bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymer blends as high explosive binders
Authors: Mark Hoffman D. , Caley Leonard E. 
Published: December 2004

AbstractAn approach to high‐density, high‐modulus binders for explosives is to blend low‐density, high‐modulus polymers with high‐density, low‐modulus polymers. Improved properties, which these pairs theoretically should have, are discussed. Two attempts to achieve miscibility between a high‐density fluoropolymer (Kel‐F 800) and high‐modulus thermoplastics (Lucite 130 and Phenoxy PKHJ) were unsuccessful. These blends are immiscible and their physical properties are additive or only slightly enhanced. Anelastic properties of the blends indicate phase separation by the presence of two glass transitions, one associated with each phase.
A methodology for describing creep‐fatigue interactions in thermoplastic components
Authors: Bowman J. , Barker M. B. 
Published: December 2004

AbstractIn service, some plastics components are subjected to intimate mixtures of creep and fatigue loading, such that both have the potential to cause component failure. This paper examines, for the case of a single design of an injection molded fitting that comprised part of a polyethylene pipeline system, the response of that fitting to fatigue loading patterns that included significant elements of creep loading. The performance of the fitting was monitored and the data interpreted in terms of the concepts of fractional fatigue and fractional creep damage. The approach helps in identifying the design criteria to be used for components that are to be subjected to complex fatigue loadings. For the cases where significant creep‐fatigue interactions occur, such that the additive damage was nonlinear, the method can identify critical frequencies at which maximum damage occurs. This style of analysis will be most useful for plastics components that are used in critical applications where failure has to be avoided.
Dynamic fracture instability in glassy polymers as studied by ultrasonic fractography
Authors: Takahashi K. 
Published: December 2004

AbstractUltrasonic fractography studies were performed on poly(methyl methacrylate) of high molecular weight. The transient fracture velocity change at the slow‐to‐fast transition during discontinuous propagation has been measured precisely. Fast fracture starts with a characteristic velocity which falls in a narrow range between 90 to 150 m/s, nearly independent of the loading speeds and the specimen temperature from −50 to 40°C. Parallel double‐cantilever‐beam specimens exhibited stick‐slip type propagation whose velocity change was also evaluated. In these specimens, the fast fracture abruptly slows down to speeds on the order of 10° m/s. These intermediate velocities have never been obtained in the slow‐to‐fast transition. Velocity measurements under hydrostatic pressure have shown that fracture velocities decrease significantly with increasing pressure, and that the slow‐to‐fast transition tends to disappear at a pressure between 5 and 10 MPa. Models have been presented concerning the mechanism of the slow‐to‐fast transition, crazing and cracking under superposed cyclic stress field, and the relationship between dynamic toughness and fracture velocity in this material.
Surface tension of polymer liquids
Authors: Couchman P. R. , Van Ness K. E. 
Published: December 2004

AbstractA cell theory for the prediction of the surface tension of simple liquids is adapted to polymer liquids. The combinatory, free volume and potential energy zero terms of the partition function are all modified to account for the preservation of connectivity when a surface is created. Theory and experiment are in good agreement without an adjustable surface parameter.
Blends of polycarbonate and poly(hexamethylene sebacate): I. Physical properties
Authors: Shih K. S. , Beatty C. L. 
Published: December 2004

AbstractThe compatibility of polymer blends of high‐molecular‐weight polycarbonate (PC) and high‐molecular‐weight poly(hexamethylene sebacate) (HMS) were characterized. Samples were prepared by solution blending them In methylene chloride followed by doctor blade casting. Optical spectroscopy, tensile stress‐strain, differential scanning calorimetry, and dielectric relaxation spectroscopy were employed to determine the physical and mechanical properties of the blends. These high‐molecular‐weight blends exhibit a limited solubility of HMS In PC as evidenced by a decrease in the glass‐transition temperature of PC. In fact, HMS solubility increases PC mobility sufficiently to allow partial crystallization of PC. Over most of the composition range, HMS phase separates and crystallizes.
Melting and crystallization behavior of an unusual compatible blend based on propylene copolymers
Authors: Shih Chi‐Kai 
Published: December 2004

