bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of the Dielectric Response of Thermosets During Isothermal and Nonisothermal Cure
Authors: Nass Kirk A. , Seferis James C. 
Published: December 2004

AbstractUsing dielectric techniques to monitor thermoset properties on‐line during processing requires a mathematical relationship between the experimentally obtained signals and the physical state of the polymer. Such a relationship accounting for the dielectric response during both isothermal and dynamic cure experiments is developed in this study. Ionic conductivity changes with cure were described using the Keinle‐Race expression, while an approach taken by Lane, Bachmann, and Seferis for modeling dipolar relaxation during isothermal cure was extended to nonisothermal cure conditions. Both of these approaches were combined in this study, providing a complete description of the dielectric changes occurring in thermosetting systems resulting from cure. Experimental results for a model epoxy/amine system were predicted with the developed methodology for isothermal cure at 140°C, 150°C, 160°C, and 170°C and cure under dynamic heating conditions at 1°C per minute.
Glass transition temperature of a fluoroelastomer‐diluent system
Authors: Serbenski Francesca , Pezzin Giovanni , Ajroldi Giuseppe 
Published: December 2004

AbstractThe glass transition temperature has been measured carefully for the fluoroelastomer, Tecnoflon, a copolymer of vinylidene fluoride and hexafluoropropene, diluted with variable amounts of 2‐butanone. Of the several different theoretical treatments found in literature, that presented by Gordon and coworkers appears to give the equation that describes well the experimental results, without making use of adjustable parameters. Some features found at very high diluent content can be interpreted with a treatment based on free volume.
A novel sliding plate rheometer for molten plastics
Authors: Giacomin A. J. , Samurkas T. , Dealy J. M. 
Published: December 2004

AbstractA novel sliding plate rheometer has been developed that is suitable for use with molten plastics, concentrated polymer solutions, raw elastomers, and other viscoelastic or thixotropic materials. It can generate steady shear rates from 0.05 to 500 s−1 and can also be used to measure linear viscoelastic properties. In addition, it can be used to measure a broad spectrum of nonlinear viscoelastic properties such as the nonlinear relaxation modulus and the shear stress growth coefficient. In order to measure these nonlinear properties it is necessary to generate large, uniform, transient deformations Involving high strain rates. Rotational and capillary melt rheometers are not capable of generating this type of deformation, and until now it was not convenient to use sliding plate rheometers for this type of application. However, the recent development of a reliable and robust shear stress transducer makes it very convenient to use the sliding plate geometry to carry out all of these tests. The new rheometer is described, and examples of the types of data it can generate are shown.
The effect of deformation history on the morphology and properties of blends of polycarbonate and a thermotropic liquid crystalline polymer
Authors: Kohli A. , Chung N. , Weiss R. A. 
Published: December 2004

AbstractThe effect of deformation history on the morphology and properties of liquid crystalline polymers (LCP) blended with polycarbonate resin was assessed. The addition of an immiscible LCP phase was found to improve the melt processability of the host thermoplastic polymer. In addition, by employing a suitable deformation history, the LCP phase may be elongated and oriented such that a microfibrillar morphology can be retained in the solid state.
A study on polymer blending microrheology: Part 5 deformation of purely elastic particles in an elongational flow field
Authors: Van Der Reijden C. , Van Heel A. S. , Sára A. , Schut J. 
Published: December 2004

AbstractThe deformation of purely elastic spheres in steady and unsteady elongational flow has been studied. Experiments were carried out in a four roller apparatus (steady elongational flow) and in the time dependent elongational flow of a converging channel. The existing theory which gives a first order approximation of the deformation of elastic spheres is extended to the non‐steady elongational flow in the cone. Both in steady and unsteady elongational flow, the theory describes the deformation of the spheres satisfactorily and under certain conditions even for higher deformations than expected.
Physical basis for a pressure‐dependent yield criterion for polymers
Authors: Lyon Richard E. 
Published: December 2004

AbstractA previously empirical pressure‐dependent yield criterion for polymeric solids is derived from linear thermoelasticity and equilibrium thermodynamics. The assumption of a critical value of the mechanical component of the internal energy density at the onset of plastic deformation leads to an explicit expression for the yield condition in terms of the stress invariants and thermomechanical properties of the material. Order of magnitude agreement between the linear theory and published experimental data is obtained for a variety of polymers, suggesting a possible physical basis for pressure‐dependent yielding.
A fundamental study of polymer melt devolatilization. IV: Some theories and models for foam‐enhanced devolatilization
Authors: Lee S. T. , Biesenberger J. A. 
Published: December 2004

