bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen bonding potential, HBP: A model for predicting resin solubilities in organic solvents
Authors: Rider Paul E. 
Published: December 2004

AbstractIn a previous paper, a two‐parameter model was described that could be used to predict the hydrogen bond enthalpy of formation between two compounds forming a single hydrogen bond. This paper describes the extension of the use of the two parameters for solvents and polymeric resins in another mathematical model that involves four terms that determine the “hydrogen bonding potential” (HBP) interaction between a resin and a given solvent. Each solvent and each resin can be assigned a donating and accepting parameter (relative to hydrogen bond formation) that combine to yield a numeric value for HBP. A negative HBP value is associated with favorable hydrogen bonding between a resin and a solvent which should correspond to a situation in which solution formation is favorable. A positive HBP value indicates unfavorable interaction which discourages solution formation. Thus, HBP becomes a predictive model of solubilities. Numerical data are presented for four resins and 26 solvents that correlate well with observed solubility behavior. Using this model, it is also possible to construct “solubility maps,” and these are also discussed.
Blowing of oriented PET bottles: Predictions of free blown size and shape
Authors: Erwin Lewis , Pollock Mark A. , Gonzalez Henry 
Published: December 2004

AbstractA model of the blowing process for polyethylene terephthalate stretch blowmolded bottles is presented. This model uses a rubber constitutive relation. The free blown diameter and the stretch balance are derived from stress equilibrium. Free blow experiments show good agreement with the predictions.
Modeling nonlinear viscoelastic response
Authors: Partom Y. , Schanin I. 
Published: December 2004

AbstractWe present a model for calculating nonlinear viscoelastic response which we call the “phases model” (PHM). In terms of a mechanical model representation the PHM is a generalized Maxwell model with nonlinear elements where each Maxwell element is referred to as a phase. The viscous material properties are represented in the model in terms of flow curves of the individual phases. The collection of flow curves form the flow diagram. We show how to calibrate the flow diagram from a family of constant rate test curves by means of a simple straightforward procedure. We give an example of such a calibration for a certain rigid polyurethane. We applied our model to the calculation of nonlinear viscoelastic response to varius loading programs in uniaxial tension, and to the creep of a simply supported beam, and obtained good agreement with experimental data.
Water‐soluble copolymers VIII. Synthesis and dilute solution rheological studies of dextran‐g‐poly(acrylamide‐co‐sodium acrylates)
Authors: McCormick C. L. , Park L. S. , Hester R. D. 
Published: December 2004

AbstractDextran‐g‐poly(acrylamide‐co‐sodium acrylates) were prepared by partial hydrolysis of dextran‐g‐poly(acrylamides) with controlled numbers and lengths of grafted chains. This hydrolysis route proved to be more effective than Ce(IV)‐induced cografting of acrylamide and sodium acrylate comonomers onto dextran in producing the desired graft‐copolymer structures. The resulting copolymers were characterized and the effects of composition, temperature, ionic strength, and shear rate on dilute solution rheological properties were studied.
Poly(p‐phenylene terephthalamide) films formed from extrusion and coagulation of liquid crystalline sulphuric acid solutions: Characterization of orientation and void structure, annealing, and upgrading of film mechanical properties
Authors: Bodaghi Hassan , Kitao Toshio , Flood John E. , Fellers John F. , White James L. 
Published: December 2004