AbstractAn unusual compatibility was observed with the melt blends of propylene/α‐olefin copolymer with isotactic homopolypropylene. The simple binary blend exhibits a single glass‐transition temperature, and, by differential scanning colorimetry, a single melting and crystallization temperature over the entire blending ratios examined. Depending on the compositions, the characteristic temperatures vary between those exhibited by the component polymers. Vigorous annealings failed to phase separate the components. The melting behavior of the annealed polymer sample suggests the crystalline components of the two polymers are cocrystallized in this unique compatible system.
The computer modeling of multicomponent, semibatch emulsion copolymerization
Authors: Omi Shinzo , Kushibiki Koji , Iso Mamoru 
Published: December 2004

AbstractA computer modeling concept was developed to deal with multicomponent emulsion copolymerization systems. Based on the model, a simulating program called NSBEC (n‐component, semibatch emulsion copolymerization) was prepared., NSBEC is capable of carrying out a variety of operations involving any number of monomers with different modes of ingredient feed. In this paper, first the basic concept of the model is explained, then several applications to the actual experimental systems (e.g., acrylonitrile‐vinylidene chloride, vinyl acetate‐butyl acrylate, and methyl methacrylate‐butyl acrylate) are discussed. Finally, the probable control of copolymer composition by means of the semibatch operation based on NSBEC is proposed. The authors expect that use of NSBEC can substantially reduce the number of experimental runs previously required to describe the system.
A fundamental study of polymer melt devolatilization: III More experiments on foam‐enhanced DV
Authors: Biesenberger Joseph A. , Lee Shau‐Tarng 
Published: December 2004

AbstractA systematic, experimental study was conducted on the elementary process of devolatilization (DV) of volatile contaminants from polymer melts. Emphasis was placed on foam‐enhanced DV from rolling melt pools, which are present in rotating machinery. All experiments were conducted in a specially designed apparatus at room temperature using poly(dimethyl siloxane) to simulate the melt, and methyl chloride together with several chlorofluorocarbons as the contaminants. The special apparatus was devoid of the flow complexities present in industrial equipment and permitted independent control of all pertinent operating parameters. Physical properties and process parameters examined include feed composition and vapor pressure of contaminant, applied vacuum level, rotational speed of the pool, viscosity of the melt, and the effect of air entrainment.
Yield stress and flow measurements in ABA block copolymer melts
Authors: Hansen Paula J. , Williams Michael C. 
Published: December 2004

AbstractA parallel‐plate constant‐stress rheometer is used to measure the yield stress τy, and the post‐yield flow curveT(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), where τ is shear stress and\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}is shear rate, for microphase‐separated triblock copolymer melts. Five polymer samples, all styrene‐butadiene‐styrene but with differing composition ratios and molecular weights, are tested at 125°C. Specimens are prepared by casting sheets from solutions made with different solvents. The τ(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) is found usually to be sigmoidal, for the range 10−5<\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}< 10−3s−1, representing different stages of microstructural degradation in flow. Measurements indicate that a true τyexists, with values in the range 100 < τy< 500 Pa for these melts. A general trend is detected for τyto decrease as the casting solvent solubility parameter increases. A scheme for correlating the dependence of τy, on composition and molecular weight is proposed for the various polymers. For selected samples, the effect of mechanical history (sequence of stress application) and a temperature variation that crossesTs(110 to 150°C) are also explored.
Optimization of the polycondensation step of polyethylene terephthalate formation in semibatch reactors
Authors: Kumar Anil , Sainath A. E. 
Published: December 2004