AbstractSome model experiments on polymer melt devolatilization (DV) conducted in our laboratories have been previously reported. Here, we examine some theories and propose some mathematical models in pursuit of an explanation of these experimental observations. Included are bubble nucleation and free volume theories as well as continuum models for bubble growth in quiescent fluids and fluid flow in rolling pools without bubbles. A modification of Harvey's cavity model seems to explain the behavior of foam formation in DV, at least qualitatively. Denson's cell model for bubble growth fits the separation data under vacuum. A simple exponential model for overall separation fits the separation data at atmospheric pressure (entrained DV).
Poly(t‐BOC‐styrene sulfone)‐based chemically amplified resists for deep‐UV lithography
Authors: Tarascon R. G. , Reichmanis E. , Houlihan F. M. , Shugard A. , Thompson L. F. 
Published: December 2004

AbstractThe unique ability of the tert‐butoxycarbonyl protecting group (t‐BOC) to be removed by a catalytic amount of strong acid has intensified the search towards new chemically amplified resist systems based on this chemistry. A series of new copolymers of t‐BOC‐styrene and sulfur dioxide have been prepared by free radical polymerization. These polysulfones function as chemical amplification positive resists for deep‐UV lithography when mixed with either 2,6‐dinitrobenzyl tosylate or triarylsulfonium salt acid precursors. The lithographic characteristics of 2:1 and 3:1 polysulfones have been evaluated. The new positive deep‐UV photoresists are aqueous base developed and are capable of 0.5 μm resolution. Even though the photoresists containing 2,6‐dinitrobenzyl tosylate are less sensitive than the onium salt formulations, they displayed greater contrast values. For example the poly(t‐BOC‐styrene sulfone) (2:1) 15 wt % tosylate resist formulation exhibits a sensitivity of 26 mJ/cm2and a contrast of ∼20.
Factors controlling the etching rate and etching profile in the O2reactive ion etching pattern transfer step in multilevel lithography
Authors: Jurgensen Charles W. , Shaqfeh Eric S. G. 
Published: December 2004

AbstractPhysical bombardment plays a dominant role in the O2reactive ion etching (RIE) pattern transfer step in multilevel lithography. Etching rates are determined by the flux and energy distribution of the bombarding ions and energetic neutrals (charge transfer products), while anisotropy is determined by their directionality. Measurements of the sheath thickness and voltage drop may be used to estimate flux, energy distribution, average energy, and angular distribution of ions and the energetic neutral products of charge transfer collisions. The estimated flux of bombarding particles allows measured etching rates to be converted into yields. The trends for the etching rate as a function of pressure, bias voltage, and other system variables reflect a single fundamental trend for the yield as a function of bombardment energy. Etching rates of an organic novolac polymer are proportional to the energy flux from bombarding particles while the yield per bombarding particle is proportional to its energy. These kinetics are combined with angular distribution and interface evolution models to predict etching profiles in multilevel lithography.
Photochemical free‐volume generation in poly(methyl methacrylate) photoresists
Authors: Limm William , Winnik Mitchell A. , Smith Barton A. 
Published: December 2004

AbstractThe dissolution rates of poly(methyl methacrylate) [PMMA] thin films on quartz substrates are studied by a combination of laser interferometry and fluorescence quenching methods. In this way one can monitor the penetration, rate of the solvent (2‐butanone, 2‐pentanone) into the film. When these films were prepared containing 2 to 8 percent Meldrum's diazo (1) as a dopant, the dopant acted as a mild retarder of film dissolution. Upon irradiation at 254 nm, 1 is converted to CO, N2 + acetone, and this process leads to a pronounced acceleration' of the PMMA film dissolution rate.
Dissolution inhibition mechanisms of naphthoquinone diazides
Authors: Koshiba Mitsunobu , Murata Makoto , Harita Yoshiyuki , Yamaoka Tsuguo 
Published: December 2004

AbstractDissolution inhibition mechanisms of naphthoquinone diazides in novolak based positive photoresists were investigated from three different aspects:

• Dipolar interaction.
• Interfacial chemical reactions.
• Chemical structures of naphthoquinone diazides.
The results suggest that there exists a hydrogen bonding interaction between the compounds with the matrix novolak resin and that naphthoquinone diazides would crosslink the resin in contact with an alkaline developer, both of which contribute to dissolution inhibition mechanisms. However, there seems to exist another dissolution inhibition mechanism; namely, 1,2‐naphthoquinone diazide does not inhibit dissolution of the matrix novolak resin at all while a clear dissolution inhibition effect Is observed for its derivatives containing sulfonyl groups. In the present paper, three dissolution inhibition mechanisms of naphthoquinone diazides will be proposed.
Novel photoresist design based on electrophilic aromatic substitution
Authors: Reck B. , Allen R. D. , Twieg R. J. , Willson C. G. , Matuszczak S. , Stover H. D. H. , Li N. H. , Fréchet J. M. J. 
Published: December 2004

