bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern generation in polyimide coatings and its application in an electrophoretic image display
Authors: Minnema L. , Van Der Zande J. M. 
Published: December 2004

AbstractDirect photo‐patterning of polyimide (PI) films was done in two ways, both based upon the modification of the PI‐precursor, the polyamic acid (PAA), by derivatives of methacrylic amide. In the first method, a photoreactive PAA is prepared by partially (25 mole percent) neutralizing PAA with N‐(N′N′‐dimethylarnino)propylmethacrylic amide and completing the neutralization with methacrylic amide (75 mole percent). In the second method the PAA is esterified, e.g. with N‐hydroxyethyl‐N‐methylmethacrylic amide, through its isourea derivative. The modified PAAs are processed like conventional negative photoresists. In the first method, the photopolymer formed by selective UV exposure is bound to the PAA by intermaeromolecular complexation, causing insolubility in the developer. The second method, which was investigated only qualitatively, provides crosslinked patterns. In both cases a pure PI film is left upon imidization at 350°C. The first method proved to be well‐suited to making the potential well structure in an electrophoretic image display. These wells must have strictly vertical walls (12 μm high) with metallized top faces. It was found that mask contact at “molecular distance” is not needed for the exposure of the photosensitive PAA: vertical walls could be made by simply adapting the developer after contact exposure. This is explained, tentatively, by the typical characteristics of the polymer‐polymer complex upon development. The potential well structure could now be made in a straightforward process.
Biaxially oriented polypropylene film in power capacitors
Authors: Nash James L. 
Published: December 2004

AbstractThe use of polymer dielectrics, particularly biaxially oriented polypropylene (BOPP), has revolutionized power distribution around the world. BOPP film of sub mil thickness has displaced impregnated Kraft paper because of superior dielectric performance, lower cost, and small volume. The polypropylene molecule has a unique set of properties which combine stable dielectric properties in the operating temperature and frequency range along with an adequate dielectric constant. High levels of orientation and a small unbalance of orientation are required to produce films of high dielectric strength over large areas of film. Control of thickness uniformities to approximately ± 5 percent are critical to the reliable operation of the capacitor under load and to control of capacitance in the product. A special fibrillated surface is required which promotes complete impregnation by the dielectric fluid.This surface is acquired by the development of a specific crystal morphology at one surface of the film. No additives are used to promote this crystalline structure since most additives effect dissipation factor and generate unwanted heat. Similarly, control of contamination (ppm and ppb) is a key factor in the manufacture of film power capacitors.
The spin‐coating process mechanism related to polymer solution properties
Authors: Weill A. , Dechenaux E. 
Published: December 2004

AbstractCoating the substrate with an amorphous polymer layer is a very common process in the manufacturing of integrated circuits, but the fundamental spin‐coating mechanism has not yet been precisely determined. This study examines the influence of the macromolecular characteristics on the spin‐coating process both experimentally and from a phenomenological point of view. It is concluded that the weight‐average molecular weight of the spun‐on solution is a pertinent parameter, and that chain entanglements in polymer solutions may be considered as the basic phenomenon responsible for the formation of the solid polymer layer.
Simulation of foaming in reaction injection molding
Authors: Tighe S. C. , Manzione L. T. 
Published: December 2004

AbstractBlowing agents are often used in the reaction injection molding process to compensate for the shrinkage that occurs upon polymerization, thereby creating a structural foam part. Controlling the thickness of the solid skin and foamed core is essential to achieve the intended mechanical properties of the molded part. A numerical model was developed to predict the foaming behavior in reaction injection molding. This algorithm employs a novel primitive cell construction to enable it to analyze complex rectangular geometries, including inserts, with a two‐dimensional, finite difference solution method. The analysis was applied to foaming of polyurethane in a rectangular cavity. The predicted skin thickness was found to be in good agreement with actual structural foam parts. Foaming as a function of cavity thickness was also treated. The algorithm Is useful for understanding and interpreting nonlinear phenomena of rapid, exothermic polymerizations such as foam formation adjacent to the mold wall or around a metal insert. The results can be used to formulate design guidelines for achieving desired skin/core thicknesses as a function of design, material, and process parameters.
Reaction injection molding of polyureas I. Kinetics study
Authors: Hsu T. J. , Lee L. J. 
Published: December 2004