AbstractPoly(p‐phenylene terephthalamide) (PPD‐T) films have been prepared by continuous extrusion of liquid crystalline 17 percent PPD‐T/sulphuric acid solutions through an annular die followed by coagulation, Films extruded without drawdown exhibit some polymer chain orientation in the machine direction. This is increased by uniaxially drawing down films. Films produced with a lubricated conical mandrel sitting between the die and the coagulation bath exhibit an equal biaxial orientation. The uniaxially oriented films exhibit highly anisotropic mechanical properties, while the mandrel‐produced film exhibits balanced properties. Heat treatment at 350°C results in significant enhancement of the tensile strength of the mandrel film. Void structures in the films have been investigated by mass density, scanning electron microscopy (SEM), and small‐angle X‐ray scattering (SAXS). Density measurement indicate a void content decreasing with decreasing film thickness and heat treatment. SEM locates micron‐size voids in the thickest films, apparently caused by rapid coagulation. SAXS indicates much smaller void sixes which are roughly prolate ellipsoids (long axis in machine direction) for uniaxial films and oblate ellipsoids (short axis in thickness direction) for the mandrel produced films. Various techniques are used to estimate mean void size.
A quantitative description for the optical properties of crystalline polymers applied to polyethylene
Authors: Wedgewood Alan R. , Seferis James C. 
Published: December 2004

AbstractA quantitative model which described the microscopic and macroscopic refractive index properties of uniaxially oriented crystalline polymers has been extended in relation to molecular bond polarizabilities in this work. Application of this extended modeling methodology in analyzing measured refractive index data for a series of unoriented and oriented samples of linear polyethylene provided Δ = 0.0585 and Δ = 0.194 as the most probable crystalline and noncrystalline intrinsic birefringences for samples exhibiting spherulitic morphology. With these intrinsic birefringences, noncrystalline orientation functions were determined from the optical measurements coupled to the model and the results compared to values obtained from infrared measurements. This comparison of noncrystalline orientation functions, as well as from low density polyethylene reported by other investigators, provided experimental justification for our modeling methodology to examine the possibility of changing intrinsic birefringences for polyethylene as a function of orientation and morphology. The results of this examination demonstrated that values for Δ = 0.0585 and Δ = 0.12 should be used for both low and high density polyethylene samples oriented above the spherulitic to fibrillar transition region.
“Living” anionic polymerizations in a continuous stirred‐tank reactor under sustained feed oscillations
Authors: Couso D. A. , Meira G. R. 
Published: December 2004

Abstract“Living” anionic polymerizations carried out in a continuous stirred‐tank reactor (CSTR) and operated under forced‐feed oscillations are theoretically studied to investigate the effects on time average values of average chain lengths, polydispersity, and reagent conversions. The instantaneous mean residence time is maintained constant. The period of the oscillations is varied between 60 and 0.05 mean residence times, and various amplitudes are considered. Some advantages are observed with the periodic forcing as compared to the steady operation; polymers with average polydispersities above 10 may be produced at low frequencies, with polydispersities below the steady‐state value of 2 at intermediate frequencies, and with polydispersities of 2 but with increased monomer conversion at fast cycling.
Flow analysis of rubber transfer molding
Authors: Lee L. J. , Griffith R. M. , Sommer J. G. 
Published: December 2004

AbstractAn experimental study has been carried out on rubber I transfer molding. It reveals that the filling is frequently limited more by the resistance of flow across the transfer pot than by resistance of flow through the sprue holes into the cavities. A mathematical model has been derived, which predicts semi‐quantitatively the molding behavior observed. The mode1 predicts that fill time is proportional to the ratio of compound viscosity divided by molding pressure raised to about the fourth power. For the common cases where most of the fill time is from the resistance to the transverse flow on the top of the sprue plate, the fill time is proportional to about the fifth power of the ratio of transverse distance divided by the charge thickness. Experimental results showed that preheating and mastication of the compound reduced transfer time substantially. The charge pattern did not seem to have a major influence on transfer time.
Molecular orientation in film extrusion of high‐density polyethylene
Authors: Picot J. J. C. 
Published: December 2004