AbstractThe polycondensation stage of polyethylene terephthalate (PET) formation is assumed to include side reactions leading to the formation of diethylene glycol, vinyl end groups, and acid end groups, in addition to the usual polymerization of bis (2‐hydroxyethyl) terephthalate (BHET) in semi‐batch reactors. A, flexible objective function has been proposed with temperature and pressure as control variables. Computations from the first variation technique show that the pressure should be reduced to the lowest limit under all possible conditions. Consequently, optimal temperature profiles in batch reactors are obtained for various lower limits of reactor pressures using the combination of first and second variation techniques. For the first variation technique, the vector iteration method of computation was used, and the near optimal profile so obtained was used as the initial guess for the second variation technique. The result of optimization shows that the lower limit of pressure and weighting parameters appearing in the objective function have profound effects on the optimum profiles. For higher pressures, it is shown that a high temperature must be used initially; but must be lowered later to minimize the formation of side products. However, for lower pressures, the temperature must be increased from a low value initially; but for large polymerization times, the temperature must be further reduced to minimize the formation of side products. It is thus seen that the optimum temperature profile for low pressures exhibits a broad maximum.
Uniaxial drawing of a copolyterephthalate based on ethylene glycol and 1,4‐cyclohexane‐dimethanol
Authors: Benavente R. , Pereña J. M. 
Published: December 2004

AbstractThe drawing of an amorphous copolyester based on poly(ethylene terephthalate) and poly(1,4 cyclohexylene‐dimethylene terephthalate) has been studied at temperatures from 20° to 100°C and various strain rates. The tensile properties, densities, and stress whitening of the stretched samples depend on whether the drawing temperature is below or above the glass transition temperature.
On the crystallinity and some structure/property relationships of poly(ethylene terephthalate)—poly(amide‐6,6) blends
Authors: Pillon L. Z. , Lara J. , Pillon D. W. 
Published: December 2004

AbstractFollowing the ester‐amide interchange reaction in the poly(ethylene terephthalate)/poly(amide‐6, 6) (PET/PA) system in the presence of p‐toluenesulfonic acid (TsOH), samples were injection molded and tested in the tensile mode. A brittle fracture was observed for these unoriented specimens. To separate the influence of the crystallinity from that of the interphases, the samples were studied using differential scanning calorimetry (DSC). The DSC results indicated an increase of crystallinity in the blends caused by enhanced nucleation of PA (which crystallizes first) and that of the copolymer resulting from the esteramide interchange reaction. It has been independently verified that neat PET samples of comparable crystallinity to that existing in the PET/PA blends show a similar behavior.
Rheology of polymers containing carbon black
Authors: Lakdawala K. , Salovey R. 
Published: December 2004

AbstractIn order to elucidate the flow behavior of electrophotographic toner systems, shear stress was measured as a function of shear rate in a cone and plate rheometer for polymer melts containing carbon blacks of surface area 24 and 625 m2/g at several concentrations and temperatures. Polymers included high and low molecular weight polystyrene and poly(butyl methacrylate). The addition of carbon black to the polymers caused a large increase in viscosity, especially at low shear rates and shear stresses. As the concentration of carbon black was increased, the viscosity at low shear rates became unbounded below a value of the shear stress designated the yield stress. The absolute magnitude of the yield stress depended primarily on the concentration and surface area of the carbon black and was independent of the polymer and temperature. Apparently, carbon black forms an independent network within the polymer at low shear rates which precludes flow. In some cases, the viscosity of polymers filled with carbon black was lower than that of the pure polymer. This effect was favored for polystyrene compared to poly(butyl methacrylate) and was facilitated by increasing the molecular weight of polystyrene, reducing the surface area and concentration of carbon black, and by increasing the temperature and shear rate.
Rheology of copolymers containing carbon black
Authors: Lakdawala K. , Salovey R. 
Published: December 2004