AbstractSummarized in this paper are the experimental results and mathematical modeling of processing of polyureas. The experimental part includes the applications of solution polymerization to study the reaction kinetics of polyureas. The theoretical part includes a kinetic and heat transfer model that can apply solution polymerization data to predict the bulk polymerization of polyurea in the reaction injection molding process.
A coextrusion process for the manufacture of short‐fiber‐reinforced thermoplastic pipe
Authors: Doshi S. R. , Charrier J.‐M, , Dealy J. M. 
Published: December 2004

AbstractThe advantageous use of short‐fiber‐reinforced thermoplastic (SFRTP) resins in the manufacture of pipe requires that the fiber orientation be controlled and that the surface finish not be adversely affected by the presence of the fibers. It is proposed here that a coextrusion process be combined with the use of a Specially designed, expanding channel die to achieve these objectives. Conventional pipe dies tend to promote the axial orientation of fibers, which has an undesirable effect on the hoop properties of pipe. The use of an expanding channel die promotes fiber orientation in the hoop direction. However, even in this case, there is still a strong component of the shear field near the wall of the die, and in this region, axial orientation still predominates, The use of a three‐layer, coextrusion process in which unreinforced resin is used for both the inner and outer layers makes it possible to minimize the shear effects on the fiber orientation in the middle SFRTP layer. At the same time, it provides a smooth, fiber‐free pipe surface. A theoretical analysis of this process is presented. The analysis shows that the presence of unreinforced surface layers increases the level and uniformity of fiber orientation. The results of an experimental study of fiber orientation in the middle SFRTP layer are found to be in qualitative agreement with the predictions of the theory.
Interface determination in bicomponent extrusion
Authors: Karagiannis A. , Mavridis H. , Hrymak A. N. , Vlachopoulos J. 
Published: December 2004

AbstractThe unidirectional flow of two immiscible fluids with different viscosities in a long die of arbitrary shape is considered. Mathematically, the problem has a continuum of solutions corresponding to arbitrarily prescribed interface shapes, but experimental evidence indicates the existence of a unique interface shape with the less viscous fluid encapsulating the more viscous fluid. With the introduction of the minimum viscous dissipation principle, which postulates that the amount of viscous dissipation is minimized for a given flow rate, the problem becomes a nonlinearly constrained optimization problem. A generalized reduced gradient/finite element method combination is used to predict the interface shape when two inelastic fluids are considered. The effect of the viscosity ratio and flow‐rate ratio on the interface shape is examined for different die geometries. Inner layer breakup phenomena are predicted and explained for complex die geometries.
X‐ray determination of encapsulation stresses on silicon wafers
Authors: Nguyen L. T. , Noyan I. C. 
Published: December 2004

AbstractPreliminary results of a systematic investigation of the behavior of encapsulating materials used in electronic packaging are reported. In this study, the radii of curvature of silicon wafers encapsulated with a filled epoxy are obtained by X‐ray diffraction. The values recorded agree closely with Dektak scanning for thin coatings. However, deviations occur with thicker layers due to the fundamental difference in the parameter measured by both techniques. Analytical solutions are proposed for both one‐and two‐sided encapsulation. Results predicted for the one‐sided coating describe a more severe state of stress within the package, and a correspondingly higher curvature than observed. X‐ray radiographs and optical micrographs of molded packages reveal the presence of internal voids and surface cracks. Such defects relax the stresses within the composite system and may account for the discrepancy observed.
A new differential scanning calorimetry based approach for the estimation of thermal conductivity of polymer solids and melts
Authors: Khanna Y. P. , Taylor T. J. , Chomyn G. 
Published: December 2004