AbstractMolecular orientation in film extrusion has been studied using an extrusion‐grade commercial polyethylene resin. First quad (take‐up) speed was varied over the range 50 to 120 m/min, Web crystallinities were found to be in the range 0.60 to 0.65 as determined by differential scanning calorimetry. Web crystalline orientation function fc was slightly negative below a takeup speed of 50 m/min and rose to a value of 0.4 at 120 m/min at a quench bath temperature of 37.8°C and a melt temperature of 251°C for one of the resins used. (Perfect orientation along the machine direction implies fc equal to 1.0). Amorphous orientation function fa remained below 0.1 and was almost constant with takeup speed. This behavior was modified in a minor way by changes in quench bath and melt temperature as well as resin lot. A qualitative model was proposed for this without definite proof. The major mechanism at work in the film‐forming process is macromolecular network structure deformation in elongational flow. Die gap variation at uniform extrusion rate has a secondary effect on web orientation. With the present state of knowledge, it is not possible to quantitatively separate the amorphous orientation function into its various conformational contributions. It was also noted that high take up speeds and low air gaps tend to freeze the web at greater widths.
Applications of a reaction‐injection‐molding process model in the analysis of premature gelling, demold time, and maximum temperature rise
Authors: Estevez S. R. , Castro J. M. 
Published: December 2004

AbstractIn this paper, we discuss a way to present results or practical interest for the reaction injection molding (RIM) process, such as guidelines to avoid premature gelling and to control demold time and maximum temperature rise. The results are presented as a set of graphs correlated using the relevant dimensionless groups of the process. Examples of applications of these graphs are given and discussed. The numerical calculations are done using the RIM process model developled by Castro and Macosko, which has been shown to agree with experimental results.
Effects of surface treatment on the mechanical properties of carbon fibers
Authors: Bahl O. P. , Mathur R. B. , Dhami T. L. 
Published: December 2004

AbstractSurface of the carbon fibers developed from PAN (polyacrylonitrile) has been modified using such methods as air oxidation, nitric acid treatment, and anodic (electrolytic) oxidation. By choosing optimum treatment parameters, the tensile strength of such fibers has been found to increase by about 60 percent over that of the untreated value. A quantitative estimation of the surface groups formed during the treatment shows an increase in number with severity of the treatment. Further, removal of these functional groups from the fiber surface during degassing at 1000°C also influences the mechanical properties of the carbon fibers considerably. Results have been discussed in detail.
Drying of plastics with time‐varying surface concentration: Experiments on slabs and application to equipment analysis
Authors: Belofsky Harold 
Published: December 2004

AbstractDrying of hygroscopic plastics in preparation for molding or extrusion is characterized by very low moisture levels in the polymers and by very low humidity in the drying air. In these circumstances, diffusivity is essentially independent of moisture concentration but surface concentration will vary with time in the general case. An exponential surface concentration/time function is derived from fundamentals and applied to the solution of the diffusion equations for slabs and spheres. Under ideal drying conditions, the solutions reduce to the elementary case in which cs = cf for θ > 0. For non‐ideal drying, the exponential factor b̃ in the surface concentration function appears in the solutions of the diffusion equations. Experiments on slabs were used to verify the analysis since ideal or non‐ideal drying conditions could readily be set up with molded slab samples. Experimental drying curves are in agreement with theory. To complete the analysis for engineering applications, equations for counter flow heat transfer in the dryer hopper are derived and combined with the diffusion solutions to generate dryer performance data.
Durability and failure analyses of a silane treated α‐Al2O3/polyethylene joint in wet environment
Authors: Kaul A. , Sung N. H. , Chin I. , Sung C. S. P. 
Published: December 2004