AbstractA new approach to resist materials that exhibit chemical amplification is based on systems comprised of three structural units at least one of which is polymeric: (a) an aromatic moiety such as poly(4‐hydroxystyrene), Novolac, or other aromatic compounds which are susceptible to electrophilic aromatic substitution; (b) a latent electrophile which may be polyfunctional and, in the case of this study, is a carbocation precursor; (c) a material which generates strong acid upon irradiation. Exposure of a film containing these three structural components affords a latent image of acid dispersed in the polymer matrix. In a subsequent baking step, the photogenerated acid reacts with the latent electrophile releasing a very reactive carbocationic species which becomes bound to the aromatic moiety. As one of the components of the resist is polymeric and multifunctional, the result is a rapid increase in molecular weight due to branching and crosslinking of the chains. In terms of imaging, this process translates into the formation of a negative image of the mask although under some conditions a positive image may also be produced. The system shows a very high sensitivity and can provide high resolution images devoid of distortion due to the absence of swelling during development.
Melt transformation coextrusion. I.
Authors: Perez M. A. , Collier J. R. 
Published: December 2004

AbstractUsing the Melt Transformation Coextrusion process it is possible to enhance the mechanical and thermal properties of polymeric extrudates directly from the melt and maintain continuous production rates. This adaption of melt transformation extrusion has significantly enhanced line speed compared to the precursor process. The required operating pressures in both processes are low enough to allow for the usage of commercial plasticating extruders as the polymer melt sources. Molecular orientation necessary to produce property enhancement is induced in the converging section of specially designed dies and retained by the core layer of the extrudate by imposing a steep temperature gradient in the land section of the die. Mechanical properties (i.e. tensile strength and modulus) and melting point elevation observed for the polypropylene core/polyethylene skin extrudates were functions of extrusion pressure. The highest values of these properties noted were: tensile modulus, 9.37 × 105 psi; tensile strength, 2.10 × 104 psi; and melting point elevation in excess of 10 K. The levels of property enhancement seem to be bound in their lower limit by a metastable liquid crystalline form. The upper theoretical limit of property enhancement should correspond to a fully extended chain morphology.
Melt transformation coextrusion. II: Flow analysis
Authors: Perez M. A. , Collier J. R. 
Published: December 2004

AbstractMelt Transformation Coextrusion for power law fluids was analyzed with particular attention being paid to the influence of the die's geometrical shape on flow patterns, and to skin layer effect on the velocity profile and shear stress at the interface between layers in a three‐layered system. Volumetric flow rate expressions were also generated for the aforementioned system, and stream and potential functions were derived for a free boundary converging film geometry. Newtonian as well as non‐Newtonian fluids were considered for this analysis in which the streamline shape changes their convergence downstream into the land section. Also, a finite element solution technique was utilized to reveal shear stress profiles that arise from the flow of high density polyethylene at 200°C in a converging fixed boundary geometry.
Numerical simulation and experimental investigation of injection mold filling with melt solidification
Authors: Chen B. S. , Liu W. H. 
Published: December 2004

AbstractA two‐phase model is presented for simulating the injection mold filling process including the effect of transient melt solidification, i.e., the phase change effect. The liquid region is governed by Hele‐Shaw flow for a non‐Newtonian fluid using a modified Cross model to describe viscosity under non‐isothermal conditions. Further, the energy equation of the solid phase is dominated by a transient condition. The interfacial energy balance equation is also proposed to predict the solidified layer thickness and temperature profile. Two well‐characterized semicrystalline materials, polypropylene and polyethylene, were used in the present work. Good agreement is obtained between the predicted results and experimental observations from this study and the previous literature concerning the thickness of solid layer, the shape of, advancing melt front, and the pressure traces. In particular, the predicted pressure based upon the two‐phase model is higher than that in terms of the single‐phase model by about 13 percent. Finally, the semicrystalline structure of the frozen skin layer and the central core were investigated with a scanning electron microscope to verify the two‐phase model.
Reaction and thermal analysis for SMC (sheet molding compound) molding in complicated geometries
Authors: Lee Ching‐Chih 
Published: December 2004

AbstractA finite element technique has been developed for coupled reaction and heat transfer analysis in which mass diffusion is negligible. The temperature unknowns are located at nodal points, while the reaction variables (species concentrations, reaction rates) are at the Gauss points in each element. With a mechanistic kinetic model, the SMC (sheet molding compound) cure in 2‐D and 3‐D geometries was analyzed. The results for plate‐and‐rib configurations show the progression of cure and heat transfer and the influence of geometry on the progression. The analysis for a flat sheet of SMC in a mold with localized heating using bubblers indicates the thermal interaction between the mold and the curing SMC. Temperature and reaction profiles are given for each case.
A nonisothermal differential scanning calorimetry study of the curing kinetics of an unsaturated polyester system
Authors: Ng H. , Manas‐zloczower I. 
Published: December 2004

AbstractNonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.
Gradient‐Index polymer materials and their optical devices
Authors: Koike Yasuhiro , Tanio Norihisa , Nihei Eisuke , Ohtsuka Yasuji 
Published: December 2004

AbstractA gradient‐index (GRIN) plastic optical fiber was prepared by a heat‐drawing process of the GRIN preform rod obtained by a new interfacial‐gel copolymerization technique. The attenuation loss of the GRIN fiber was 179 kB/km at 650‐nm wave‐length and its numerical aperture was 0.20‐0.25. To attain low loss and highly dense integrated circuits, steric radial‐GRIN optical waveguide components such as GRIN branching, star coupler, multi‐coupler, and a 2‐D GRIN lens array, were monolithically fabricated by this technique. A novel spherical GRIN sphere lens, whose index function is symmetrical about the center of the sphere, with a low spherical aberration, was prepared by a modified suspension polymerization technique. A W‐shaped GRIN sphere has been newly proposed to further reduce the spherical aberration, compared with the parabolic GRIN sphere previously proposed.
Control of transesterification in polyester blends
Authors: Golovoy A. , Cheung M.‐F. , Carduner K. R. , Rokosz M. J. 
Published: December 2004

AbstractPolyester blends may undergo transesterification during processing, resulting in molecular rearrangements, transient properties, and eventually, degradation. To suppress transesterifcation, the use of organophosphites has been suggested in the patent and technical literature. The effectiveness of organophosphites, however, is variable and sometimes inconsistent. Our recent studies suggest a clue to the inconsistent behavior and provide a simple way to enhance the effectiveness of these stabilizers. Using solid state 31P NMR it was shown that for bis(2,4‐di‐t‐butylphenyl)pentaerythritol diphosphite a conversion of the phosphite group to a phosphonate, via hydrolysis, is a prerequisite for an effective inhibition of transesterification. This conversion occurs readily during melt compounding if the polymers are not completely dry. However, if rigorous drying is employed and phosphite conversion does not occur, then transesterification is not arrested. It was also found that over a period of time the conversion of the phosphite to a phosphonate may take place at room temperature as well. After aging for about a year in the laboratory, the originally ineffective compound, has become a very effective inhibitor of transesterification in blends containing poly(ethylene terephthalate), poly(butylene terephthalate), polycarbonate, and polyarylate. Thus, a simple way to enhance the phosphate effectiveness is to expose it to a humid environment prior to blending.
Crystallization behavior of poly(ethylene terephthalate)
Authors: Jabarin S. A. 
Published: December 2004

AbstractThe crystallization behavior of poly(ethylene terephthalate) (PET) was studied by the methods of small angle light scattering, depolarized light intensity and density measurements. Spherulite growth rates and the overall rates of crystallization were determined at various temperatures. A detailed analysis of the crystallization course has been made with special emphasis on the early stages of crystallization. The results indicate that a significant amount of crystallization takes place in the extraspherulitie material during isothermal crystallization.
Adhesive bonding of polymer composites
Authors: Vinson Jack R. 
Published: December 2004

AbstractIn structures composed of polymer matrix composite materials, components must be joined such that the overall structure retains its structural integrity while it is performing its, intended function which can include both mechanical loads (static and dynamic) and environmental loads (temperature and humidity). The use of composite materials in complex structures almost always reduces the number of components in the structures compared to the use of metallic alloys for the same structure. Thus, using composite materials not only results in great savings in weight, but also through a reduced number of joining operations, results in significant savings in assembly, inspection, parts storage, and movement, resulting in increased reliability and lower cost. Yet joining is still required. Joining metallic structures is a mature technology involving riveting, bolting, welding, glueing, brazing, soldering, and other methods. However, for most polymer matrix composites only adhesive bonding and mechanical fastening can be utilized. Attention has been given recently, however, to localized welding of thermoplastic polymer matrix composites, and this will be discussed briefly later. Inherently, adhesive bonding is preferable to mechanical fastening because of the continuous connection, whereas in drilling holes for bolts or rivets, fibers or other reinforcements are cut, and large stress concentrations occar at each discrete fastener hole. The following is a review of much of the literature dealing with adhesive bonding of polymer matrix composite structures. It is Intended not only to be a review, but also a background for detailed study of the referenced and other documents, and a catalyst for future research.