AbstractA new concept based on differential scanning calorimetry (DSG) is introduced which enables us to make a rapid estimation of the thermal conductivity of materials. This technique is shown to give reasonable agreement with the literature data and offers unique advantages, e.g. short analysis time, no instrument modification, small thermal radients across the sample, spall sample size requirements, and most importantly it can be applied to polymer melts. Although our data falls within the literature range, it is difficult to comment on its accuracy since the literature itself shows a wide variation. The precision of our measurements is better than ±20 percent which is considered adequate for thermal conductivity evaluation. As a matter of convenience, we have also presented briefly, a background of the thermal conductivity measuring techniques.
Application of nitrile butadiene rubber for flexible, chemically protective coating
Authors: Hoontrakul Pat , Szamosi Janos , Tobing Singa D. 
Published: December 2004

AbstractRheological properties of toluene solutions of nitrile butadiene rubber, of different molecular weights (Mw, 290,000,320,000, and 450,000) and acrylonitrile contents (30 and 40 percent), were investigated at low (0.1 S−1) to medium (20,0 S−1) shear rates, in order to determine their feasibility for dip‐coating applications. The effect of a surface‐active additive, bentonite, and the solid content (15 and 20 wt percent) on solution viscosity was of main interest. At low zero‐shear viscosity (<50 Pa·S) an excessive sagging of the wet film was experienced; at high zeroshear viscosity (>100 Pa‐·S) the coating showed poor leveling. Zeroshear viscosity was found to be less affected by bentonite than oligomer‐based solutions, at the same time, the solid content and the molecular weight of the polymer had more pronounced effects. With a proper balance of the parameters, seamless coating films were achieved, with excellent tensile and tear properties, and good permeation resistance against benzene.
Thermal analysis of polycarbonate/linear low‐density polyethylene
Authors: Mielke W. 
Published: December 2004

AbstractIn a cooperative testing of polymer blends of polycarbonate (PC) and linear low‐density polyethylene (LLDPE), 17 laboratories from six countries contributed measurements of differential scanning calorimetry (DSC) or differential thermal analysis (DTA) and of thermogravimetric analysis (TGA). This work is part of the activity of the VAMAS* Technical Working Party–Polymer Blends (TWP–PB), which provided the samples and coordinated the tests. Thermal analysis proved to be a, rapid means of assessing the miscibility of polymers using small samples. The system PC/LLDPE investigated in this test is found immiscible. The results of this cooperative test are a basis to elaborate a standard procedure for the characterization of polymer blends.
Miscibility and morphology of the poly(vinyl chloride)/styrene‐acrylonitrile copolymer/poly(methyl methacrylate) ternary blend system
Authors: Huarng J. C. , Min Kyonsuku , White James L. 
Published: December 2004

AbstractThe phase equilibrium of the ternary system poly (vinyl chloride) (PVC)/styrene‐acrylonitrile copolymer (77/23) (SAN)/poly (methyl methacrylate) (PMMA) was investigated using a combination of turbidity, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) measurements. Both turbidity and DSC were used to determine room temperature ternary phase diagrams. The results are basically similar, but the formulation based on the DSC results and the presumed phase model would seem more reliable since it is possible that immiscible blends may well have different phases with similar refractive indices.
Characteristics of hydroxybenzoic acid‐ethylene terephthalate copolymers and their blends with polystyrene, polycarbonate, and polyethylene terephthalate
Authors: Zhuang Ping , Kyu Thein , White James L. 
Published: December 2004

AbstractWe present a basic study of the thermal, dielectric, Theological, and mechanical properties of hydroxybenzoic acid‐ethylene terephthalate copolymers (PHB‐PET). It is argued that they have two‐phase structures, one rich in ethylene terephthalate (PET) and one rich in hydroxybenzoic acid (PHB). Polystyrene (PS) is immiscible in 60% PHB‐PET (60‐PHB‐PET) blends. Polycarbonate (PC) is partially miscible with the high PET phase of 60‐PHB‐PET. PET seems completely miscible with this high PET phase. Shear viscosity measurements on blends indicate that 60‐PHB‐PET gives rise to large reductions of viscosity. Extrudates and melt‐spun fibers have been prepared. The phase morphologies of low PHB‐PET blends as determined by scanning electron microscopy indicate ellipsoids or long fibrils of the, 60‐PHB‐PET in PS or PC matrices. High extrusion rates and melt spinning produce fibrillar structures. The mechanical properties of films, extrudates, and melt‐spun fibers were studied. Blends with 10% 60‐PHB‐PET exhibited significant increases in Young's modulus and tensile strength.
Blends of a chlorinated poly(vinyl chloride) compound and a thermotropic liquid crystalline copolyester: Some rheological behavior and spiral mold flow
Authors: Lee Biing‐Lin 
Published: December 2004