AbstractThe durability of the joints, consisting of α‐Al2O3 primed with γ‐aminopropyl triethoxysilane (γ‐APS) and polyethylene (PE), in wet environment is investigated as a function of the γ‐APS thickness, dehydration of γ‐APS prior to joint formation and redrying the joint after a certain exposure. The joint strength measured by 180°s peel is found to decrease with exposure time in wet environment more rapidly in water than in 100 percent RH. With exposure time, the debonded area increases from the edges toward the central area of the joint. Relatively thin γ‐APS treatments on α‐Al2O3 appear to provide a more durable joint than thicker γ‐APS treatments resulting in an optimal thickness in the range of 0.3 ∼ 1 percent γ‐APS concentration level. Dehydration of γ‐APS leads to more durable joints with an optimal condition found between 1 ∼ 2 days of dehydration at 100°C in vacuum. Regardless of the γ‐APS thickness and dehydration history, the failure in the de‐bonded area seems to occur by the hydrolysis of γ‐APS near the α‐Al2O3 side and by the deformation of polyethylene (cohesive failure) in the peeled area, as characterized by SEM and ESCA. The debonded area in the dried joint recovers little strength, but in the central bonded areas, the strength is mostly recovered, characterized by cohesive failure of polyethylene. Diffusion of water in γ‐APS near the α‐Al2O3 side rather than the PE side can explain at least qualitatively most of the observed trends. The effects of γ‐APS thickness and dehydration on the durability in wet environments are compared with those on adhesion promotion in dry environments as well as on their respective failure mode.
Interactions in polymer blends‐relationship between thermodynamic and scattering measurements
Authors: Higgins J. S. , Walsh D. J. 
Published: December 2004

AbstractMethods of preparation and of determining miscibility limits for partially miscible binary polymer blends are described. An equation‐of‐state, theoretical description of this behavior is introduced and the terms describing interactions within the system discussed, Values of these interaction terms are obtained by fitting the models to measured cloud point curves, heats of mixing data, etc. The use of neutron scattering experiments to obtain molecular conformation and interaction parameters is described and a comparison made with values extracted from the thermodynamic measurements.
On the scale‐up of plasticating extruder screws
Authors: Chung Chan I. 
Published: December 2004

AbstractIn the most commonly used scale‐up method of plasticating extruder screws, the screw channel depth is increased by the square root of the diameter ratio while the screw RPM is decreased by the square root of the diameter ratio such that the output rate increases proportionally to the square of the diameter ratio. This scale‐up method, largely based on the pumping function of the screw, often leads to a higher melt temperature, a higher screw horsepower consumption per unit output rate and an inferior melt quality from the larger diameter screw. Analysis of the common scale‐up method reveals that, although the shear rate in the melt is kept constant, the average residence time and the peripheral screw speed are increased for the larger diameter screw. Our recent study on the melting mechanism also reveals that the melting capacity increases less than the pumping capacity. A detailed examination of the common scale‐up method in this paper shows that the pumping capacity and the solid conveying capacity increase more than necessary while the melting capacity increases insufficiently.
Modification of surface structure and crystallinity in compression‐molded poly(phenylene sulfide)
Authors: Radhakrishnan S. , Nadkarni V. M. 
Published: December 2004

AbstractThe structural modifications and the changes in crystallinity of poly(phenylenesulfide) (PPS) during high‐pressure molding and curing have been investigated as a function of pressure and temperature using wide‐angle X‐ray scattering (WAXS), infrared absorption (IR) and scanning electron microscopy (SEM). It has been found that the crystalline content of the molds varies with applied pressure as Pα where α is 1.5. Major changes in the IR spectra are found in the range of 800 to 600 cm−1 and attributed to structural modifications which have also been noted in the scanning electron micrographs. These various results have been mainly explained on the basis of plastic deformation and flow during the high‐pressure molding process.
General treatment of polymer crystallization kinetics—Part 1. A new macrokinetic equation and its experimental verification
Authors: Malkin A. Ya. , Beghishev V. P. , Keapin I. A. , Bolgov S. A. 
Published: December 2004

AbstractA new macrokinetic equation of the autocatalytic type is proposed to describe the polymer crystallization process. The derived equation is compared with the known Avrami equation. It is shown to be consistent with the results of isothermal experiments.
Properties of a transparent polycarbonate copolyester blend
Authors: Avakian Roger W. , Allen Richard B. 
Published: December 2004

