymer melts. Following the same asymptotic approach, we successfully developed accompanying analytical equations for predicting the stress required to slide fully compacted solid polymers on a heated metal surface. The accuracy of these analytical stress equations was found to be reasonable, although not fully satisfactory, by comparing their predictions to the experimentally measured values. The accuracy of the stress calculation is directly related to the accuracy of the viscosity values at high shear rates. The consideration of the temperature and shear dependencies of melt viscosity is most important for accurate prediction of the stress, just as it is for the melting rate. The stress not only depends on the melt rheological properties of the polymer but also on the thermodynamic properties.
Parameter design model for corrugated tubing
Authors: Krein H. L. 
Published: December 2004

AbstractIt is of interest to produce plastic corrugated tubing as strong as possible with a minimum amount of material. Simultaneously, the tubing has to resist stretching, and maintain flexibility for transport purposes. To find the optimum profile geometry, two mathematical models were employed. One model was used to calculate the strength of the tubing per unit length and a second model was used to predict the elongation of corrugated tubing for a given load. Data was then generated for different profile configurations, and plotted for an optimum design procedure. The results showed that, while the wall thickness can be varied during production, the most critical parameter is the corrugation depth. The corrugation depth is fixed by the moldblock design, and the data presented can be used to obtain an optimum geometry.
Vulcanization shrinkage of rubber articles with rigid armoring parts
Authors: Tukachinski L. I. 
Published: December 2004

AbstractThis paper discusses the shrinkage characteristics of armored (reinforced) rubber articles for two types of boundary conditions: (a) cases where the armoring material is neither flexible nor thermoexpansive, and (b) cases where the armoring material has a finite thermal expansion between room and vulcanization temperature. A quantiative analysis of shrinkage strains and stresses is developed for the two boundary conditions.
An observation on the han‐villamizar critical pressure concept in thermoplastic foams
Authors: Throne J. L. 
Published: December 2004

AbstractThis note draws together the Han‐Villamizar experimental observations on the critical pressure at which gas bubbles became visible in flowing thermoplastic melts and a simple method of predicting the equilibrium pressure based on gas solubility. It is shown that the observed pressure is 40 to 75 percent of the calculated pressure.