AbstractRheological and spiral mold flow measurements were made on blends of a chlorinated poly (vinyl chloride) (CPVC) compound and a thermotropic liquid crystalline copolyester of p‐hydroxybenzoic acid/poly (ethylene terephthalate) (60/40), hereafter referred to as LCC, at 210°C. Several interesting flow phenomena have been observed. While the shape of the flow curve (i.e., G′ vs. ω; G″ vs. ω) of LCC is solidlike, those of the blends are pseudoplastic. The dynamic viscosity of the blends increases as the concentration of LCC increases. However, the shear viscosity of the blends is reduced with LCC and may be described using the relationship of additivity of fluidity. Although the melt elasticity of the blends is increased with the concentration of LCC, the extrudate swell of the blends after extrusion from a capillary is decreased. This phenomenon, however, is complicated. A Theological analysis based on an idealized runner system is used to describe the spiral flow length as a function of the Theological properties of the molten polymers and also the operating conditions. The relative improvement of the spiral flow length of the CPVC compound due to blending with LCC could be correlated with the power‐law fluid model at high shear rates.
Mechanical behavior of polycarbonate/phenoxy blends before and after interchange reactions
Authors: Mondragón I. , Gaztelumendi M. , Nazábal J. 
Published: December 2004

AbstractMelt‐mixed blends of polycarbonate/phenoxy were obtained before and after Interchange reactions by controlling the processing time. The dynamic mechanical analysis of the physical and reacted blends confirmed the immiscibility of the pair and the displacement of the glass‐transition temperatures of the mixtures; this displacement was seen more clearly in the reacted mixtures, and at phenoxy‐rich contents, even a single phase can appear. The exchange reactions resulted in a mechanical behavior that showed both a higher modulus and greater tensile strength in the reacted blends. The ductility was close to linearity for the physical blends and probably would be improved in the reacted mixture with a lower processing time.
Thermal, dynamic mechanical, and rheological behavior of linear low‐density polyethylene/poly(octadecene‐co‐maleic anhydride) blends
Authors: O'Connor K. M. , Orler E. B. 
Published: December 2004

AbstractBlends of linear low‐density polyethylene (LLDPE) and a 50:50 copolymer of octadecene and maleic anhydride (C18‐MAH) were characterized by calorimetry, dynamic mechanical testing, and rheometry. In the solid state, the blends are essentially immiscible. No evidence was obtained for cocrystallization of the LLDPE with the paraf‐finic side‐chains of the C18‐MAH. Interactions between the blend components were observed in three ways. First, presence of the C18‐MAH in the LLDPE melt increases the nucleation rate for LLDPE crystallization. Second, side‐chain crystallization in a portion of the C18‐MAH component equivalent to approximately 15% of the total blend is apparently suppressed in the blends. Third, although the mechanical loss of the blends is essentially a sum of the pure components, the β relaxation of the LLDPE is absent in blends containing more than 20% C18‐MAH. The blends are also immiscible in the melt. The steady and dynamic shear rheology is dominated by the immiscibility and mismatch in viscosity, η, between the two polymers. A linear dependence on blend composition was found for log η in dynamic (small strain) tests. Nonlinear behavior with positive and negative deviations from linearity was found for log η in steady shear (large strain) tests.
Tg‐Composition analysis of miscible polymer blends
Authors: Aubin Madeleine , Prud'Homme Robert E. 
Published: December 2004