AbstractIn recent years only a few totally new plastics have been developed, since suppliers are finding it quicker and less expensive to tailor existing resins to meet the requirements of a specific application by alloying. The properties of an alloy of polycarbonate and a proprietary copolyester have been fully characterized. Thermal analysis shows that the polymers are miscible in all proportions. Transparency, glass transition temperature, barrier properties, tensile, and flexural properties of the alloy all fall between those of the neat components. Certain synergistic properties were observed upon blending the polycarbonate and polyester. The tendency of the blend not to yellow during γ‐sterilization is remarkably better than can be predicted by an additive relationship. Chemical resistance of the blends behaves in a similar manner. The excellent balance of properties exhibited by the blend such as transparency, impact strength, γ‐radiation resistance, and chemical resistance makes it useful in applications such as medical disposables and filter bowls.
Hydrodynamic analysis of a spiral disc extruder
Authors: Krein H. L. , Plumtree A. , Rudin A. 
Published: December 2004

AbstractThe flow of polymer melts in a rotating disc extruder is analyzed with the development of a mathematical model for drag flow in a contoured rotating disc. The model assumes a fully melted material which exhibits Newtonian flow behavior under isothermal conditions. Flow is evaluated in successive sections of the flow path, and the drag flow component is calculated by assuming a zero pressure gradient by analogy to the analysis of single screw extruder performance. The final expression involves a computer‐assisted numerical solution. Results of the drag flow model are presented for three different disc geometries. A mathematical model of negative flow, and a comparison of the results with experimental data will be presented in followup papers.
Melt rheology and extrudability of polyethylenes
Authors: Utracki L. A. , Catani A. M. 
Published: December 2004

AbstractCommercial high density polyethylene (HDPE), low density polythylene (LDPE), and linear low density polyethylene (LLDPE) resins were tested at 150, 170, and 190°C in steady state, dynamic, and extensional modes. Within the low rates of deformation \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω ≤ 0.3, the steady state and dynamic functions agreed: η = η′ and N1 = 2G′; at the higher rates, the steady state parameters were larger. The elongational viscosity, ηe, was measured under a constant rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, or stress, σ, condition. In the first case for LLDPE, the transient η reached an equilibrium plateau value, ηe. For HDPE, η increased up to the break point. For LDPE, stress hardening was recorded. Under constant stress the ηe, could always be determined; its value, within experimental error, agreed with the maximum value of η determined in a constant \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document} experiment. The maximum strain at break was only ε = 1.5 for HDPE and 3, to 4 for LDPE and LLDPE. The rate of deformation dependence of the η (or η′) and ηn may be discussed in terms of the Trouton ratio, RT = ηe/3η at \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} = ω = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon$ \end{document}: RT ≤ 1.2 for LLDPE, RT ≤ 2.5 for HDPE, and RT ≤ 15 for LDPE. The PE resins were extruded at 190°C through a laboratory extruder equipped with a slit or rod die. The rotational speed of the screw varied from 0 to 90 rpm. Extrusion pressure, output, and energy were measured and correlated with the rheological parameters of the resins.
A thermodynamic prediction of tie chain length distribution in drawn semicrystalline polymers
Authors: Popli Rakesh , Roylance David 
Published: December 2004

AbstractThe mechanism underlying fracture of many oriented semicrystalline polymers is hypothesized to be a thermally activated, stress‐aided rate process in which the tie chains connecting crystalline units suffer thermomechanical dissociation. Some previous numerical models based on this concept have assumed a Gaussian distribution of tie chain contour lengths which are ruptured progressively by successively higher specimen strains, and have used electron spin resonance (ESR) spectroscopy to obtain the numerical parameters of the distribution. The distribution of tie chain lengths in the intererystalline region is calculated theoretically in this paper, based on minimization of free energy. Our results, although in basic agreement with earlier models, suggest a reinterpretation of some of the ESR findings with regard to molecular fracture processes.