AbstractThe rheological response of random copolymers of styrene and butyl methacrylate containing carbon black simulates the behavior of toner in the electrophotographic process. Both the relative viscosity and the dependence of viscosity on shear rate were increased by raising the temperature and raising the concentration and surface area of carbon black. For high concentrations and surface areas of carbon black and at elevated temperatures, a well‐defined yield stress varied from 2.5 × 102 to 1.6 × 104 Pa, depending on the concentration and nature of the carbon black but independent of the type of polymer and temperature, implying the formation of a carbon black network. Plasticization by carbon black was favored at low surface area and concentration of carbon black and at elevated temperatures.
Effect of die temperature on the flow of polymer melts. Part I: Flow inside the die
Authors: Yang Bing , Lee L. James 
Published: December 2004

AbstractThe effect of die wall temperature on the flow of polymer melts in circular capillary dies was studied. At constant flow rates, it was found that die wall temperature had a greater effect on the pressure drop than melt temperature. A capillary die with two circular channels with different diameters was designed to simulate the profile extrusion. Changes of wall temperature varied the flow rate ratio between the two channels. An implicit finite difference method was used to simulate the velocity and temperature profiles inside the die. Values predicted by this model matched well with experimental data for both dies.
Effect of die temperature on the flow of polymer melts. Part II: Extrudate swell
Authors: Yang Bing , Lee L. James 
Published: December 2004

AbstractThe effect of die wall temperature on the extrudate swell of polymer melts flowing through dies with single and dual circular channels was studied. Extrudate swell was measured at constant flow rates using an Instron capillary rheometer with a modified die section. It was found that under isothermal conditions, extrudate swell plotted against the average wall shear stress gave rise to a temperature independent correlation for polystyrene. Under non‐isothermal conditions, such a correlation did not exist, which might be due to the change of wall shear stress in the axial direction. The extrudate swell in the non‐isothermal cases can be better correlated with the wall shear stress at die exit. For the two‐hole die, changes of die wall temperature varied both the flow rate ratio and the extru date swell ratio. The latter is, however, much less sensitive to the die wall temperature than the former.
Fatigue and environmental resistance of polyester and nylon fibers
Authors: Mandell J. F. , Steckel M. G. , Chung S.‐S. , Kenney M. C. 
Published: December 2004

AbstractThe fatigue resistance of individual synthetic fibers can govern the performance of complex fiber assemblies such as tire cord and marine rope under certain loading conditions. This paper explores the relative performance of polyester and nylon 6,6 fibers and yarns, both dry and in aqueous solutions, primarily synthetic seawater. Fiber failure over a range of loading conditions and frequencies was found to occur at a critical cumulative strain, governed by a creep rupture process; the cyclic lifetime for both fibers is predictable using a simple creep rupture based theory. Polyester is more resistant to creep rupture, and consequently outperforms nylon 6,6 in cyclic fatigue. The advantage of polyester is considerably greater in aqueous solutions, where the performance of the nylon is diminished. Other comparisons indicate that the particular polyester fibers studied have higher stiffness and strength, lower strain to failure, and much lower hysteresis energy absorption compared with the nylon. The actual fatigue performance of complex fiber assemblies such as ropes is also limited under many conditions by factors not present in single fiber or yarn fatigue, including hysteric heating and internal and external abrasion.
Effects of strain‐induced crystallization on the elastic and thermoelastic properties of some fluoroelastomers
Authors: Hsu Y.‐H. , Mark J. E. 
Published: December 2004