AbstractSeveral authors have suggested a monotonic variation of the glass transition temperature (Tg) of miscible polymer blends as a function of composition. They usually express the results in terms of equations proposed by Couchman‐Karasz, Gordon‐Taylor, Fox, and several others. However, we have noticed that numerous systems exhibit a cusp when Tg is plotted as a function of composition (after correction for the presence of crystallinity when semi‐crystalline polymers are involved). This cusp cannot appear when the Tg's of the two homopolymers involved are separated by less than about 52 degrees., It will be shown that this observation is quite general since it has been observed with several polyester/chlorinated polymer blends, polycaprolactone/nitrocellulose blends, and polystyrene/poly(vinylmethylether) blends; It will also be shown that this behavior is predicted in the framework of the free volume theory, with equations derived by Kovacs. According to this theory, above a critical concentration ϕc (relative to the plasticizer) and below a critical temperature Tc, the high‐Tc, polymer no longer contributes to the free volume of the mixture whereas it does above Tc. This difference leads to a Tg‐composition variation which has to be expressed by two different equations, one below Tc and the other above Tc, the cusp defining the limit of applicability of each equation.
Solution blending of polystyrene and poly(methyl methacrylate)
Authors: Burns Charles M. , Kim Woo Nyon 
Published: December 2004

AbstractBlends of poly(methyl methacrylate) (PMMA) and polystyrene (PS) have been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were made of a low molecular weight PS with three PMMAs having number‐average molecular weights of (1) 18,300, (2) 37,000, and (3) 211,000, The blend was found to be partially miscible. The composition‐dependent values of the polymer‐polymer interaction parameter (g12) were determined and found to be from 0.015 to 0.029 for solution casting at 25°C. The interaction parameter (g12) increases with increasing PMMA molecular weights in the PMMA/PS blend systems. This result is consistent with the behavior of the glass transition temperatures and with the microscopy study which indicate that compatibility is greater in the PMMA‐1/PS blends having the low molecular weight of PMMA than in the PMMA‐3/PS blends having the higher molecular weights of PMMA.
Viscoelastic behavior of polymer blends
Authors: Utracki L. A. 
Published: December 2004

AbstractThere is a reciprocal relation between flow and structure in multiphase systems such as polymer blends or composites. For this reason characterization of these materials must be carried out under conditions which guarantee minimum modification of structure. Capillary rheometry is particularly ill suited as a test tool, but the small strain dynamic oscillatory method may provide the true material responses, Most frequently these are expressed as frequency, ω, dependent storage and loss shear moduli, G′ and G″, or real and imaginary viscosities, η′ = G″/ω and η″ = G′/ω. However, two other methods of data presentation seem to be more sensitive to melt structure. They are the Cole‐Cole plot of η″ vs. η′ and the relaxation spectrum. Frequently, both of them indicate a binomial response. Various mechanisms leading to such behavior will be discussed.
The effect of cryogenically ground rubber on some mechanical properties of an unsaturated polyester resin
Authors: Rodriguez E. L. 
Published: December 2004

AbstractThe effect of Cryogenically Ground Rubber (CGR) from old tires on some mechanical properties of an unsaturated polyester resin is presented. A delay in the free radical cure reaction of the unsaturated polyester resin was observed upon the addition of ground rubber. This delay in the cure reaction could be overcome with the further addition of the free radical initiator. The particle size, surface chemistry, and the chemical composition of the rubber had an effect on the cure and on the final properties of the rubber‐filled composites. It was also found that the rubber particles decreased the tensile, flexural, and storage shear modulus of the unsaturated polyester. Composites made from silane‐treated ground rubber showed better mechanical properties than composites made from untreated CGR. Finally, the particle size of the ground rubber was apparently too large to produce a toughening effect on the filled materials.
Classification of ionic polymers
Authors: Ibidapo T. Adesanya 
Published: December 2004

AbstractIonic polymers are polymers, either organic or inorganic, which contain both covalent and ionic bonds in their molecular structure. This is the basic characteristic feature that distinguishes the ionic polymers from their conventional counterparts. There is no accepted definition of, or method of classifying, ionic polymers. The few previous classifications were not only restricted to particular groups but also cannot completely accommodate the current existing range of ionic polymers. This work considers the existing modes of classification of ionic polymers as well as the range of ionic polymers in the establishment of a simple and straightforward classification. It ensures, firstly, that a reflection of their different background structures can always be obtained; secondly, materials with similar properties or behavior are brought together; and lastly, it enables the prediction of new entries that might subsequently have to be Included in the scheme.