AbstractA Viton copolymer containing vinylidene fluoride (VF2) and hexafluoropropylene (HFP), and a terpolymer containing VF2, HFP, and tetrafluoroethylene (TFE) were cross linked using varying amounts of Bisphenol AF to yield two series of fluoroelastomer networks, Stress‐strain isotherms in elongation were determined for these samples at several temperatures and at two degrees of swelling with phenyl acetate. Strain‐induced crystallization was observed, as evidenced by upturns in the isotherms at high elongations. It appears to be more pronounced in the terpolymer samples, presumably because the TFE units not only can crystallize themselves, but can co‐crystallize with the VF2 units. The crystallization was found to persist upon moderate increase in temperature, but was suppressed when the networks were swollen, Thermoelastic (force‐temperature) measurements were used to obtain values of the fraction fe/f of the elastic force that is due to energetic effects. Negative values were obtained for both types of samples and, in the case of two samples studied in detail, their magnitudes increased with increase in elongation. The magnitudes were larger and the increases more pronounced in the case of the terpolymer networks, as would be expected from a greater tendency for straininduced crystallization.
Analysis of reaction injection molding process of polyurethane‐unsaturated polyester blends. Part I: Computer simulation
Authors: Kim J. H. , Kim S. C. 
Published: December 2004

AbstractA computer simulation model was developed to analyze the reaction injection molding (RIM) process of polyurethane and unsaturated polyester blends. The reaction kinetics and viscosity functions of each component were obtained through actual experiments, and a mathematical scheme for numerical calculation was set up in cylindrical coordinates to predict the temperature and conversion profiles within a disc‐type mold. The temperature change calculated from the simulation was compared with the temperature rise measured in actual RIM experiments. The effects of the feed temperature, wall temperature, and catalyst levels on the maximum exothermic temperature and the demolding time were evaluated in a search for the optimum processing conditions.
Injection‐molding process control—A review
Authors: Agrawal A. R. , Pandelidis I. O. , Pecht M. 
Published: December 2004

AbstractThis paper reviews control strategies employed in the injection‐molding process. For clarity, the controlled variables have been categorized into all‐phase control, phase‐dependent control, and cycle‐to‐cycle control. All‐phase control includes variables that must be monitored and controlled at all times; i.e., in all the phases. Control of variables that are triggered during a specific phase are discussed under phase‐dependent control. In cycle‐to‐cycle control, previous data are used to predict future trends and take appropriate corrective actions, The cyclic, dynamic, and unsteady state nature of the injection‐molding process is discussed with respect to the conventional proportional‐integral (PI) and proportional‐ integral‐derivative (PID) controllers as well as the more advanced control schemes such as self‐tuning control, optimal control, and statistical process control. Suggestions involving specific advanced control schemes and recommendations for future research in injection‐molding process control also are made.
Functional polymers LI: Characterization and property analysis of ω‐functionally substituted polyolefins; novel polyolefin ionomers
Authors: Purgett Mark D. , MacKnight William J. , Vogl Otto 
Published: December 2004

AbstractHomopolymers of 2,6‐dimethylphenyl 10‐undecenoate and copolymers of 2,6‐dimethylphenyl 10‐undecenoate with α‐olefins, prepared by coordination initiators using aluminum activated titanium trichloride, and the corresponding sodium carboxylate and carboxylic acid derivatives have been characterized. IR and NMR investigations gave the normal; spectral characteristics typical for estersubstituted polyolefins and their derivatives. The thermal behavior of the polymeric esters, investigated by differential scanning calorimetry, showed glass transitions characteristic of poly(α‐olefins). Polymeric acids and salts presented quite different behavior; most notably the polymeric salt showed no glass transition, but rather an exothermic transition, resembling a broad melting peak at 250‐270°C, which is characteristic of a crystalline polymer. We interpret this behavior as the melting of carboxylate cluster domains, which according to our WAXD analysis has a domain size of about 25 Å.
The importance of enthalpic interactions in polymeric systems
Authors: Barlow J. W. , Paul D. R. 
Published: December 2004

AbstractEnthalpic interactions between blend components primarily determine the state of miscibility and many of the physical properties of the blend. Recent applications of these thermodynamic considerations are reviewed for a variety of systems, including binary and ternary blends of homopolymers, binary blends of copolymers with homopolymers, and polymer‐solvent mixtures. Recent advances toward predicting polymer blend miscibility through use of a modified quasichemical thermodynamic model and heats of mixing data for liquids are also discussed.